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Kallioniemi E, Awiszus F, Pitkänen M, Julkunen P. Fast acquisition of resting motor threshold with a stimulus-response curve - Possibility or hazard for transcranial magnetic stimulation applications? Clin Neurophysiol Pract 2022; 7:7-15. [PMID: 35024510 PMCID: PMC8733273 DOI: 10.1016/j.cnp.2021.10.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 09/15/2021] [Accepted: 10/05/2021] [Indexed: 11/24/2022] Open
Abstract
Objective Previous research has suggested that transcranial magnetic stimulation (TMS) related cortical excitability measures could be estimated quickly using stimulus-response curves with short interstimulus intervals (ISIs). Here we evaluated the resting motor threshold (rMT) estimated with these curves. Methods Stimulus-response curves were measured with three ISIs: 1.2-2 s, 2-3 s, and 3-4 s. Each curve was formed with 108 stimuli using stimulation intensities ranging from 0.75 to 1.25 times the rMTguess, which was estimated based on motor evoked potential (MEP) amplitudes of three scout responses. Results The ISI did not affect the rMT estimated from the curves (F = 0.235, p = 0.683) or single-trial MEP amplitudes at the group level (F = 0.90, p = 0.405), but a significant subject by ISI interaction (F = 3.64; p < 0.001) was detected in MEP amplitudes. No trend was observed which ISI was most excitable, as it varied between subjects. Conclusions At the group level, the stimulus-response curves are unaffected by the short ISI. At the individual level, these curves are highly affected by the ISI. Significance Estimating rMT using stimulus-response curves with short ISIs impacts the rMT estimate and should be avoided in clinical and research TMS applications.
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Key Words
- APB, abductor pollicis brevis
- EMG, electromyography
- ISI, interstimulus interval
- Interstimulus interval
- MEP, motor evoked potential
- MRI, magnetic resonance imaging
- MSO, maximum stimulator output
- Motor evoked potential
- Motor threshold
- SI, stimulation intensity
- Stimulus-response curve
- TMS, transcranial magnetic stimulation
- rMT, resting motor threshold
- rMTRR, resting motor threshold estimated with the Rossini-Rothwell method
- rMTestimate, resting motor threshold estimated with stimulus–response curves
- rMTguess, resting motor threshold estimated with prior information and three scout pulses
- rMTthreshold, resting motor threshold estimated with the threshold-hunting method
- rMTtrue, true resting motor threshold in simulations
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Affiliation(s)
- Elisa Kallioniemi
- Department of Psychiatry, UT Southwestern Medical Center, Dallas, TX, United States
| | - Friedemann Awiszus
- Neuromuscular Research Group at the Department of Orthopaedics, Otto-von-Guericke University, Magdeburg, Germany
| | - Minna Pitkänen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Petro Julkunen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.,Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland
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Bihemispheric sensorimotor oscillatory network states determine cortical responses to transcranial magnetic stimulation. Brain Stimul 2021; 15:167-178. [PMID: 34896304 DOI: 10.1016/j.brs.2021.12.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 12/05/2021] [Accepted: 12/07/2021] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Brain responses to external stimuli vary with fluctuating states of neuronal activity. Previous work has demonstrated effects of phase and power of the ongoing local sensorimotor μ-alpha-oscillation on responses to transcranial magnetic stimulation (TMS) of motor cortex (M1). However, M1 is part of a distributed network, and the effects of oscillatory activity in this network on TMS-evoked EEG responses (TEPs) have not been explored. OBJECTIVES To determine the effects of oscillatory activity in the bihemispheric sensorimotor network on TEPs. METHODS 31 healthy subjects received single-pulse TMS of the left M1 hand area during EEG recording. Ongoing bihemispheric sensorimotor cortex oscillatory states were reconstructed from the EEG directly preceding TMS, and inferred by a data-driven method combining a multivariate autoregressive model and a Hidden Markov model. TEP amplitudes (P25, N45, P70, N100 and P180) were then compared between different bihemispheric sensorimotor cortex oscillatory states. RESULTS Four bihemispheric sensorimotor cortex oscillatory states were identified, with different interhemispheric expressions of theta and alpha oscillations. High alpha-power states in the stimulated sensorimotor cortex increased P25 amplitude. Alpha power in the alpha-alpha state (stimulated - non-stimulated hemisphere) correlated in both hemispheres with N45 amplitude. Theta power in the alpha-theta state correlated in the non-stimulated hemisphere with P70 amplitude. CONCLUSIONS Bihemispheric sensorimotor cortex oscillatory states contribute to TEPs, with a relevance shift from stimulated to non-stimulated M1 from P25 over N45 to P70. This significantly extends previous findings: not only ongoing local oscillations but distributed network oscillatory states determine cortical responsiveness to external stimuli.
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Hassanzahraee M, Zoghi M, Jaberzadeh S. Longer Transcranial Magnetic Stimulation Intertrial Interval Increases Size, Reduces Variability, and Improves the Reliability of Motor Evoked Potentials. Brain Connect 2020; 9:770-776. [PMID: 31744309 DOI: 10.1089/brain.2019.0714] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
High rates of variability in the amplitude of transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs), a popular method for assessing corticospinal excitability (CSE), make it essential to examine inherent reliability of the MEP amplitude. We aimed to investigate the effects of different intertrial intervals (ITIs) of single-pulse TMS on the amplitude, variability, and test-retest reliability of MEPs. Twenty-five TMS single pulses were recorded at four different ITIs of 5, 10, 15, and 20 sec from 15 healthy participants who attended two experimental sessions. Repeated measures analysis of variance (rmANOVA) and standardized z-value standard deviations (SDs) were used to investigate the effects of ITIs on MEP amplitudes and variability. Test-retest reliability of MEP amplitudes was also assessed using rmANOVA and intraclass correlation (ICC). rmANOVA revealed significantly larger MEP amplitudes following ITIs of 10, 15, and 20 sec compared with ITI 5, with no significant increases between ITIs of 15 and 20 sec. Standardized z-value SDs revealed variability rate reduction following longer ITIs with significant reductions occurring following ITIs of 10, 15, and 20 sec compared with ITI 5 with no significant difference between ITIs of 15 and 20 sec. rmANOVA showed no significant Time main effect on the MEP changes confirming within- and between-session agreement. ICCs reported significant within- and between-session reliability in all selected ITIs. The findings of the current study indicate that longer ITIs up to 15 sec can significantly induce larger MEPs with lower variability and higher reliability. The increase in ITIs not only reduces the chance of TMS-induced changes in CSE but also helps us to use this assessment tool in studies with smaller sample sizes.
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Affiliation(s)
- Maryam Hassanzahraee
- Noninvasive Brain Stimulation and Neuroplasticity Laboratory, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Melbourne, Australia
| | - Maryam Zoghi
- Department of Rehabilitation, Nutrition and Sport, School of Allied Health, La Trobe University, Melbourne, Australia
| | - Shapour Jaberzadeh
- Noninvasive Brain Stimulation and Neuroplasticity Laboratory, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Melbourne, Australia
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4
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Fresnoza S, Christova M, Feil T, Gallasch E, Körner C, Zimmer U, Ischebeck A. The effects of transcranial alternating current stimulation (tACS) at individual alpha peak frequency (iAPF) on motor cortex excitability in young and elderly adults. Exp Brain Res 2018; 236:2573-2588. [PMID: 29943239 PMCID: PMC6153871 DOI: 10.1007/s00221-018-5314-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 06/14/2018] [Indexed: 11/28/2022]
Abstract
Transcranial alternating current stimulation (tACS) can modulate brain oscillations, cortical excitability and behaviour. In aging, the decrease in EEG alpha activity (8–12 Hz) in the parieto-occipital and mu rhythm in the motor cortex are correlated with the decline in cognitive and motor functions, respectively. Increasing alpha activity using tACS might therefore improve cognitive and motor function in the elderly. The present study explored the influence of tACS on cortical excitability in young and old healthy adults. We applied tACS at individual alpha peak frequency for 10 min (1.5 mA) to the left motor cortex. Transcranial magnetic stimulation was used to assess the changes in cortical excitability as measured by motor-evoked potentials at rest, before and after stimulation. TACS increased cortical excitability in both groups. However, our results also suggest that the mechanism behind the effects was different, as we observed an increase and decrease in intracortical inhibition in the old group and young group, respectively. Our results indicate that both groups profited similarly from the stimulation. There was no indication that tACS was more effective in conditions of low alpha power, that is, in the elderly.
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Affiliation(s)
- Shane Fresnoza
- Institute of Psychology, University of Graz, Graz, Austria. .,Institute of Physiology, Medical University of Graz, Graz, Austria.
| | - Monica Christova
- Otto Loewi Research Center, Physiology Section, Medical University of Graz, Graz, Austria.,Department of Physiotherapy, University of Applied Sciences FH-Joanneum Graz, Graz, Austria
| | - Theresa Feil
- Institute of Psychology, University of Graz, Graz, Austria
| | - Eugen Gallasch
- Institute of Physiology, Medical University of Graz, Graz, Austria.,BioTechMed, Graz, Austria
| | - Christof Körner
- Institute of Psychology, University of Graz, Graz, Austria.,BioTechMed, Graz, Austria
| | - Ulrike Zimmer
- Institute of Psychology, University of Graz, Graz, Austria.,Faculty of Human Sciences, Medical School Hamburg (MSH), Hamburg, Germany
| | - Anja Ischebeck
- Institute of Psychology, University of Graz, Graz, Austria.,BioTechMed, Graz, Austria
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Pellicciari MC, Veniero D, Miniussi C. Characterizing the Cortical Oscillatory Response to TMS Pulse. Front Cell Neurosci 2017; 11:38. [PMID: 28289376 PMCID: PMC5326778 DOI: 10.3389/fncel.2017.00038] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 02/07/2017] [Indexed: 12/15/2022] Open
Affiliation(s)
| | - Domenica Veniero
- Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of GlasgowGlasgow, UK
| | - Carlo Miniussi
- Cognitive Neuroscience Section, IRCCS Centro San Giovanni di Dio FatebenefratelliBrescia, Italy
- Center for Mind/Brain Sciences - CIMeC, University of TrentoRovereto, Italy
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6
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Noh NA. Exploring Cortical Plasticity and Oscillatory Brain Dynamics via Transcranial Magnetic Stimulation and Resting-State Electroencephalogram. Malays J Med Sci 2016; 23:5-16. [PMID: 27660540 DOI: 10.21315/mjms2016.23.4.2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 04/21/2016] [Indexed: 01/08/2023] Open
Abstract
Transcranial magnetic stimulation (TMS) is a non-invasive, non-pharmacological technique that is able to modulate cortical activity beyond the stimulation period. The residual aftereffects are akin to the plasticity mechanism of the brain and suggest the potential use of TMS for therapy. For years, TMS has been shown to transiently improve symptoms of neuropsychiatric disorders, but the underlying neural correlates remain elusive. Recently, there is evidence that altered connectivity of brain network dynamics is the mechanism underlying symptoms of various neuropsychiatric illnesses. By combining TMS and electroencephalography (EEG), the functional connectivity patterns among brain regions, and the causal link between function or behaviour and a specific brain region can be determined. Nonetheless, the brain network connectivity are highly complex and involve the dynamics interplay among multitude of brain regions. In this review article, we present previous TMS-EEG co-registration studies, which explore the functional connectivity patterns of human cerebral cortex. We argue the possibilities of neural correlates of long-term potentiation/depression (LTP-/LTD)-like mechanisms of synaptic plasticity that drive the TMS aftereffects as shown by the dissociation between EEG and motor evoked potentials (MEP) cortical output. Here, we also explore alternative explanations that drive the EEG oscillatory modulations post TMS. The precise knowledge of the neurophysiological mechanisms underlying TMS will help characterise disturbances in oscillatory patterns, and the altered functional connectivity in neuropsychiatric illnesses.
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Affiliation(s)
- Nor Azila Noh
- Department of Medical Science I, Faculty of Medicine and Health Sciences, Universiti Sains Islam Malaysia, Pandan Indah, 55100 Kuala Lumpur, Malaysia
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7
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Farzan F, Vernet M, Shafi MMD, Rotenberg A, Daskalakis ZJ, Pascual-Leone A. Characterizing and Modulating Brain Circuitry through Transcranial Magnetic Stimulation Combined with Electroencephalography. Front Neural Circuits 2016; 10:73. [PMID: 27713691 PMCID: PMC5031704 DOI: 10.3389/fncir.2016.00073] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 09/07/2016] [Indexed: 12/18/2022] Open
Abstract
The concurrent combination of transcranial magnetic stimulation (TMS) with electroencephalography (TMS-EEG) is a powerful technology for characterizing and modulating brain networks across developmental, behavioral, and disease states. Given the global initiatives in mapping the human brain, recognition of the utility of this technique is growing across neuroscience disciplines. Importantly, TMS-EEG offers translational biomarkers that can be applied in health and disease, across the lifespan, and in humans and animals, bridging the gap between animal models and human studies. However, to utilize the full potential of TMS-EEG methodology, standardization of TMS-EEG study protocols is needed. In this article, we review the principles of TMS-EEG methodology, factors impacting TMS-EEG outcome measures, and the techniques for preventing and correcting artifacts in TMS-EEG data. To promote the standardization of this technique, we provide comprehensive guides for designing TMS-EEG studies and conducting TMS-EEG experiments. We conclude by reviewing the application of TMS-EEG in basic, cognitive and clinical neurosciences, and evaluate the potential of this emerging technology in brain research.
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Affiliation(s)
- Faranak Farzan
- Temerty Centre for Therapeutic Brain Intervention, Centre for Addiction and Mental Health, University of Toronto Toronto, ON, Canada
| | - Marine Vernet
- Berenson-Allen Center for Non-invasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School Boston, MA, USA
| | - Mouhsin M D Shafi
- Berenson-Allen Center for Non-invasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School Boston, MA, USA
| | - Alexander Rotenberg
- Berenson-Allen Center for Non-invasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical SchoolBoston, MA, USA; Neuromodulation Program, Department of Neurology, Boston Children's Hospital, Harvard Medical SchoolBoston, MA, USA
| | - Zafiris J Daskalakis
- Temerty Centre for Therapeutic Brain Intervention, Centre for Addiction and Mental Health, University of Toronto Toronto, ON, Canada
| | - Alvaro Pascual-Leone
- Berenson-Allen Center for Non-invasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School Boston, MA, USA
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8
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Fedele T, Blagovechtchenski E, Nazarova M, Iscan Z, Moiseeva V, Nikulin VV. Long-Range Temporal Correlations in the amplitude of alpha oscillations predict and reflect strength of intracortical facilitation: Combined TMS and EEG study. Neuroscience 2016; 331:109-19. [DOI: 10.1016/j.neuroscience.2016.06.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 06/03/2016] [Accepted: 06/09/2016] [Indexed: 12/01/2022]
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9
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Resting state brain dynamics and its transients: a combined TMS-EEG study. Sci Rep 2016; 6:31220. [PMID: 27488504 PMCID: PMC4973226 DOI: 10.1038/srep31220] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 07/14/2016] [Indexed: 11/08/2022] Open
Abstract
The brain at rest exhibits a spatio-temporally rich dynamics which adheres to systematic behaviours that persist in task paradigms but appear altered in disease. Despite this hypothesis, many rest state paradigms do not act directly upon the rest state and therefore cannot confirm hypotheses about its mechanisms. To address this challenge, we combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) to study brain's relaxation toward rest following a transient perturbation. Specifically, TMS targeted either the medial prefrontal cortex (MPFC), i.e. part of the Default Mode Network (DMN) or the superior parietal lobule (SPL), involved in the Dorsal Attention Network. TMS was triggered by a given brain state, namely an increase in occipital alpha rhythm power. Following the initial TMS-Evoked Potential, TMS at MPFC enhances the induced occipital alpha rhythm, called Event Related Synchronisation, with a longer transient lifetime than TMS at SPL, and a higher amplitude. Our findings show a strong coupling between MPFC and the occipital alpha power. Although the rest state is organized around a core of resting state networks, the DMN functionally takes a special role among these resting state networks.
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10
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Ongoing cumulative effects of single TMS pulses on corticospinal excitability: An intra- and inter-block investigation. Clin Neurophysiol 2016; 127:621-628. [DOI: 10.1016/j.clinph.2015.03.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 03/04/2015] [Accepted: 03/09/2015] [Indexed: 11/20/2022]
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Transcranial focused ultrasound modulates intrinsic and evoked EEG dynamics. Brain Stimul 2014; 7:900-8. [PMID: 25265863 DOI: 10.1016/j.brs.2014.08.008] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 08/26/2014] [Accepted: 08/27/2014] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND The integration of EEG recordings and transcranial neuromodulation has provided a useful construct for noninvasively investigating the modification of human brain circuit activity. Recent evidence has demonstrated that focused ultrasound can be targeted through the human skull to affect the amplitude of somatosensory evoked potentials and its associated spectral content. OBJECTIVE/HYPOTHESIS The present study tests whether focused ultrasound transmitted through the human skull and targeted to somatosensory cortex can affect the phase and phase rate of cortical oscillatory dynamics. METHODS A computational model was developed to gain insight regarding the insertion behavior of ultrasound induced pressure waves in the human head. The instantaneous phase and phase rate of EEG recordings before, during, and after transmission of transcranial focused ultrasound (tFUS) to human somatosensory cortex were examined to explore its effects on phase dynamics. RESULTS Computational modeling results show the skull effectively reinforces the focusing of tFUS due to curvature of material interfaces. Neurophysiological recordings show that tFUS alters the phase distribution of intrinsic brain activity for beta frequencies, but not gamma. This modulation was accompanied by a change in phase rate of both beta and gamma frequencies. Additionally, tFUS modulated phase distributions in the beta band of early sensory-evoked activity but did not affect late sensory-evoked activity, lending support to the spatial specificity of tFUS for neuromodulation. This spatial specificity was confirmed through an additional experiment where the ultrasound transducer was moved 1 cm laterally from the original cortical target. CONCLUSIONS Focused ultrasonic energy can alter EEG oscillatory dynamics through local mechanical perturbation of discrete cortical circuits.
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Kelso JAS, Dumas G, Tognoli E. Outline of a general theory of behavior and brain coordination. Neural Netw 2013; 37:120-31. [PMID: 23084845 PMCID: PMC3914303 DOI: 10.1016/j.neunet.2012.09.003] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 09/01/2012] [Accepted: 09/02/2012] [Indexed: 11/30/2022]
Abstract
Much evidence suggests that dynamic laws of neurobehavioral coordination are sui generis: they deal with collective properties that are repeatable from one system to another and emerge from microscopic dynamics but may not (even in principle) be deducible from them. Nevertheless, it is useful to try to understand the relationship between different levels while all the time respecting the autonomy of each. We report a program of research that uses the theoretical concepts of coordination dynamics and quantitative measurements of simple, well-defined experimental model systems to explicitly relate neural and behavioral levels of description in human beings. Our approach is both top-down and bottom-up and aims at ending up in the same place: top-down to derive behavioral patterns from neural fields, and bottom-up to generate neural field patterns from bidirectional coupling between astrocytes and neurons. Much progress can be made by recognizing that the two approaches--reductionism and emergentism--are complementary. A key to understanding is to couch the coordination of very different things--from molecules to thoughts--in the common language of coordination dynamics.
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Affiliation(s)
- J A Scott Kelso
- Human Brain & Behavior Laboratory, Center for Complex Systems & Brain Sciences, Florida Atlantic University, Boca Raton, FL 33435, USA.
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13
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Stamoulis C, Gruber LJ, Schomer DL, Chang BS. High-frequency neuronal network modulations encoded in scalp EEG precede the onset of focal seizures. Epilepsy Behav 2012; 23:471-80. [PMID: 22410338 PMCID: PMC3320023 DOI: 10.1016/j.yebeh.2012.01.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 12/30/2011] [Accepted: 01/08/2012] [Indexed: 11/29/2022]
Abstract
Modulations of neuronal network interactions by seizure precursors are only partially understood and difficult to measure, in part due to inherent intra- and inter-patient seizure heterogeneities and EEG variability. This study investigated preictal neuromodulations associated with seizures originating in the temporal and/or frontal lobes, using information theoretic parameters estimated from awake scalp EEGs in two frequency ranges, ≤100 Hz and >100 Hz, respectively. Seizure-related activity at high frequencies has not been extensively estimated in awake scalp EEGs. Based on the statistical similarity of preictal and ictal information parameters, preictal network interactions appeared to be specifically modulated at frequencies >100 Hz, but not at lower frequencies. The dynamics of these parameters varied distinctly according to the origin of seizure onset (temporal versus frontal). Although preliminary, and based on a small patient sample for which the potential heterogeneity of multiple anticonvulsive medications was difficult to control, these results suggest that preictal modulations may be estimated from high-frequency scalp EEGs using directional information measures with high specificity to ictal events, and may thus be promising for improving seizure prediction.
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Affiliation(s)
| | - Lawrence J. Gruber
- Beth Israel Deaconess Medical Center, Department of Neurology, Boston MA
| | - Donald L. Schomer
- Harvard Medical School,Beth Israel Deaconess Medical Center, Department of Neurology, Boston MA
| | - Bernard S. Chang
- Harvard Medical School,Beth Israel Deaconess Medical Center, Department of Neurology, Boston MA
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