Persistent Single-Neuron Activity during Working Memory in the Human Medial Temporal Lobe

Simon Kornblith; Rodrigo Quian Quiroga; Christof Koch; Itzhak Fried; Florian Mormann

doi:10.1016/j.cub.2017.02.013

Persistent Single-Neuron Activity during Working Memory in the Human Medial Temporal Lobe

Curr Biol. 2017 Apr 3;27(7):1026-1032. doi: 10.1016/j.cub.2017.02.013. Epub 2017 Mar 16.

Authors

Simon Kornblith¹, Rodrigo Quian Quiroga², Christof Koch³, Itzhak Fried⁴, Florian Mormann⁵

Affiliations

¹ Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
² Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA; Centre for Systems Neuroscience and Department of Engineering, University of Leicester, 9 Salisbury Road, Leicester LE1 7QR, UK.
³ Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA; Allen Institute for Brain Science, 615 North Westlake Avenue, Seattle, WA 98109, USA.
⁴ Department of Neurosurgery and Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, 760 Westwood Plaza, Los Angeles, CA 90024, USA; Functional Neurosurgery Unit, Tel Aviv Sourasky Medical Center and Sackler Faculty of Medicine, Tel Aviv University, 6 Weizmann Street, Tel Aviv 64239, Israel.
⁵ Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA; Department of Neurosurgery and Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, 760 Westwood Plaza, Los Angeles, CA 90024, USA; Department of Epileptology, University of Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany. Electronic address: florian.mormann@ukb.uni-bonn.de.

Abstract

Working memory is an essential component of human cognition. Persistent activity related to working memory has been reported in many brain areas, including the inferior temporal and prefrontal cortex [1-8]. The medial temporal lobe (MTL) contains "concept cells" that respond invariantly to specific individuals or places whether presented as images, text, or speech [9, 10]. It is unknown, however, whether the MTL also participates in working memory processes. We thus sought to determine whether human MTL neurons respond to images held in working memory. We recorded from patients with chronically intractable epilepsy as they performed a task that required them to remember three or four sequentially presented pictures across a brief delay. 48% of visually selective neurons continued to carry image-specific information after image offset, but most ceased to encode previously presented images after a subsequent presentation of a different image. However, 8% of visually selective neurons encoded previously presented images during a final maintenance period, despite presentation of further images in the intervening interval. Population activity of stimulus-selective neurons predicted behavioral outcome in terms of correct and incorrect responses. These findings indicate that the MTL is part of a brain-wide network for working memory.

Keywords: Sternberg Task; human; medial temporal lobe; microwires; persistent activity; single units; working memory.

MeSH terms

Epilepsy
Humans
Memory, Short-Term / physiology*
Mental Recall*
Neurons / physiology*
Temporal Lobe / physiology*

Grants and funding

R01 NS033221/NS/NINDS NIH HHS/United States