CCN Forum: Probing cortical inhibition in visual cortex with transcranial magnetic stimulation

Abstract:
Paired-pulse transcranial magnetic stimulation (TMS) is a non-invasive method to stimulate localized brain regions and is a useful tool for examining GABA-mediated inhibitory function. Despite widespread use in motor cortex, paired-pulse TMS is seldom performed in sensory areas due to variable, qualitative metrics. In this talk, I will discuss a project in which we assessed the reliability and validity of tracing TMS-induced phosphenes (short-lived artificial percepts) to investigate the stimulation parameters necessary to elicit decreased visual cortex excitability with paired-pulse TMS. I will then present preliminary data exploring how this newly developed measure of visual cortical inhibition relates to Magnetic Resonance Spectroscopy measures of GABA concentration, and how it can be applied to the study of aging. Previous literature reveals that GABA concentration declines with age across many brain regions; I will therefore also provide preliminary results that investigate age differences in this TMS measure of visual inhibitory activity.