Distributed encoding of spatial and object categories in primate hippocampal microcircuits

Ioan Opris, Lucas M. Santos, Greg A. Gerhardt, Dong Song, Theodore W. Berger, Robert E. Hampson, Sam A. Deadwyler

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


The primate hippocampus plays critical roles in the encoding, representation, categorization and retrieval of cognitive information. Such cognitive abilities may use the transformational input-output properties of hippocampal laminar microcircuitry to generate spatial representations and to categorize features of objects, images, and their numeric characteristics. Four nonhuman primates were trained in a delayed-match-to-sample (DMS) task while multi-neuron activity was simultaneously recorded from the CA1 and CA3 hippocampal cell fields. The results show differential encoding of spatial location and categorization of images presented as relevant stimuli in the task. Individual hippocampal cells encoded visual stimuli only on specific types of trials in which retention of either, the Sample image, or the spatial position of the Sample image indicated at the beginning of the trial, was required. Consistent with such encoding, it was shown that patterned microstimulation applied during Sample image presentation facilitated selection of either Sample image spatial locations or types of images, during the Match phase of the task. These findings support the existence of specific codes for spatial and numeric object representations in primate hippocampus which can be applied on differentially signaled trials. Moreover, the transformational properties of hippocampal microcircuitry, together with the patterned microstimulation are supporting the practical importance of this approach for cognitive enhancement and rehabilitation, needed for memory neuroprosthetics.

Original languageEnglish
Article number317
JournalFrontiers in Neuroscience
Issue numberOCT
StatePublished - 2015

Bibliographical note

Publisher Copyright:
© 2015 Opris, Santos, Gerhardt, Song, Berger, Hampson and Deadwyler.


  • CA1
  • CA3
  • Cognitive function
  • Hippocampus
  • Numeric categorization
  • Patterned microstimulation
  • Rhesus macaque monkey
  • Spatial representation

ASJC Scopus subject areas

  • General Neuroscience


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