We intend to use focused ultrasound to stimulate or suppress brain activity in patients with epilepsy. We hypothesize that focused ultrasound is capable of brain stimulation or suppression visible with functional MRI, and will not cause tissue damage.

Inclusion Criteria:

• Subjects with clinical evidence from their diagnostic evaluations of unilateral hippocampal dysfunction and epileptogenicity.
• Subjects with seizures that have been refractory to treatment with at least three currently marketed antiepileptic drugs.
• Subjects with epilepsy who would clearly benefit from surgical intervention.
• Subjects who have been offered a non-dominant anterior-mesial temporal lobe resection as treatment for medication refractory epilepsy.

Exclusion Criteria:

• Subjects with a cognitive or psychiatric disorder that limits the ability to give informed consent or are unable to cooperate with the testing.
• Subjects with dementia, delirium and psychotic symptoms. - Subjects with ferromagnetic materials in the head.
• Subjects with severe cardiac disease, increased intracranial pressure, or a TENS unit.
• Subjects who exhibit primary generalized seizures or pseudoseizures.
• Subjects who have seizures secondary to drugs, alcohol, metabolic illness or progressive degenerative disease.
• Subjects who have experienced status epilepticus during the 3-week baseline period prior to the operation.
• Subjects (females) who are pregnant.