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Evan Center, Monica Fabiani, Gabriele Gratton, Diane Beck; Elucidating Mechanisms of TMS-induced Visual Suppression. Journal of Vision 2017;17(10):1349. doi: https://doi.org/10.1167/17.10.1349.
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Transcranial magnetic stimulation (TMS) visual suppression refers to poorer visual detection or discrimination performance during a specific interval when single-pulse TMS is applied over occipital cortex; typically such suppression is observed in an 80-100ms post-stimulus interval. Drawing on retino-cortical transmission time estimates, some have proposed that TMS is interfering with feedback or recurrent processing in the visual stream. However, there is considerable variability in cortical transmission times across stimuli. Thus, in order to test the feedback hypothesis, both a measure of cortical transmission time and a measure of visual suppression are needed for identical stimuli and subjects. This project seeks to be the first to accomplish exactly that. Cortical transmission time is estimated using the C1 event-related potential (ERP) component, while in another session the same subjects undergo TMS pulses of variable lags (0-176 ms post-stimulus) used to suppress the same stimuli that elicited the C1. The difference in time between the C1 ERP component latency and optimal suppression point latency within subjects, aided by known estimates of cortico-cortical transmission times, allows for differentiation between competing hypotheses of feedforward or feedback mechanisms of TMS-induced visual suppression. Preliminary results evidence a window of time between peak C1 activity and peak suppression that is too small to support an account positing interruption of feedback/recurrent processes, and instead suggests interruption of the feedforward signal.
Meeting abstract presented at VSS 2017
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