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Curr Biol. 2017 May 8;27(9):1251-1258. doi: 10.1016/j.cub.2017.03.028. Epub 2017 Apr 20.

Direct Brain Stimulation Modulates Encoding States and Memory Performance in Humans.

Author information

1
Department of Psychology, University of Pennsylvania, Philadelphia, PA 19104, USA.
2
Department of Neurological Surgery, University of California, San Francisco Medical Center, San Francisco, CA 94143, USA.
3
Department of Neurology, Thomas Jefferson University Hospital, Philadelphia, PA 19107, USA.
4
Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA.
5
Department of Neurology, Hospital of the University of Pennsylvania, Philadelphia, PA 19104, USA.
6
Department of Neurosurgery, Hospital of the University of Pennsylvania, Philadelphia, PA 19104, USA.
7
Department of Neurosurgery, Emory University Hospital, Atlanta, GA 30322, USA.
8
Department of Neurosurgery, University of Texas Southwestern, Dallas, TX 75390, USA.
9
Department of Neurology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA.
10
Department of Neurosurgery, Columbia University Medical Center, New York, NY 10032, USA.
11
Surgical Neurology Branch, National Institutes of Health, Bethesda, MD 20814, USA.
12
Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
13
Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, PA 19104, USA.
14
Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA 19107, USA.
15
Department of Psychology, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address: kahana@sas.upenn.edu.

Abstract

People often forget information because they fail to effectively encode it. Here, we test the hypothesis that targeted electrical stimulation can modulate neural encoding states and subsequent memory outcomes. Using recordings from neurosurgical epilepsy patients with intracranially implanted electrodes, we trained multivariate classifiers to discriminate spectral activity during learning that predicted remembering from forgetting, then decoded neural activity in later sessions in which we applied stimulation during learning. Stimulation increased encoding-state estimates and recall if delivered when the classifier indicated low encoding efficiency but had the reverse effect if stimulation was delivered when the classifier indicated high encoding efficiency. Higher encoding-state estimates from stimulation were associated with greater evidence of neural activity linked to contextual memory encoding. In identifying the conditions under which stimulation modulates memory, the data suggest strategies for therapeutically treating memory dysfunction.

KEYWORDS:

deep brain stimulation; epilepsy; episodic memory; free recall; intracranial EEG; local field potential; multivariate classification

PMID:
28434860
DOI:
10.1016/j.cub.2017.03.028
[Indexed for MEDLINE]
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