Persistent Single-Neuron Activity during Working Memory in the Human Medial Temporal Lobe.
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.
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.
Simon
S
Kornblith
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.
Rodrigo
R
Quian Quiroga
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.
Christof
C
Koch
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.
Itzhak
I
Fried
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.
Florian
F
Mormann
D004827:Epilepsy; D006801:Humans; D008570:Memory, Short-Term / Q000502:physiology*; D011939:Mental Recall; D009474:Neurons / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*
Sternberg Task; human; medial temporal lobe; microwires; persistent activity; single units; working memory