stimulation protocols by introducing a uniﬁed representation for various
Keywords: Software architecture, Neuronavigation, Stimulation sequence
planning, Brain-computer interface
LARGE-SCALE EEG NEURAL NETWORK CHANGES IN RESPONSE TO
, Michael Gold
, Christine Schremp
, Shiwen Yuan
, Linda Carpenter
Brown University Warren Alpert Medical
School, Providence, RI, USA;
Butler Hospital, Providence, RI, USA;
University, Providence, RI, USA
Transcranial magnetic stimulation (TMS) likely induces functional con-
nectivity changes in aberrant circuits implicated in depression. Electro-
encephalography (EEG) “microstates”are voltage topographies
hypothesized to represent large-scale resting networks. Canonical micro-
states have recently been proposed as markers for major depressive dis-
order (MDD), but it is not known if or how they change following TMS.
Resting EEG was obtained from 49 patients with MDD before and after six
weeks of daily TMS. Polarity-insensitive modiﬁed k-means clustering was
used to segment EEGs into constituent microstates. Microstates were
localized via sLORETA. Microstate changes over time, and between TMS
responder and non-responder groups, were compared with t-tests. Six
microstates (MS1-MS6) were identiﬁed. Response to TMS was associated
with an increase in occurrence and coverage of MS 2, and decreased
occurrence and coverage of MS 3. Non-responders showed no signiﬁcant
changes in any microstate. Changes in both MS 2 and MS 3 occurrence and
coverage correlated with symptom change. Localization of MS2 suggests
that TMS may upregulate the positive affect “reward”network (improve-
ment in anhedonia) in responders while MS3 localization may represent
diminished inhibitory activity of the frontoparietal network, possibly
related to emergence from the cognitive “fog”of depression.
Keywords: EEG, TMS, Microstates, Networks
A COMPUTATIONAL COMPARISON OF THE ELECTRICAL FIELDS INDUCED
BY ELECTRODE MONTAGE TYPES FOR TRANSCRANIAL DIRECT CURRENT
STIMULATION eA PRELIMINARY STUDY
Jongseung Lee, TaeYeong Kim, Bongsuk Ko, Donghyeon Kim. Neurophet
Inc, Seoul, Republic of Korea
The tDCS electrode montage, a spatial relationship between anodes and
cathodes, determine the distribution of electric ﬁeld throughout the brain.
This could address the differences between published clinical outcomes of
the tDCS-guided motor recovery. However, a quantitative variation of a
montage-dependent electrical ﬁeld has been rarely investigated.
This study was aimed to qualitatively investigate the difference between
electrical effects of two tDCS montages, especially, the position of a cath-
ode, based on the computational simulation with MRI-derived brain
models in terms of electric ﬁeld.
For this study, twenty head mesh models were reconstructed from the MR
image sets of twenty normal subjects and simulated with the two mon-
tages under the assumption of those brains being post-stroke ones with
right hand motor impairments. The two widely-used montages, using a
pair of conventional 7x5 cm rectangular electrodes, were (M1) anodal
tDCS: anode on C3 and cathode on Fp2, (M2) dual anodal-cathodal tDCS:
C3-C4. The current intensity was 2 mA. The strength of electrical ﬁeld, E(V/
m) and its axial components, E
, and E
, at the ipsilesional primary motor cortices (C3) were compared.
The strengths of the induced electrical ﬁeld at C3 by the two montages
were M1:0.2450±0.0663 and M2:0.2476±0.0578 (mean±sd). There was no
signiﬁcant difference (p¼0.6949). However, the directions of the electrical
ﬁelds were signiﬁcantly different as follows: for E
M2:0.2369±0.0568 (p¼0.0144), for E
M2:0.0247±0.0331 (p<0.0001), and for E
, M1:-0.0649±0.0498, M2:-
0.0191±0.0398 (p¼0.0043). All the statistical analysis was performed with
Wilcoxon rank sum test.
The result of this preliminary study based on the computational simulation
of tDCS demonstrated that the position of a cathode could not affect the
induced electrical ﬁeld at the stimulation site with a ﬁxed anode, but it
could affect the direction of electrical ﬁeld.
Keywords: Computaion Simulation, Computational Modeling, tDCS, tDCS
VASOVAGAL SYNCOPE AS A SPECIFIC SIDE EFFECT OF RTMS: A
FRONTAL-VAGAL DOSE-FINDING STUDY
, Eva Dijkstra
, Iris Van Oostrom
, Alexander Sack
, Hanneke Van Dijk
neuroCare Group, The Netherlands;
Brainclinics, Nijmegen, The Netherlands;
Neurowave, The Netherlands;
Syneada Psycho Medisch Centrum, The Netherlands;
University, Maastricht, The Netherlands;
University of Amsterdam,
Amsterdam, The Netherlands
In the treatment of depression using repetitive Transcranial Magnetic
Stimulation (rTMS), the intensity of stimulatio n is established based on the
motor threshold (MT). Neuro-Cardiac-Guided TMS (NCG-TMS) is a newly
developed method to optimize and individualize target location and to
determine the intensity of treatment. In this method, the frontal threshold
is established by evaluating the effect of stimulation of the DLPFC on heart
rate variability and may be a better proxy for frontal excitability thresh-
olds. In our pilot study (n¼10), aimed at further optimizing NCG-TMS, one
of the subjects experienced a syncope during the stimulation.
In this case 10Hz stimulation (ITI 11 sec) was applied to the left Beam-F3
site in increasing intensities. Intensity was started at a low intensity and
was increased in 5% points of machine output in 7 consequent steps, where
intensity corresponded to 100% of the MT. ECG was measured
simultaneously using a Brainquiry PET EEG device and BioExplorer soft-
ware. ECG data were analyzed ofﬂine using Kubios software.
During the assessment the resting heart rate dropped from 80BPM to
60BPM and HRV increased. The ﬁrst cardiac effects already appeared at a
stimulation intensity of 45% machine output, which represented 75% of the
individual MT. The subject experienced feelings of dizziness and light-
headedness during the stimulation. The HR-data of the subject’s Fitbit
collected over the prior month demonstrated an average HR of 67.6 BPM
and a minimum HR of 65 BPM. This suggests that the DLPFC-rTMS spe-
ciﬁcally induced a HR-deceleration below the subject’s minimum HR.
Presumably, the syncope was caused by overstimulation relative to the
frontal excitability threshold.
This may suggest that vasovagal syncope is a speciﬁc side effect of applying
rTMS over the DLPFC. To avoid unwanted side effects of over stimulation,
future studies should focus on frontal thresholding when applying rTMS.
Keywords: Frontal Thresholding, Syncope, NCG-TMS, rTMS
BRAIN PLASTICITY IN FRONTAL TRAUMATIC BRAIN INJURY.
BIOMARKER OF SEVERIT Y AND INTERVENTION EFFICACY
, Juan Pablo Romero Mu~
, Raquel Viejo-
, Elena M. Marr
Cognitive NeuroLab. Universitat Oberta de
Universidad Francisco de Vitoria, Spain;
Unit. Hospital Beata María Ana, Spain
Traumatic brain injury (TBI) causes severe motor, cognitive and behavioral
symptoms, resulting in chronic disability. Although great efforts are being
made to better understand the nature of this injury and its impact, its
neurophysiological and deﬁcits’recovery are still not well understood.
Brain plasticity assessment provides an objective neurophysiological
measure of brain func tioning in TBI, before and after intervention, being an
Abstracts Brain Stimulation 14 (2021) 1589e1707
excellent biomarker of its efﬁcacy. Plasticity can be assessed in a safe and
non-invasive way by transcranial magnetic stimulation combined with
other neurophysiological techniques, such as electromyogram.
This study aims to deepen the neurophysiological mechanisms associated
with cognitive alterations in TBI and provide a biomarker of neuropsy-
chological intervention efﬁcacy.
A random, crossover, double-blind study will be performed. 84 volunteers
(42 frontal-TBI, 42 healthy) will undergo a neuropsychological assessment
and two experimental conditions to assess brain plasticity at baseline
(continuous -cTBS- and intermittent -iTBS- theta-burst stimulation plus
motor evoked potential assessment -MEP-). TBI patients will undergo the
same assessment after a 3-months neuropsychological intervention.
We expect to ﬁnd: a) more adaptative plasticity measures (i.e., reduction of
MEP after cTBS; increase of MEP after iTBS) in healthy subjects compared
to patients, and plasticity-cognitive performance correlation in both; b)
higher cognitive and functional improvement in patients with more
adaptative plasticity measures in comparison to those with worse mea-
sures at pre-assessment; c) more adaptative post-intervention plasticity
measures in all patients compared to pre-intervention; and d) cognitive
and functional post-intervention improvement correlating to plasticity
changes in patients.
Evaluating brain plasticity, its correlation with cognitive and functional
performance, and their changes in pre/post-intervention will allow to
deepen the brain functioning in TBI. The ﬁnal goal is to contribute to un-
derstanding the neural mechanisms and neuropsychological functioning
in frontal injury and provide an objective biomarker of the neuropsycho-
logical intervention efﬁcacy.
Keywords: Transcranial magnetic stimulation, Plasticity, Traumatic brain
SIMULATION-BASED INVESTIGATION OF THE EFFECT OF THE ROTATION
OF A RECTANGULAR ELECTRODE ON THE ELECTRICAL FIELD AT THE
CENTER OF THE ELECTRODE
, TaeYeong Kim
, Jongseung Lee
Neurophet Inc, Republic of Korea;
Neurophet Inc, Seoul, Republic
Transcranial Direct Current Stimulation (tDCS) is non-invasive brain
stimulation methods that could modulate cortical excitability by elec-
trodes with weak direct current and electric ﬁeld incuded by tDCS heavely
depends on the stimulation conﬁguration(shape, location, angle of elec-
trode). However there is no study to ﬁnd relationship between angle of
electrodes and electric ﬁeld distribution.
In this study, we aimed to ﬁnd relationship between angle of electrodes
and electric ﬁeld distribution and magnitude.
Using 5x7 electrodes that placed over C3/C4 location to stimulate M1
cortex and rotated their angle from 0 degree to 180 degree at 20 degree
intervals with 8 subjects. We measured electric ﬁeld magnitude on the
region of interest (ROI) which below C3 and compared the distribution
There are no signiﬁcant differences in the Enorm peak point value and
location within ROI in 8 samples as changing electrode angles.
Even though the rotation, the magnitude of electric ﬁeld in ROI did not
change signiﬁcantly. However, the peak location of electric ﬁeld magni-
tude changes depending on the angles.
Keywords: Transcranial direct current stimulation, Non-invasive brain
stimulation, Electrode angle, computation simulation
COMPARATIVE EFFECTIVENESS OF MULTISESSION TRANSCRANIAL
DIRECT CURRENT STIMULATION AND PERIPHERAL NERVE
SOMATOSENSORY STIMULATION FOR ENHANCING CORTICOSPINAL
EXCITABILITY AND IMPROVING HAND FUNCTION IN INDIVIDUALS
WITH CHRONIC CERVICAL SPINAL CORD INJURY
Anastasia Zarkou, Jennifer Iddings, Edelle Field-Fote.Shepherd Center,
Atlanta, GA, USA
Objective: Restoration of upper extremity (UE) function is a primary
rehabilitation goal for individuals with cervical spinal cord injury (cSCI).
Transcranial direct current stimulation (tDCS) and peripheral nerve so-
matosensory stimulation (PNSS) have been shown to improve UE function
in persons with cSCI via direct and indirect effects on corticospinal excit-
ability, respectively. However, the effectiveness of multisession application
of these two stimulation modalities has yet to be compared. The goal of
this pragmatic study was to investigate the effectiveness of tDCS, PNSS and
sham-tDCS in individuals with cSCI when utilized as an adjunct to func-
tional task practice (FTP) in a clinical neurorehabilitation setting.
Methods: Individuals with limitations in hand function due to chronic cSCI
(1 year post-injury) participated in 12 one-hour intervention sessions
comprised of FTP combined with stimulation. Participants were randomly
assigned to receive tDCS, PNSS or sham tDCS. Corticospinal excitability
(transcranial magnetic stimulation [TMS] motor evoked potential [MEP]
amplitude) and UE function/sensation (Graded Redeﬁned Assessment of
Strength Sensibility and Prehension [GRASSP]) were measured before and
after the intervention period.
Results and Conclusions: Of the 18 enrolled participants, 15 completed
the study. The application of both tDCS and PNSS as an adjunct to FTP was
feasible in the clinical neurorehabilitation setting. Overall, tDCS and PNSS
were well tolerated. One participant in the tDCS group was discharged
from the study due to occurrence of headaches during the intervention
period; two other participants withdrew for reasons unrelated to the
study. Analyses comparing changes in corticospinal excitability and UE
function/sensation between participants receiving tDCS, PNSS and sham
tDCS are ongoing.
Keywords: tDCS, MEP, tetraplegia, TMS
EFFECT OF NON-INVASIVE NEUROMODULATION ON NEURAL AND
BEHAVIOURAL SIGNATURES OF COGNITIVE CONTROL
, Alek Pogosyan
, Huiling Tan
Nufﬁeld Department of Clinical Neurosciences, University of
Oxford, Oxford, OX3 9DU, Oxford, UK;
MRC Brain Network Dynamics Unit,
University of Oxford, Oxford, OX13TH, UK;
Nufﬁeld Department of Clinical
Neurosciences, University of Oxford, Oxford, OX3 9DU, UK
How quickly and ﬂexibly we respond to unexpected external inputs and
learn from the errors and feedback could be vital for successful navigation
in this world. This cognitive construct referred to as 'cognitive control',
combines response inhibition and conﬂict processing, and plays a vital role
in healthy behaviour and neuropsychiatric disorders such as Parkinson's
disease. Previous research has shown that the medial prefrontal cortex
(mPFC), in conjunction with the subthalamic nucleus (STN), play a vital
role in cognitive control. Endogenous neural rhythms recorded from these
structures correlate with behaviour such as reaction time and accuracy.
Abstracts Brain Stimulation 14 (2021) 1589e1707