Direct Current Stimulation (HD-tDCS)

High-Definition transcranial
Direct Current Stimulation
(HD-tDCS)
Marom Bikson
Lucas Parra, Jacek Dmochowski,
Asif Rahman, Dennis Truong,
Abhishek Datta, Davide Reato,
Belen Lafon, Gregory Kronberg,
Thomas Radman
Department of Biomedical Engineering, The City College
of New, New York, NY
$ NIH (NINDS, NCI), NSF, Epilepsy FoundaDon, Wallace
Coulter FoundaDon, DoD (USAF, AFOSR)

Disclosure:
Soterix Medical Inc. produces tDCS and High-Defini=on
tDCS. Marom Bikson is co- founder of Soterix Medical.
Some of the clinical data presented may be supported by
Soterix Medical.
The City University of New York has patents on tDCS and
High-Defini=on tDCS with Marom Bikson as inventor.
tDCS and HD-tDCS are regulated as inves=ga=onal
devices in the USA.

Transcranial Direct Current S=mula=on (tDCS)
• Non-invasive, portable, well-tolerated.
• Low-intensity (~2 mA) current passed
between scalp electrodes (~20 min).
• For rehabiliaDon, neuropsychiatric
treatment, neuroenhacment.
Ø Can a “simple” interven=on modulate brain func=on?
Ø How is specificity of ac=on achieved?

Neuromodula=on: Electrotherapy Delivery PlaRorms
Deep Brain
S=mula=on (invasive)
Transcranial Magne=c
S=mula=on
transcranial Direct
Current Stimulation
C
B
A
Decreasing Cost
Decreasing Risk
Increasing Efficacy, Specificity
• Deployable, compact
• Minimal supervision
• Adverse events:
itching, erythema
• IRB / FDA “NSR”
? tDCS Specificity

What makes tDCS specific?
Given the diversity of tDCS applica=on spanning neuropsychiatric
treatment, rehabilita=on, and learning in healthy individuals.
• Anatomical targe=ng (specificity)
The control of tDCS electrode placement to
guide current flow to brain targets
Design facilitated by current flow models.
• Func=onal targe=ng (specificity)
The use of tDCS adjunct to behavioral / cogniDve
training to facilitate the outcomes of training.
Design facilitated by animal models of plasDcity. ?

Anatomical targeting with tDCS
• “Conventional” tDCS varies the
position of two large electrodes.
• Montage specific effects
on behavior and
neurophysiology well
documented.
• “Shaping” outcomes vs
“targeting” brain regions.
ConvenDonal bipolar large electrodes

Anatomical targeting with tDCS
ConvenDonal bipolar large electrodes

Anatomical targeting with tDCS
High-DefiniDon electrodes in “4x1” configuraDon
Datta et. al. Brain Stim 2009
ConvenDonal bipolar large electrodes

Non-invasive targeting while maintaining
tolerability and deployable advantages.

Anatomical targeting with tDCS
High-DefiniDon electrodes in “4x1” configuraDon
Datta et. al. Brain Stim 2009
Dmochowski Neural Engr. 2011

Anatomical targeting with tDCS
High-DefiniDon electrodes in “4x1” configuraDon
Datta et. al. Brain Stim 2009
Dmochowski Neural Engr. 2011
OpDmized tDCS is a “closed” problem
But “best” montage different for:
a) Maximum intensity at target.
b) Focality (minimizing relaDve
intensity outside of target).

Anatomical targeting with tDCS
Consider a three-electrode setup
Dmochowski Neural Engr. 2011
Bikson Brain Stim. 2014
1 mA
1 mA
I 1
I 2
E 1 E 2 I 1 E 1 +I 2 E 2
1) Linearity of Lead-Fields
+ 2) “Quasi-Uniform Assumption”: Region E α Neuromodulation

Anatomical targeting with tDCS
Dmochowski Neural Engr. 2011
Bikson Brain Stim. 2014
E 1
I 1
E
E 2
I 2
Σ
E M
I M
Optimization algorithm
S I = E
Linear optimized is “closed” problem: real-time,
individualized, and subject to any constraints

Customized targeting with tDCS
Super-obese
Obesity / Craving / AddicDon
Pediatric
Epilepsy / ADHD / CP
Stroke
RehabilitaDon
(motor, aphasia)
Truong Neuroimage 2013
Datta Brain Stimulation 2011
Dmochowski Neuroimage 2013
Kessler PLoS ONE 2013
Gillick Frontiers 2014

tDCS mechanisms: Neuromodula=on
High-intensity Pulses
Low-intensity DC
Over-driving a
neural network
NeuromodulaDon comes from
secondary non-linear changes

tDCS mechanisms: Neuromodula=on
High-intensity Pulses
Low-intensity DC
Over-driving a
neural network

tDCS mechanisms: Neuromodula=on
High-intensity Pulses
Low-intensity DC
Over-driving a
neural network

tDCS mechanisms: Neuromodula=on
High-intensity Pulses
Over-driving a
neural network
Low-intensity DC
InteracDng with
specific acDvity
in a neural
network
(NeuromodulaDon)

Anatomical targeting with brain stimulation
Supra-threshold
s=mula=on
Up / down stream
and axons of
passage stimulated.
Circuit.
DBS M1s TMS
Sub-threshold
s=mula=on
Stimulation primary
neuromodulation
target. Endogenous
circuit.
• “Quasi-Uniform” HD-tDCS assumption: 4x1 Neuromodulation is
linear with local electric field magnitude. Bikson Brain Stim 2010

From Anatomical Targe=ng to Func=onal Targe=ng
Network of interest (e.g.
depression, math cells)
Other networks – not targets
for neuromodula=on
Preferen=al modula=on
of more ac=ve network
(ac=vity dependent)
Current flow across en=re
region

What makes tDCS specific?
Given the diversity of tDCS applica=on spanning neuropsychiatric
treatment, rehabilita=on, and learning in healthy individuals.
• Anatomical targe=ng (specificity)
The control of tDCS electrode placement to
guide current flow to brain targets
Design facilitated by current flow models.
Treats eact
region by
sliding scale
-
+
• Func=onal targe=ng (specificity)
The use of tDCS adjunct to behavioral / cogniDve
training to facilitate the outcomes of training.
Design facilitated by animal models of plasDcity. ?
Ac=vity-
Dependent

The theory of Func=onal Targe=ng
How could weights helps
with so many sports?
It’s a tool to enhance
specific training.
How could Electroceuticals
(tDCS) treat many disorders?
It’s tool to enhance cognitive
training and therapy.

The theory of Func=onal Targe=ng

The theory of Func=onal Targe=ng
How does tDCS just enhance
the trained task?
+
Cellular mechanism:
Functional Selectivity
Bikson et. al. Front Human Neuro 2013

Biophysical basis of tDCS func=onal selec=vity
1 tDCS produces a sustained weak
polariza=on of neuronal membranes
2 Weak polariza=on modulates
synap=c efficacy and plas=city

Biophysical basis of tDCS func=onal selec=vity
1 tDCS produces a sustained weak
polariza=on of neuronal membranes
2 Weak polariza=on modulates
synap=c efficacy

Direct Current

tDCS: Sustained weak polariza=on
Brain slice: Optical Mapping with Voltage Sensitive Dyes
Bikson J Physiol. 2004

tDCS: Sustained weak polariza=on
Brain slice: Optical Mapping with Voltage Sensitive Dyes
DC On
Direct Current
(~ 0.2 mV)
Bikson J Physiol. 2004

Biophysical basis of tDCS func=onal selec=vity
1 tDCS produces a sustained weak
polariza=on of neuronal membranes
2 Weak polariza=on modulates
synap=c efficacy

Biophysical basis of tDCS func=onal selec=vity
1 tDCS produces a sustained weak
polariza=on of neuronal membranes
2 Weak polariza=on modulates
synap=c efficacy

Biophysical basis of tDCS func=onal selec=vity
Theta-burst plasDcity session, no tDCS
Theta-burst session plasDcity session with tDCS
Theta-burst
session
Accelerated plasDcity
when tDCS is present

Biophysical basis of tDCS func=onal selec=vity
Theta-burst plasDcity session, no tDCS
Theta-burst session plasDcity session with tDCS
Theta-burst
session
Theta-burst
session
Theta-burst
session
Theta-burst
session
Boosted maximum
plasDcity

Biophysical basis of tDCS func=onal selec=vity

High-Definition transcranial
Direct Current Stimulation
(HD-tDCS)
Marom Bikson
Lucas Parra, Jacek Dmochowski,
Asif Rahman, Dennis Truong,
Abhishek Datta, Davide Reato,
Belen Lafon, Gregory Kronberg,
Thomas Radman
Department of Biomedical Engineering, The City College
of New, New York, NY
$ NIH (NINDS, NCI), NSF, Epilepsy FoundaDon, Wallace
Coulter FoundaDon, DoD (USAF, AFOSR)