Effects of non-invasive brain stimulation on brain activity and brain chemicals in healthy adults

ISRCTN	ISRCTN84570603
DOI	https://doi.org/10.1186/ISRCTN84570603
Sponsor	National Yang Ming Chiao Tung University
Funder	Ministry of Science and Technology, Taiwan

Submission date: 14/05/2026
Registration date: 14/05/2026
Last edited: 14/05/2026

Recruitment status: No longer recruiting
Overall study status: Completed
Condition category: Other

Prospectively registered

Protocol

Statistical analysis plan

Results

Individual participant data

Record updated in last year

Plain English summary of protocol

Not provided at time of registration

Contact information

Prof Li-Hung Chang
Principal investigator, Public, Scientific

No. 155, Sec. 2, Linong St
Taipei City
112
Taiwan

Phone	+886 (0)228267977
Email	lihung@nycu.edu.tw

Study information

Primary study design	Interventional
Allocation	Randomized controlled trial
Masking	Blinded (masking used)
Control	Placebo
Assignment	Parallel
Purpose	Basic science
Scientific title	Effects of intermittent theta burst stimulation compared with sham stimulation on magnetic resonance imaging and neurochemical measures in the visual cortex of healthy adults
Study objectives	This study aimed to systematically evaluate the effects of a single session of standard intermittent theta burst stimulation (iTBS) on the healthy human visual cortex, with a focus on its neurochemical, physiological, and temporal characteristics. Specifically, the objectives were to: 1. Assess neurochemical effects of iTBS: Determine whether iTBS modulates cortical metabolite levels, including Glx and GABA+, measured using magnetic resonance spectroscopy (MRS). 2. Examine changes in excitation/inhibition (E/I) balance: Evaluate whether iTBS alters the Glx/GABA+ ratio as an index of cortical excitatory–inhibitory balance. 3. Evaluate effects on cortical excitability: Investigate changes in cortical excitability using phosphene threshold (PT) measurements. 4. Characterize temporal dynamics of stimulation effects: Assess neurochemical and physiological changes across multiple post-stimulation time points (0.5 h, 3.5 h, and 24 h). 5. Compare expected plasticity effects with prior rTMS findings: Determine whether a single session of iTBS induces measurable plasticity-like effects in the visual cortex, in contrast to previously reported effects of 10 Hz high-frequency rTMS.
Ethics approval(s)	Approved 19/01/2016, Institutional Review Board of National Yang Ming Chiao Tung University (No. 155, Sec. 2, Linong St, Taipei City, 112, Taiwan; +886 (0)228267000; irb.ym@nycu.edu.tw), ref: YM104122E
Health condition(s) or problem(s) studied	Healthy volunteers
Intervention	Participants were randomly assigned to either an intermittent theta burst stimulation (iTBS) group or a sham-control group. The order of active and sham stimulation sessions was counterbalanced across participants using computer-generated randomization. The active stimulation consisted of a single session of standard iTBS delivered over the occipital cortex (visual cortex). The iTBS protocol followed the conventional theta burst pattern, consisting of bursts of high-frequency stimulation (3 pulses at 50 Hz) repeated at 5 Hz (i.e., every 200 ms). Each iTBS train lasted 2 seconds and was repeated every 10 seconds for a total of 20 trains, resulting in 600 pulses in total. Stimulation was delivered at 100% of the participant’s phosphene threshold (PT). Coil positioning was guided and maintained over the visual cortex throughout the session. For the sham-control condition, stimulation was delivered using the sham coil. All participants received only one stimulation session, and all subsequent neurochemical and physiological measurements were conducted at predefined post-stimulation timepoints.
Intervention type	Device
Phase	Not Applicable
Drug / device / biological / vaccine name(s)	Magstim Rapid², 3T Siemens MRI Scanners
Primary outcome measure(s)	1H magnetic resonance spectroscopy (MRS) measured using MRS-derived neurometabolite concentrations at baseline, 0.5 h, 3.5 h, and 24 h after iTBS/sham stimulation TMS-based phosphene threshold (PT) assessment measured using phosphene threshold at baseline and multiple post-stimulation timepoints (0 h, 4.5 h, and 24 h)
Key secondary outcome measure(s)
Completion date	31/10/2020

Eligibility

Participant type(s)
Age group	Adult
Lower age limit	20 Years
Upper age limit	35 Years
Sex	All
Target sample size at registration	30
Total final enrolment	24
Key inclusion criteria	1. Healthy adults with no history of neurological, medical, visual, or cognitive impairments 2. No contraindications to MRI or TMS, such as a history of seizures or epilepsy, metallic implants, implanted electronic devices (e.g., pacemakers), or pregnancy
Key exclusion criteria	1. A history of neurological, medical, visual, or cognitive impairments 2. Any contraindications to magnetic resonance imaging or transcranial magnetic stimulation, including a history of seizures or epilepsy, metallic implants, implanted electronic devices such as pacemakers, or pregnancy 3. Unable to reliably perceive phosphenes 4. Magnetic resonance imaging or magnetic resonance spectroscopy data did not meet established quality assurance standards
Date of first enrolment	29/04/2016
Date of final enrolment	31/10/2019

Locations

Countries of recruitment

Taiwan

Study participating centres

Results and Publications

Individual participant data (IPD) Intention to share	No
IPD sharing plan

Editorial Notes

14/05/2026: Study's existence confirmed by the Institutional Review Board of National Yang Ming Chiao Tung University.