| CTRI Number |
CTRI/2026/04/108519 [Registered on: 16/04/2026] Trial Registered Prospectively |
| Last Modified On: |
15/04/2026 |
| Post Graduate Thesis |
No |
| Type of Trial |
Interventional |
|
Type of Study
|
Other (Specify) [Transcranial electrical stimulation] |
| Study Design |
Randomized, Crossover Trial |
|
Public Title of Study
|
Role of theta brain stimulation on working memory performance |
|
Scientific Title of Study
|
Causal role of parietal theta activity in working memory: An HD-tACS and EEG study comparing individualized vs. standardized theta stimulation |
| Trial Acronym |
NIL |
|
Secondary IDs if Any
|
| Secondary ID |
Identifier |
| NIL |
NIL |
|
|
Details of Principal Investigator or overall Trial Coordinator (multi-center study)
|
| Name |
Suriya Prakash Muthukrishnan |
| Designation |
Associate Professor |
| Affiliation |
All India Institute of Medical Sciences, New Delhi |
| Address |
Room 6019, Department of Physiology, Convergence Block, AIIMS, New Delhi.
South
DELHI
110029
India |
| Phone |
9650812987 |
| Fax |
|
| Email |
dr.suriyaprakash@aiims.edu |
|
Details of Contact Person
Scientific Query
|
| Name |
Suriya Prakash Muthukrishnan |
| Designation |
Associate Professor |
| Affiliation |
All India Institute of Medical Sciences, New Delhi |
| Address |
Room 6019, Department of Physiology, Convergence Block, AIIMS, New Delhi.
South
DELHI
110029
India |
| Phone |
9650812987 |
| Fax |
|
| Email |
dr.suriyaprakash@aiims.edu |
|
Details of Contact Person
Public Query
|
| Name |
Suriya Prakash Muthukrishnan |
| Designation |
Associate Professor |
| Affiliation |
All India Institute of Medical Sciences, New Delhi |
| Address |
Room 6019, Department of Physiology, Convergence Block, AIIMS, New Delhi.
South
DELHI
110029
India |
| Phone |
9650812987 |
| Fax |
|
| Email |
dr.suriyaprakash@aiims.edu |
|
|
Source of Monetary or Material Support
|
| All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India, 110029. |
|
|
Primary Sponsor
|
| Name |
Suriya Prakash Muthukrishnan |
| Address |
Room 6019, Department of Physiology, Convergence Block, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India, 110029. |
| Type of Sponsor |
Other [SELF] |
|
|
Details of Secondary Sponsor
|
|
|
Countries of Recruitment
|
India |
|
Sites of Study
|
| No of Sites = 1 |
| Name of Principal
Investigator |
Name of Site |
Site Address |
Phone/Fax/Email |
| Suriya Prakash M |
All India Institute of Medical Sciences, New Delhi |
Room 6019, Department of Physiology, Convergence Block, AIIMS, New Delhi.
South
DELHI |
09650812987
dr.suriyaprakash@aiims.edu |
|
|
Details of Ethics Committee
|
| No of Ethics Committees= 1 |
| Name of Committee |
Approval Status |
| Institute Ethics Committee, All India Institute of Medical Sciences, New Delhi |
Approved |
|
|
Regulatory Clearance Status from DCGI
|
|
|
Health Condition / Problems Studied
|
| Health Type |
Condition |
| Healthy Human Volunteers |
N: 60
Inclusion criteria
• Healthy participants
• 19-40 years
• Male and female participants
• Right-handed
• Able to perform the required computer task
• Corrected visual acuity should be 6/6
|
|
|
Intervention / Comparator Agent
|
| Type |
Name |
Details |
| Intervention |
Real Standardized theta tACS protocol (Group 1), Real Individualized theta tACS protocol (Group 2). |
Each participant will undergo two experimental sessions: one involving real HD-tACS and the other sham stimulation in a counterbalanced, single-blind crossover design. A 2-weeks interval will separate the two sessions. Each session will be for 30 minutes. Total duration of intervention will be 1 hour (30 mins x 2 sessions).
Real Standardized theta tACS protocol: Participants will undergo 30 minutes of 4 Hz theta transcranial alternating current stimulation (tACS) at 2 mA, with stimulation targeting left parietal brain region (P3).
Real Individualized theta tACS protocol: Participants will undergo 30 minutes of individualized theta transcranial alternating current stimulation (tACS) at 2 mA, with stimulation targeting left parietal brain region (P3). Individualized theta frequency will be derived by subtracting 5 Hz from each participants individual alpha peak frequency (IAF) (Jaušovec et al., 2014). IAF will be computed by averaging peak alpha frequencies across all EEG electrodes during an eyes-closed resting-state EEG. |
| Comparator Agent |
Sham Standardized theta tACS protocol (Group 1), Sham Individualized theta tACS protocol (Group 2) |
Sham Standardized theta tACS protocol: Participants in this group will receive 2 mA 4 Hz theta tACS over P3 for 15 seconds (5-s ramp-up to 2 mA, 5-s plateau at 2 mA, 5-s ramp-down to 0 mA) at both the start and the end of each 30-minute session. During the 30-minute session, there is no stimulation occurring between the initial 15-second tACS at the sessions onset and the 15-second tACS at the sessions end. This sham protocol has been observed to elicit a skin sensation that is virtually indistinguishable from the skin sensation elicited by active tES protocols.
Sham Individualized theta tACS protocol: Participants in this group will receive 2 mA individualized theta tACS over P3 for 15 seconds (5-s ramp-up to 2 mA, 5-s plateau at 2 mA, 5-s ramp-down to 0 mA) at both the start and the end of each 30-minute session. During the 30-minute session, there is no stimulation occurring between the initial 15-second tACS at the sessions onset and the 15-second tACS at the sessions end.
|
|
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Inclusion Criteria
|
| Age From |
19.00 Year(s) |
| Age To |
40.00 Year(s) |
| Gender |
Male |
| Details |
1. Healthy participants
2. Age: between 19-40 years
3. Sex: Male participants
4. Right-handed (assessed using the Edinburgh Handedness Inventory)
5. Able to perform the required computer task
6. Written informed consent
7. Corrected visual acuity should be 6/6
|
|
| ExclusionCriteria |
| Details |
1. History of psychiatric disorders
2. History of neurological diseases
3. History of substance abuse
4. History of chronic physical illness
5. Patients with metal implants
6. Patients with implanted electronic device
|
|
|
Method of Generating Random Sequence
|
Permuted block randomization, fixed |
|
Method of Concealment
|
On-site computer system |
|
Blinding/Masking
|
Participant Blinded |
|
Primary Outcome
|
| Outcome |
TimePoints |
To evaluate the effects of theta frequency HD-tACS over left parietal region on working memory:
WM storage capacity will be measured using span scores from the Corsi and Digit Span tasks.
Executive function will be assessed using accuracy scores from the n-back task and visuospatial working memory task. |
Time points: Outcome will be assessed at baseline (pre-intervention) and Day 0 (immediately after intervention).
Each participant will undergo two experimental sessions: one involving real HD-tACS and the other sham stimulation in a counterbalanced, single-blind crossover design. 2 weeks interval will separate 2 sessions. |
|
|
Secondary Outcome
|
| Outcome |
TimePoints |
| Secondary outcome measures are functional brain connectivity & complex network measures - To investigate the neurophysiological mechanisms underlying tACS-induced effects (Objective 3) |
Time points: Outcome will be assessed at baseline (pre-intervention) & Day 0 (immediately after intervention).
Each participant will undergo two experimental sessions: one involving real HD-tACS & the other sham stimulation in a counterbalanced, single-blind crossover design. 2 weeks interval will separate 2 sessions. |
|
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Target Sample Size
|
Total Sample Size="60"
Sample Size from India="60"
Final Enrollment numbers achieved (Total)= "Applicable only for Completed/Terminated trials"
Final Enrollment numbers achieved (India)="Applicable only for Completed/Terminated trials" |
|
Phase of Trial
|
Phase 2 |
|
Date of First Enrollment (India)
|
01/05/2026 |
| Date of Study Completion (India) |
Applicable only for Completed/Terminated trials |
| Date of First Enrollment (Global) |
Date Missing |
| Date of Study Completion (Global) |
Applicable only for Completed/Terminated trials |
|
Estimated Duration of Trial
|
Years="3"
Months="0"
Days="0" |
|
Recruitment Status of Trial (Global)
|
Not Yet Recruiting |
| Recruitment Status of Trial (India) |
Not Yet Recruiting |
|
Publication Details
|
N/A |
|
Individual Participant Data (IPD) Sharing Statement
|
Will individual participant data (IPD) be shared publicly (including data dictionaries)?
Response - NO
|
|
Brief Summary
|
Working memory (WM) refers to the
cognitive system responsible for the temporary storage and manipulation of
information, either recently perceived or retrieved from long-term memory. WM
engages a distributed fronto-parietal network, particularly dorsolateral
prefrontal cortex (DLPFC) for central executive control of WM, and left
intraparietal area (LIP) for amodal or multimodal storage of information.
Theta oscillations (4–7 Hz) are
known to facilitate synchronization across brain regions and serve as a gating
mechanism for optimal WM. Our research group found that theta oscillations in
specific brain networks, particularly involving parietal cortices, are
implicated in the formation of working memory traces during encoding,
reinforcing the notion that WM formation is a rate-limiting process underlying
memory capacity limit (Muthukrishnan et al., 2020).
In recent years, noninvasive
brain stimulation techniques such as transcranial electrical stimulation (tES)
have become valuable tools for modulating brain activity and investigating
causal mechanisms of cognition. Most studies targeting WM have applied tES,
particularly anodal tDCS or tACS over left DLPFC to enhance executive
functions. However, stimulation of parietal regions remains less explored,
despite evidence supporting their involvement in WM.
A previous study found that
individualized theta tACS over left parietal area (P3) enhanced WM storage,
while frontal stimulation showed no effect, highlighting the causal role of
parietal theta activity. Similarly, another study reported improved WM with
standard theta (4 Hz) tACS over parietal cortex. These findings support the use
of HD-tACS over parietal brain regions (P3) at theta frequency to enhance WM by
entraining endogenous rhythms.
The current study aims to evaluate
to compare the effects of individualized parietal theta tACS and standardized
tACS on WM performance. We hypothesize that transcranial electrical stimulation
of parietal regions will enhance working memory storage and that individualized
theta-frequency tACS will produce greater improvements in cognitive performance
than standardized theta stimulation. The study objectives are: (1) to assess
the efficacy of theta frequency HD-tACS over left parietal region in improving
working memory performance relative to sham stimulation, (2) to compare
cognitive outcomes between stimulation at standardized theta frequency (4 Hz)
and individualized theta frequency, (3) to investigate the neurophysiological
mechanisms underlying tACS-induced effects using EEG.
The proposed study findings will have implications for
optimizing noninvasive cognitive enhancement strategies in both healthy and
clinical populations. In addition, this study will provide causal evidence for
the parietal cortex’s role in WM storage by examining how theta-frequency tACS
modulates endogenous oscillations in WM-relevant networks, offering mechanistic
insights into neural entrainment and its correlation with cognitive
enhancement. |