Neurophysiology of cortical stimulation.

This review presents the neurophysiologic principles of the various invasive and noninvasive techniques of cortical stimulation that could serve therapeutic purpose. Cortical stimulation may activate, inhibit, or otherwise interfere with the activity of neural networks, depending on stimulus frequency and intensity, current polarity, and electric field configuration. In the spatial domain, neuronal activity changes may be distant from the site of stimulation because axonal projections are more prone to be activated than local cell bodies. In the temporal domain, functional and clinical effects may occur during or beyond the time of stimulation, delayed effects being related to synaptic plasticity processes.