Excitation and inhibition during motor cortex stimulation: A combined transcranial brain stimulation and event-related fMRI study

What does the BOLD response tell us about excitation and inhibition? Current approaches of fMRI are limited by an ambiguity in correlating BOLD effects with either a predominant inhibitory or excitatory neuronal activity. Transcranial electrical cortex stimulation (TES) was combined with simultaneous fMRI to study the relationship between the activity of inhibitory and excitatory neuronal circuits and the thereby induced BOLD signal changes. In a previous contribution (DGKN 2003) we were able to show that TES will induce similar effects on the motor cortex to TMS if a particular direction of the current flow is…