Stimulation of Entorhinal Cortex Enhances Memory
(HealthDay News) – Focal electrical stimulation to the entorhinal cortex is associated with enhanced memory, according to a study published in the Feb. 9 issue of the New England Journal of Medicine.
Using intracranial depth electrodes implanted into seven individuals to identify seizure-onset zones before epilepsy surgery, Nanthia Suthana, PhD, from the University of California in Los Angeles, and colleagues investigated whether deep-brain stimulation of the hippocampus or entorhinal cortex alters memory performance. The participants completed a spatial learning task, memorizing destinations within virtual environments; during half the tasks, focal electrical stimulation below the threshold that elicits an afterdischarge (ie, a neuronal discharge that occurs after termination of the stimulus) was given.
The investigators found that entorhinal stimulation applied during learning enhanced the subsequent memory of the locations of landmarks, compared with the memory of locations learned without stimulation. Based on the hippocampal electroencephalogram, entorhinal stimulation was shown to result in resetting of the theta rhythm phase. There was no effect of direct hippocampal stimulation. In addition, there were no adverse effects associated with the procedure.
"Our results show that spatial learning in humans can be enhanced by electrical stimulation of the entorhinal region," the authors write. "Our preliminary results support the hypothesis that stimulation that enhances memory also induces theta-phase resetting and provide evidence supporting a possible mechanism for stimulation-induced memory enhancement in humans."
The author of the editorial disclosed financial ties to pharmaceutical companies as well as a patent application related to cognitive assessment tools and methods.