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Timofeev I. Neuronal plasticity and thalamocortical sleep and waking oscillations. PROGRESS IN BRAIN RESEARCH 2011; 193:121-44. [PMID: 21854960 DOI: 10.1016/b978-0-444-53839-0.00009-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Throughout life, thalamocortical (TC) network alternates between activated states (wake or rapid eye movement sleep) and slow oscillatory state dominating slow-wave sleep. The patterns of neuronal firing are different during these distinct states. I propose that due to relatively regular firing, the activated states preset some steady state synaptic plasticity and that the silent periods of slow-wave sleep contribute to a release from this steady state synaptic plasticity. In this respect, I discuss how states of vigilance affect short-, mid-, and long-term synaptic plasticity, intrinsic neuronal plasticity, as well as homeostatic plasticity. Finally, I suggest that slow oscillation is intrinsic property of cortical network and brain homeostatic mechanisms are tuned to use all forms of plasticity to bring cortical network to the state of slow oscillation. However, prolonged and profound shift from this homeostatic balance could lead to development of paroxysmal hyperexcitability and seizures as in the case of brain trauma.
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Affiliation(s)
- Igor Timofeev
- The Centre de recherche Université Laval Robert-Giffard (CRULRG), Laval University, Québec, Canada.
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52
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Intermittent spike-wave dynamics in a heterogeneous, spatially extended neural mass model. Neuroimage 2010; 55:920-32. [PMID: 21195779 DOI: 10.1016/j.neuroimage.2010.12.074] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 12/15/2010] [Accepted: 12/24/2010] [Indexed: 12/24/2022] Open
Abstract
Generalised epileptic seizures are frequently accompanied by sudden, reversible transitions from low amplitude, irregular background activity to high amplitude, regular spike-wave discharges (SWD) in the EEG. The underlying mechanisms responsible for SWD generation and for the apparently spontaneous transitions to SWD and back again are still not fully understood. Specifically, the role of spatial cortico-cortical interactions in ictogenesis is not well studied. We present a macroscopic, neural mass model of a cortical column which includes two distinct time scales of inhibition. This model can produce both an oscillatory background and a pathological SWD rhythm. We demonstrate that coupling two of these cortical columns can lead to a bistability between out-of-phase, low amplitude background dynamics and in-phase, high amplitude SWD activity. Stimuli can cause state-dependent transitions from background into SWD. In an extended local area of cortex, spatial heterogeneities in a model parameter can lead to spontaneous reversible transitions from a desynchronised background to synchronous SWD due to intermittency. The deterministic model is therefore capable of producing absence seizure-like events without any time dependent adjustment of model parameters. The emergence of such mechanisms due to spatial coupling demonstrates the importance of spatial interactions in modelling ictal dynamics, and in the study of ictogenesis.
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53
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Correlation of cognitive performance and morphological changes in neocortical pyramidal neurons in aging. Neurobiol Aging 2010; 33:1466-80. [PMID: 21163553 DOI: 10.1016/j.neurobiolaging.2010.10.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 10/12/2010] [Accepted: 10/16/2010] [Indexed: 12/24/2022]
Abstract
It is well established that the cerebral cortex undergoes extensive remodeling in aging. In this study, we used behaviorally characterized rats to correlate age-related morphological changes with cognitive impairment. For this, young and aged animals were tested in the Morris water maze to evaluate their cognitive performance. Following behavioral characterization, the animals were perfused and a combination of intracellular labeling and immunohistochemistry was applied. Using this approach, we characterized the dendritic morphology of cortical pyramidal neurons as well as the pattern of glutamatergic and GABAergic appositions on their cell bodies and dendrites. We focused on the association region of the parietal cortex (LtPA) and the medial prefrontal cortex (mPFC) for their involvement in the Morris water maze task. We found an age-related atrophy of distal basal dendrites that did not differ between aged cognitively unimpaired (AU) and aged cognitively impaired animals (AI). Dendritic spines and glutamatergic appositions generally decreased from young to AU and from AU to AI rats. On the other hand, GABAergic appositions only showed a trend towards a decrease in AU rats. Collectively, the data show that the ratio of excitatory/inhibitory inputs was only altered in AI animals. When cortical cholinergic varicosities were labeled on alternate sections, we found that AI animals also had a significant reduction of cortical cholinergic boutons compared with AU or young animals. In aged animals, the density of cortical cholinergic varicosities correlated with the excitatory/inhibitory ratio. Our data suggest that both cholinergic atrophy and an imbalance towards inhibition may contribute to the observed age-associated behavioral impairment.
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54
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Visual representations by cortical somatostatin inhibitory neurons--selective but with weak and delayed responses. J Neurosci 2010; 30:14371-9. [PMID: 20980594 DOI: 10.1523/jneurosci.3248-10.2010] [Citation(s) in RCA: 162] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Somatostatin-expressing inhibitory (SOM) neurons in the sensory cortex consist mostly of Martinotti cells, which project ascending axons to layer 1. Due to their sparse distribution, the representational properties of these neurons remain largely unknown. By two-photon imaging guided cell-attached recordings, we characterized visual response and receptive field (RF) properties of SOM neurons and parvalbumin-expressing inhibitory (PV) neurons genetically labeled in the mouse primary visual cortex. In contrast to PV neurons, SOM neurons exhibit broader spikes, lower spontaneous firing rates, smaller On/Off subfields, and broader ranges of basic RF properties such as On/Off segregation, orientation and direction tunings. Notably, the level of orientation and direction selectivity is comparable to that of excitatory neurons, from weakly-tuned to highly selective, whereas PV neurons are in general unselective. Strikingly, the evoked spiking responses of SOM cells are ∼3- to 5-fold weaker and 20-25 ms delayed compared with those of PV neurons. The onset latency of the latter is consistent with that of inhibitory input to excitatory neurons. These functional differences between SOM and PV neurons exist in both layer 2/3 and 4. Our results suggest that SOM and PV neurons engage in cortical circuits in different manners: while PV neurons provide fast, strong but untuned feedforward inhibition to excitatory neurons, likely serving as a general gain control for the processing of ascending inputs, SOM neurons with their selective but delayed and weak inhibition may provide more specific gating of later arriving intracortical excitatory inputs on the distal dendrites.
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55
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Molaee-Ardekani B, Benquet P, Bartolomei F, Wendling F. Computational modeling of high-frequency oscillations at the onset of neocortical partial seizures: From ‘altered structure’ to ‘dysfunction’. Neuroimage 2010; 52:1109-22. [PMID: 20034581 DOI: 10.1016/j.neuroimage.2009.12.049] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Revised: 12/09/2009] [Accepted: 12/10/2009] [Indexed: 11/29/2022] Open
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56
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Khanbabaie R, Nesse WH, Longtin A, Maler L. Kinetics of fast short-term depression are matched to spike train statistics to reduce noise. J Neurophysiol 2010; 103:3337-48. [PMID: 20357065 DOI: 10.1152/jn.00117.2010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Short-term depression (STD) is observed at many synapses of the CNS and is important for diverse computations. We have discovered a form of fast STD (FSTD) in the synaptic responses of pyramidal cells evoked by stimulation of their electrosensory afferent fibers (P-units). The dynamics of the FSTD are matched to the mean and variance of natural P-unit discharge. FSTD exhibits switch-like behavior in that it is immediately activated with stimulus intervals near the mean interspike interval (ISI) of P-units (approximately 5 ms) and recovers immediately after stimulation with the slightly longer intervals (>7.5 ms) that also occur during P-unit natural and evoked discharge patterns. Remarkably, the magnitude of evoked excitatory postsynaptic potentials appear to depend only on the duration of the previous ISI. Our theoretical analysis suggests that FSTD can serve as a mechanism for noise reduction. Because the kinetics of depression are as fast as the natural spike statistics, this role is distinct from previously ascribed functional roles of STD in gain modulation, synchrony detection or as a temporal filter.
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Affiliation(s)
- Reza Khanbabaie
- Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Rd., Ottawa, Ontario K1H 8M5, Canada.
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57
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Atencio CA, Schreiner CE. Columnar connectivity and laminar processing in cat primary auditory cortex. PLoS One 2010; 5:e9521. [PMID: 20209092 PMCID: PMC2831079 DOI: 10.1371/journal.pone.0009521] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Accepted: 02/10/2010] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Radial intra- and interlaminar connections form a basic microcircuit in primary auditory cortex (AI) that extracts acoustic information and distributes it to cortical and subcortical networks. Though the structure of this microcircuit is known, we do not know how the functional connectivity between layers relates to laminar processing. METHODOLOGY/PRINCIPAL FINDINGS We studied the relationships between functional connectivity and receptive field properties in this columnar microcircuit by simultaneously recording from single neurons in cat AI in response to broadband dynamic moving ripple stimuli. We used spectrotemporal receptive fields (STRFs) to estimate the relationship between receptive field parameters and the functional connectivity between pairs of neurons. Interlaminar connectivity obtained through cross-covariance analysis reflected a consistent pattern of information flow from thalamic input layers to cortical output layers. Connection strength and STRF similarity were greatest for intralaminar neuron pairs and in supragranular layers and weaker for interlaminar projections. Interlaminar connection strength co-varied with several STRF parameters: feature selectivity, phase locking to the stimulus envelope, best temporal modulation frequency, and best spectral modulation frequency. Connectivity properties and receptive field relationships differed for vertical and horizontal connections. CONCLUSIONS/SIGNIFICANCE Thus, the mode of local processing in supragranular layers differs from that in infragranular layers. Therefore, specific connectivity patterns in the auditory cortex shape the flow of information and constrain how spectrotemporal processing transformations progress in the canonical columnar auditory microcircuit.
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Affiliation(s)
- Craig A Atencio
- Berkeley Bioengineering Graduate Group, University of California, Berkeley, California, United States of America.
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58
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Castro-Alamancos MA. Cortical up and activated states: implications for sensory information processing. Neuroscientist 2010; 15:625-34. [PMID: 19321459 DOI: 10.1177/1073858409333074] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The neocortex generates spontaneous slow oscillations that consist of up and down states during quiescence. Up states are short epochs of persistent activity that resemble the state of cortical activation during arousal and cognition. The excitability of cortical cells and synaptic networks is impacted by up states. This review describes the characteristics and putative functional role of up states and their similarity with activated states.
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Affiliation(s)
- Manuel A Castro-Alamancos
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, USA.
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59
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Nathanson JL, Jappelli R, Scheeff ED, Manning G, Obata K, Brenner S, Callaway EM. Short Promoters in Viral Vectors Drive Selective Expression in Mammalian Inhibitory Neurons, but do not Restrict Activity to Specific Inhibitory Cell-Types. Front Neural Circuits 2009; 3:19. [PMID: 19949461 PMCID: PMC2783723 DOI: 10.3389/neuro.04.019.2009] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Accepted: 10/13/2009] [Indexed: 12/05/2022] Open
Abstract
Short cell-type specific promoter sequences are important for targeted gene therapy and studies of brain circuitry. We report on the ability of short promoter sequences to drive fluorescent protein expression in specific types of mammalian cortical inhibitory neurons using adeno-associated virus (AAV) and lentivirus (LV) vectors. We tested many gene regulatory sequences derived from fugu (Takifugu rubripes), mouse, human, and synthetic composite regulatory elements. All fugu compact promoters expressed in mouse cortex, with only the somatostatin (SST) and the neuropeptide Y (NPY) promoters largely restricting expression to GABAergic neurons. However these promoters did not control expression in inhibitory cells in a subtype specific manner. We also tested mammalian promoter sequences derived from genes putatively coexpressed or coregulated within three major inhibitory interneuron classes (PV, SST, VIP). In contrast to the fugu promoters, many of the mammalian sequences failed to express, and only the promoter from gene A930038C07Rik conferred restricted expression, although as in the case of the fugu sequences, this too was not inhibitory neuron subtype specific. Lastly and more promisingly, a synthetic sequence consisting of a composite regulatory element assembled with PAX6 E1.1 binding sites, NRSE and a minimal CMV promoter showed markedly restricted expression to a small subset of mostly inhibitory neurons, but whose commonalities are unknown.
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Affiliation(s)
- Jason L Nathanson
- Systems Neurobiology Laboratories, Salk Institute for Biological Studies La Jolla, CA, USA
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60
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Pilgram GSK, Potikanond S, Baines RA, Fradkin LG, Noordermeer JN. The roles of the dystrophin-associated glycoprotein complex at the synapse. Mol Neurobiol 2009; 41:1-21. [PMID: 19899002 PMCID: PMC2840664 DOI: 10.1007/s12035-009-8089-5] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2009] [Accepted: 10/15/2009] [Indexed: 12/30/2022]
Abstract
Duchenne muscular dystrophy is caused by mutations in the dystrophin gene and is characterized by progressive muscle wasting. A number of Duchenne patients also present with mental retardation. The dystrophin protein is part of the highly conserved dystrophin-associated glycoprotein complex (DGC) which accumulates at the neuromuscular junction (NMJ) and at a variety of synapses in the peripheral and central nervous systems. Many years of research into the roles of the DGC in muscle have revealed its structural function in stabilizing the sarcolemma. In addition, the DGC also acts as a scaffold for various signaling pathways. Here, we discuss recent advances in understanding DGC roles in the nervous system, gained from studies in both vertebrate and invertebrate model systems. From these studies, it has become clear that the DGC is important for the maturation of neurotransmitter receptor complexes and for the regulation of neurotransmitter release at the NMJ and central synapses. Furthermore, roles for the DGC have been established in consolidation of long-term spatial and recognition memory. The challenges ahead include the integration of the behavioral and mechanistic studies and the use of this information to identify therapeutic targets.
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Affiliation(s)
- Gonneke S K Pilgram
- Department of Molecular and Cell Biology, Leiden University Medical Center, The Netherlands
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61
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Abstract
Adult primary sensory cortex is not hard wired, but adapts to sensory experience. The cellular basis for cortical plasticity involves a combination of functional and structural changes in cortical neurons and the connections between them. Functional changes such as synaptic strengthening have been the focus of many investigations. However, structural modifications to the connections between neurons play an important role in cortical plasticity. In this review, the authors focus on structural remodeling that leads to rewiring of cortical circuits. Recent work has identified axonal remodeling, growth of new dendritic spines, and synapse turnover as important structural mechanisms for experience-dependent plasticity in mature cortex. These findings have begun to unravel how rewiring occurs in adult neocortex and offer new insights into the cellular mechanisms for learning and memory.
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Affiliation(s)
- Samuel J. Barnes
- MRC Centre for Neurodegeneration Research, Institute of Psychiatry, London, UK
| | - Gerald T. Finnerty
- MRC Centre for Neurodegeneration Research, Institute of Psychiatry, London, UK,
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62
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Papoutsi A, Sidiropoulou K, Poirazi P. Mechanisms underlying persistent activity in a model PFC microcircuit. BMC Neurosci 2009. [DOI: 10.1186/1471-2202-10-s1-p42] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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63
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Abstract
In his theory of functional polarity, Ramon y Cajal first identified the soma and dendrites as the principal recipient compartments of a neuron and the axon as its main output structure. Despite notable exceptions in other parts of the nervous system (Schoppa and Urban, 2003; Wässle, 2004; Howard et al., 2005), this route of signal propagation has been shown to underlie the functional properties of most neocortical circuits studied so far. Recent evidence, however, suggests that neocortical excitatory cells may trigger the release of the inhibitory neurotransmitter GABA by directly depolarizing the axon terminals of inhibitory interneurons, thus bypassing their somatodendritic compartments (Ren et al., 2007). By using a combination of optical and electrophysiological approaches, we find that synaptically released glutamate fails to trigger GABA release through a direct action on GABAergic terminals under physiological conditions. Rather, our evidence suggests that glutamate triggers GABA release only after somatodendritic depolarization and action potential generation at GABAergic interneurons. These data indicate that neocortical inhibition is recruited by classical somatodendritic integration rather than direct activation of interneuron axon terminals.
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64
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Abstract
More than 90% of geniculocortical axons from the dorsal lateral geniculate nucleus of the thalamus innervate layer 4 (L4) of V1 (primary visual cortex). Excitatory neurons, which comprise >80% of the neuronal population in L4, synapse mainly onto adjacent L4 neurons and layer 2/3 (L2/3) neurons. It has been suggested that intralaminar L4-L4 connections contribute to amplifying and refining thalamocortical signals before routing to L2/3. To unambiguously probe the properties of the synaptic outputs from these L4 excitatory neurons, we used multiple simultaneous whole-cell patch-clamp recording and stimulation from two to four neighboring L4 neurons. We recorded uEPSCs (evoked unitary synaptic currents) in response to pairs of action potentials elicited in single presynaptic L4 neurons for 102 L4 cell pairs and found that their properties are more diverse than previously described. Averaged unitary synaptic response peak amplitudes spanned almost three orders of magnitude, from 0.42 to 192.92 pA. Although connections were, on average, reliable (average failure rate, 25%), we recorded a previously unknown subset of unreliable (failure rates from 30 to 100%) and weak (averaged response amplitudes, <5 pA) connections. Reliable connections with high probability of neurotransmitter release responded to paired presynaptic pulses with depression, whereas unreliable connections underwent paired-pulse facilitation. Recordings from interconnected sets of L4 triplets revealed that synaptic response amplitudes and reliability were equally variable between independent cell pairs and those that shared a common presynaptic or postsynaptic cell, suggesting local perisynaptic influences on the development and/or state of synaptic function.
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65
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Rigas P, Castro-Alamancos MA. Impact of persistent cortical activity (up States) on intracortical and thalamocortical synaptic inputs. J Neurophysiol 2009; 102:119-31. [PMID: 19403750 DOI: 10.1152/jn.00126.2009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The neocortex generates short epochs of persistent activity called up states, which are associated with changes in cellular and network excitability. Using somatosensory thalamocortical slices, we studied the impact of persistent cortical activity during spontaneous up states on intrinsic cellular excitability (input resistance) and on excitatory synaptic inputs of cortical cells. At the intrinsic excitability level, we found that the expected decrease in input resistance (high conductance) resulting from synaptic barrages during up states is counteracted by an increase in input resistance due to depolarization per se. The result is a variable but on average relatively small reduction in input resistance during up states. At the synaptic level, up states enhanced a late synaptic component of short-latency thalamocortical field potential responses but suppressed intracortical field potential responses. The thalamocortical enhancement did not reflect an increase in synaptic strength, as determined by measuring the evoked postsynaptic current, but instead an increase in evoked action potential (spike) probability due to depolarization during up states. In contrast, the intracortical suppression was associated with a reduction in synaptic strength, apparently driven by increased presynaptic intracortical activity during up states. In addition, intracortical suppression also reflected a reduction in evoked spike latency caused by depolarization and the abolishment of longer-latency spikes caused by stronger inhibitory drive during up states. In conclusion, depolarization during up states increases the success of excitatory synaptic inputs to reach firing. However, activity-dependent synaptic depression caused by increased presynaptic firing during up states and the enhancement of evoked inhibitory drive caused by depolarization suppress excitatory intracortical synaptic inputs.
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Affiliation(s)
- Pavlos Rigas
- Department of Neurobiology, Drexel University College of Medicine, 2900 Queen Ln., Philadelphia, PA 19129, USA
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66
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Gourévitch B, Eggermont JJ. Maximum decoding abilities of temporal patterns and synchronized firings: application to auditory neurons responding to click trains and amplitude modulated white noise. J Comput Neurosci 2009; 29:253-277. [PMID: 19373548 DOI: 10.1007/s10827-009-0149-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 02/10/2009] [Accepted: 03/16/2009] [Indexed: 11/29/2022]
Abstract
Simultaneous recordings of an increasing number of neurons have recently become available, but few methods have been proposed to handle this activity. Here, we extract and investigate all the possible temporal neural activity patterns based on synchronized firings of neurons recorded on multiple electrodes, or based on bursts of single-electrode activity in cat primary auditory cortex. We apply this to responses to periodic click trains or sinusoïdal amplitude modulated noise by obtaining for each pattern its temporal modulation transfer function. An algorithm that maximizes the mutual information between all patterns and stimuli subsequently leads to the identification of patterns that optimally decode modulation frequency (MF). We show that stimulus information contained in multi-electrode synchronized firing is not redundant with single-electrode firings and leads to improved efficiency of MF decoding. We also show that the combined use of firing rate and temporal codes leads to a better discrimination of the MF.
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Affiliation(s)
- Boris Gourévitch
- Department of Physiology and Biophysics, Department of Psychology, University of Calgary, Calgary, AB, Canada
| | - Jos J Eggermont
- Department of Physiology and Biophysics, Department of Psychology, University of Calgary, Calgary, AB, Canada. .,Department of Psychology, University of Calgary, 2500 University Drive N.W., Calgary, AB, T2N 1N4, Canada.
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67
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Polysynaptic subcircuits in the neocortex: spatial and temporal diversity. Curr Opin Neurobiol 2009; 18:332-7. [PMID: 18801433 DOI: 10.1016/j.conb.2008.08.009] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Revised: 08/15/2008] [Accepted: 08/18/2008] [Indexed: 11/23/2022]
Abstract
Inhibitory pathways in the neocortex display a variety of temporal and spatial patterns, maintaining a dynamic balance with excitatory synaptic activity. Recent studies have revealed prevalent polysynaptic subcircuits within the neocortical microcircuitry. These subcircuits involve excitatory and inhibitory connections that are activated by neurons both in supragranular and infragranular cortical layers and mediated by different mechanisms. Interestingly, in these subcircuits inhibition is induced by discharge of pyramidal cells, and excitation is caused by specific types of GABAergic interneurons. The different polysynaptic subcircuits are discussed with respect to their spatial and temporal properties and their possible functional role in cortical processing.
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68
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Medalla M, Barbas H. Synapses with inhibitory neurons differentiate anterior cingulate from dorsolateral prefrontal pathways associated with cognitive control. Neuron 2009; 61:609-20. [PMID: 19249280 DOI: 10.1016/j.neuron.2009.01.006] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Revised: 01/07/2009] [Accepted: 01/08/2009] [Indexed: 11/30/2022]
Abstract
The primate dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC) focus attention on relevant signals and suppress noise in cognitive tasks. However, their synaptic interactions and unique roles in cognitive control are unknown. We report that two distinct pathways to DLPFC area 9, one from the neighboring area 46 and the other from the functionally distinct ACC, similarly innervate excitatory neurons associated with selecting relevant stimuli. However, ACC has more prevalent and larger synapses with inhibitory neurons and preferentially innervates calbindin inhibitory neurons, which reduce noise by inhibiting excitatory neurons. In contrast, area 46 mostly innervates calretinin inhibitory neurons, which disinhibit excitatory neurons. These synaptic specializations suggest that ACC has a greater impact in reducing noise in dorsolateral areas during challenging cognitive tasks involving conflict, error, or reversing decisions, mechanisms that are disrupted in schizophrenia. These observations highlight the unique roles of the DLPFC and ACC in cognitive control.
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Affiliation(s)
- Maria Medalla
- Department of Health Sciences, Boston University and School of Medicine, Boston, MA 02215, USA
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69
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Higgs MH, Spain WJ. Conditional bursting enhances resonant firing in neocortical layer 2-3 pyramidal neurons. J Neurosci 2009; 29:1285-99. [PMID: 19193876 PMCID: PMC6666063 DOI: 10.1523/jneurosci.3728-08.2009] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Revised: 12/10/2008] [Accepted: 12/10/2008] [Indexed: 11/21/2022] Open
Abstract
The frequency response properties of neurons are critical for signal transmission and control of network oscillations. At subthreshold membrane potential, some neurons show resonance caused by voltage-gated channels. During action potential firing, resonance of the spike output may arise from subthreshold mechanisms and/or spike-dependent currents that cause afterhyperpolarizations (AHPs) and afterdepolarizations (ADPs). Layer 2-3 pyramidal neurons (L2-3 PNs) have a fast ADP that can trigger bursts. The present study investigated what stimuli elicit bursting in these cells and whether bursts transmit specific frequency components of the synaptic input, leading to resonance at particular frequencies. We found that two-spike bursts are triggered by step onsets, sine waves in two frequency bands, and noise. Using noise adjusted to elicit firing at approximately 10 Hz, we measured the gain for modulation of the time-varying firing rate as a function of stimulus frequency, finding a primary peak (7-16 Hz) and a high-frequency resonance (250-450 Hz). Gain was also measured separately for single and burst spikes. For a given spike rate, bursts provided higher gain at the primary peak and lower gain at intermediate frequencies, sharpening the high-frequency resonance. Suppression of bursting using automated current feedback weakened the primary and high-frequency resonances. The primary resonance was also influenced by the SK channel-mediated medium AHP (mAHP), because the SK blocker apamin reduced the sharpness of the primary peak. Our results suggest that resonance in L2-3 PNs depends on burst firing and the mAHP. Bursting enhances resonance in two distinct frequency bands.
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Affiliation(s)
- Matthew H. Higgs
- Neurology Section, Veterans Affairs Puget Sound Health Care System, Seattle, Washington 98108, and
- Departments of Physiology and Biophysics and
| | - William J. Spain
- Neurology Section, Veterans Affairs Puget Sound Health Care System, Seattle, Washington 98108, and
- Departments of Physiology and Biophysics and
- Neurology, University of Washington, Seattle, Washington 98195
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70
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Anderson WS, Kudela P, Weinberg S, Bergey GK, Franaszczuk PJ. Phase-dependent stimulation effects on bursting activity in a neural network cortical simulation. Epilepsy Res 2009; 84:42-55. [PMID: 19185465 DOI: 10.1016/j.eplepsyres.2008.12.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 12/12/2008] [Accepted: 12/18/2008] [Indexed: 01/19/2023]
Abstract
PURPOSE A neural network simulation with realistic cortical architecture has been used to study synchronized bursting as a seizure representation. This model has the property that bursting epochs arise and cease spontaneously, and bursting epochs can be induced by external stimulation. We have used this simulation to study the time-frequency properties of the evolving bursting activity, as well as effects due to network stimulation. METHODS The model represents a cortical region of 1.6 mm x 1.6mm, and includes seven neuron classes organized by cortical layer, inhibitory or excitatory properties, and electrophysiological characteristics. There are a total of 65,536 modeled single compartment neurons that operate according to a version of Hodgkin-Huxley dynamics. The intercellular wiring is based on histological studies and our previous modeling efforts. RESULTS The bursting phase is characterized by a flat frequency spectrum. Stimulation pulses are applied to this modeled network, with an electric field provided by a 1mm radius circular electrode represented mathematically in the simulation. A phase dependence to the post-stimulation quiescence is demonstrated, with local relative maxima in efficacy occurring before or during the network depolarization phase in the underlying activity. Brief periods of network insensitivity to stimulation are also demonstrated. The phase dependence was irregular and did not reach statistical significance when averaged over the full 2.5s of simulated bursting investigated. This result provides comparison with previous in vivo studies which have also demonstrated increased efficacy of stimulation when pulses are applied at the peak of the local field potential during cortical after discharges. The network bursting is synchronous when comparing the different neuron classes represented up to an uncertainty of 10 ms. Studies performed with an excitatory chandelier cell component demonstrated increased synchronous bursting in the model, as predicted from experimental work. CONCLUSIONS This large-scale multi-neuron neural network simulation reproduces many aspects of evolving cortical bursting behavior as well as the timing-dependent effects of electrical stimulation on that bursting.
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Affiliation(s)
- William S Anderson
- Harvard Medical School, Department of Neurosurgery, Brigham and Women's Hospital, 75 Francis Street CA 138F, Boston, MA 02115, USA.
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71
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Karameh FN, Massaquoi SG. Intracortical Augmenting Responses in Networks of Reduced Compartmental Models of Tufted Layer 5 Cells. J Neurophysiol 2009; 101:207-33. [DOI: 10.1152/jn.01280.2007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Augmenting responses (ARs) are characteristic recruitment phenomena that can be generated in target neural populations by repetitive intracortical or thalamic stimulation and that may facilitate activity transmission from thalamic nuclei to the cortex or between cortical areas. Experimental evidence suggests a role for cortical layer 5 in initiating at least one form of augmentation. We present a three-compartment model of tufted layer 5 (TL5) cells that faithfully reproduces a wide range of dynamics in these neurons that previously has been achieved only partially and in much more complex models. Using this model, the simplest network exhibiting AR was a single pair of TL5 and inhibitory (IN5) neurons. Intracellularly, AR initiation was controlled by low-threshold Ca2+ current ( IT), which promoted TL5 rebound firing, whereas AR strength was dictated by inward-rectifying current ( Ih), which regulated TL5 multiple-spike firing and also prevented excessive firing under high-amplitude stimuli. Synaptically, AR was significantly more salient under concurrent stimulus delivery to superficial and deep dendritic zones of TL5 cells than under conventional single-zone stimuli. Moreover, slow GABA-B–mediated inhibition in TL5 cells controlled AR strength and frequency range. Finally, a network model of two cortical populations interacting across functional hierarchy showed that intracortical AR occurred prominently upon exciting superficial cortical layers either directly or via intrinsic connections, with AR frequency dictated by connection strength and background activity. Overall, the investigation supports a central role for a TL5–IN5 skeleton network in low-frequency cortical dynamics in vivo, particularly across functional hierarchies, and presents neuronal models that facilitate accurate large-scale simulations.
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72
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Burkhalter A. Many specialists for suppressing cortical excitation. Front Neurosci 2008; 2:155-67. [PMID: 19225588 PMCID: PMC2622740 DOI: 10.3389/neuro.01.026.2008] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2008] [Accepted: 09/18/2008] [Indexed: 12/30/2022] Open
Abstract
Cortical computations are critically dependent on GABA-releasing neurons for dynamically balancing excitation with inhibition that is proportional to the overall level of activity. Although it is widely accepted that there are multiple types of interneurons, defining their identities based on qualitative descriptions of morphological, molecular and physiological features has failed to produce a universally accepted ‘parts list’, which is needed to understand the roles that interneurons play in cortical processing. A list of features has been published by the Petilla Interneurons Nomenclature Group, which represents an important step toward an unbiased classification of interneurons. To this end some essential features have recently been studied quantitatively and their association was examined using multidimensional cluster analyses. These studies revealed at least 3 distinct electrophysiological, 6 morphological and 15 molecular phenotypes. This is a conservative estimate of the number of interneuron types, which almost certainly will be revised as more quantitative studies will be performed and similarities will be defined objectively. It is clear that interneurons are organized with physiological attributes representing the most general, molecular characteristics the most detailed and morphological features occupying the middle ground. By themselves, none of these features are sufficient to define classes of interneurons. The challenge will be to determine which features belong together and how cell type-specific feature combinations are genetically specified.
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Affiliation(s)
- Andreas Burkhalter
- Department of Anatomy and Neurobiology, Washington University School of Medicine St. Louis, MO, USA
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73
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Zaitsev AV, Povysheva NV, Gonzalez-Burgos G, Rotaru D, Fish KN, Krimer LS, Lewis DA. Interneuron diversity in layers 2-3 of monkey prefrontal cortex. ACTA ACUST UNITED AC 2008; 19:1597-615. [PMID: 19015370 DOI: 10.1093/cercor/bhn198] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The heterogeneity of gamma-aminobutyric acid interneurons in the rodent neocortex is well-established, but their classification into distinct subtypes remains a matter of debate. The classification of interneurons in the primate neocortex is further complicated by a less extensive database of the features of these neurons and by reported interspecies differences. Consequently, in this study we characterized 8 different morphological types of interneurons from monkey prefrontal cortex, 4 of which have not been previously classified. These interneuron types differed in their expression of molecular markers and clustered into 3 different electrophysiological classes. The first class consisted of fast-spiking parvalbumin-positive chandelier and linear arbor cells. The second class comprised 5 different morphological types of continuous-adapting calretinin- or calbindin-positive interneurons that had the lowest level of firing threshold. However, 2 of these morphological types had short spike duration, which is not typical for rodent adapting cells. Neurogliaform cells (NGFCs), which coexpressed calbindin and neuropeptide Y, formed the third class, characterized by strong initial adaptation. They did not exhibit the delayed spikes seen in rodent NGFCs. These results indicate that primate interneurons have some specific properties; consequently, direct translation of classification schemes developed from studies in rodents to primates might be inappropriate.
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74
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Brette R, Piwkowska Z, Monier C, Rudolph-Lilith M, Fournier J, Levy M, Frégnac Y, Bal T, Destexhe A. High-resolution intracellular recordings using a real-time computational model of the electrode. Neuron 2008; 59:379-91. [PMID: 18701064 DOI: 10.1016/j.neuron.2008.06.021] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 06/03/2008] [Accepted: 06/16/2008] [Indexed: 11/26/2022]
Abstract
Intracellular recordings of neuronal membrane potential are a central tool in neurophysiology. In many situations, especially in vivo, the traditional limitation of such recordings is the high electrode resistance and capacitance, which may cause significant measurement errors during current injection. We introduce a computer-aided technique, Active Electrode Compensation (AEC), based on a digital model of the electrode interfaced in real time with the electrophysiological setup. The characteristics of this model are first estimated using white noise current injection. The electrode and membrane contribution are digitally separated, and the recording is then made by online subtraction of the electrode contribution. Tests performed in vitro and in vivo demonstrate that AEC enables high-frequency recordings in demanding conditions, such as injection of conductance noise in dynamic-clamp mode, not feasible with a single high-resistance electrode until now. AEC should be particularly useful to characterize fast neuronal phenomena intracellularly in vivo.
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Affiliation(s)
- Romain Brette
- Unité de Neurosciences Intégratives et Computationnelles (UNIC), CNRS, 91198 Gif-sur-Yvette, France.
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75
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Short term synaptic depression model—Analytical solution and analysis. J Theor Biol 2008; 254:82-8. [DOI: 10.1016/j.jtbi.2008.05.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Revised: 05/15/2008] [Accepted: 05/15/2008] [Indexed: 11/23/2022]
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76
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Melamed O, Barak O, Silberberg G, Markram H, Tsodyks M. Slow oscillations in neural networks with facilitating synapses. J Comput Neurosci 2008; 25:308-16. [DOI: 10.1007/s10827-008-0080-z] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 01/20/2008] [Accepted: 01/23/2008] [Indexed: 11/28/2022]
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77
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Larsen DD, Wickersham IR, Callaway EM. Retrograde tracing with recombinant rabies virus reveals correlations between projection targets and dendritic architecture in layer 5 of mouse barrel cortex. Front Neural Circuits 2008; 1:5. [PMID: 18946547 PMCID: PMC2526280 DOI: 10.3389/neuro.04.005.2007] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Accepted: 02/11/2008] [Indexed: 11/23/2022] Open
Abstract
A recombinant rabies virus was used as a retrograde tracer to allow complete filling of the axonal and dendritic arbors of identified projection neurons in layer 5 of mouse primary somatosensory cortex (S1) in vivo. Previous studies have distinguished three types of layer 5 pyramids in S1: tall-tufted, tall-simple, and short. Layer 5 pyramidal neurons were retrogradely labeled from several known targets: contralateral S1, superior colliculus, and thalamus. The complete dendritic arbors of labeled cells were reconstructed to allow for unambiguous classification of cell type. We confirmed that the tall-tufted pyramids project to the superior colliculus and thalamus and that short layer 5 pyramidal neurons project to contralateral cortex, as previously described. We found that tall-simple pyramidal neurons contribute to corticocortical connections. Axonal reconstructions show that corticocortical projection neurons have a large superficial axonal arborization locally, while the subcortically projecting neurons limit axonal arbors to the deep layers. Furthermore, reconstructions of local axons suggest that tall-simple cell axons have extensive lateral spread while those of the short pyramids are more columnar. These differences were revealed by the ability to completely label dendritic and axonal arbors in vivo and have not been apparent in previous studies using labeling in brain slices.
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Affiliation(s)
- Delaine D Larsen
- Systems Neurobiology Laboratories, The Salk Institute for Biological Studies, Neurosciences Graduate Program, University of California San Diego, La Jolla, CA, USA
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78
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Hoshino O. Extrasynaptic-GABA-mediated neuromodulation in a sensory cortical neural network. NETWORK (BRISTOL, ENGLAND) 2008; 19:95-117. [PMID: 18569723 DOI: 10.1080/09548980701840343] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Simulating a neural network model of an early sensory cortical area, we investigated how gamma-aminobutyric acid (GABA) accumulated in extracellular space (ambient GABA), which depends on the synaptic activity of GABAergic interneurons, acts on the GABAa-receptors located on extrasynaptic membrane regions of principal cells (P), feedback inhibitory cells (F) and lateral inhibitory cells (L). The ambient GABA enhanced the selective responsiveness of P-cells to a target feature stimulus, if it acted on the extrasynaptic GABAa-receptors of P-cells. The ambient GABA led to depolarizing P-cells during ongoing (spontaneous) neuronal-activity periods, if it acted on the extrasynaptic GABAa-receptors of F or L cells. This membrane depolarization contributed to establishing an ongoing subthreshold neuronal state, by which the P-cells could respond quickly to the target stimulus. We suggest that the combinatorial inhibition of P, F, and L cells, meditated by extrasynaptic GABAa-receptors recognizing ambient GABA, is crucial for processing the information of relevant sensory features and for establishing an ongoing subthreshold cortical state that prepares as a ready state for subsequent sensory input. A failure in neuronal-activity-dependent regulation of ambient GABA, stemming largely from the depletion of GABA in extracellular space during senescence, may cause the degeneration of intracortical inhibition that leads to cognitive dysfunction in old animals.
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Affiliation(s)
- Osamu Hoshino
- Department of Intelligent Systems Engineering, Ibaraki University, Hitachi, Ibaraki, 316-8511, Japan.
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79
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Medalla M, Lera P, Feinberg M, Barbas H. Specificity in inhibitory systems associated with prefrontal pathways to temporal cortex in primates. Cereb Cortex 2007; 17 Suppl 1:i136-50. [PMID: 17725996 DOI: 10.1093/cercor/bhm068] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The prefrontal cortex selects relevant signals and suppresses irrelevant stimuli for a given task through mechanisms that are not understood. We addressed this issue using as a model system the pathways from the functionally distinct prefrontal areas 10 and 32 to auditory association cortex, and investigated their relationship to inhibitory neurons labeled for calbindin (CB) or parvalbumin (PV), which differ in mode of inhibition. Projection neurons in area 10 originated mostly in layers 2-3 and were intermingled with CB inhibitory neurons. In contrast, projections from area 32 originated predominantly in layers 5-6 among PV inhibitory neurons. Prefrontal axonal boutons terminating in layers 2-3 of auditory association cortex were larger than those terminating in layer 1. Most prefrontal axons synapsed on spines of excitatory neurons but a significant number targeted dendritic shafts of inhibitory neurons. Axons from area 10 targeted CB and PV inhibitory neurons, whereas axons from area 32 targeted PV inhibitory neurons. The preferential association of the 2 prefrontal pathways with distinct classes of inhibitory neurons at their origin and termination may reflect the specialization of area 10 in working memory functions and area 32 in emotional communication. These findings suggest diversity in inhibitory control by distinct prefrontal pathways.
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Affiliation(s)
- M Medalla
- Departments of Health Sciences, Boston University, School of Medicine, MA 02215, USA
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80
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Abstract
The prefrontal cortex in primates guides behavior by selecting relevant stimuli for the task at hand, mediated through excitatory bidirectional pathways with structures associated with sensory processing, memory, and emotions. The prefrontal cortex also has a key role in suppressing irrelevant stimuli through a mechanism that is not well understood. Recent findings indicate that prefrontal pathways interface with laminar-specific neurochemical classes of inhibitory neurons in sensory cortices, terminate extensively in the frontal and sensory sectors of the inhibitory thalamic reticular nucleus, and target the inhibitory intercalated masses of the amygdala. Circuit-based models suggest that prefrontal pathways can select relevant signals and efficiently suppress distractors, in processes that are disrupted in schizophrenia and in other disorders affecting prefrontal cortices.
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Affiliation(s)
- Helen Barbas
- Department of Health Sciences, Boston University, Boston, MA
- Program in Neuroscience, Boston University, Boston, MA
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81
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Ohki K, Reid RC. Specificity and randomness in the visual cortex. Curr Opin Neurobiol 2007; 17:401-7. [PMID: 17720489 PMCID: PMC2951601 DOI: 10.1016/j.conb.2007.07.007] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Accepted: 07/12/2007] [Indexed: 11/25/2022]
Abstract
Research on the functional anatomy of visual cortical circuits has recently zoomed in from the macroscopic level to the microscopic. High-resolution functional imaging has revealed that the functional architecture of orientation maps in higher mammals is built with single-cell precision. By contrast, orientation selectivity in rodents is dispersed on visual cortex in a salt-and-pepper fashion, despite highly tuned visual responses. Recent studies of synaptic physiology indicate that there are disjoint subnetworks of interconnected cells in the rodent visual cortex. These intermingled subnetworks, described in vitro, may relate to the intermingled ensembles of cells tuned to different orientations, described in vivo. This hypothesis may soon be tested with new anatomic techniques that promise to reveal the detailed wiring diagram of cortical circuits.
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82
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Anderson WS, Kudela P, Cho RJ, Bergey GK, Franaszczuk P. Studies of stimulus parameters for seizure disruption using neural network simulations. BIOLOGICAL CYBERNETICS 2007; 97:173-94. [PMID: 17619199 PMCID: PMC2738632 DOI: 10.1007/s00422-007-0166-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Accepted: 05/10/2007] [Indexed: 05/15/2023]
Abstract
A large scale neural network simulation with realistic cortical architecture has been undertaken to investigate the effects of external electrical stimulation on the propagation and evolution of ongoing seizure activity. This is an effort to explore the parameter space of stimulation variables to uncover promising avenues of research for this therapeutic modality. The model consists of an approximately 800 mum x 800 mum region of simulated cortex, and includes seven neuron classes organized by cortical layer, inhibitory or excitatory properties, and electrophysiological characteristics. The cell dynamics are governed by a modified version of the Hodgkin-Huxley equations in single compartment format. Axonal connections are patterned after histological data and published models of local cortical wiring. Stimulation induced action potentials take place at the axon initial segments, according to threshold requirements on the applied electric field distribution. Stimulation induced action potentials in horizontal axonal branches are also separately simulated. The calculations are performed on a 16 node distributed 32-bit processor system. Clear differences in seizure evolution are presented for stimulated versus the undisturbed rhythmic activity. Data is provided for frequency dependent stimulation effects demonstrating a plateau effect of stimulation efficacy as the applied frequency is increased from 60 to 200 Hz. Timing of the stimulation with respect to the underlying rhythmic activity demonstrates a phase dependent sensitivity. Electrode height and position effects are also presented. Using a dipole stimulation electrode arrangement, clear orientation effects of the dipole with respect to the model connectivity is also demonstrated. A sensitivity analysis of these results as a function of the stimulation threshold is also provided.
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Affiliation(s)
- William S. Anderson
- Resident in Neurosurgery, The Johns Hopkins Hospital, Department of Neurosurgery, Meyer 8-161, 600 North Wolfe Street, Baltimore, MD USA 21287, , (o) +1(443)287-8295, (f) +1(410)502-2507
| | - Pawel Kudela
- Instructor, The Johns Hopkins Hospital, Department of Neurology, Meyer 2-147, 600 North Wolfe Street, Baltimore, MD USA 21287, , (o) +1(443)287-8295, (f) +1(410)955-0751
| | - Ryan J. Cho
- Undergraduate Assistant, The Johns Hopkins Hospital, Department of Neurology, Meyer 2-147, 600 North Wolfe Street, Baltimore, MD USA 21287, , (o) +1(410)614-8770, (f) +1(410)955-0751
| | - Gregory K. Bergey
- Professor, The Johns Hopkins Hospital, Department of Neurology, Meyer 2-147, 600 North Wolfe Street, Baltimore, MD USA 21287, , (o) +1(410)955-7338, (f) +1(410)502-2507
| | - Piotr Franaszczuk
- Associate Professor, The Johns Hopkins Hospital, Department of Neurology, Meyer 2-147, 600 North Wolfe Street, Baltimore, MD USA 21287, , (o) +1(410)614-8770, (f) +1(410)955-0751
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83
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Wittenberg GF, Bastings EP, Fowlkes AM, Morgan TM, Good DC, Pons TP. Dynamic course of intracortical TMS paired-pulse responses during recovery of motor function after stroke. Neurorehabil Neural Repair 2007; 21:568-73. [PMID: 17522261 DOI: 10.1177/1545968307302438] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Recovery of motor function after stroke may be associated with changes in inhibitory and facilitatory circuits within the motor cortex. OBJECTIVE We explored such changes longitudinally after stroke, using transcranial magnetic stimulation (TMS). METHODS Subjects (N = 27) with a single cerebral infarction affecting movement of either hand were studied at <10 days poststroke, 1 month, and 6 months. Age-matched control subjects (N = 9) were studied at 2 times. RESULTS In contrast to previous studies, paired-pulse inhibition was increased in patients with a subcortical stroke compared to control subjects. After a cortical stroke, paired-pulse facilitation was also increased. Stroke location affected the time course of inhibition. Subcortical stroke resulted in increased inhibition initially that decreased over time, whereas cortical stroke had no significant effect on inhibition and a more immediate and lasting effect on facilitation. CONCLUSIONS The time course of a decline in inhibition based on TMS after subcortical stroke followed the gain in motor recovery. Increased facilitation in cortical stroke patients is more likely to represent the effect of early cortical circuit disruption and may not play a role in subacute changes in motor function.
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Affiliation(s)
- George F Wittenberg
- Department of Neurology, Wake Forest University Health Sciences, Winston Salem, NC, USA.
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84
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Ren M, Yoshimura Y, Takada N, Horibe S, Komatsu Y. Specialized inhibitory synaptic actions between nearby neocortical pyramidal neurons. Science 2007; 316:758-61. [PMID: 17478724 DOI: 10.1126/science.1135468] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We found that, in the mouse visual cortex, action potentials generated in a single layer-2/3 pyramidal (excitatory) neuron can reliably evoke large, constant-latency inhibitory postsynaptic currents in other nearby pyramidal cells. This effect is mediated by axo-axonic ionotropic glutamate receptor-mediated excitation of the nerve terminals of inhibitory interneurons, which connect to the target pyramidal cells. Therefore, individual cortical excitatory neurons can generate inhibition independently from the somatic firing of inhibitory interneurons.
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Affiliation(s)
- Ming Ren
- Department of Neuroscience, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan
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85
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Kapfer C, Glickfeld LL, Atallah BV, Scanziani M. Supralinear increase of recurrent inhibition during sparse activity in the somatosensory cortex. Nat Neurosci 2007; 10:743-53. [PMID: 17515899 PMCID: PMC3518866 DOI: 10.1038/nn1909] [Citation(s) in RCA: 310] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2007] [Accepted: 04/16/2007] [Indexed: 11/09/2022]
Abstract
The balance between excitation and inhibition in the cortex is crucial in determining sensory processing. Because the amount of excitation varies, maintaining this balance is a dynamic process; yet the underlying mechanisms are poorly understood. We show here that the activity of even a single layer 2/3 pyramidal cell in the somatosensory cortex of the rat generates widespread inhibition that increases disproportionately with the number of active pyramidal neurons. This supralinear increase of inhibition results from the incremental recruitment of somatostatin-expressing inhibitory interneurons located in layers 2/3 and 5. The recruitment of these interneurons increases tenfold when they are excited by two pyramidal cells. A simple model demonstrates that the distribution of excitatory input amplitudes onto inhibitory neurons influences the sensitivity and dynamic range of the recurrent circuit. These data show that through a highly sensitive recurrent inhibitory circuit, cortical excitability can be modulated by one pyramidal cell.
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Affiliation(s)
- Christoph Kapfer
- Neuroscience Graduate Program and Neurobiology Section, Division of Biology, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0634, USA
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86
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Abstract
Recent sensory experience affects both perception and the response properties of visual neurons. Here I review a rapid form of experience-dependent plasticity that follows adaptation, the presentation of a particular stimulus or ensemble of stimuli for periods ranging from tens of milliseconds to minutes. Adaptation has a rich history in psychophysics, where it is often used as a tool for dissecting the perceptual mechanisms of vision. Although we know comparatively little about the neurophysiological effects of adaptation, work in the last decade has revealed a rich repertoire of effects. This review focuses on this recent physiological work, the cellular and biophysical mechanisms that may underlie the observed effects, and the functional benefit that they may afford. I conclude with a brief discussion of some important open questions in the field.
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Affiliation(s)
- Adam Kohn
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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87
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Gong P, van Leeuwen C. Dynamically maintained spike timing sequences in networks of pulse-coupled oscillators with delays. PHYSICAL REVIEW LETTERS 2007; 98:048104. [PMID: 17358818 DOI: 10.1103/physrevlett.98.048104] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2006] [Indexed: 05/14/2023]
Abstract
We demonstrate the widespread occurrence of dynamically maintained spike timing sequences in recurrent networks of pulse-coupled spiking neurons with large time delays. The sequences occur in transient, quasistable phase-locking states. The system spontaneously jumps between these states. This collective dynamics enables the system to generate a large number of distinct precise spike timing sequences. Distributed time delays play a constructive role by enhancing the dominance in parameter space of the dynamics responsible for producing the large variety of spike timing sequences.
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Affiliation(s)
- Pulin Gong
- Laboratory for Perceptual Dynamics, RIKEN Brain Science Institute, Hirosawa 2-1, Wako, Saitama 351-0198, Japan
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88
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Eggermont JJ. Correlated neural activity as the driving force for functional changes in auditory cortex. Hear Res 2007; 229:69-80. [PMID: 17296278 DOI: 10.1016/j.heares.2007.01.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Revised: 10/31/2006] [Accepted: 01/03/2007] [Indexed: 10/23/2022]
Abstract
The functional role of neural synchrony is reflected in cortical tonotopic map reorganization and in the emergence of pathological phenomena such as tinnitus. First of all experimenter-centered and subject-centered views of neural activity will be contrasted; this argues against the use of stimulus-correction procedures and favors the use of a correction procedure based on neural activity without reference to stimulus timing. Within a cortical column neurons fired synchronously with on average about 6% of their spikes in a 1 ms bin and occasionally showing 30% or more of such coincident spikes. For electrode separations exceeding 200 microm the average peak correlation strength only occasionally reached 3%. The experimental evidence for coincidence of neural activity, neural correlation and neural synchrony shows that horizontal fibers activity can induce strong neural correlations. Cortico-cortical connections for a large part connect cell groups with characteristic frequencies differing by more than one octave. Such neurons have generally non-overlapping receptive fields but still can have sizeable peak cross-correlations. Correlated neural activity and heterotopic neural interconnections are presented as the substrates for cortical reorganization; increased neural synchrony and tonotopic map reorganization go hand in hand. This links cortical reorganization with hypersynchrony that can be considered as an important driving force underlying tinnitus.
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Affiliation(s)
- Jos J Eggermont
- Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada.
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89
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Gourévitch B, Eggermont JJ. Evaluating information transfer between auditory cortical neurons. J Neurophysiol 2007; 97:2533-43. [PMID: 17202243 DOI: 10.1152/jn.01106.2006] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Transfer entropy, presented as a new tool for investigating neural assemblies, quantifies the fraction of information in a neuron found in the past history of another neuron. The asymmetry of the measure allows feedback evaluations. In particular, this tool has potential applications in investigating windows of temporal integration and stimulus-induced modulation of firing rate. Transfer entropy is also able to eliminate some effects of common history in spike trains and obtains results that are different from cross-correlation. The basic transfer entropy properties are illustrated with simulations. The information transfer through a network of 16 simultaneous multiunit recordings in cat's auditory cortex was examined for a large number of acoustic stimulus types. Application of the transfer entropy to a large database of multiple single-unit activity in cat's primary auditory cortex revealed that most windows of temporal integration found during spontaneous activity range between 2 and 15 ms. The normalized transfer entropy shows similarities and differences with the strength of cross-correlation; these form the basis for revisiting the neural assembly concept.
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Affiliation(s)
- Boris Gourévitch
- Department of Physiology and Biophysics and Department of Psychology, University of Calgary, Calgary, Alberta, Canada
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90
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91
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Duret F, Shumikhina S, Molotchnikoff S. Neuron participation in a synchrony-encoding assembly. BMC Neurosci 2006; 7:72. [PMID: 17069653 PMCID: PMC1633739 DOI: 10.1186/1471-2202-7-72] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Accepted: 10/27/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Synchronization of action potentials between neurons is considered to be an encoding process that allows the grouping of various and multiple features of an image leading to a coherent perception. How this coding neuronal assembly is configured is debated. We have previously shown that the magnitude of synchronization between excited neurons is stimulus-dependent. In the present investigation we compare the levels of synchronization between synchronizing individual neurons and the synchronizing pool of cells to which they belong. RESULTS Even though neurons belonged to their respective pools, some cells synchronized for all presented stimuli while others were rather selective and only a few stimulating conditions produced a significant synchronization. In addition the experiments show that one synchronizing pair rarely replicates the level of synchrony between corresponding groups of units. But when synchronizing clusters of neurons increase in number, the correlation (measured as a coefficient of determination) between unit synchronization and the synchronization between the entire pools of cells to which individual neurons belong improves. CONCLUSION These results prompt the hypothesis that random or spontaneous synchronization becomes progressively less important, whereas coincident spikes related to encoding properties of targets gain significance because a particular configuration of an image biases the excitatory inputs in favor of connections driven by the applied features of the stimulus.
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Affiliation(s)
| | - Svetlana Shumikhina
- Département de Sciences Biologiques, Université de Montréal, CP 6128 Succ. centre-ville, Montréal, PQ, H3C 3J7, Canada
| | - Stéphane Molotchnikoff
- Département de Sciences Biologiques, Université de Montréal, CP 6128 Succ. centre-ville, Montréal, PQ, H3C 3J7, Canada
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92
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Karameh FN, Dahleh MA, Brown EN, Massaquoi SG. Modeling the contribution of lamina 5 neuronal and network dynamics to low frequency EEG phenomena. BIOLOGICAL CYBERNETICS 2006; 95:289-310. [PMID: 16897093 DOI: 10.1007/s00422-006-0090-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Accepted: 05/24/2006] [Indexed: 05/11/2023]
Abstract
The Electroencephalogram (EEG) is an important clinical and research tool in neurophysiology. With the advent of recording techniques, new evidence is emerging on the neuronal populations and wiring in the neocortex. A main challenge is to relate the EEG generation mechanisms to the underlying circuitry of the neocortex. In this paper, we look at the principal intrinsic properties of neocortical cells in layer 5 and their network behavior in simplified simulation models to explain the emergence of several important EEG phenomena such as the alpha rhythms, slow-wave sleep oscillations, and a form of cortical seizure. The models also predict the ability of layer 5 cells to produce a resonance-like neuronal recruitment known as the augmenting response. While previous models point to deeper brain structures, such as the thalamus, as the origin of many EEG rhythms (spindles), the current model suggests that the cortical circuitry itself has intrinsic oscillatory dynamics which could account for a wide variety of EEG phenomena.
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Affiliation(s)
- Fadi N Karameh
- Department of Electrical and Computer Engineering, American University of Beirut, Beirut, Lebanon.
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93
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Feldmeyer D, Lübke J, Sakmann B. Efficacy and connectivity of intracolumnar pairs of layer 2/3 pyramidal cells in the barrel cortex of juvenile rats. J Physiol 2006; 575:583-602. [PMID: 16793907 PMCID: PMC1819447 DOI: 10.1113/jphysiol.2006.105106] [Citation(s) in RCA: 196] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Synaptically coupled layer 2/3 (L2/3) pyramidal neurones located above the same layer 4 barrel ('barrel-related') were investigated using dual whole-cell voltage recordings in acute slices of rat somatosensory cortex. Recordings were followed by reconstructions of biocytin-filled neurones. The onset latency of unitary EPSPs was 1.1 +/- 0.4 ms, the 20-80% rise time was 0.7 +/- 0.2 ms, the average amplitude was 1.0 +/- 0.7 mV and the decay time constant was 15.7 +/- 4.5 ms. The coefficient of variation (c.v.) of unitary EPSP amplitudes decreased with increasing EPSP peak and was 0.33 +/- 0.18. Bursts of APs in the presynaptic pyramidal cell resulted in EPSPs that, over a wide range of frequencies (5-100 Hz), displayed amplitude depression. Anatomically the barrel-related pyramidal cells in the lower half of layer 2/3 have a long apical dendrite with a small terminal tuft, while pyramidal cells in the upper half of layer 2/3 have shorter and often more 'irregularly' shaped apical dendrites that branch profusely in layer 1. The number of putative excitatory synaptic contacts established by the axonal collaterals of a L2/3 pyramidal cell with a postsynaptic pyramidal cell in the same column varied between 2 and 4, with an average of 2.8 +/- 0.7 (n = 8 pairs). Synaptic contacts were established predominantly on the basal dendrites at a mean geometric distance of 91 +/- 47 mum from the pyramidal cell soma. L2/3-to-L2/3 connections formed a blob-like innervation domain containing 2.8 mm of the presynaptic axon collaterals with a bouton density of 0.3 boutons per mum axon. Within the supragranular layers of its home column a single L2/3 pyramidal cell established about 900 boutons suggesting that 270 pyramidal cells in layer 2/3 are innervated by an individual pyramidal cell. In turn, a single pyramidal cell received synaptic inputs from 270 other L2/3 pyramidal cells. The innervation domain of L2/3-to-L2/3 connections superimposes almost exactly with that of L4-to-L2/3 connections. This suggests that synchronous feed-forward excitation of L2/3 pyramidal cells arriving from layer 4 could be potentially amplified in layer 2/3 by feedback excitation within a column and then relayed to the neighbouring columns.
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Affiliation(s)
- Dirk Feldmeyer
- Institut für Neurowissenschaften und Biophysik, AG Zelluläre Neurobiologie-Medizin, Forschungszentrum Jülich GmbH, Leo-Brandt-Strasse, D-52425 Jülich, Germany.
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94
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Abstract
The response of a neuron in primary visual cortex (V1) to an optimal stimulus in its classical receptive field (CRF) can be reduced by the presence of an orthogonal mask, a phenomenon known as cross-orientation suppression. The presence of a parallel stimulus outside the CRF can have a similar effect, in this case known as surround suppression. We used a novel stimulus to probe the time course of cross-orientation suppression and found that it is very fast, starting even before the response to optimal excitatory stimuli. However, it occurs with some delay after the offset response, considered to be a measure of the earliest excitatory signals that reach the CRF. We also examined the time course of response to a stimulus presented outside the CRF and found that cross-orientation suppression begins substantially earlier than surround suppression measured in the same cells. Together, these findings suggest that cross-orientation suppression is attributable to either direct feedforward signal paths to V1 neurons or a circuit involving fast local interneurons within V1. Feedback from higher cortical areas is implicated in surround suppression, but our results make this an implausible mechanism for cross-orientation suppression. We conclude that suppression from inside and outside the CRF occur through different mechanisms.
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Affiliation(s)
- Matthew A Smith
- Center for Neural Science, New York University, New York, New York 10003, USA.
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95
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Morishima M, Kawaguchi Y. Recurrent connection patterns of corticostriatal pyramidal cells in frontal cortex. J Neurosci 2006; 26:4394-405. [PMID: 16624959 PMCID: PMC6674016 DOI: 10.1523/jneurosci.0252-06.2006] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Corticostriatal pyramidal cells are heterogeneous in the frontal cortex. Here, we show that subpopulations of corticostriatal neurons in the rat frontal cortex are selectively connected with each other based on their subcortical targets. Using paired recordings of retrogradely labeled cells, we investigated the synaptic connectivity between two projection cell types: those projecting to the pons [corticopontine (CPn) cell], often with collaterals to the striatum, and those projecting to both sides of the striatum but not to the pons [crossed corticostriatal (CCS) cell]. The two types were morphologically differentiated in regard to their apical tufts. The dendritic morphologies of CCS cells were correlated with their somatic depth within the cortex. CCS cells had reciprocal synaptic connections with each other and also provided synaptic input to CPn cells. However, connections from CPn to CCS cells were rarely found, even in pairs showing CCS to CPn connectivity. Additionally, CCS cells preferentially innervated the basal dendrites of other CCS cells but made contacts onto both the basal and apical dendrites of CPn cells. The amplitude of synaptic responses was to some extent correlated with the contact site number. Ratios of the EPSC amplitude to the contact number tended to be larger in the CCS to CCS connection. Therefore, our data demonstrate that these two types of corticostriatal cells distinct in their dendritic morphologies show directional and domain-dependent preferences in their synaptic connectivity.
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96
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Xiang H, Chen HX, Yu XX, King MA, Roper SN. Reduced excitatory drive in interneurons in an animal model of cortical dysplasia. J Neurophysiol 2006; 96:569-78. [PMID: 16641376 DOI: 10.1152/jn.01133.2005] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cortical dysplasia (CD) is strongly associated with epilepsy. Enhanced excitability in dysplastic neuronal networks is believed to contribute to epileptogenesis, but the underlying mechanisms for the hyperexcitability are poorly understood. Cortical GABAergic interneurons provide the principal inhibition in the neuronal networks by forming inhibitory synapses on excitatory neurons. The aim of the present study was to determine if the function of interneurons in CD is compromised. In a rat model of CD, in utero irradiation, we studied spontaneous and miniature excitatory postsynaptic currents (sEPSCs and mEPSCs) in cortical interneurons using whole cell recording techniques. Two types of interneurons, type I and type II, were identified based on their distinctive spike patterns and short-term synaptic plasticity. We found that the frequencies of sEPSCs and mEPSCs were significantly decreased in both types of interneurons in CD. However, the amplitude and kinetics of sEPSCs and mEPSCs were not different. Five-pulse, 20-Hz stimulation produced short-term depression in type I interneurons in both CD and control tissue. Type II interneurons showed a robust short-term facilitation in both CD and control tissue. Morphological analysis of biocytin-filled neurons revealed that dendritic trees of both types of interneurons were not altered in CD. Our results demonstrate that the excitatory drive, namely sEPSCs and mEPSCs, in two main types of interneuron is largely attenuated in CD, probably due to a reduction in the number of excitatory synapses on both types of interneurons in CD.
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Affiliation(s)
- Hui Xiang
- Department of Neurological Surgery and McKnight Brain Institute, University of Florida College of Medicine, Gainesville, USA
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97
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Falconbridge MS, Stamps RL, Badcock DR. A Simple Hebbian/Anti-Hebbian Network Learns the Sparse, Independent Components of Natural Images. Neural Comput 2006; 18:415-29. [PMID: 16378520 DOI: 10.1162/089976606775093891] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Slightly modified versions of an early Hebbian/anti-Hebbian neural network are shown to be capable of extracting the sparse, independent linear components of a prefiltered natural image set. An explanation for this capability in terms of a coupling between two hypothetical networks is presented. The simple networks presented here provide alternative, biologically plausible mechanisms for sparse, factorial coding in early primate vision.
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98
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Grabska-Barwińska A, Zygierewicz J. A model of event-related EEG synchronization changes in beta and gamma frequency bands. J Theor Biol 2006; 238:901-13. [PMID: 16099472 DOI: 10.1016/j.jtbi.2005.07.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2005] [Revised: 07/01/2005] [Accepted: 07/05/2005] [Indexed: 11/17/2022]
Abstract
During preparation, execution and recovery from simple movements, the EEG power spectrum undergoes a sequence of changes. The power in the beta band (13-25 Hz) decreases during preparation and execution of movement, but during recovery it reaches a level higher than that in the reference period (not affected by the event). These effects are known as event-related beta desynchronization and beta rebound. The power in the gamma band (>30 Hz) increases significantly just before the onset of the movement. This effect is known as event-related gamma synchronization. There are numerous observations concerning these effects but the underlying physiological mechanisms and functional role are not clear. We propose a lumped computational model of a cortical circuit. The model consists only of a pyramidal and an interneuronal population. Each population represents averaged properties of constituting neurons. The output of the model represents a local field potential, with a power spectrum peak either in the beta or in the gamma band. The model elucidates the mechanisms of transition between slower and faster rhythms, gamma synchronization and beta desynchronization and rebound effects. The sufficient conditions to observe the effects in the model are changes of the external excitation level and of the connection strength between excitatory and inhibitory populations attributed to short-time plasticity. The present model presents the role of the pyramidal neurons to interneuron connection in the oscillatory behavior of the two populations. We conclude that the pronounced facilitation of the pyramidal to fast spiking interneuron connections, initiated by robust excitation of the motor cortex neurons, may be essential for the effect of beta rebound. Further experiments concerning short-time plasticity during behavioral tasks would be of great value in studies of functional local cortical circuits.
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Affiliation(s)
- Agnieszka Grabska-Barwińska
- Department of Biomedical Physics, Institute of Experimental Physics, Warsaw University, Hoza 69, 00-681 Warsaw, Poland
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99
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Burnashev N, Rozov A. Presynaptic Ca2+ dynamics, Ca2+ buffers and synaptic efficacy. Cell Calcium 2005; 37:489-95. [PMID: 15820398 DOI: 10.1016/j.ceca.2005.01.003] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2004] [Accepted: 01/06/2005] [Indexed: 11/30/2022]
Abstract
In synapses neurotransmitter release is triggered by elevation of Ca2+ concentration at a Ca2+ sensor of the release machinery. The Ca2+ concentration at the release site at the given time point is determined by Ca2+ dynamics within presynaptic terminal. It depends on a source of Ca2+ (usually voltage-gated Ca2+ channels), diffusional distance between the source of Ca2+ and the Ca2+ sensor and Ca2+ buffering by endogenous Ca2+ buffers. In many synapses transmitter release can be enhanced (facilitated) during repetitive activity of neurons. The main source of facilitation is activity-dependent increase of Ca2+ concentration at the release site. Several mechanisms of facilitation have been proposed, namely, accumulation of residual Ca2+, multi-site (X receptor) mechanism and partial Ca2+ buffer saturation mechanism. In this review we discuss theoretical and experimental evidence in favor of one or the other of proposed mechanisms.
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Affiliation(s)
- Nail Burnashev
- Department of Experimental Neurophysiology, Faculty of Earth and Life Sciences, CNCR, Vrije Universiteit Amsterdam, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands.
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100
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Bannister AP. Inter- and intra-laminar connections of pyramidal cells in the neocortex. Neurosci Res 2005; 53:95-103. [PMID: 16054257 DOI: 10.1016/j.neures.2005.06.019] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Revised: 06/06/2005] [Accepted: 06/28/2005] [Indexed: 11/28/2022]
Abstract
The flow of excitation through cortical columns has long since been predicted by studying the axonal projection patterns of excitatory neurones situated within different laminae. In grossly simplified terms and assuming random connectivity, such studies predict that input from the thalamus terminates primarily in layer 4, is relayed 'forward' to layer 3, then to layers 5 and 6 from where the modified signal may exit the cortex. Projection patterns also indicate 'back' projections from layer 5 to 3 and layer 6 to 4. More recently it has become clear that the interconnections between these layers are not random; forward projections primarily contact specific pyramidal subclasses and intracortical back projections innervate interneurones. This indicates that presynaptic axons or postsynaptic dendrites are capable of selecting their synaptic partners and that this selectivity is layer dependent. For the past decade, we and others have studied pyramidal cell targeting in circuits both within, and between laminae using paired intracellular recordings with biocytin filling and have begun to identify further levels of selectivity through the preferential targeting of electrophysiologically and/or morphologically distinct pyramidal subtypes. Presented here, therefore, is a brief overview of current thinking on the layer and subclass specific connectivity of neocortical principle excitatory cells.
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Affiliation(s)
- A Peter Bannister
- Department of Pharmacology, The School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK.
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