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Li CX, Zhang X. Evaluation of prolonged administration of isoflurane on cerebral blood flow and default mode network in macaque monkeys anesthetized with different maintenance doses. Neurosci Lett 2018; 662:402-408. [PMID: 29055725 PMCID: PMC5722273 DOI: 10.1016/j.neulet.2017.10.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Revised: 09/27/2017] [Accepted: 10/17/2017] [Indexed: 12/30/2022]
Abstract
OBJECT Isoflurane is a commonly used volatile anesthetic agent in clinical anesthesia and biomedical research. Prior study suggested the cerebral blood flow (CBF) and default mode network (DMN) could be changed after prolonged administration of isoflurane. The normal maintenance doses of isoflurane may vary from light (∼0.75%) to deep (∼1.5 or 2%) anesthesia. However, it is not clear how the duration effects are affected by the altered doses. The present study is aimed to examine if the duration effects are affected when isoflurane concentration is altered within normal maintenance doses. MATERIALS AND METHODS Adult rhesus monkeys (n=5, 8-12 years old, 8-10kg) were anesthetized and maintained at isoflurane levels 0.89±0.03%, 1.05±0.12%, or 1.19±0.08%. CBF and DMN of monkeys were examined using arterial spin-labeling perfusion and resting state functional MRI techniques. RESULTS the functional connectivity (FC) in the dominant DMN (posterior cingulate cortex (PCC) to anterior cingulated cortex (ACC) or media prefrontal cortex (MPFC)) decreased substantially and similarly during 4-h administration of isoflurane at any given maintenance dosage. CBF changes varied with isoflurane dosage. At the low dose (∼0.89%), CBF decreased in most brain regions. In contrast, no obvious changes was seen in those regions (except for the subcortex) when higher doses of isoflurane were applied. CONCLUSION FC in DMN was reduced substantially during prolonged administration of isoflurane. The FC reduction was not varying significantly with maintenance doses of isoflurane but the duration effect on CBF was dose-dependent. Such duration effects of isoflurane administration on DMN and CBF should be considered in the interpretation of the outcome in related neuroimaging studies of anesthetized subjects.
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Affiliation(s)
- Chun-Xia Li
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, United States
| | - Xiaodong Zhang
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, United States; Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA, 30329, United States.
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Altwegg-Boussac T, Schramm AE, Ballestero J, Grosselin F, Chavez M, Lecas S, Baulac M, Naccache L, Demeret S, Navarro V, Mahon S, Charpier S. Cortical neurons and networks are dormant but fully responsive during isoelectric brain state. Brain 2017; 140:2381-2398. [PMID: 29050394 DOI: 10.1093/brain/awx175] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 05/29/2017] [Indexed: 01/30/2023] Open
Abstract
A continuous isoelectric electroencephalogram reflects an interruption of endogenously-generated activity in cortical networks and systematically results in a complete dissolution of conscious processes. This electro-cerebral inactivity occurs during various brain disorders, including hypothermia, drug intoxication, long-lasting anoxia and brain trauma. It can also be induced in a therapeutic context, following the administration of high doses of barbiturate-derived compounds, to interrupt a hyper-refractory status epilepticus. Although altered sensory responses can be occasionally observed on an isoelectric electroencephalogram, the electrical membrane properties and synaptic responses of individual neurons during this cerebral state remain largely unknown. The aim of the present study was to characterize the intracellular correlates of a barbiturate-induced isoelectric electroencephalogram and to analyse the sensory-evoked synaptic responses that can emerge from a brain deprived of spontaneous electrical activity. We first examined the sensory responsiveness from patients suffering from intractable status epilepticus and treated by administration of thiopental. Multimodal sensory responses could be evoked on the flat electroencephalogram, including visually-evoked potentials that were significantly amplified and delayed, with a high trial-to-trial reproducibility compared to awake healthy subjects. Using an analogous pharmacological procedure to induce prolonged electro-cerebral inactivity in the rat, we could describe its cortical and subcortical intracellular counterparts. Neocortical, hippocampal and thalamo-cortical neurons were all silent during the isoelectric state and displayed a flat membrane potential significantly hyperpolarized compared with spontaneously active control states. Nonetheless, all recorded neurons could fire action potentials in response to intracellularly injected depolarizing current pulses and their specific intrinsic electrophysiological features were preserved. Manipulations of the membrane potential and intracellular injection of chloride in neocortical neurons failed to reveal an augmented synaptic inhibition during the isoelectric condition. Consistent with the sensory responses recorded from comatose patients, large and highly reproducible somatosensory-evoked potentials could be generated on the inactive electrocorticogram in rats. Intracellular recordings revealed that the underlying neocortical pyramidal cells responded to sensory stimuli by complex synaptic potentials able to trigger action potentials. As in patients, sensory responses in the isoelectric state were delayed compared to control responses and exhibited an elevated reliability during repeated stimuli. Our findings demonstrate that during prolonged isoelectric brain state neurons and synaptic networks are dormant rather than excessively inhibited, conserving their intrinsic properties and their ability to integrate and propagate environmental stimuli.
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Affiliation(s)
- Tristan Altwegg-Boussac
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France
| | - Adrien E Schramm
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France
| | - Jimena Ballestero
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France
| | - Fanny Grosselin
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France
| | - Mario Chavez
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France
| | - Sarah Lecas
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France.,UPMC Univ Paris 06, F-75005, Paris, France
| | - Michel Baulac
- Epilepsy Unit, Clinical Neurophysiology Department, AP-HP, Hôpital Pitié-Salpêtrière, F-75013, Paris, France
| | - Lionel Naccache
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France.,Evoked Potential Unit, Neurophysiology Department, AP-HP, Hôpital Pitié-Salpêtrière, F-75013, Paris, France
| | - Sophie Demeret
- Intensive Care Unit of Neurology, Neurology Department, AP-HP, Hôpital Pitié-Salpêtrière, F-75013, Paris, France
| | - Vincent Navarro
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France.,Epilepsy Unit, Clinical Neurophysiology Department, AP-HP, Hôpital Pitié-Salpêtrière, F-75013, Paris, France
| | - Séverine Mahon
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France
| | - Stéphane Charpier
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France.,UPMC Univ Paris 06, F-75005, Paris, France
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DeSimone JC, Pappas SS, Febo M, Burciu RG, Shukla P, Colon-Perez LM, Dauer WT, Vaillancourt DE. Forebrain knock-out of torsinA reduces striatal free-water and impairs whole-brain functional connectivity in a symptomatic mouse model of DYT1 dystonia. Neurobiol Dis 2017; 106:124-132. [PMID: 28673740 PMCID: PMC5555738 DOI: 10.1016/j.nbd.2017.06.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 06/15/2017] [Accepted: 06/20/2017] [Indexed: 01/10/2023] Open
Abstract
Multiple lines of evidence implicate striatal dysfunction in the pathogenesis of dystonia, including in DYT1, a common inherited form of the disease. The impact of striatal dysfunction on connected motor circuits and their interaction with other brain regions is poorly understood. Conditional knock-out (cKO) of the DYT1 protein torsinA from forebrain cholinergic and GABAergic neurons creates a symptomatic model that recapitulates many characteristics of DYT1 dystonia, including the developmental onset of overt twisting movements that are responsive to antimuscarinic drugs. We performed diffusion MRI and resting-state functional MRI on cKO mice of either sex to define abnormalities of diffusivity and functional connectivity in cortical, subcortical, and cerebellar networks. The striatum was the only region to exhibit an abnormality of diffusivity, indicating a selective microstructural deficit in cKO mice. The striatum of cKO mice exhibited widespread increases in functional connectivity with somatosensory cortex, thalamus, vermis, cerebellar cortex and nuclei, and brainstem. The current study provides the first in vivo support that direct pathological insult to forebrain torsinA in a symptomatic mouse model of DYT1 dystonia can engage genetically normal hindbrain regions into an aberrant connectivity network. These findings have important implications for the assignment of a causative region in CNS disease.
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Affiliation(s)
- Jesse C DeSimone
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL 32611, USA
| | - Samuel S Pappas
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Marcelo Febo
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Roxana G Burciu
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL 32611, USA
| | - Priyank Shukla
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL 32611, USA
| | - Luis M Colon-Perez
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32611, USA
| | - William T Dauer
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Veteran Affairs Ann Arbor Healthcare System, University of Michigan, Ann Arbor, MI 48105, USA
| | - David E Vaillancourt
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL 32611, USA; Department of Neurology, College of Medicine, University of Florida, Gainesville, FL 32610, USA; Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611, USA.
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54
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Zavou C, Kkoushi A, Koutsou A, Christodoulou C. Synchrony measure for a neuron driven by excitatory and inhibitory inputs and its adaptation to experimentally-recorded data. Biosystems 2017; 161:46-56. [PMID: 28923483 DOI: 10.1016/j.biosystems.2017.09.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 09/10/2017] [Accepted: 09/10/2017] [Indexed: 10/18/2022]
Abstract
The aim of the current work is twofold: firstly to adapt an existing method measuring the input synchrony of a neuron driven only by excitatory inputs in such a way so as to account for inhibitory inputs as well and secondly to further appropriately adapt this measure so as to be correctly utilised on experimentally-recorded data. The existing method uses the normalized pre-spike slope (NPSS) of the membrane potential, resulting from observing the slope of depolarization of the membrane potential of a neuron prior to the moment of crossing the threshold within a short period of time, to identify the response-relevant input synchrony and through it to infer the operational mode of a neuron. The first adaptation of NPSS is made such that its upper bound calculation accommodates for the higher possible slope values caused by the lower average and minimum membrane potential values due to inhibitory inputs. Results indicate that when the input spike trains arrive randomly, the modified NPSS works as expected inferring that the neuron is operating as a temporal integrator. When the input spike trains arrive in perfect synchrony though, the modified NPSS works as expected only when the level of inhibition is much higher than the level of excitation. This suggests that calculation of the upper bound of the NPSS should be a function of the ratio between excitatory and inhibitory inputs in order to be able to correctly capture perfect synchrony at a neuron's input. In addition, we effectively demonstrate a process which has to be followed when aiming to use the NPSS on real neuron recordings. This process, which relies on empirical observations of the slope of depolarisation for estimating the bounds for the range of observed interspike interval lengths, is successfully applied to experimentally-recorded data showing that through it both a real neuron's operational mode and the amount of input synchrony that caused its firing can be inferred.
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Affiliation(s)
- Christina Zavou
- Department of Computer Science, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.
| | - Antria Kkoushi
- Department of Computer Science, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.
| | - Achilleas Koutsou
- Department of Computer Science, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.
| | - Chris Christodoulou
- Department of Computer Science, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.
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Temporal Processing in the Visual Cortex of the Awake and Anesthetized Rat. eNeuro 2017; 4:eN-NWR-0059-17. [PMID: 28791331 PMCID: PMC5547194 DOI: 10.1523/eneuro.0059-17.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 07/16/2017] [Accepted: 07/17/2017] [Indexed: 12/18/2022] Open
Abstract
The activity pattern and temporal dynamics within and between neuron ensembles are essential features of information processing and believed to be profoundly affected by anesthesia. Much of our general understanding of sensory information processing, including computational models aimed at mathematically simulating sensory information processing, rely on parameters derived from recordings conducted on animals under anesthesia. Due to the high variety of neuronal subtypes in the brain, population-based estimates of the impact of anesthesia may conceal unit- or ensemble-specific effects of the transition between states. Using chronically implanted tetrodes into primary visual cortex (V1) of rats, we conducted extracellular recordings of single units and followed the same cell ensembles in the awake and anesthetized states. We found that the transition from wakefulness to anesthesia involves unpredictable changes in temporal response characteristics. The latency of single-unit responses to visual stimulation was delayed in anesthesia, with large individual variations between units. Pair-wise correlations between units increased under anesthesia, indicating more synchronized activity. Further, the units within an ensemble show reproducible temporal activity patterns in response to visual stimuli that is changed between states, suggesting state-dependent sequences of activity. The current dataset, with recordings from the same neural ensembles across states, is well suited for validating and testing computational network models. This can lead to testable predictions, bring a deeper understanding of the experimental findings and improve models of neural information processing. Here, we exemplify such a workflow using a Brunel network model.
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56
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Li CX, Zhang X. Effects of Long-Duration Administration of 1% Isoflurane on Resting Cerebral Blood Flow and Default Mode Network in Macaque Monkeys. Brain Connect 2017; 7:98-105. [PMID: 28030956 DOI: 10.1089/brain.2016.0445] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Isoflurane is an inhalational anesthetic that is widely used in medical procedures or biomedical research. The duration of anesthesia administration varies from minutes to hours. It is known that isoflurane has dose-dependent effects on brain functionality and physiology, and long-duration anesthesia administration could cause neurocognitive decline in animals and humans. However, the duration effect of isoflurane on the brain physiology and functionality still remains poorly understood. In the present study, cerebral blood flow (CBF) and functional connectivity of adult rhesus monkeys (maintained with 1% isoflurane for 4 h) were examined by using magnetic resonance imaging. The results demonstrate that long-duration isoflurane exposure could result in CBF reduction in most brain areas and functional connectivity decrease in the dominant default-mode network. This study reveals the anesthetic duration effects in the central nervous system of anesthetized subjects and suggests that such duration effects should be considered in examining the brain function of anesthetized animals or humans with contemporary neuroimaging approaches.
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Affiliation(s)
- Chun-Xia Li
- 1 Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University , Atlanta, Georgia
| | - Xiaodong Zhang
- 1 Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University , Atlanta, Georgia .,2 Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Emory University , Atlanta, Georgia
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57
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Moldovan M, Calin A, Kumaraswamy VM, Braver D, Simon MV. Burst-Suppression Ratio on Electrocorticography Depends on Interelectrode Distance. J Clin Neurophysiol 2017; 33:127-32. [PMID: 26690549 DOI: 10.1097/wnp.0000000000000248] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
INTRODUCTION With deepening of anesthesia-induced comatose states, the EEG becomes fragmented by increasing periods of suppression. When measured from conventional EEG recordings, the binary burst-suppression signal (BS) appears similar across the scalp. As such, the BS ratio (BSR), quantifying the fraction of time spent in suppression, is clinically considered a global index of brain function in sedation monitoring. Recent studies indicate that BS may be considerably asynchronous when measured with higher spatial resolution such as on electrocorticography. The authors investigated the magnitude of BSR changes with cortical recording interelectrode distance. METHODS The authors selected fronto-parietal electrocorticography recordings showing propofol-induced BS recorded via 8-electrode strips (1-cm interelectrode distance) during cortical motor mapping in 31 patients. For 1-minute epochs, bipolar recordings were computed between each electrode pair. The median BSR, burst duration (BD), and bursting frequency were derived for each interelectrode distance. RESULTS At 1-cm interelectrode distance, with increasing BSR, BD decreased exponentially. For a BSR between 50% and 80%, BD reached a plateau of 2.1 seconds while the bursting frequency decreased from 14 to 6 bursts per minute. With increasing interelectrode distance, BD increased at a rate of 0.2 seconds per cm. This correlated with a decrease in BSR with distance that reached the rate of -4.4 percentage per centimeters during deepest anesthesia. CONCLUSIONS With increasing cortical interelectrode recording distance, burst summation leads to an increasing BD associated with a reduction in BSR. Standardization of interelectrode distance is important for cortical BSR measurements.
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Affiliation(s)
- Mihai Moldovan
- *Division of Physiology and Neuroscience, Department of Functional Sciences, "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania; †Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark; ‡Intraoperative Neurophysiology Unit, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; §Department of Pharmacology, University of Oxford, Oxford, United Kingdom; and ‖Department of Neurology, University Hospitals Case Medical Center, Cleveland, Ohio
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Williams AJ, Zhou C, Sun QQ. Enhanced Burst-Suppression and Disruption of Local Field Potential Synchrony in a Mouse Model of Focal Cortical Dysplasia Exhibiting Spike-Wave Seizures. Front Neural Circuits 2016; 10:93. [PMID: 27891080 PMCID: PMC5102891 DOI: 10.3389/fncir.2016.00093] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 10/31/2016] [Indexed: 11/28/2022] Open
Abstract
Focal cortical dysplasias (FCDs) are a common cause of brain seizures and are often associated with intractable epilepsy. Here we evaluated aberrant brain neurophysiology in an in vivo mouse model of FCD induced by neonatal freeze lesions (FLs) to the right cortical hemisphere (near S1). Linear multi-electrode arrays were used to record extracellular potentials from cortical and subcortical brain regions near the FL in anesthetized mice (5–13 months old) followed by 24 h cortical electroencephalogram (EEG) recordings. Results indicated that FL animals exhibit a high prevalence of spontaneous spike-wave discharges (SWDs), predominately during sleep (EEG), and an increase in the incidence of hyper-excitable burst/suppression activity under general anesthesia (extracellular recordings, 0.5%–3.0% isoflurane). Brief periods of burst activity in the local field potential (LFP) typically presented as an arrhythmic pattern of increased theta-alpha spectral peaks (4–12 Hz) on a background of low-amplitude delta activity (1–4 Hz), were associated with an increase in spontaneous spiking of cortical neurons, and were highly synchronized in control animals across recording sites in both cortical and subcortical layers (average cross-correlation values ranging from +0.73 to +1.0) with minimal phase shift between electrodes. However, in FL animals, cortical vs. subcortical burst activity was strongly out of phase with significantly lower cross-correlation values compared to controls (average values of −0.1 to +0.5, P < 0.05 between groups). In particular, a marked reduction in the level of synchronous burst activity was observed, the closer the recording electrodes were to the malformation (Pearson’s Correlation = 0.525, P < 0.05). In a subset of FL animals (3/9), burst activity also included a spike or spike-wave pattern similar to the SWDs observed in unanesthetized animals. In summary, neonatal FLs increased the hyperexcitable pattern of burst activity induced by anesthesia and disrupted field potential synchrony between cortical and subcortical brain regions near the site of the cortical malformation. Monitoring the altered electrophysiology of burst activity under general anesthesia with multi-dimensional micro-electrode arrays may serve to define distinct neurophysiological biomarkers of epileptogenesis in human brain and improve techniques for surgical resection of epileptogenic malformed brain tissue.
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Affiliation(s)
- Anthony J Williams
- Department of Zoology and Physiology, University of Wyoming Laramie, WY, USA
| | - Chen Zhou
- Department of Zoology and Physiology, University of Wyoming Laramie, WY, USA
| | - Qian-Quan Sun
- Department of Zoology and Physiology, University of Wyoming Laramie, WY, USA
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DeSimone JC, Febo M, Shukla P, Ofori E, Colon-Perez LM, Li Y, Vaillancourt DE. In vivo imaging reveals impaired connectivity across cortical and subcortical networks in a mouse model of DYT1 dystonia. Neurobiol Dis 2016; 95:35-45. [PMID: 27404940 PMCID: PMC5010949 DOI: 10.1016/j.nbd.2016.07.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 06/27/2016] [Accepted: 07/08/2016] [Indexed: 12/12/2022] Open
Abstract
Developing in vivo functional and structural neuroimaging assays in Dyt1 ΔGAG heterozygous knock-in (Dyt1 KI) mice provide insight into the pathophysiology underlying DYT1 dystonia. In the current study, we examined in vivo functional connectivity of large-scale cortical and subcortical networks in Dyt1 KI mice and wild-type (WT) controls using resting-state functional magnetic resonance imaging (MRI) and an independent component analysis. In addition, using diffusion MRI we examined how structural integrity across the basal ganglia and cerebellum directly relates to impairments in functional connectivity. Compared to WT mice, Dyt1 KI mice revealed increased functional connectivity across the striatum, thalamus, and somatosensory cortex; and reduced functional connectivity in the motor and cerebellar cortices. Further, Dyt1 KI mice demonstrated elevated free-water (FW) in the striatum and cerebellum compared to WT mice, and increased FW was correlated with impairments in functional connectivity across basal ganglia, cerebellum, and sensorimotor cortex. The current study provides the first in vivo MRI-based evidence in support of the hypothesis that the deletion of a 3-base pair (ΔGAG) sequence in the Dyt1 gene encoding torsinA has network level effects on in vivo functional connectivity and microstructural integrity across the sensorimotor cortex, basal ganglia, and cerebellum.
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Affiliation(s)
- Jesse C DeSimone
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
| | - Marcelo Febo
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Priyank Shukla
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
| | - Edward Ofori
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
| | - Luis M Colon-Perez
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Yuqing Li
- Department of Neurology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - David E Vaillancourt
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA; Department of Neurology, College of Medicine, University of Florida, Gainesville, FL, USA; Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA.
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Liu S, Ching S. Homeostatic dynamics, hysteresis and synchronization in a low-dimensional model of burst suppression. J Math Biol 2016; 74:1011-1035. [PMID: 27549764 DOI: 10.1007/s00285-016-1048-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 05/03/2016] [Indexed: 01/24/2023]
Abstract
Burst suppression, a pattern of the electroencephalogram characterized by quasi-periodic alternation of high-voltage activity (burst) and isoelectric silence (suppression), is typically associated with states of unconsciousness, such as in deep general anesthesia and certain etiologies of coma. Recent computational models for burst suppression have attributed the slow (up to tens of seconds) time-scale of burst termination and re-initiation to cycling in supportive physiological process, such as cerebral metabolism. That is, activity-dependent substrate ('energy') depletion during bursts, followed by substrate recovery during suppression. Such a model falls into the category of a fast-slow dynamical system, commonly used to describe neuronal bursting more generally. Here, following this basic paradigm, we develop a low dimensional mean field model for burst suppression that adds several new features and capabilities to previous models. Most notably, this new model includes explicit homeostatic interactions wherein the rates of substrate recovery are tied to neuronal activity in a supply demand loop, creating a physiologically consistent, reciprocal interaction between the neural and substrate processes. We develop formal analysis of the model dynamics, showing, in particular, the capability of the model to produce burst-like activity as a consequence of neuronal downregulation only, without any direct perturbation to the substrate dynamics. Further, we use a synchronization analysis to contrast different mechanisms for spatially local versus global bursting. The analysis performed generates characterizations that are consistent with experimental observations of spatiotemporal features such as burst onset, duration, and spatial organization and, moreover, generates predictions regarding the presence of bistability and hysteresis in the underlying system. Thus, the model provides new dynamical insight into the mechanisms of burst suppression and, moreover, a tractable platform for more detailed future characterizations.
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Affiliation(s)
- Sensen Liu
- Department of Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - ShiNung Ching
- Department of Electrical and Systems Engineering, Division of Biology and Biomedical Sciences, Washington University in St. Louis, St. Louis, MO, 63130, USA.
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Differential Suppression of Spontaneous and Noxious-evoked Somatosensory Cortical Activity by Isoflurane in the Neonatal Rat. Anesthesiology 2016; 124:885-98. [PMID: 26808637 DOI: 10.1097/aln.0000000000001017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND The effect of neonatal anesthesia and pain on the developing brain is of considerable clinical importance, but few studies have evaluated noxious surgical input to the infant brain under anesthesia. Herein, the authors tested the effect of increasing isoflurane concentration on spontaneous and evoked nociceptive activity in the somatosensory cortex of rats at different postnatal ages. METHODS Intracortical extracellular field potentials evoked by hind paw C-fiber electrical stimulation were recorded in the rat somatosensory cortex at postnatal day (P) 7, P14, P21, and P30 during isoflurane anesthesia (n = 7 per group). The amplitudes of evoked potentials and the energies of evoked oscillations (1 to 100 Hz over 3 s) were measured after equilibration at 1.5% isoflurane and during step increases in inspired isoflurane. Responses during and after plantar hind paw incision were compared at P7 and P30 (n = 6 per group). RESULTS At P7, cortical activity was silent at 1.5% isoflurane but noxious-evoked potentials decreased only gradually in amplitude and energy with step increases in isoflurane. The resistance of noxious-evoked potentials to isoflurane at P7 was significantly enhanced after surgical hind paw incision (69 ± 16% vs. 6 ± 1% in nonincised animals at maximum inspired isoflurane). This resistance was age dependent; at P14 to P30, noxious-evoked responses decreased sharply with increasing isoflurane (step 3 [4%] P7: 50 ± 9%, P30: 4 ± 1% of baseline). Hind paw incision at P30 sensitized noxious-evoked potentials, but this was suppressed by higher isoflurane concentrations. CONCLUSIONS Despite suppression of spontaneous activity, cortical-evoked potentials are more resistant to isoflurane in young rats and are further sensitized by surgical injury.
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Nita DA, Moldovan M, Sharma R, Avramescu S, Otsubo H, Hahn CD. Burst-suppression is reactive to photic stimulation in comatose children with acquired brain injury. Clin Neurophysiol 2016; 127:2921-2930. [PMID: 27266662 DOI: 10.1016/j.clinph.2016.03.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 02/19/2016] [Accepted: 03/09/2016] [Indexed: 11/29/2022]
Abstract
OBJECTIVE Burst-suppression is an electroencephalographic pattern observed during coma. In individuals without known brain pathologies undergoing deep general anesthesia, somatosensory stimulation transiently increases the occurrence of bursts. We investigated the reactivity of burst-suppression in children with acquired brain injury. METHODS Intensive care unit electroencephalographic monitoring recordings containing burst-suppression were obtained from 5 comatose children with acquired brain injury of various etiologies. Intermittent photic stimulation was performed at 1Hz for 1min to assess reactivity. We quantified reactivity by measuring the change in the burst ratio (fraction of time in burst) following photic stimulation. RESULTS Photic stimulation evoked bursts in all patients, resulting in a transient increase in the burst ratio, while the mean heart rate remained unchanged. The regression slope of the change in burst ratio, referred to as the standardized burst ratio reactivity, correlated with subjects' Glasgow Coma Scale scores. CONCLUSIONS Reactivity of the burst-suppression pattern to photic stimulation occurs across diverse coma etiologies. Standardized burst ratio reactivity appears to reflect coma severity. SIGNIFICANCE Measurement of burst ratio reactivity could represent a simple method to monitor coma severity in critically ill children.
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Affiliation(s)
- Dragos A Nita
- Division of Neurology and Program in Neurosciences and Mental Health, The Hospital for Sick Children, and Department of Paediatrics, University of Toronto, Toronto, Canada
| | - Mihai Moldovan
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; Division of Physiology and Fundamental Neuroscience, "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania
| | - Roy Sharma
- Division of Neurology and Program in Neurosciences and Mental Health, The Hospital for Sick Children, and Department of Paediatrics, University of Toronto, Toronto, Canada
| | - Sinziana Avramescu
- Department of Anaesthesia, Sunnybrook Health Sciences Centre, and Department of Anaesthesia, University of Toronto, Toronto, Canada
| | - Hiroshi Otsubo
- Division of Neurology and Program in Neurosciences and Mental Health, The Hospital for Sick Children, and Department of Paediatrics, University of Toronto, Toronto, Canada
| | - Cecil D Hahn
- Division of Neurology and Program in Neurosciences and Mental Health, The Hospital for Sick Children, and Department of Paediatrics, University of Toronto, Toronto, Canada.
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Lissek T, Obenhaus HA, Ditzel DAW, Nagai T, Miyawaki A, Sprengel R, Hasan MT. General Anesthetic Conditions Induce Network Synchrony and Disrupt Sensory Processing in the Cortex. Front Cell Neurosci 2016; 10:64. [PMID: 27147963 PMCID: PMC4830828 DOI: 10.3389/fncel.2016.00064] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/29/2016] [Indexed: 12/19/2022] Open
Abstract
General anesthetics are commonly used in animal models to study how sensory signals are represented in the brain. Here, we used two-photon (2P) calcium activity imaging with cellular resolution to investigate how neuronal activity in layer 2/3 of the mouse barrel cortex is modified under the influence of different concentrations of chemically distinct general anesthetics. Our results show that a high isoflurane dose induces synchrony in local neuronal networks and these cortical activity patterns closely resemble those observed in EEG recordings under deep anesthesia. Moreover, ketamine and urethane also induced similar activity patterns. While investigating the effects of deep isoflurane anesthesia on whisker and auditory evoked responses in the barrel cortex, we found that dedicated spatial regions for sensory signal processing become disrupted. We propose that our isoflurane-2P imaging paradigm can serve as an attractive model system to dissect cellular and molecular mechanisms that induce the anesthetic state, and it might also provide important insight into sleep-like brain states and consciousness.
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Affiliation(s)
- Thomas Lissek
- Department of Molecular Neurobiology, Max Planck Institute for Medical ResearchHeidelberg, Germany; Department of Neurobiology, Interdisciplinary Center for Neurosciences, University of HeidelbergHeidelberg, Germany
| | - Horst A Obenhaus
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research Heidelberg, Germany
| | - Désirée A W Ditzel
- Department of Molecular Neurobiology, Max Planck Institute for Medical ResearchHeidelberg, Germany; Max Planck Research Group at the Institute for Anatomy and Cell Biology, Heidelberg UniversityHeidelberg, Germany
| | - Takeharu Nagai
- Laboratory for Nanosystems Physiology, Hokkaido University Hokkaido, Japan
| | - Atsushi Miyawaki
- RIKEN-Brain Science Institute, Laboratory for Cell Function Dynamics Saitama, Japan
| | - Rolf Sprengel
- Department of Molecular Neurobiology, Max Planck Institute for Medical ResearchHeidelberg, Germany; Max Planck Research Group at the Institute for Anatomy and Cell Biology, Heidelberg UniversityHeidelberg, Germany
| | - Mazahir T Hasan
- Department of Molecular Neurobiology, Max Planck Institute for Medical ResearchHeidelberg, Germany; Molecular Neurobiology, Neurocure Cluster of Excellence, Charite-UniversitätsmedizinBerlin, Germany
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Kum JE, Han HB, Choi JH. Pupil Size in Relation to Cortical States during Isoflurane Anesthesia. Exp Neurobiol 2016; 25:86-92. [PMID: 27122995 PMCID: PMC4844567 DOI: 10.5607/en.2016.25.2.86] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 02/15/2016] [Accepted: 02/15/2016] [Indexed: 11/19/2022] Open
Abstract
In neuronal recording studies on anesthetized animals, reliable measures for the transitional moment of consciousness are frequently required. Previous findings suggest that pupil fluctuations reflect the neuronal states during quiet wakefulness, whose correlation was unknown for the anesthetized condition. Here, we investigated the pupillary changes under isoflurane anesthesia simultaneously with the electroencephalogram (EEG) and electromyogram (EMG). The pupil was tracked by using a region-based active contour model. The dose was given to the animal in a stepwise increasing mode (simulating induction of anesthesia) or in a stepwise decreasing mode (simulating emergence of anesthesia). We found that the quickly widening pupil action (mydriasis) characterizes the transitional state in anesthesia. Mydriasis occurred only in the light dose in the emergence phase, and the events were accompanied by an increase of burst activity in the EEG followed by EMG activity in 47% of the mydriasis events. Our findings suggest that recording such pupil changes may offer a noncontact monitoring tool for indexing the transitional state of the brain, particularly when a lower threshold dose is applied.
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Affiliation(s)
- Jeung Eun Kum
- Center for Neuroscience, Korea Institute of Science and Technology, Seoul 02792, Korea.; Department of Neuroscience, University of Science and Technology, Daejon 34113, Korea
| | - Hio-Been Han
- Center for Neuroscience, Korea Institute of Science and Technology, Seoul 02792, Korea.; Department of Psychology, Yonsei University, Seoul 03722, Korea
| | - Jee Hyun Choi
- Center for Neuroscience, Korea Institute of Science and Technology, Seoul 02792, Korea.; Department of Neuroscience, University of Science and Technology, Daejon 34113, Korea
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Lustig B, Wang Y, Pastalkova E. Oscillatory patterns in hippocampus under light and deep isoflurane anesthesia closely mirror prominent brain states in awake animals. Hippocampus 2015; 26:102-9. [DOI: 10.1002/hipo.22494] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/14/2015] [Indexed: 02/05/2023]
Affiliation(s)
- Brian Lustig
- Department of Neurobiology, Neuroscience Graduate Program; University of Chicago; Illinois
- Janelia Research Campus; Ashburn Virginia
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Sampath D, Shmueli D, White AM, Raol YH. Flupirtine effectively prevents development of acute neonatal seizures in an animal model of global hypoxia. Neurosci Lett 2015; 607:46-51. [PMID: 26365409 DOI: 10.1016/j.neulet.2015.09.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 08/18/2015] [Accepted: 09/07/2015] [Indexed: 12/16/2022]
Abstract
Current first-line drugs for the treatment of neonatal seizures have limited efficacy and are associated with side effects. Uncontrolled seizures may exacerbate brain injury and contribute to later-life neurological disability. Therefore, it is critical to develop a treatment for neonatal seizures that is effective and safe. In early-life, when the γ-aminobutyric acid (GABA) inhibitory system is not fully developed, potassium channels play an important role in controlling excitability. An earlier study demonstrated that flupirtine, a KCNQ potassium channel opener, is more efficacious than diazepam and phenobarbital for the treatment of chemoconvulsant-induced neonatal seizures. In newborns, seizures are most commonly associated with hypoxic-ischemic encephalopathy (HIE). Thus, in the present study, we examined the efficacy of flupirtine to treat neonatal seizures in an animal model of global hypoxia. Our results showed that flupirtine dose dependently blocks the occurrence of behavioral seizures in pups during hypoxia. Additionally, flupirtine inhibits the development of hypoxia-induced clinical seizures and associated epileptiform discharges, as well as purely electrographic (subclinical) seizures. These results suggest that flupirtine is an effective anti-seizure drug, and that further studies should be conducted to determine the time window within which it's administration can effectively treat neonatal seizures.
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Affiliation(s)
- Dayalan Sampath
- Department of Pediatrics, Division of Neurology, School of Medicine, Translational Epilepsy Research Program, University of Colorado, School of Medicine, Aurora, CO 80045, United States
| | - Doron Shmueli
- Department of Pediatrics, Division of Neurology, School of Medicine, Translational Epilepsy Research Program, University of Colorado, School of Medicine, Aurora, CO 80045, United States
| | - Andrew M White
- Department of Pediatrics, Division of Neurology, School of Medicine, Translational Epilepsy Research Program, University of Colorado, School of Medicine, Aurora, CO 80045, United States
| | - Yogendra H Raol
- Department of Pediatrics, Division of Neurology, School of Medicine, Translational Epilepsy Research Program, University of Colorado, School of Medicine, Aurora, CO 80045, United States.
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Noda T, Kanzaki R, Takahashi H. Population activity in auditory cortex of the awake rat revealed by recording with dense microelectrode array. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2013:1538-41. [PMID: 24109993 DOI: 10.1109/embc.2013.6609806] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cortical mechanisms of auditory perception include temporal interaction between neuronal ensembles in a functional cortical structure such as a place code of frequency, or tonotopic map. To investigate the mechanism, a recording method is needed to densely map spatio-temporal activity pattern within the predefined tonotopic organization specifically in the awake condition. The present study has proposed and developed an experimental system that is capable of simultaneous neural recording with a grid array of 100 sites with 400-µm inter-electrode distance in the 4(th) layer of auditory cortex of awake rat. Both multiunit activities (MUA) and local field potentials (LFPs) confirmed the tonotopic map in the auditory cortex. In addition, spectral powers in higher frequency components (4-120 Hz) were enhanced and a lower frequency component (1-4 Hz) was reduced during waking. Phase synchronization between recording sites in the gamma-band oscillatory activity was generally smaller in the awake cortex than in the anesthetized cortex. These results have proven the feasibility of our recording and will open a new avenue to investigate neural activities in the functional map of awake cortex.
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Abstract
This paper describes the various electroencephalographic (EEG) patterns expressed by the comatose brain, starting with the sleep-like oscillations associated with light coma. Deeper coma generally displays a burst-suppression pattern characterized by alternating episodes of isoelectric (flat) EEG and bursting slow waves. The latter are the result of cortical hyperexcitability, as demonstrated by intracellular recordings in anesthetized animals. Further deepening of the coma yields to continuous isoelectric electroencephalogram and eventually results in a newly discovered type of spiky waves that have been termed Nu-complexes. The paper discusses the structures participating in the genesis of burst suppression, the afferent mechanisms, and the reasons for which this activity should or should not be regarded as an epileptic disorder. This article is part of a Special Issue entitled "Status Epilepticus".
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Affiliation(s)
- Florin Amzica
- Department of Stomatology, School of Dentistry, Université de Montreal, Montreal, Canada; Department of Neurosciences, School of Medicine, Université de Montreal, Montreal, Canada.
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69
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Stitt I, Galindo-Leon E, Pieper F, Engler G, Fiedler E, Stieglitz T, Engel AK. Intrinsic coupling modes reveal the functional architecture of cortico-tectal networks. SCIENCE ADVANCES 2015; 1:e1500229. [PMID: 26601226 PMCID: PMC4643805 DOI: 10.1126/sciadv.1500229] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 06/24/2015] [Indexed: 06/05/2023]
Abstract
In the absence of sensory stimulation or motor output, the brain exhibits complex spatiotemporal patterns of intrinsically generated neural activity. Analysis of ongoing brain dynamics has identified the prevailing modes of cortico-cortical interaction; however, little is known about how such patterns of intrinsically generated activity are correlated between cortical and subcortical brain areas. We investigate the correlation structure of ongoing cortical and superior colliculus (SC) activity across multiple spatial and temporal scales. Ongoing cortico-tectal interaction was characterized by correlated fluctuations in the amplitude of delta, spindle, low gamma, and high-frequency oscillations (>100 Hz). Of these identified coupling modes, topographical patterns of high-frequency coupling were the most consistent with patterns of anatomical connectivity, reflecting synchronized spiking within cortico-tectal networks. Cortico-tectal coupling at high frequencies was temporally parcellated by the phase of slow cortical oscillations and was strongest for SC-cortex channel pairs that displayed overlapping visual spatial receptive fields. Despite displaying a high degree of spatial specificity, cortico-tectal coupling in lower-frequency bands did not match patterns of cortex-to-SC anatomical connectivity. Collectively, our findings demonstrate that neural activity is spontaneously coupled between cortex and SC, with high- and low-frequency modes of coupling reflecting direct and indirect cortico-tectal interactions, respectively.
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Affiliation(s)
- Iain Stitt
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Edgar Galindo-Leon
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Florian Pieper
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Gerhard Engler
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Eva Fiedler
- Department of Microsystems Engineering, University of Freiburg, 79110 Freiburg, Germany
| | - Thomas Stieglitz
- Department of Microsystems Engineering, University of Freiburg, 79110 Freiburg, Germany
| | - Andreas K. Engel
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
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Callahan JW, Abercrombie ED. Relationship between subthalamic nucleus neuronal activity and electrocorticogram is altered in the R6/2 mouse model of Huntington's disease. J Physiol 2015; 593:3727-38. [PMID: 25952461 DOI: 10.1113/jp270268] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 05/05/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Neural synchrony between the subthalamic nucleus (STN) and cortex is critical for proper information processing in basal ganglia circuits. Using in vivo extracellular recordings in urethane-anaesthetized mice, we demonstrate that single units and local field potentials from the STN exhibit oscillatory entrainment to low-frequency (0.5-4 Hz) rhythms when the cortex is in a synchronized state. Here we report novel findings in the R6/2 transgenic mouse model of Huntington's disease (HD) by demonstrating that STN activity is reduced and less phase-locked to cortical low-frequency oscillations. The spectral power of low-frequency oscillations in ECoG recordings of R6/2 mice is diminished while the spectral power of higher frequencies is augmented and such altered cortical patterning could lead to decreased synchrony in corticosubthalamic circuits. Our data establish that cortical entrainment of STN neural activity is disrupted in R6/2 mice and may be one of the mechanisms contributing to disordered motor control in HD. ABSTRACT Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder in which impairments in the processing of information between the cortex and basal ganglia are fundamental to the onset and progression of the HD phenotype. The corticosubthalamic hyperdirect pathway plays a pivotal role in motor selection and blockade of neuronal activity in the subthalamic nucleus (STN) results in a hyperkinetic movement syndrome, similar to the HD phenotype. The aim of the present study was to examine the relationship between neuronal activity in the STN and cortex in an animal model of HD. We performed in vivo extracellular recordings in the STN to measure single-unit activity and local field potentials in the R6/2 transgenic mouse model of HD. These recordings were obtained during epochs of simultaneously acquired electrocorticogram (ECoG) in discrete brain states representative of global cortical network synchronization or desynchronization. Cortically patterned STN neuronal activity was less phase-locked in R6/2 mice, which is likely to result in less efficient coding of cortical inputs by the basal ganglia. In R6/2 mice, the power of the ECoG in lower frequencies (0.5-4 Hz) was diminished while the power expressed in higher frequencies (13-100 Hz) was increased. In addition, the spontaneous activity of STN neurons in R6/2 mice was reduced and neurons exhibited a more irregular firing pattern. Glutamatergic STN neurons provide the major excitatory drive to the output nuclei of the basal ganglia and altered discharge patterns could lead to aberrant basal ganglia output and disordered motor control in HD.
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Affiliation(s)
- Joshua W Callahan
- Center for Molecular and Behavioural Neuroscience, Rutgers University, Newark, NJ, 07102, USA
| | - Elizabeth D Abercrombie
- Center for Molecular and Behavioural Neuroscience, Rutgers University, Newark, NJ, 07102, USA
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Bojak I, Stoyanov ZV, Liley DTJ. Emergence of spatially heterogeneous burst suppression in a neural field model of electrocortical activity. Front Syst Neurosci 2015; 9:18. [PMID: 25767438 PMCID: PMC4341547 DOI: 10.3389/fnsys.2015.00018] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 02/02/2015] [Indexed: 11/17/2022] Open
Abstract
Burst suppression in the electroencephalogram (EEG) is a well-described phenomenon that occurs during deep anesthesia, as well as in a variety of congenital and acquired brain insults. Classically it is thought of as spatially synchronous, quasi-periodic bursts of high amplitude EEG separated by low amplitude activity. However, its characterization as a “global brain state” has been challenged by recent results obtained with intracranial electrocortigraphy. Not only does it appear that burst suppression activity is highly asynchronous across cortex, but also that it may occur in isolated regions of circumscribed spatial extent. Here we outline a realistic neural field model for burst suppression by adding a slow process of synaptic resource depletion and recovery, which is able to reproduce qualitatively the empirically observed features during general anesthesia at the whole cortex level. Simulations reveal heterogeneous bursting over the model cortex and complex spatiotemporal dynamics during simulated anesthetic action, and provide forward predictions of neuroimaging signals for subsequent empirical comparisons and more detailed characterization. Because burst suppression corresponds to a dynamical end-point of brain activity, theoretically accounting for its spatiotemporal emergence will vitally contribute to efforts aimed at clarifying whether a common physiological trajectory is induced by the actions of general anesthetic agents. We have taken a first step in this direction by showing that a neural field model can qualitatively match recent experimental data that indicate spatial differentiation of burst suppression activity across cortex.
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Affiliation(s)
- Ingo Bojak
- Systems Neuroscience Research Group, School of Systems Engineering, University of Reading Reading, UK
| | - Zhivko V Stoyanov
- Systems Neuroscience Research Group, School of Systems Engineering, University of Reading Reading, UK
| | - David T J Liley
- Brain and Psychological Sciences Research Centre, School of Health Sciences, Swinburne University of Technology Hawthorn, VIC, Australia
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Toda Y, Kobayashi K, Hayashi Y, Inoue T, Oka M, Endo F, Yoshinaga H, Ohtsuka Y. High-frequency EEG activity in epileptic encephalopathy with suppression-burst. Brain Dev 2015; 37:230-6. [PMID: 24796721 DOI: 10.1016/j.braindev.2014.04.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 04/07/2014] [Accepted: 04/08/2014] [Indexed: 10/25/2022]
Abstract
OBJECTIVE We explored high-frequency activity in the suppression-burst (SB) pattern of interictal electroencephalogram (EEG) in early infantile epileptic encephalopathy including Ohtahara syndrome (OS) and early myoclonic encephalopathy (EME) to investigate the pathophysiological characteristics of SB. METHODS Subjects included six patients with the SB EEG pattern related to OS or EME (Group SB). The results were evaluated in comparison to tracé alternant (TA) observed during the neonatal period in nine patients to rule out possible nonspecific relationships between high-frequency activity and periodic EEG patterns (Group TA). EEG was digitally recorded with a sampling rate of 500Hz and the analysis was performed in each of the particular bipolar channel-pairs. We visually selected 20 typical consecutive burst sections and 160 inter-burst sections for comparison from the sleep record of each patient and performed the time-frequency analysis. We investigated the maximum frequencies of power enhancement in each derivation in both groups. RESULTS In Group SB, a significant increase in power at a frequency of 80-150Hz was observed in association with the bursts, particularly in the bilateral parieto-occipital derivations, in all patients. In Group TA, on the contrary, no significant increase in high-frequency power was found. The maximum frequencies of power enhancement were significantly higher in Group SB than in Group TA (p<0.001 by repeated-measures ANOVA). CONCLUSION Interictal high frequencies of up to 150Hz were detected in the suppression-burst EEG patterns in epileptic encephalopathy in early infancy. Further studies will be necessary to identify the role of the interictal high-frequency activity in the pathophysiology of such early epileptic encephalopathy.
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Affiliation(s)
- Yoshihiro Toda
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences and Okayama University Hospital, Okayama, Japan; Department of Pediatrics, School of Medicine, University of Tokushima, Tokushima, Japan
| | - Katsuhiro Kobayashi
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences and Okayama University Hospital, Okayama, Japan.
| | - Yumiko Hayashi
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences and Okayama University Hospital, Okayama, Japan
| | - Takushi Inoue
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences and Okayama University Hospital, Okayama, Japan
| | - Makio Oka
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences and Okayama University Hospital, Okayama, Japan
| | - Fumika Endo
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences and Okayama University Hospital, Okayama, Japan
| | - Harumi Yoshinaga
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences and Okayama University Hospital, Okayama, Japan
| | - Yoko Ohtsuka
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences and Okayama University Hospital, Okayama, Japan; Asahigawaso Rehabilitation and Medical Center, Okayama, Japan
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The human burst suppression electroencephalogram of deep hypothermia. Clin Neurophysiol 2015; 126:1901-1914. [PMID: 25649968 DOI: 10.1016/j.clinph.2014.12.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 11/27/2014] [Accepted: 12/27/2014] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Deep hypothermia induces 'burst suppression' (BS), an electroencephalogram pattern with low-voltage 'suppressions' alternating with high-voltage 'bursts'. Current understanding of BS comes mainly from anesthesia studies, while hypothermia-induced BS has received little study. We set out to investigate the electroencephalogram changes induced by cooling the human brain through increasing depths of BS through isoelectricity. METHODS We recorded scalp electroencephalograms from eleven patients undergoing deep hypothermia during cardiac surgery with complete circulatory arrest, and analyzed these using methods of spectral analysis. RESULTS Within patients, the depth of BS systematically depends on the depth of hypothermia, though responses vary between patients except at temperature extremes. With decreasing temperature, burst lengths increase, and burst amplitudes and lengths decrease, while the spectral content of bursts remains constant. CONCLUSIONS These findings support an existing theoretical model in which the common mechanism of burst suppression across diverse etiologies is the cyclical diffuse depletion of metabolic resources, and suggest the new hypothesis of local micro-network dropout to explain decreasing burst amplitudes at lower temperatures. SIGNIFICANCE These results pave the way for accurate noninvasive tracking of brain metabolic state during surgical procedures under deep hypothermia, and suggest new testable predictions about the network mechanisms underlying burst suppression.
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74
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Liu S, Ching S. A mean field model for neural-metabolic homeostatic coupling in burst suppression. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:4852-5. [PMID: 25571078 DOI: 10.1109/embc.2014.6944710] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Burst suppression is an inactivated brain state in which the electroencephalogram is characterized by intermittent periods of isoelectric quiescence. Recent modeling studies have suggested an important role for brain metabolic processes in governing the very slow time scales that underlie the duration of bursts and suppressions. In these models, a reduction in metabolism leads to substrate depletion and consequent suppression of action potential firing. Such a mechanism accounts for the appearance of burst suppression when metabolism is directly down-regulated. However, in many cases such as general anesthesia, metabolic down-regulation occurs in part as a homeostatic consequence of reduced neuronal activity. Here, we develop a mean-field model for neuronal activity with metabolic homeostatic mechanisms. We show that with such mechanisms, a simple reduction in neuronal activity due, for example, to increased neuronal inhibition, will give rise to bistability due to a bifurcation in the combined neuronal and metabolic dynamics. The model reconciles a purely metabolic mechanism for burst suppression with one that includes important dynamical feedback from the neuronal activity itself. The resulting fast-slow dynamical description forms a useful model for further development of novel methods for managing burst suppression clinically.
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Kenny JD, Westover MB, Ching S, Brown EN, Solt K. Propofol and sevoflurane induce distinct burst suppression patterns in rats. Front Syst Neurosci 2014; 8:237. [PMID: 25565990 PMCID: PMC4270179 DOI: 10.3389/fnsys.2014.00237] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 11/27/2014] [Indexed: 12/30/2022] Open
Abstract
Burst suppression is an EEG pattern characterized by alternating periods of high-amplitude activity (bursts) and relatively low amplitude activity (suppressions). Burst suppression can arise from several different pathological conditions, as well as from general anesthesia. Here we review current algorithms that are used to quantify burst suppression, its various etiologies, and possible underlying mechanisms. We then review clinical applications of anesthetic-induced burst suppression. Finally, we report the results of our new study showing clear electrophysiological differences in burst suppression patterns induced by two common general anesthetics, sevoflurane and propofol. Our data suggest that the circuit mechanisms that generate burst suppression activity may differ among general anesthetics.
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Affiliation(s)
- Jonathan D Kenny
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital Boston, MA, USA
| | - M Brandon Westover
- Department of Neurology, Harvard Medical School Boston, MA, USA ; Department of Neurology, Massachusetts General Hospital Boston, MA, USA
| | - ShiNung Ching
- Department of Electrical and Systems Engineering, Washington University in St. Louis St. Louis, Missouri, USA
| | - Emery N Brown
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital Boston, MA, USA ; Department of Anaesthesia, Harvard Medical School Boston, MA, USA ; Institute for Medical Engineering and Science, Massachusetts Institute of Technology Cambridge, MA, USA ; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology Cambridge, MA, USA
| | - Ken Solt
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital Boston, MA, USA ; Department of Anaesthesia, Harvard Medical School Boston, MA, USA
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76
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Zhang Y, Li Z, Dong H, Yu T. Effects of general anesthesia with propofol on thalamocortical sensory processing in rats. J Pharmacol Sci 2014; 126:370-81. [PMID: 25427432 DOI: 10.1254/jphs.14153fp] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
The effects of anesthetics on the transmission and processing of sensory information within the thalamocortical pathway and the underlying mechanism are not fully understood. Using the extracellular recording technique, we investigated the changes of spontaneous and stimulation-evoked activities within and between the ventral posteromedial nucleus (VPM) and primary somatosensory cortex barrel field (S1BF) of the rat in vivo during propofol anesthesia. Spontaneous local field potentials, whiskers deflection–elicited somatosensory evoked potentials, and multi-unit activities in VPM/S1BF were assessed at different depths of propofol anesthesia. In VPM and S1BF, powers of spontaneous and stimulation-evoked activities, coupled with stimulation-evoked multi-unit, were decreased with increasing of propofol anesthesia. Cortical onset latency increased during intermediate/deep level propofol anesthesia, whereas thalamic onset latencies were not changed even at different depths of anesthesia. In addition, spontaneous and whisker deflectionevoked alpha oscillations were observed during propofol anesthesia, which is similar to sleep spindles, These data suggest that propofol affects processing of sensory information by 1) attenuating respective neuronal activities in VPM and S1BF, 2) delaying the ascending signal transmission from VPM to S1BF, and 3) inducing a natural-sleep type of anesthesia.
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Affiliation(s)
- Yi Zhang
- Department of Anesthesiology, the Affiliated Hospital of Zunyi Medical College, Guizhou Key Laboratory of Anesthesia and Organ Protection, China
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77
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Garcia-Rodriguez P, Hutt A. Bursting suppression in propofol-induced general anesthesia as bi-stability in a non-linear neural mass model. BMC Neurosci 2014. [PMCID: PMC4125039 DOI: 10.1186/1471-2202-15-s1-p139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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78
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Altwegg-Boussac T, Chavez M, Mahon S, Charpier S. Excitability and responsiveness of rat barrel cortex neurons in the presence and absence of spontaneous synaptic activity in vivo. J Physiol 2014; 592:3577-95. [PMID: 24732430 DOI: 10.1113/jphysiol.2013.270561] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The amplitude and temporal dynamics of spontaneous synaptic activity in the cerebral cortex vary as a function of brain states. To directly assess the impact of different ongoing synaptic activities on neocortical function, we performed in vivo intracellular recordings from barrel cortex neurons in rats under two pharmacological conditions generating either oscillatory or tonic synaptic drive. Cortical neurons membrane excitability and firing responses were compared, in the same neurons, before and after complete suppression of background synaptic drive following systemic injection of a high dose of anaesthetic. Compared to the oscillatory state, the tonic pattern resulted in a more depolarized and less fluctuating membrane potential (Vm), a lower input resistance (Rm) and steeper relations of firing frequency versus injected current (F-I). Whatever their temporal dynamics, suppression of background synaptic activities increased mean Vm, without affecting Rm, and induced a rightward shift of F-I curves. Both types of synaptic drive generated a high variability in current-induced firing rate and patterns in cortical neurons, which was much reduced after removal of spontaneous activity. These findings suggest that oscillatory and tonic synaptic patterns differentially facilitate the input-output function of cortical neurons but result in a similar moment-to-moment variability in spike responses to incoming depolarizing inputs.
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Affiliation(s)
- Tristan Altwegg-Boussac
- Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, UPMC; INSERM U 1127; CNRS UMR 7225, Hôpital Pitié-Salpêtrière, F-75013, Paris, France
| | - Mario Chavez
- Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, UPMC; INSERM U 1127; CNRS UMR 7225, Hôpital Pitié-Salpêtrière, F-75013, Paris, France
| | - Séverine Mahon
- Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, UPMC; INSERM U 1127; CNRS UMR 7225, Hôpital Pitié-Salpêtrière, F-75013, Paris, France
| | - Stéphane Charpier
- Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, UPMC; INSERM U 1127; CNRS UMR 7225, Hôpital Pitié-Salpêtrière, F-75013, Paris, France UPMC Univ Paris 06, F-75005, Paris, France
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79
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Intraoperative Somatosensory Evoked Potential Monitoring Decreases EEG Burst Suppression Ratio During Deep General Anesthesia. J Clin Neurophysiol 2014; 31:133-7. [DOI: 10.1097/wnp.0000000000000034] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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80
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Magnuson ME, Thompson GJ, Pan WJ, Keilholz SD. Time-dependent effects of isoflurane and dexmedetomidine on functional connectivity, spectral characteristics, and spatial distribution of spontaneous BOLD fluctuations. NMR IN BIOMEDICINE 2014; 27:291-303. [PMID: 24449532 PMCID: PMC4465547 DOI: 10.1002/nbm.3062] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 11/17/2013] [Accepted: 11/22/2013] [Indexed: 05/05/2023]
Abstract
Anesthesia is often necessary to perform fMRI experiments in the rodent model; however, commonly used anesthetic protocols may manifest changing brain conditions over the duration of the study. This possibility was explored in the current work. Eleven rats were anesthetized with 2% isoflurane anesthesia; four rats were anesthetized for a short period (30 min, simulating induction and fMRI setup) and seven rats were anesthetized for a long period (3 h, simulating surgical preparation). Following the initial anesthetic period, isoflurane was discontinued, and a dexmedetomidine bolus (0.025 mg/kg) and continuous subcutaneous infusion (0.05 mg/kg/h) were administered. Blood-oxygen-level dependent resting state imaging was performed every 30 min from 0.75 h post dexmedetomidine bolus until 5.75 h post-bolus. Evaluation of power spectra obtained from time courses in the primary somatosensory cortex revealed, in general, a monotonic increase in low-frequency power (0.05-0.3 Hz) in both groups over the duration of resting state imaging. Greater low-band spectral power (0.05-0.15 Hz) is present in the short isoflurane group for the first 2.75 h, but the spectra become highly uniform at 3.25 h. The emergence of a ~0.18 Hz peak, beginning at the 3.75 h time point, exists in both groups and evolves similarly, increasing in strength as the duration of dexmedetomidine sedation (and time since isoflurane cessation) extends. In the long isoflurane group only, bilateral functional connectivity strengthens with anesthetic duration, and correlation is linearly linked to low-band spectral power. Convergence of connectivity and spectral metrics between the short and long isoflurane groups occurs at ~3.25 h, suggesting the effects of isoflurane have subsided. Researchers using dexmedetomidine following isoflurane for functional studies should be aware of the duration specific effects of the pre-scan isoflurane durations as well as the continuing influences of long-term imaging under dexmedetomidine.
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Affiliation(s)
| | | | - Wen-Ju Pan
- Correspondence to: W.-J. Pan and S. D. Keilholz, Georgia Institute of Technology and Emory University, Biomedical Engineering, Atlanta, GA, USA., ;
| | - Shella Dawn Keilholz
- Correspondence to: W.-J. Pan and S. D. Keilholz, Georgia Institute of Technology and Emory University, Biomedical Engineering, Atlanta, GA, USA., ;
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81
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Sitdikova G, Zakharov A, Janackova S, Gerasimova E, Lebedeva J, Inacio AR, Zaynutdinova D, Minlebaev M, Holmes GL, Khazipov R. Isoflurane suppresses early cortical activity. Ann Clin Transl Neurol 2013; 1:15-26. [PMID: 25356379 PMCID: PMC4207500 DOI: 10.1002/acn3.16] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 09/29/2013] [Accepted: 09/30/2013] [Indexed: 11/08/2022] Open
Abstract
Objective Isoflurane and other volatile anesthetics are widely used in children to induce deep and reversible coma, but they may also exert neurotoxic actions. The effects of volatile anesthetics on the immature brain activity remain elusive, however. Methods The effects of isoflurane on spontaneous and sensory-evoked activity were explored using intracortical extracellular field potential and multiple unit recordings in the rat barrel cortex from birth to adulthood. Results During the first postnatal week, isoflurane suppressed cortical activity in a concentration-dependent manner. At surgical anesthesia levels (1.5–2%), isoflurane completely suppressed the electroencephalogram and silenced cortical neurons. Although sensory potentials evoked by the principal whisker deflection persisted, sensory-evoked early gamma and spindle-burst oscillations were completely suppressed by isoflurane. Isoflurane-induced burst-suppression pattern emerged during the second postnatal week and matured through the first postnatal month. Bursts in adolescent and adult rats were characterized by activation of entire cortical columns with a leading firing of infragranular neurons, and were triggered by principal and adjacent whiskers stimulation, and by auditory and visual stimuli, indicating an involvement of horizontal connections in their generation and horizontal spread. Interpretation The effects of isoflurane on cortical activity shift from total suppression of activity to burst-suppression pattern at the end of the first postnatal week. Developmental emergence of bursts likely involves a development of the intracortical short-and long-range connections. We hypothesize that complete suppression of cortical activity under isoflurane anesthesia during the first postnatal week may explain neuronal apoptosis stimulated by volatile anesthetics in the neonatal rats.
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Affiliation(s)
- Guzel Sitdikova
- INMED, INSERM U-901 Marseille, France ; Aix-Marseille University Marseille, France ; Laboratory of Neurobiology, Kazan Federal University Kazan, Russia
| | - Andrei Zakharov
- Laboratory of Neurobiology, Kazan Federal University Kazan, Russia
| | - Sona Janackova
- INMED, INSERM U-901 Marseille, France ; Aix-Marseille University Marseille, France
| | - Elena Gerasimova
- Laboratory of Neurobiology, Kazan Federal University Kazan, Russia
| | - Julia Lebedeva
- Laboratory of Neurobiology, Kazan Federal University Kazan, Russia
| | - Ana R Inacio
- Aix-Marseille University Marseille, France ; Laboratory of Neurobiology, Kazan Federal University Kazan, Russia
| | - Dilyara Zaynutdinova
- Aix-Marseille University Marseille, France ; Laboratory of Neurobiology, Kazan Federal University Kazan, Russia
| | - Marat Minlebaev
- INMED, INSERM U-901 Marseille, France ; Aix-Marseille University Marseille, France ; Laboratory of Neurobiology, Kazan Federal University Kazan, Russia
| | - Gregory L Holmes
- Department of Neurological Sciences, University of Vermont College of Medicine Burlington, Vermont
| | - Roustem Khazipov
- INMED, INSERM U-901 Marseille, France ; Aix-Marseille University Marseille, France ; Laboratory of Neurobiology, Kazan Federal University Kazan, Russia
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82
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Kroeger D, Florea B, Amzica F. Human brain activity patterns beyond the isoelectric line of extreme deep coma. PLoS One 2013; 8:e75257. [PMID: 24058669 PMCID: PMC3776755 DOI: 10.1371/journal.pone.0075257] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 08/12/2013] [Indexed: 11/30/2022] Open
Abstract
The electroencephalogram (EEG) reflects brain electrical activity. A flat (isoelectric) EEG, which is usually recorded during very deep coma, is considered to be a turning point between a living brain and a deceased brain. Therefore the isoelectric EEG constitutes, together with evidence of irreversible structural brain damage, one of the criteria for the assessment of brain death. In this study we use EEG recordings for humans on the one hand, and on the other hand double simultaneous intracellular recordings in the cortex and hippocampus, combined with EEG, in cats. They serve to demonstrate that a novel brain phenomenon is observable in both humans and animals during coma that is deeper than the one reflected by the isoelectric EEG, and that this state is characterized by brain activity generated within the hippocampal formation. This new state was induced either by medication applied to postanoxic coma (in human) or by application of high doses of anesthesia (isoflurane in animals) leading to an EEG activity of quasi-rhythmic sharp waves which henceforth we propose to call ν-complexes (Nu-complexes). Using simultaneous intracellular recordings in vivo in the cortex and hippocampus (especially in the CA3 region) we demonstrate that ν-complexes arise in the hippocampus and are subsequently transmitted to the cortex. The genesis of a hippocampal ν-complex depends upon another hippocampal activity, known as ripple activity, which is not overtly detectable at the cortical level. Based on our observations, we propose a scenario of how self-oscillations in hippocampal neurons can lead to a whole brain phenomenon during coma.
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Affiliation(s)
- Daniel Kroeger
- Department of Stomatology, School of Dentistry, Université de Montreal, Montreal, Canada
| | | | - Florin Amzica
- Department of Stomatology, School of Dentistry, Université de Montreal, Montreal, Canada
- * E-mail:
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83
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Lewis LD, Ching S, Weiner VS, Peterfreund RA, Eskandar EN, Cash SS, Brown EN, Purdon PL. Local cortical dynamics of burst suppression in the anaesthetized brain. ACTA ACUST UNITED AC 2013; 136:2727-37. [PMID: 23887187 PMCID: PMC3754454 DOI: 10.1093/brain/awt174] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Burst suppression is an electroencephalogram pattern that consists of a quasi-periodic alternation between isoelectric ‘suppressions’ lasting seconds or minutes, and high-voltage ‘bursts’. It is characteristic of a profoundly inactivated brain, occurring in conditions including hypothermia, deep general anaesthesia, infant encephalopathy and coma. It is also used in neurology as an electrophysiological endpoint in pharmacologically induced coma for brain protection after traumatic injury and during status epilepticus. Classically, burst suppression has been regarded as a ‘global’ state with synchronous activity throughout cortex. This assumption has influenced the clinical use of burst suppression as a way to broadly reduce neural activity. However, the extent of spatial homogeneity has not been fully explored due to the challenges in recording from multiple cortical sites simultaneously. The neurophysiological dynamics of large-scale cortical circuits during burst suppression are therefore not well understood. To address this question, we recorded intracranial electrocorticograms from patients who entered burst suppression while receiving propofol general anaesthesia. The electrodes were broadly distributed across cortex, enabling us to examine both the dynamics of burst suppression within local cortical regions and larger-scale network interactions. We found that in contrast to previous characterizations, bursts could be substantially asynchronous across the cortex. Furthermore, the state of burst suppression itself could occur in a limited cortical region while other areas exhibited ongoing continuous activity. In addition, we found a complex temporal structure within bursts, which recapitulated the spectral dynamics of the state preceding burst suppression, and evolved throughout the course of a single burst. Our observations imply that local cortical dynamics are not homogeneous, even during significant brain inactivation. Instead, cortical and, implicitly, subcortical circuits express seemingly different sensitivities to high doses of anaesthetics that suggest a hierarchy governing how the brain enters burst suppression, and emphasize the role of local dynamics in what has previously been regarded as a global state. These findings suggest a conceptual shift in how neurologists could assess the brain function of patients undergoing burst suppression. First, analysing spatial variation in burst suppression could provide insight into the circuit dysfunction underlying a given pathology, and could improve monitoring of medically-induced coma. Second, analysing the temporal dynamics within a burst could help assess the underlying brain state. This approach could be explored as a prognostic tool for recovery from coma, and for guiding treatment of status epilepticus. Overall, these results suggest new research directions and methods that could improve patient monitoring in clinical practice.
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Affiliation(s)
- Laura D Lewis
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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84
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Liu X, Zhu XH, Zhang Y, Chen W. The change of functional connectivity specificity in rats under various anesthesia levels and its neural origin. Brain Topogr 2013; 26:363-77. [PMID: 23208517 PMCID: PMC3622140 DOI: 10.1007/s10548-012-0267-5] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 11/15/2012] [Indexed: 01/26/2023]
Abstract
Spatiotemporal correlations of spontaneous blood oxygenation level dependent (BOLD) signals measured in the resting brain have been found to imply many resting-state coherent networks under both awake/conscious and anesthetized/unconscious conditions. To understand the resting-state brain networks in the unconscious state, spontaneous BOLD signals from the rat sensorimotor cortex were studied across a wide range of anesthesia levels induced by isoflurane. Distinct resting-state networks covering functionally specific sub-regions of the sensorimotor system were observed under light anesthesia with 1.0% isoflurane; however, they gradually merged into a highly synchronized and spatially less-specific network under deep anesthesia with 1.8% isoflurane. The EEG power correlations recorded using three electrodes from a separate group of rats showed similar dependency on anesthesia depth, suggesting the neural origin of the change in functional connectivity specificity. The specific-to-less-specific transition of resting-state networks may reflect a functional reorganization of the brain at different anesthesia levels or brain states.
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Affiliation(s)
- Xiao Liu
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, 2021 6th St. SE, Minneapoli, MN 55455, USA
- Department of Biomedical Engineering, University of Minnesota, 2021 6th St. SE, Minneapoli, MN 55455, USA
| | - Xiao-Hong Zhu
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, 2021 6th St. SE, Minneapoli, MN 55455, USA
| | - Yi Zhang
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, 2021 6th St. SE, Minneapoli, MN 55455, USA
| | - Wei Chen
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, 2021 6th St. SE, Minneapoli, MN 55455, USA
- Department of Biomedical Engineering, University of Minnesota, 2021 6th St. SE, Minneapoli, MN 55455, USA
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85
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Liley DTJ, Walsh M. The Mesoscopic Modeling of Burst Suppression during Anesthesia. Front Comput Neurosci 2013; 7:46. [PMID: 23641211 PMCID: PMC3639728 DOI: 10.3389/fncom.2013.00046] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 04/05/2013] [Indexed: 11/13/2022] Open
Abstract
The burst-suppression pattern is well recognized as a distinct feature of the mammalian electroencephalogram (EEG) waveform. Consisting of alternating periods of high amplitude oscillatory and isoelectric activity, it can be induced in health by deep anesthesia as well as being evoked by a range of pathophysiological processes that include coma and anoxia. While the electroencephalographic phenomenon and clinical implications of burst suppression have been studied extensively, the physiological mechanisms underlying its emergence remain unresolved and obscure. Because electroencephalographic bursting phenomenologically resembles the bursting observed in single neurons, it would be reasonable to assume that the theoretical insights developed to understand bursting at the cellular ("microscopic") level would enable insights into the dynamical genesis of bursting at the level of the whole brain ("macroscopic"). In general action potential bursting is the result of the interplay of two time scales: a fast time scale responsible for spiking, and a slow time scale that modulates such activity. We therefore hypothesize that such fast-slow systems dynamically underpin electroencephalographic bursting. Here we show that a well-known mean field dynamical model of the electroencephalogram, the Liley model, while unable to produce burst suppression unmodified, is able to give rise to a wide variety of burst-like activity by the addition of one or more slow systems modulating model parameters speculated to be major "targets" for anesthetic action. The development of a physiologically plausible theoretical framework to account for burst suppression will lead to a more complete physiological understanding of the EEG and the mechanisms that serve to modify ongoing brain activity necessary for purposeful behavior and consciousness.
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Affiliation(s)
- David T J Liley
- Brain and Psychological Sciences Research Centre, Faculty of Life and Social Sciences, Swinburne University of Technology Hawthorn, VIC, Australia
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86
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Dulac O. Epileptic encephalopathy with suppression-bursts and nonketotic hyperglycinemia. HANDBOOK OF CLINICAL NEUROLOGY 2013; 113:1785-1797. [PMID: 23622401 DOI: 10.1016/b978-0-444-59565-2.00048-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Bursts of paroxysmal activity alternating with lack of activity define the suppression-burst (SB) pattern that may be acute, in hypoxic-ischemic encephalopathy and barbiturate intoxication, or chronic in the course of early epileptic and neonatal myoclonic (NME) encephalopathies. Malformations, namely Aicardi syndrome and hemimegalencephaly, gene mutations - of ARX and MUNC18 -, and inborn errors of metabolism, namely glycine encephalopathy, are the main causes, with spasms indicating more likely a malformation whereas myoclonus indicates metabolic disorders. Although glycine encephalopathy has a very severe outcome in its classical expression, it may be transient in the neonatal period, for reasons yet not identified. Although glycine encephalopathy is the main identified cause of NME, the disorder may not cause SB, especially in cases with later onset. The biochemical bases, due to changes in one of the four proteins that compose the enzyme, are well understood, but there is no phenotype-genotype correlation. Prenatal diagnosis is based on villous biopsy. The mechanism of SB partly depends on glutamate - or glycine, the co-neurotransmitter for NMDA transmission - overflow, mainly in the immature brain but also in cases due to barbiturate intoxication. Energy supply defect may also be involved in some inborn errors of metabolism.
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Affiliation(s)
- Olivier Dulac
- Department of Pediatric Neurology, Hôpital Necker-Enfants Malades, INSERM U663, Paris, France.
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87
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Levy M, Schramm AE, Kara P. Strategies for mapping synaptic inputs on dendrites in vivo by combining two-photon microscopy, sharp intracellular recording, and pharmacology. Front Neural Circuits 2012; 6:101. [PMID: 23248588 PMCID: PMC3521157 DOI: 10.3389/fncir.2012.00101] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 11/19/2012] [Indexed: 12/03/2022] Open
Abstract
Uncovering the functional properties of individual synaptic inputs on single neurons is critical for understanding the computational role of synapses and dendrites. Previous studies combined whole-cell patch recording to load neurons with a fluorescent calcium indicator and two-photon imaging to map subcellular changes in fluorescence upon sensory stimulation. By hyperpolarizing the neuron below spike threshold, the patch electrode ensured that changes in fluorescence associated with synaptic events were isolated from those caused by back-propagating action potentials. This technique holds promise for determining whether the existence of unique cortical feature maps across different species may be associated with distinct wiring diagrams. However, the use of whole-cell patch for mapping inputs on dendrites is challenging in large mammals, due to brain pulsations and the accumulation of fluorescent dye in the extracellular milieu. Alternatively, sharp intracellular electrodes have been used to label neurons with fluorescent dyes, but the current passing capabilities of these high impedance electrodes may be insufficient to prevent spiking. In this study, we tested whether sharp electrode recording is suitable for mapping functional inputs on dendrites in the cat visual cortex. We compared three different strategies for suppressing visually evoked spikes: (1) hyperpolarization by intracellular current injection, (2) pharmacological blockade of voltage-gated sodium channels by intracellular QX-314, and (3) GABA iontophoresis from a perisomatic electrode glued to the intracellular electrode. We found that functional inputs on dendrites could be successfully imaged using all three strategies. However, the best method for preventing spikes was GABA iontophoresis with low currents (5–10 nA), which minimally affected the local circuit. Our methods advance the possibility of determining functional connectivity in preparations where whole-cell patch may be impractical.
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Affiliation(s)
- Manuel Levy
- Department of Neurosciences, Medical University of South Carolina Charleston, SC, USA
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88
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Abstract
Temperature fluctuations significantly impact neurological injuries in intensive care units. As the benefits of therapeutic hypothermia continue to unfold, many of these discoveries are generated by studies in animal models undergoing experimental procedures under the influence of anesthetics. We studied the effect of induced hypothermia on neural electrophysiological signals of an uninjured brain in a rodent model while under isoflurane. Fourteen rats were divided into 2 groups (n=7 each), on the basis of electrode placement at either frontal-occipital or primary somatosensory cortical locations. Neural signals were recorded during normothermia (T=36.5 to 37.5°C), mild hypothermia (T=32 to 34°C), and hyperthermia (T=38.5 to 39.5°C). The burst-suppression ratio was used to evaluate electroencephalography (EEG), and amplitude-latency analysis was used to assess somatosensory-evoked potentials (SSEPs). Hypothermia was characterized by an increased burst-suppression ratio (mean±SD) of 0.58±0.06 in hypothermia versus 0.16±0.13 in normothermia, P<0.001 in frontal-occipital; and 0.30±0.13 in hypothermia versus 0.04±0.04 in normothermia, P=0.006 in somatosensory. There was potentiation of SSEP (2.89±1.24 times the normothermic baseline in hypothermia, P=0.02) and prolonged peak latency (N10: 10.8±0.4 ms in hypothermia vs. 9.1±0.3 ms in normothermia; P15: 16.2±0.8 ms in hypothermia vs. 13.7±0.6 ms in normothermia; P<0.001), whereas hyperthermia was primarily marked by shorter peak latencies (N10: 8.6±0.2 ms, P15: 12.6±0.4 m; P<0.001). In the absence of brain injury in a rodent model, hypothermia induces significant increase to the SSEP amplitude while increasing SSEP latency. Hypothermia also suppressed EEGs at different regions of the brain by different degrees. The changes to SSEP and EEG are both reversible with subsequent rewarming.
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89
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Humphries MD, Gurney K. Network effects of subthalamic deep brain stimulation drive a unique mixture of responses in basal ganglia output. Eur J Neurosci 2012; 36:2240-51. [PMID: 22805068 DOI: 10.1111/j.1460-9568.2012.08085.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Deep brain stimulation (DBS) is a remarkably successful treatment for the motor symptoms of Parkinson's disease. High-frequency stimulation of the subthalamic nucleus (STN) within the basal ganglia is a main clinical target, but the physiological mechanisms of therapeutic STN DBS at the cellular and network level are unclear. We set out to begin to address the hypothesis that a mixture of responses in the basal ganglia output nuclei, combining regularized firing and inhibition, is a key contributor to the effectiveness of STN DBS. We used our computational model of the complete basal ganglia circuit to show how such a mixture of responses in basal ganglia output naturally arises from the network effects of STN DBS. We replicated the diversification of responses recorded in a primate STN DBS study to show that the model's predicted mixture of responses is consistent with therapeutic STN DBS. We then showed how this 'mixture of response' perspective suggests new ideas for DBS mechanisms: first, that the therapeutic frequency of STN DBS is above 100 Hz because the diversification of responses exhibits a step change above this frequency; and second, that optogenetic models of direct STN stimulation during DBS have proven therapeutically ineffective because they do not replicate the mixture of basal ganglia output responses evoked by electrical DBS.
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Affiliation(s)
- Mark D Humphries
- Group for Neural Theory, Department d'Etudes Cognitives, Ecole Normale Superieure, 29 rue d'Ulm, 75005 Paris, France.
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90
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Vizuete JA, Pillay S, Diba K, Ropella KM, Hudetz AG. Monosynaptic functional connectivity in cerebral cortex during wakefulness and under graded levels of anesthesia. Front Integr Neurosci 2012; 6:90. [PMID: 23091451 PMCID: PMC3469825 DOI: 10.3389/fnint.2012.00090] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 09/20/2012] [Indexed: 11/13/2022] Open
Abstract
The balance between excitation and inhibition is considered to be of significant importance for neural computation and cognitive function. Excitatory and inhibitory functional connectivity in intact cortical neuronal networks in wakefulness and graded levels of anesthesia has not been systematically investigated. We compared monosynaptic excitatory and inhibitory spike transmission probabilities using pairwise cross-correlogram (CCG) analysis. Spikes were measured at 64 sites in the visual cortex of rats with chronically implanted microelectrode arrays during wakefulness and three levels of anesthesia produced by desflurane. Anesthesia decreased the number of active units, the number of functional connections, and the strength of excitatory connections. Connection probability (number of connections per number of active unit pairs) was unaffected until the deepest anesthesia level, at which a significant increase in the excitatory to inhibitory ratio of connection probabilities was observed. The results suggest that the excitatory–inhibitory balance is altered at an anesthetic depth associated with unconsciousness.
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Affiliation(s)
- Jeannette A Vizuete
- Department of Biomedical Engineering, Marquette University Milwaukee, WI, USA
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91
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Abstract
Burst suppression is an electroencepholagram (EEG) pattern in which high-voltage activity alternates with isoelectric quiescence. It is characteristic of an inactivated brain and is commonly observed at deep levels of general anesthesia, hypothermia, and in pathological conditions such as coma and early infantile encephalopathy. We propose a unifying mechanism for burst suppression that accounts for all of these conditions. By constructing a biophysical computational model, we show how the prevailing features of burst suppression may arise through the interaction between neuronal dynamics and brain metabolism. In each condition, the model suggests that a decrease in cerebral metabolic rate, coupled with the stabilizing properties of ATP-gated potassium channels, leads to the characteristic epochs of suppression. Consequently, the model makes a number of specific predictions of experimental and clinical relevance.
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92
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Wu D, Xiong W, Jia X, Geocadin RG, Thakor NV. Short- and long-latency somatosensory neuronal responses reveal selective brain injury and effect of hypothermia in global hypoxic ischemia. J Neurophysiol 2011; 107:1164-71. [PMID: 22157111 DOI: 10.1152/jn.00681.2011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Evoked potentials recorded from the somatosensory cortex have been shown to be an electrophysiological marker of brain injury in global hypoxic ischemia (HI). The evoked responses in somatosensory neurons carry information pertaining to signal from the ascending pathway in both the subcortical and cortical areas. In this study, origins of the subcortical and cortical signals are explored by decomposing the evoked neuronal activities into short- and long-latency responses (SLR and LLR), respectively. We evaluated the effect of therapeutic hypothermia on SLR and LLR during early recovery from cardiac arrest (CA)-induced HI in a rodent model. Twelve rats were subjected to CA, after which half of them were treated with hypothermia (32-34°C) and the rest were kept at normal temperature (36-37°C). Evoked neuronal activities from the primary somatosensory cortex, including multiunit activity (MUA) and local field potential (LFP), were continuously recorded during injury and early recovery. Results showed that upon initiation of injury, LLR disappeared first, followed by the disappearance of SLR, and after a period of isoelectric silence SLR reappeared prior to LLR. This suggests that cortical activity, which primarily underlies the LLR, may be more vulnerable to ischemic injury than SLR, which relates to subcortical activity. Hypothermia potentiated the SLR but suppressed the LLR by delaying its recovery after CA (hypothermia: 38.83 ± 5.86 min, normothermia: 23.33 ± 1.15 min; P < 0.05) and attenuating its amplitude, suggesting that hypothermia may selectively downregulate cortical activity as an approach to preserve the cerebral cortex. In summary, our study reveals the vulnerability of the somatosensory neural structures to global HI and the differential effects of hypothermia on these structures.
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Affiliation(s)
- Dan Wu
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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93
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Abstract
This paper describes the various electroencephalographic (EEG) patterns expressed by the comatose brain, starting with the sleep-like oscillations associated with light coma. Deeper coma generally displays a burst-suppression pattern characterized by alternating episodes of isoelectric (flat) EEG and bursting slow waves. The latter are the result of cortical hyperexcitability, as demonstrated by intracellular recordings in anesthetized animals. Further deepening of the coma yields to continuous isoelectric EEG and eventually results in a newly discovered type of spiky waves that have been termed ν-complexes. They originate in the hippocampus as a result of intrinsically generated oscillations (ripples) in the delta range.
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Affiliation(s)
- Florin Amzica
- Université de Montreal, succursale Centre-ville, Montreal, QC, Canada.
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94
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Putrino DF, Chen Z, Ghosh S, Brown EN. Motor cortical networks for skilled movements have dynamic properties that are related to accurate reaching. Neural Plast 2011; 2011:413543. [PMID: 22007332 PMCID: PMC3191785 DOI: 10.1155/2011/413543] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 07/14/2011] [Accepted: 08/11/2011] [Indexed: 11/18/2022] Open
Abstract
Neurons in the Primary Motor Cortex (MI) are known to form functional ensembles with one another in order to produce voluntary movement. Neural network changes during skill learning are thought to be involved in improved fluency and accuracy of motor tasks. Unforced errors during skilled tasks provide an avenue to study network connections related to motor learning. In order to investigate network activity in MI, microwires were implanted in the MI of cats trained to perform a reaching task. Spike trains from eight groups of simultaneously recorded cells (95 neurons in total) were acquired. A point process generalized linear model (GLM) was developed to assess simultaneously recorded cells for functional connectivity during reaching attempts where unforced errors or no errors were made. Whilst the same groups of neurons were often functionally connected regardless of trial success, functional connectivity between neurons was significantly different at fine time scales when the outcome of task performance changed. Furthermore, connections were shown to be significantly more robust across multiple latencies during successful trials of task performance. The results of this study indicate that reach-related neurons in MI form dynamic spiking dependencies whose temporal features are highly sensitive to unforced movement errors.
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Affiliation(s)
- David F. Putrino
- Neuroscience Statistics Research Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
- Department of Brain and Cognitive Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Zhe Chen
- Neuroscience Statistics Research Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
- Department of Brain and Cognitive Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Soumya Ghosh
- Centre for Neuromuscular and Neurological Disorders, University of Western Australia, QEII Medical Centre, Nedlands, WA 6009, Australia
| | - Emery N. Brown
- Neuroscience Statistics Research Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
- Department of Brain and Cognitive Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Neuroscience Statistics Research Laboratory, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
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95
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Abstract
Identifying similar spike-train patterns is a key element in understanding neural coding and computation. For single neurons, similar spike patterns evoked by stimuli are evidence of common coding. Across multiple neurons, similar spike trains indicate potential cell assemblies. As recording technology advances, so does the urgent need for grouping methods to make sense of large-scale datasets of spike trains. Existing methods require specifying the number of groups in advance, limiting their use in exploratory analyses. I derive a new method from network theory that solves this key difficulty: it self-determines the maximum number of groups in any set of spike trains, and groups them to maximize intragroup similarity. This method brings us revealing new insights into the encoding of aversive stimuli by dopaminergic neurons, and the organization of spontaneous neural activity in cortex. I show that the characteristic pause response of a rat's dopaminergic neuron depends on the state of the superior colliculus: when it is inactive, aversive stimuli invoke a single pattern of dopaminergic neuron spiking; when active, multiple patterns occur, yet the spike timing in each is reliable. In spontaneous multineuron activity from the cortex of anesthetized cat, I show the existence of neural ensembles that evolve in membership and characteristic timescale of organization during global slow oscillations. I validate these findings by showing that the method both is remarkably reliable at detecting known groups and can detect large-scale organization of dynamics in a model of the striatum.
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96
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Implication of Kir4.1 channel in excess potassium clearance: an in vivo study on anesthetized glial-conditional Kir4.1 knock-out mice. J Neurosci 2010; 30:15769-77. [PMID: 21106816 DOI: 10.1523/jneurosci.2078-10.2010] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The K(ir)4.1 channel is crucial for the maintenance of the resting membrane potential of glial cells, and it is believed to play a main role in the homeostasis of extracellular potassium. To understand its importance in these two phenomena, we have measured in vivo the variations of extracellular potassium concentration ([K(+)](o)) (with potassium-sensitive microelectrodes) and membrane potential of glial cells (with sharp electrodes) during stimulations in wild-type (WT) mice and glial-conditional knock-out (cKO) K(ir)4.1 mice. The conditional knockout was driven by the human glial fibrillary acidic protein promoter, gfa2. Experiments were performed in the hippocampus of anesthetized mice (postnatal days 17-24). Low level stimulation (<20 stimuli, 10 Hz) induced a moderated increase of [K(+)](o) (<2 mm increase) in both WT and cKO mice. However, cKO mice exhibited slower recovery of [K(+)](o) levels. With long-lasting stimulation (300 stimuli, 10 Hz), [K(+)](o) in WT and cKO mice displayed characteristic ceiling level (>2 mm increase) and recovery undershoot, with a more pronounced and prolonged undershoot in cKO mice. In addition, cKO glial cells were more depolarized, and, in contrast to those from WT mice, their membrane potential did not follow the stimulation-induced [K(+)](o) changes, reflecting the loss of their high potassium permeability. Our in vivo results support the role of K(ir)4.1 in setting the membrane potential of glial cells and its contribution to the glial potassium permeability. In addition, our data confirm the necessity of the K(ir)4.1 channel for an efficient uptake of K(+) by glial cells.
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97
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Monitoring the depth of anaesthesia. SENSORS 2010; 10:10896-935. [PMID: 22163504 PMCID: PMC3231065 DOI: 10.3390/s101210896] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 09/29/2010] [Accepted: 11/22/2010] [Indexed: 11/25/2022]
Abstract
One of the current challenges in medicine is monitoring the patients’ depth of general anaesthesia (DGA). Accurate assessment of the depth of anaesthesia contributes to tailoring drug administration to the individual patient, thus preventing awareness or excessive anaesthetic depth and improving patients’ outcomes. In the past decade, there has been a significant increase in the number of studies on the development, comparison and validation of commercial devices that estimate the DGA by analyzing electrical activity of the brain (i.e., evoked potentials or brain waves). In this paper we review the most frequently used sensors and mathematical methods for monitoring the DGA, their validation in clinical practice and discuss the central question of whether these approaches can, compared to other conventional methods, reduce the risk of patient awareness during surgical procedures.
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98
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Zawadzki L, Stafstrom CE. Status epilepticus treatment and outcome in children: what might the future hold? Semin Pediatr Neurol 2010; 17:201-5. [PMID: 20727491 DOI: 10.1016/j.spen.2010.06.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Status epilepticus is a life-threatening emergency that requires urgent treatment. Over the past decade, numerous advances have been made in the management of status epilepticus. Clinical studies have now established the benefit of early, aggressive treatment of status epilepticus with benzodiazepines in both prehospital and hospital settings. Neuroscientific advances are revealing mechanisms of status epilepticus that could translate into targets for treating acute status epilepticus and even reducing epileptogenesis. This article discusses future trends in the diagnosis, neurobiology, and treatment of status epilepticus.
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Affiliation(s)
- Lucyna Zawadzki
- Department of Neurology, Section of Pediatric Neurology, University of Wisconsin, Madison, WI 53705, USA
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99
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Williams KA, Magnuson M, Majeed W, LaConte SM, Peltier SJ, Hu X, Keilholz SD. Comparison of alpha-chloralose, medetomidine and isoflurane anesthesia for functional connectivity mapping in the rat. Magn Reson Imaging 2010; 28:995-1003. [PMID: 20456892 DOI: 10.1016/j.mri.2010.03.007] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Revised: 01/18/2010] [Accepted: 03/11/2010] [Indexed: 12/19/2022]
Abstract
Functional connectivity measures based upon low-frequency blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD fMRI) signal fluctuations have become a widely used tool for investigating spontaneous brain activity in humans. Still unknown, however, is the precise relationship between neural activity, the hemodynamic response and fluctuations in the MRI signal. Recent work from several groups had shown that correlated low-frequency fluctuations in the BOLD signal can be detected in the anesthetized rat - a first step toward elucidating this relationship. Building on this preliminary work, through this study, we demonstrate that functional connectivity observed in the rat depends strongly on the type of anesthesia used. Power spectra of spontaneous fluctuations and the cross-correlation-based connectivity maps from rats anesthetized with alpha-chloralose, medetomidine or isoflurane are presented using a high-temporal-resolution imaging sequence that ensures minimal contamination from physiological noise. The results show less localized correlation in rats anesthetized with isoflurane as compared with rats anesthetized with alpha-chloralose or medetomidine. These experiments highlight the utility of using different types of anesthesia to explore the fundamental physiological relationships of the BOLD signal and suggest that the mechanisms contributing to functional connectivity involve a complicated relationship between changes in neural activity, neurovascular coupling and vascular reactivity.
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Affiliation(s)
- Kathleen A Williams
- Department of Radiology, Center for Biomedical Imaging, New York University School of Medicine, New York, NY 10012, USA
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100
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Affiliation(s)
- Florin Amzica
- Department of Stomatology, Université de Montreal, succursale Centre-ville, QC, Canada.
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