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Updated: Jan 30, 2026

Online Transcranial Magnetic Stimulation Protocol for Measuring Cortical Physiology Associated with Response Inhibition
Published on: February 8, 2018
Probing short-latency cortical inhibition in the visual cortex with transcranial magnetic stimulation: A reliability
Dalia Khammash1, Molly Simmonite2, Thad A Polk2
1School of Kinesiology, University of Michigan, 401 Washtenaw Ave, 41809, Ann Arbor, MI, USA; Department of Psychology, University of Michigan, 530 Church Street, 48109, Ann Arbor, MI, USA.
Background:
Transcranial magnetic stimulation (TMS) is a non-invasive method to stimulate localized brain regions. Despite widespread use in motor cortex, TMS is seldom performed in sensory areas due to variable, qualitative metrics.
Objective:
Assess the reliability and validity of tracing phosphenes, and to investigate the stimulation parameters necessary to elicit decreased visual cortex excitability with paired-pulse TMS at short inter-stimulus intervals.
Methods:
Across two sessions, single and paired-pulse recruitment curves were derived by having participants outline elicited phosphenes and calculating resulting average phosphene sizes.
Results:
Phosphene size scaled with stimulus intensity, similar to motor cortex. Paired-pulse recruitment curves demonstrated inhibition at lower conditioning stimulus intensities than observed in motor cortex. Reliability was high across sessions.
Conclusions:
TMS-induced phosphenes are a valid and reliable tool for measuring cortical excitability and inhibition in early visual areas. Our results also provide appropriate stimulation parameters for measuring short-latency intracortical inhibition in visual cortex.
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