- Email: [email protected]
Modelling the interactions of ongoing brain activity and transcranial magnetic stimulation of the motor cortex
Abstracts / Brain Stimulation 10 (2017) 346e540
TMS to the primary motor cortex with a figure-of-8-coil. EMG was recorded from the right dorsal interosseus muscle I. We employed TMS paired pulse protocols with interstimulus intervals of 3 ms, 10 ms and 100 ms to test short interval intracortical inhibition (SICI), intracortical facilitation (ICF) and long interval intracortical inhibition (LICI) in relation to a single pulse. Results: Neither inhibition (SICI: t(65)¼0,70, p ¼ 0,49; LICI: t(65) ¼ -0,03, p ¼ 0,98) nor facilitation (ICF: t(65) ¼ 1,27, p ¼ 0,21) differed between ASD and the control group. Discussion: We could not confirm alterations of cortical inhibition or facilitation in ASD compared to typically developing controls. Our results do not support a generally abnormal E-I-balance in ASD. Discrepancies with previous TMS experiments reporting reduced SICI in adults with ASD may be due to differences in the studied populations. Specifically, as our sample consisted of children and adolescents developmental effects may play a role. Reduced SICI may only be present in subgroups of ASD. Keywords: Autism Spectrum Disorder, TMS, Inhibition
483
[0568] THE EFFICACY OF PAIRED-ASSOCIATIVE STIMULATION FOR INDUCING NEUROPLASTICITY IN MOTOR CORTEX OF HEALTHY INDIVIDUALS: A QUALITATIVE REVIEW
based on Simulink. A sliding window of data is used to estimate the sources that give rise to the EEG signal using a spatial filter computation executed on the processor as the signal is acquired. The forward model is computed based on the MRI data using a FEM model to solve the forward problem. The leadfields are calculated using the neuronavigated electrode positions and then they are employed to compute the real-time LCMV beamforming. Instantaneous phase is estimated at multiple source-level location simultaneously using parallel sliding windows of band-pass filtered data preceding the current time, each extended into the future in real-time using autoregressive model, with instantaneous phase estimated using a Hilbert transform. Results: A latency of < 1 millisecond is achieved in estimating the phase at source level with custom real-time software. A validation study with healthy individuals shows that the instantaneous phase of three distinctly localized brain areas within the motor network both intra- and interhemispherically can be estimated in real-time with reliable accuracy. Discussion: A novel technique enabling TMS triggered by the instantaneous phase-state of the individual network is presented. This is a significant extension of the current state-of-the-art and could enable the development of more effective personalized closed-loop neuromodulatory stimulation protocols. Keywords: Closed Loop TMS, Real-Time Stimulation, Source Localization, EEG Beamforming
M. Minkovich*1, R. Zomorrodi 1, 2, Y. Noda 1, 2, D.M. Blumberger 1, 2, Z.J. Daskalakis 1, 2, T.K. Rajji 1. 1 Centre for Addiction and Mental Health, Canada; 2 University of Toronto, Canada
[0570] MODELLING THE INTERACTIONS OF ONGOING BRAIN ACTIVITY AND TRANSCRANIAL MAGNETIC STIMULATION OF THE MOTOR CORTEX
Introduction: Paired associative stimulation (PAS) is a transcranial magnetic stimulation (TMS) paradigm that assesses neuroplasticity in the human cortex. PAS consists of pairing peripheral nerve stimulation (PNS) with a subsequent TMS repeatedly over the primary motor cortex (M1). To date, PAS is known to be among the most robust methods to induce neuroplasticity in the cerebral cortex. However, inter-individual variabilities in PAS response are well known. This review aims to systematically synthesize the literature on PAS parameters and confounding factors that have significant influences in the induction of neuroplasticity. Methods: PubMed, ProQuest and OVID (2000-2016) were searched under the set terms. Two authors reviewed each article and came to consensus on the inclusion and exclusion criteria. All eligible studies were reviewed, duplicates were removed, and data were extracted individually. Only 52 articles met the criteria. Results: Various factors appear to have significant impact on PAS effects: attention, time of day (i.e., morning vs. afternoon session), exercise, age, pharmacological manipulations (i.e., GABA, Glut and Ca2+channel agonist/ antagonist), biological factors (i.e., cortical thickness), recent synaptic history (i.e., PAS and another brain stimulation paradigm), anatomical location (i.e., ipsi/contra lateral), method of measurement (i.e., absolute or logarithmic ratio of amplitudes), and PAS parameters (i.e., TMS and PNS intensity, interval and number of pulses). Discussion: Significant methodological variability in PAS protocols limits the ability to generalize conclusions. Further research is needed to standardize PAS administration, minimize its variation, and individualize it based on subjects’ specific characteristics. Keywords: TMS, paired associative stimulation, review, efficacy
N. Schaworonkow*, J. Triesch. Frankfurt Institute for Advanced Studies, Germany
[0569] REAL-TIME SOURCE-LEVEL EEG NETWORK ACTIVITY STATE TRIGGERED TMS WITH MILLISECOND RESOLUTION P. Belardinelli*, D. Desideri, C. Zrenner, U. Ziemann. University Hospital of Tuebingen, Germany Introduction: Closed-loop methods that trigger the TMS pulse based on the EEG signal are increasingly available. However, current systems rely on data of a small number of channels and the signal at sensor level cannot be localized in a specific brain area. The challenge is to analyze a sufficient number of EEG channels in real-time to enable spatially localized estimation of individual brain network activity. Methods: EEG data is acquired using a high-density TMS compatible recording system and streamed online to a real-time digital processing system
Introduction: Variability of responses to transcranial magnetic stimulation greatly limits its applicability in a clinical setting. Several recent TMSEEG studies have shown a dependency of TMS responses on features of brain activity at stimulation onset. Here, we investigate the interaction of background activity and stimulation pulses in a TMS I-wave model and test for systematic effects of triggering the TMS pulse with respect to different features of a background oscillatory rhythm. Methods: The circuit model consists of multi-compartmental layer 5 cells each receiving input from 300 excitatory and inhibitory layer 2/3 point neurons, which receive oscillatory input. TMS is modeled as a current injection; the pulse onset was varied with respect to oscillatory background activity phase, for different levels of oscillatory power. We use single-pulse and paired-pulse stimulation, and vary inter-stimulus intervals (ISIs). Results: The model shows systematic modulation of layer 5 firing rate depending on the phase at which the TMS pulse is applied, as well as a systematic effect on amplitude and number of Iwaves. The largest response is elicited when layer 5 neurons are close to depolarized state, with the difference between peak and trough response regulated by stimulation intensity. Also depending on pulse strength, amplitude and latency of Iwaves is modulated by the level of background activity at TMS pulse onset, due to short-term synaptic depression. Our model reproduces the physiological paired-pulse result that short ISIs between the two pulses lead to a depression and long ISIs lead to a facilitation of I-wave amplitudes. But when considering individual phases, a differential pattern arises, due to the influence of ongoing activity on synaptic short-term depression. Discussion: Our network model including oscillatory background activity reveals interactions between TMSresponses and background activity and can parsimoniously explain how cortical rhythms contribute to the variability of TMS effects. Keywords: TMS, modeling, I-waves, variability [0573] DORSOLATERAL PREFRONTAL CORTEX TMS REDUCES COCAINE USE: A PILOT STUDY A. Terraneo*, L. Leggio, M. Saladinie, M. Ermanie, A. Bonci, L. Gallimberti. 1 IRCCS, Italy; 2 National Institute of Drug Abuse, USA Background: Recent animal studies demonstrate that compulsive cocaine seeking strongly reduces prelimbic frontal cortex activity, while optogenetic stimulation of this brain area significantly inhibits compulsive
TMS to the primary motor cortex with a figure-of-8-coil. EMG was recorded from the right dorsal interosseus muscle I. We employed TMS paired pulse protocols with interstimulus intervals of 3 ms, 10 ms and 100 ms to test short interval intracortical inhibition (SICI), intracortical facilitation (ICF) and long interval intracortical inhibition (LICI) in relation to a single pulse. Results: Neither inhibition (SICI: t(65)¼0,70, p ¼ 0,49; LICI: t(65) ¼ -0,03, p ¼ 0,98) nor facilitation (ICF: t(65) ¼ 1,27, p ¼ 0,21) differed between ASD and the control group. Discussion: We could not confirm alterations of cortical inhibition or facilitation in ASD compared to typically developing controls. Our results do not support a generally abnormal E-I-balance in ASD. Discrepancies with previous TMS experiments reporting reduced SICI in adults with ASD may be due to differences in the studied populations. Specifically, as our sample consisted of children and adolescents developmental effects may play a role. Reduced SICI may only be present in subgroups of ASD. Keywords: Autism Spectrum Disorder, TMS, Inhibition
483
[0568] THE EFFICACY OF PAIRED-ASSOCIATIVE STIMULATION FOR INDUCING NEUROPLASTICITY IN MOTOR CORTEX OF HEALTHY INDIVIDUALS: A QUALITATIVE REVIEW
based on Simulink. A sliding window of data is used to estimate the sources that give rise to the EEG signal using a spatial filter computation executed on the processor as the signal is acquired. The forward model is computed based on the MRI data using a FEM model to solve the forward problem. The leadfields are calculated using the neuronavigated electrode positions and then they are employed to compute the real-time LCMV beamforming. Instantaneous phase is estimated at multiple source-level location simultaneously using parallel sliding windows of band-pass filtered data preceding the current time, each extended into the future in real-time using autoregressive model, with instantaneous phase estimated using a Hilbert transform. Results: A latency of < 1 millisecond is achieved in estimating the phase at source level with custom real-time software. A validation study with healthy individuals shows that the instantaneous phase of three distinctly localized brain areas within the motor network both intra- and interhemispherically can be estimated in real-time with reliable accuracy. Discussion: A novel technique enabling TMS triggered by the instantaneous phase-state of the individual network is presented. This is a significant extension of the current state-of-the-art and could enable the development of more effective personalized closed-loop neuromodulatory stimulation protocols. Keywords: Closed Loop TMS, Real-Time Stimulation, Source Localization, EEG Beamforming
M. Minkovich*1, R. Zomorrodi 1, 2, Y. Noda 1, 2, D.M. Blumberger 1, 2, Z.J. Daskalakis 1, 2, T.K. Rajji 1. 1 Centre for Addiction and Mental Health, Canada; 2 University of Toronto, Canada
[0570] MODELLING THE INTERACTIONS OF ONGOING BRAIN ACTIVITY AND TRANSCRANIAL MAGNETIC STIMULATION OF THE MOTOR CORTEX
Introduction: Paired associative stimulation (PAS) is a transcranial magnetic stimulation (TMS) paradigm that assesses neuroplasticity in the human cortex. PAS consists of pairing peripheral nerve stimulation (PNS) with a subsequent TMS repeatedly over the primary motor cortex (M1). To date, PAS is known to be among the most robust methods to induce neuroplasticity in the cerebral cortex. However, inter-individual variabilities in PAS response are well known. This review aims to systematically synthesize the literature on PAS parameters and confounding factors that have significant influences in the induction of neuroplasticity. Methods: PubMed, ProQuest and OVID (2000-2016) were searched under the set terms. Two authors reviewed each article and came to consensus on the inclusion and exclusion criteria. All eligible studies were reviewed, duplicates were removed, and data were extracted individually. Only 52 articles met the criteria. Results: Various factors appear to have significant impact on PAS effects: attention, time of day (i.e., morning vs. afternoon session), exercise, age, pharmacological manipulations (i.e., GABA, Glut and Ca2+channel agonist/ antagonist), biological factors (i.e., cortical thickness), recent synaptic history (i.e., PAS and another brain stimulation paradigm), anatomical location (i.e., ipsi/contra lateral), method of measurement (i.e., absolute or logarithmic ratio of amplitudes), and PAS parameters (i.e., TMS and PNS intensity, interval and number of pulses). Discussion: Significant methodological variability in PAS protocols limits the ability to generalize conclusions. Further research is needed to standardize PAS administration, minimize its variation, and individualize it based on subjects’ specific characteristics. Keywords: TMS, paired associative stimulation, review, efficacy
N. Schaworonkow*, J. Triesch. Frankfurt Institute for Advanced Studies, Germany
[0569] REAL-TIME SOURCE-LEVEL EEG NETWORK ACTIVITY STATE TRIGGERED TMS WITH MILLISECOND RESOLUTION P. Belardinelli*, D. Desideri, C. Zrenner, U. Ziemann. University Hospital of Tuebingen, Germany Introduction: Closed-loop methods that trigger the TMS pulse based on the EEG signal are increasingly available. However, current systems rely on data of a small number of channels and the signal at sensor level cannot be localized in a specific brain area. The challenge is to analyze a sufficient number of EEG channels in real-time to enable spatially localized estimation of individual brain network activity. Methods: EEG data is acquired using a high-density TMS compatible recording system and streamed online to a real-time digital processing system
Introduction: Variability of responses to transcranial magnetic stimulation greatly limits its applicability in a clinical setting. Several recent TMSEEG studies have shown a dependency of TMS responses on features of brain activity at stimulation onset. Here, we investigate the interaction of background activity and stimulation pulses in a TMS I-wave model and test for systematic effects of triggering the TMS pulse with respect to different features of a background oscillatory rhythm. Methods: The circuit model consists of multi-compartmental layer 5 cells each receiving input from 300 excitatory and inhibitory layer 2/3 point neurons, which receive oscillatory input. TMS is modeled as a current injection; the pulse onset was varied with respect to oscillatory background activity phase, for different levels of oscillatory power. We use single-pulse and paired-pulse stimulation, and vary inter-stimulus intervals (ISIs). Results: The model shows systematic modulation of layer 5 firing rate depending on the phase at which the TMS pulse is applied, as well as a systematic effect on amplitude and number of Iwaves. The largest response is elicited when layer 5 neurons are close to depolarized state, with the difference between peak and trough response regulated by stimulation intensity. Also depending on pulse strength, amplitude and latency of Iwaves is modulated by the level of background activity at TMS pulse onset, due to short-term synaptic depression. Our model reproduces the physiological paired-pulse result that short ISIs between the two pulses lead to a depression and long ISIs lead to a facilitation of I-wave amplitudes. But when considering individual phases, a differential pattern arises, due to the influence of ongoing activity on synaptic short-term depression. Discussion: Our network model including oscillatory background activity reveals interactions between TMSresponses and background activity and can parsimoniously explain how cortical rhythms contribute to the variability of TMS effects. Keywords: TMS, modeling, I-waves, variability [0573] DORSOLATERAL PREFRONTAL CORTEX TMS REDUCES COCAINE USE: A PILOT STUDY A. Terraneo*, L. Leggio, M. Saladinie, M. Ermanie, A. Bonci, L. Gallimberti. 1 IRCCS, Italy; 2 National Institute of Drug Abuse, USA Background: Recent animal studies demonstrate that compulsive cocaine seeking strongly reduces prelimbic frontal cortex activity, while optogenetic stimulation of this brain area significantly inhibits compulsive