Distributed encoding of spatial and object categories in primate hippocampal microcircuits.
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.
Department of Physiology and Pharmacology, Wake Forest University School of Medicine Winston-Salem, NC, USA.
Ioan
I
Opris
Department of Physiology and Pharmacology, Wake Forest University School of Medicine Winston-Salem, NC, USA.
Lucas M
LM
Santos
Department of Anatomy and Neurobiology, University of Kentucky Lexington, KY, USA.
Greg A
GA
Gerhardt
Department of Biomedical Engineering, University of Southern California Los Angeles, CA, USA.
Dong
D
Song
Department of Biomedical Engineering, University of Southern California Los Angeles, CA, USA.
Theodore W
TW
Berger
Department of Physiology and Pharmacology, Wake Forest University School of Medicine Winston-Salem, NC, USA.
Robert E
RE
Hampson
Department of Physiology and Pharmacology, Wake Forest University School of Medicine Winston-Salem, NC, USA.
Sam A
SA
Deadwyler
CA1; CA3; cognitive function; hippocampus; numeric categorization; patterned microstimulation; rhesus macaque monkey; spatial representation