Stimulation of the human medial temporal lobe between learning and recall selectively enhances forgetting

Abstract

Background: Direct electrical stimulation applied to the human medial temporal lobe (MTL) typically disrupts performance on memory tasks, however, the mechanism underlying this effect is not known.

Objective: To study the effects of MTL stimulation on memory performance.

Methods: We studied the effects of MTL stimulation on memory in five patients undergoing invasive electrocorticographic monitoring during various phases of a memory task (encoding, distractor, recall).

Results: We found that MTL stimulation disrupted memory performance in a timing-dependent manner; we observed greater forgetting when applying stimulation during the delay between encoding and recall, compared to when it was applied during encoding or recall.

Conclusions: The results suggest that recall is most dependent on the MTL between learning and retrieval.

Keywords: Electrical stimulation; Epilepsy; Free recall memory; Human; Medial temporal lobe.