 There are limited opportunities to manipulate human brain activity in a targeted way. Recent use of transcranial magnetic stimulation to activate or suppress neural activity has provided illumination, but such interventions are coarse-grained. Ultimately, to locate an explanatory correlate for specific conscious contents, we will need more fine-grained interventions in brain tissue. In humans, such opportunities are generally confined to manipulation before surgical interventions, say for brain tumors or epilepsy (see  section 5.3.3  for work with epilepsy patients).