Post on 07-Apr-2018
tCS and EEG
1
Faranak Farzan, PhD
Assistant Professor, Simon Fraser University
Chair in Technology Innovations for Youth Addiction Recovery and Mental Health
Email: ffarzan@sfu.ca
Guess Game: Maximum Voltage a Torpedo Fish Can Generate?
http://www.painbytes.com/images/History/Electroanalgesia/EAFig.png
8 to 220 volts
Where Did It All Begin?
46 AD
Torpedo Fish
3
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Galvanism
Charles Le Roy
Treating blind with
electricity
1755
Luigi Galvani
Late 18th century
founder of
bioelectromagnetics
famous for his animal
experiments
46 AD Late 1700s
Galvani
Le Roy
4
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Aldini’s Showmanship
DC current stimulation mostly ignored in scientific community
Giovanni Aldini
1804: First report of electricity for
treating psychosis and melancholia
46 AD Late 1700s
Galvani
Le Roy
Galvanism
5
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6
1934
ECT
1980
TES
1985
TMS
2000
tDCS
46 AD Late 1700s
Galvani
Le Roy
1800s
Faraday
D’Arsonval
1900s
Thompson
Kolin
1982
Anthony Barker
Reza Jalinous
Ian Freeston
MST
2000
Today…
2008
tACs
Nitsche
Paulus
Antal
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tCS Application
• Basic & Cognitive Neuroscience
• Intervene with a function to examine causality
• Clinical Application• Depression
• Pain
• Addiction
• ADHD Do Not
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tCS Outcome?
20 ms
1 m
V
Latency
Peak-to-Peak
AmplitudeMotor Evoked
Potentials
Nitsche & Paulus, 2000: Changes in cortical excitability in humans demonstrated using TMS Motor-Evoked Potentials (MEP)s as a metric
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tCS Outcome?Nitsche et al, 2003: After 5 or 7 minutes of stimulation MEP amplitudes
return to baseline within a few minutes. After 9 minutes, effects last for at least 60 minutes.
20 ms
1 m
V
Latency
Peak-to-Peak
AmplitudeMotor Evoked
Potentials
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Kuo et al, 2012: 4x1 ring tDCS stimulates a
smaller area, but the
resulting change in cortical
excitability is dramatically
different
20 ms
1 m
V
Latency
Peak-to-Peak
AmplitudeMotor Evoked
Potentials
tCS Outcome?
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tCS Outcome Depends on Many Factors
• Stimulation Parameters
• Duration of stimulation
• Number of electrodes
• Electrode size and shape
• Electrode positions
• Current intensity
• Brain State Do Not
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We know relatively little about the neurophysiologicalmechanisms in humans; little we know about local effect, andmuch less about the network effect; Difficulty tailoring itsparameters for desired impact.
Brain Recording to Rescue?
tCS-Induced Outcomes?
20 ms
1 m
V
Latency
Peak-to-Peak
AmplitudeMotor Evoked
Potentials
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Brain Recording? EEG, fMR, PET, DTI, …
EPSP + IPSP generated bysynchronous activity ofneurons. Interplay betweenexcitatory pyramidal neuronsand inhibitory interneurons.
http://www.nature.com/scitable/content/ion-channels-14615258
A change in membranepotential, release ofneurotransmitters, change inconcentration of ions channelsmay change the state ofmembrane channels and giverise to an oscillatory activity.
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Added Value of tCS+EEG
1- Detailed understanding of the tCS-induced effect on neural activityo To not fall for the “circular experimental results/conclusions”o Examine both local and network effects in humans, non-invasively
2- Monitor brain stateo Brain state influences the tCS effecto Improve tCS protocols considering brain state dynamicso By monitoring dynamical state, design closed-loop systems
3- Guide the tCS input parameters o An infinite number of stimulation parameters to choose fromo Guide the Location, Stimulation Parameters, Time of Delivery
EEG may tell us about: Excitability of cortical tissue; excitation/inhibition balance; brain state; the integrity of local
and distributed networks.
More efficacious treatmentsBetter understanding of brain-behavior relationship
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TCS + EEG
Retrieved from: http://3.bp.blogspot.com/_-sFohRgxOBI/RiH4NDo37zI/AAAAAAAAAG8/ZwS5CBfB3qI/
s320/Married+couple+fighting.jpg
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tCS+EEG Approaches
• Offline
• Online
• EEG-Guided (Online or Offline)
Record EEG(Rest/+Event)
Stop EEGApply tCS
Stop tCSRecord EEG
(Rest/+Event)
Record EEG(Rest/+Event)
Record EEG&
Apply tCS
Stop tCSRecord EEG
(Rest/+Event)
Record EEG(Rest/+Event)
Apply tCSguided by
EEG
Stop tCSRecord EEG
(Rest/+Event)
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EEG language
Amplitude (or Power)
Frequency
Phase
# of Cycles/Second (Hz)
Strength
(µV or µV2)
10Hz
20Hz
π0
(Radians)
F
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When/How to Record EEG?
• Anesthesia, • Sleep• Resting (eyes open/closed)
• Sensory, motor, cognitive processing
Continuous Recording (No Event)
Trial 1
Trial 2
Trial 100
Event/Stimulus
Time: Event Related Potential or Evoked potentialsFrequency: Event Related Spectral Perturbation
Phase
Relative to An Event/Stimulation
• Electrical stimulation
F
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EEG Features
(2) Connectivity
(1) Local
Response
12
3
1 2 3
Θ
(3) Global Dynamic
Adapted from Khanna A, Pascual-
Leone A, Farzan F, 2014
Adapted from Shafi et al., 2012
26
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tCS Outcomes: Local Effects
Continuous EEG Recording (No Event)
Jacobson et al., 2012Montage: Anodal rIFG, cathodal lOFC tDCsResting EEG: Selective decrease of theta band
Zaehle., 2012 (EEG-guided)Montage: Posterior tACs at individual alpha oscillationsResting EEG: Increase in alpha in parieto-central electrodes
Change in PowerP
ow
er
Frequency (Hz)
10 20 30 40 50
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EEG + Event
50 ms
20
µV
Change in ERP
Change in ERSP or ERD/ERS
Keeser et al., 2011 • Montage: Anodal tDCS on LDLPFC, cathode on contralateral supraorbital region • EEG Rest: Reduced left frontal delta, source analysis localized this to ACC and orbitofrontal regions• EEG+ Working Memory: Increased P2 and P3 ERP amplitudes• Performance: Reduced error rates in working memory
tCS Outcomes: Local Effects
Matsumoto et al., 2010• Montage: Anodal/cathodal tDCS on MC• EEG+ Motor Imagery: Mu rhythms ERD increased after anodal tDCS
Zaehle., 2011• Montage: anodal or cathodal left DLPFC tDCS• EEG+ Working Memory: Enhanced performance and amplified oscillatory power in the theta and alpha bands after anodal tDCS
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tCS Outcomes: Network Effects
Polania et al, Human Brain Mapping 2011• M1 anodal + contralateral frontopolar cathodal stimulation
• shifted brain network connectivity at rest and especially during task performance
Sham (before vs after)Sham vs active
Real (before vs after)
Gamma during voluntary hand movementDo N
ot Cop
y
tCS Outcomes: Network Effects
Polania et al, Human Brain Mapping 2011• M1 anodal + contralateral frontopolar cathodal stimulation shifted brain
network connectivity at rest and especially during task performance
Beta
Pre
Post
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50 ms
20 µ
V
5 ms
20 µ
V
20 ms
1
mV
Cortical
Evoked
Potentials
Descending
Volleys
Motor Evoked
Potentials
I1 I4D
P30
N100
Latency
Peak-to-Peak
Amplitude
TMS Pulse
Magnetic
Field
32
TMS-EEG
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Inhibition, Connectivity, Plasticity, …
Farzan et al., 2013, NeuroImage
Neural inhibition
Neural inhibition
Motor DLPF
C
Farzan et al., 2009, Neuropsychopharmacology
Voineskos*, Farzan *et al., 2010. Biological Psychiatry
Interhemispheric connectivity
Inhibition mediated modulation
of oscillations
Daskalakis, Farzan et al., 2008, Neuropsychopharmacology
M1 DLPFCMarkersLICIMC
LICIDLPFC
MarkersISPMC
ISPDLPFC
MarkersLICIMCδ
,LICIDLPFCδLICIMCΘ
,LICIDLPFCΘLICIMCα
,LICIDLPFCαLICIMCβ
,LICIDLPFCβLICIMC
,LICIDLPFC
MarkersTEPAmp
TEPDur
TEPPeaks
TEPPower
GMFAAMP
GMFADur
GMFAPeaks
GMFAPower33
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34Farzan F et al., Frontiers in Neural Circuits , 2016
TMS-EEG in extracting Markers of Health
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tCS Outcomes: TMS-EEG
Bai, 2017
Differential changes in tDCS-induced
cortical excitability in MCS and VS.
50 ms
20 µ
V
Cortical
Evoked
Potentials
P30
N100
Magnetic
Field
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tCS Outcomes: TMS-EEG
Hill, 2017
HD tDCS induced changes in P60.
50 ms
20 µ
V
Cortical
Evoked
Potentials
P30
N100
Magnetic
Field
P60
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EEG-Guided Input Location
Faria 2012EEG evaluation of a patient
with continuous spike-wave
discharges during slow-wave
sleep allowed identification of
a spike focus.
Cathodal tDCS over the spike
focus resulted in a significant
decrease in interictal spikes
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EEG-Guided Frequency of tACs
Zaehle., 2012Montage: Posterior tACs at individual alpha oscillationsResting EEG: Increase in alpha in parieto-central electrodes
EEG-Guided
Po
we
r
Frequency (Hz)
10 20 30 40 50
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EEG-Guided Input Time
Polania et al., 2012 Protocol: 6Hz tACs at 0 or 180 phase difference to frontal and parietal regions during taskResult: Exogenously induced fronto-parietal theta synchronization (0 degrees) significantly improved visual memory-matching reaction times. Desyncronization (180 degree) deteriorated performance. Brain-Behavior Relationship: Evidence of causality of theta phase-coupling of distant cortical areas for cognitive performance in healthy humans
Fronto-Parietal Theta-Phase coupling during a delayed letter discrimination task
F3
P3
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Cancelli et al, 2016Simple ad hoc approaches achieved reasonable targeting for the case of a cortical
dipole. Only 2–8 electrodes and no need for a model of the head
Verified directly only for a theoretically localized source, but may be
potentially applied to an arbitrary EEG topography. Can be applied to static (tDCS),
time-variant (e.g., tACS, tRNS, tPCS), or closed-loop tES
EEG-Guided tCS
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EEG-Guided tCS
Dmochowski, 2017
Optimal use of EEG for targeting tCS (e.g., determine montage)
without making assumptions about the underlying source
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Closed-Loop Studies in Animal
Berenyi et al, 2012: In a rodent model of generalized epilepsy, detection of
interictal spikes triggers TES, and aborts the spike-wave discharge bursts
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Technical Issues
Challenges:
o Placement of EEG and tCS Electrodes
o Current may be shunted through EEG electrodes
o Stimulation artifact
• tDCS: A DC drift and maybe rhythmic frequencies
• tACs: Rhythmic frequencies that coincide with the frequency of cortical oscillations
Record EEG(Rest/+Event)
Stop EEGApply tES Stop tES
Record EEG (Rest/+Event)Record EEG
&Apply tES
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Previous Online Studies
tDCS:• Same kind of sintered AgCl electrodes for DC stimulation as for EEG recording• Current delivered through Phoresor 850 current source• 3 Anodes (Fp1, FpZ, FP1 electrodes shorted)• 1 Cathode (CP5 electrodes)
F
Faria et al., 2012
EEG: • 24 Electrodes • Ground and reference electrodes placed contralateral to the stimulation site on the mastoid area
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Online Studies
Record EEGRecord EEG
&Apply tCS
Faria et al., 2012
Artifact correction can significantly remove the noise
Artifact Correction• Software package developed for removing gradient artifacts in the MRI environment• Independent component analysis (ICA)
Artifact• High frequency artifact in the neighborhood of cathode • Small AC component with a 12Hz multiple• period characteristics of the Phoresor 850
functioning
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Sehm et al., 2013
Online Studies
• SEPs were recorded in the bore of the tDCS ring electrode. • no tDCS-induced artifacts could be observed after the application of a standard EEG filter.
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online studies
Witkowski, 2016: tACs + MEG
- Amplitude-modulated tACs using a carrier frequency well beyond the frequencies of
interest (e.g. 220 Hz) and modulates the amplitude of the carrier frequency at the
frequency of interest (e.g., 23 Hz).
- Amplitude-modulated high-frequency tACs may enable the artefact-free assessment of the lower frequency of interest
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http://fc01.deviantart.net/fs70/f/2012/015/a/7/an
gry_eye_by_sawsa-d4meu5q.jpg
http://sci-ence.org/wp-content/uploads/2011/07/Sensory-
Homunculus1.jpg
Problems Solutions
AmplifierSaturation
• Pin-and-Hold• High Sensitivity, Operational
Range • DC-Coupling, High Sampling
Rate
Electrode Heating• Small Pellet Electrodes
• Plastic interface
Eddy Current • Sensor placement
Capacitor Recharge
• Proper Setting in Biphasic
Movement • Sensor-wire Arrangement
Capacitance Built up, Slow Decay
• Algorithmically
Auditory Evoked Potentials
• Ear plugs, • Play Noise
• Sham•Algorithmically**
Blinks •Algorithmically**
Muscle • Algorithmically
SEP • Subthreshold Control
Somatosensory • Spatial topographies http://www.staceyreid.com/news/wp-
content/uploads/2011/09/Muscles.png52
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Matthew Frehlich
Masters of
Engineering
University of
Toronto
Sravya Atluri
PhD
Biomedical
Engineering
University of
Toronto
TMS-EEG Software Development
Frank Mei
Postdoc
Electrical
Engineering
Luis G. Dominguez
Postdoc
Physics53
Atluri et al., 2016, Frontiers in Neural
Circuits
Nigel Rogasch, PhD
Monash University, Australia
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TMS-EEG Software TMSEEG App
Matthew Frehlich
Masters of Engineering
University of Toronto
Sravya Atluri
PhD
Biomedical
Engineering
University of
TorontoFrank Mei
Postdoc
Electrical
Engineering
Luis G. Dominguez
Postdoc
Physics54
Atluri et al., 2016, Frontiers in Neural
Circuits
Nigel Rogasch, PhD
School of Psychological Sciences
and Monash Biomedical Imaging
Monash University, Australia
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TCS + EEG
Retrieved from: http://3.bp.blogspot.com/_-sFohRgxOBI/RiH4NDo37zI/AAAAAAAAAG8/ZwS5CBfB3qI/
s320/Married+couple+fighting.jpg
RECAP
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Added Value of tCS+EEG
1- Detailed understanding of the tCS-induced effect on neural activityo To not fall for the “circular experimental results/conclusions”o Examine both local and network effects in humans, non-invasively
2- Monitor brain stateo Brain state influences the tCS effecto Improve tCS protocols considering brain state dynamicso By monitoring dynamical state, design closed-loop systems
3- Guide the tCS input parameters o An infinite number of stimulation parameters to choose fromo Guide the Location, Stimulation Parameters, Time of Delivery
EEG may tell us about: Excitability of cortical tissue; excitation/inhibition balance; brain state; the integrity of local
and distributed networks.
More efficacious treatmentsBetter understanding of brain-behavior relationship
Do Not
Copy