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Proc Natl Acad Sci U S A. 2015 Jan 13;112(2):E214-9. doi: 10.1073/pnas.1410130112. Epub 2014 Dec 24.

Differential roles of delay-period neural activity in the monkey dorsolateral prefrontal cortex in visual-haptic crossmodal working memory.

Author information

1
Key Laboratory of Brain Functional Genomics (Ministry of Education & Science and Technology Commission of Shanghai Municipality), Institute of Cognitive Neuroscience, School of Psychology and Cognitive Science, East China Normal University, Shanghai 200062, China; NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, Shanghai 200062, China;
2
Key Laboratory of Brain Functional Genomics (Ministry of Education & Science and Technology Commission of Shanghai Municipality), Institute of Cognitive Neuroscience, School of Psychology and Cognitive Science, East China Normal University, Shanghai 200062, China;
3
Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218; Department of Neuroscience, Johns Hopkins University, Baltimore, MD 21205;
4
Department of Neurosurgery, Johns Hopkins University, Baltimore, MD 21287;
5
MIND Research Institute, Irvine, CA 92617; and.
6
Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218; Department of Neurosurgery, Johns Hopkins University, Baltimore, MD 21287; yzhou12@jhmi.edu.
7
Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, CA 90024.

Abstract

Previous studies have shown that neurons of monkey dorsolateral prefrontal cortex (DLPFC) integrate information across modalities and maintain it throughout the delay period of working-memory (WM) tasks. However, the mechanisms of this temporal integration in the DLPFC are still poorly understood. In the present study, to further elucidate the role of the DLPFC in crossmodal WM, we trained monkeys to perform visuo-haptic (VH) crossmodal and haptic-haptic (HH) unimodal WM tasks. The neuronal activity recorded in the DLPFC in the delay period of both tasks indicates that the early-delay differential activity probably is related to the encoding of sample information with different strengths depending on task modality, that the late-delay differential activity reflects the associated (modality-independent) action component of haptic choice in both tasks (that is, the anticipation of the behavioral choice and/or active recall and maintenance of sample information for subsequent action), and that the sustained whole-delay differential activity likely bridges and integrates the sensory and action components. In addition, the VH late-delay differential activity was significantly diminished when the haptic choice was not required. Taken together, the results show that, in addition to the whole-delay differential activity, DLPFC neurons also show early- and late-delay differential activities. These previously unidentified findings indicate that DLPFC is capable of (i) holding the coded sample information (e.g., visual or tactile information) in the early-delay activity, (ii) retrieving the abstract information (orientations) of the sample (whether the sample has been haptic or visual) and holding it in the late-delay activity, and (iii) preparing for behavioral choice acting on that abstract information.

KEYWORDS:

cross-modal working memory; delay activity; monkey; prefrontal; single unit

PMID:
25540412
PMCID:
PMC4299181
DOI:
10.1073/pnas.1410130112
[Indexed for MEDLINE]
Free PMC Article

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