Transcranial magnetic stimulation, causal structure-function mapping and networks of functional relevance.

Transcranial magnetic stimulation is now a well-established tool for inducing transient changes in brain activity non-invasively in conscious human volunteers. During the past couple of years, the ability to actively interfere with neural processing during behavioral performance has been used increasingly for the investigation of causal brain-behavior relationships in higher cognitive functions. The simultaneous combination of transcranial magnetic stimulation with methods of functional brain imaging, however, promises to be of especially great value for our understanding of the human brain, as it provides the opportunity to stimulate brain circuits while simultaneously monitoring changes in brain activity and behavior. Such an approach could help us to identify brain networks of functional relevance, and might enable causal brain-behavior inferences across the entire brain.