title: Neurons and networks organizing and sequencing memories.
abstract: Hippocampal CA1 and CA3 neurons sampled randomly in large numbers in primate brain show conclusive examples of hierarchical encoding of task specific information. Hierarchical encoding allows multi-task utilization of the same hippocampal neural networks via distributed firing between neurons that respond to subsets, attributes or "categories" of stimulus features which can be applied in events in different contexts. In addition, such networks are uniquely adaptable to neural systems unrestricted by rigid synaptic architecture (i.e. columns, layers or "patches") which physically limits the number of possible task-specific interactions between neurons. Also hierarchical encoding is not random; it requires multiple exposures to the same types of relevant events to elevate synaptic connectivity between neurons for different stimulus features that occur in different task-dependent contexts. The large number of cells within associated hierarchical circuits in structures such as hippocampus provides efficient processing of information relevant to common memory-dependent behavioral decisions within different contextual circumstances. This article is part of a Special Issue entitled SI: Brain and Memory.
authors.affiliation: Department of Physiology & Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1083, USA. Electronic address: sdeadwyl@wfubmc.edu.
authors.forename: Sam A
authors.initials: SA
authors.lastname: Deadwyler
authors.affiliation: Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, 1042 Downey Way (DRB140), Los Angeles, CA 90089-1111, USA.
authors.forename: Theodore W
authors.initials: TW
authors.lastname: Berger
authors.affiliation: Department of Physiology & Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1083, USA.
authors.forename: Ioan
authors.initials: I
authors.lastname: Opris
authors.affiliation: Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, 1042 Downey Way (DRB140), Los Angeles, CA 90089-1111, USA.
authors.forename: Dong
authors.initials: D
authors.lastname: Song
authors.affiliation: Department of Physiology & Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1083, USA.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Hampson
mesh_terms: D000818:Animals; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008568:Memory / Q000502:physiology*; D008959:Models, Neurological; D009415:Nerve Net / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D046709:Pattern Recognition, Physiological / Q000502:physiology
keywords: Hierarchical encoding; Hippocampal neurons; Memory; Nonhuman primates; Nonlinear hierarchical model; Retention and retrieval