Imaging causal interactions during sensorimotor processing.

We review three ways in which transcranial magnetic stimulation (TMS) has been used to investigate causal interactions between different brain areas: (1) combined with functional imaging; (2) combined with EEG; and (3) applied successively over two brain areas. We discuss the theoretical advantages of each technique, illustrated by examples from the literature, and highlight the potential of these approaches to provide novel insights into the neural bases of action control.