GABAergic modulation of gating, timing and theta phase precession of hippocampal neuronal activity during theta oscillations

Cutsuridis, Vassilis and Hasselmo, Michael (2012) GABAergic modulation of gating, timing and theta phase precession of hippocampal neuronal activity during theta oscillations. Hippocampus, 22 (7). pp. 1597-1621. ISSN 1050-9631


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Successful spatial exploration requires gating, storage, and
retrieval of spatial memories in the correct order. The hippocampus is
known to play an important role in the temporal organization of spatial information.
Temporally ordered spatial memories are encoded and
retrieved by the firing rate and phase of hippocampal pyramidal cells and
inhibitory interneurons with respect to ongoing network theta oscillations
paced by intra- and extrahippocampal areas. Much is known about the anatomical,
physiological, and molecular characteristics as well as the connectivity
and synaptic properties of various cell types in the hippocampal
microcircuits, but how these detailed properties of individual neurons give
rise to temporal organization of spatial memories remains unclear. We
present a model of the hippocampal CA1 microcircuit based on observed
biophysical properties of pyramidal cells and six types of inhibitory interneurons:
axo-axonic, basket, bistratistified, neurogliaform, ivy, and oriens
lacunosum-moleculare cells. The model simulates a virtual rat running on
a linear track. Excitatory transient inputs come from the entorhinal cortex
(EC) and the CA3 Schaffer collaterals and impinge on both the pyramidal
cells and inhibitory interneurons, whereas inhibitory inputs from the
medial septum impinge only on the inhibitory interneurons. Dopamine
operates as a gate-keeper modulating the spatial memory flow to the PC
distal dendrites in a frequency-dependent manner. A mechanism for spiketiming-
dependent plasticity in distal and proximal PC dendrites consisting
of three calcium detectors, which responds to the instantaneous calcium
level and its time course in the dendrite, is used to model the plasticity
effects. The model simulates the timing of firing of different hippocampal
cell types relative to theta oscillations, and proposes functional roles for
the different classes of the hippocampal and septal inhibitory interneurons
in the correct ordering of spatial memories as well as in the generation
and maintenance of theta phase precession of pyramidal cells (place cells)
in CA1. The model leads to a number of experimentally testable predictions
that may lead to a better understanding of the biophysical computations
in the hippocampus and medial septum.

Keywords:computer model; hippocampus; inhibitory interneurons; STDP; dopamine
Subjects:B Subjects allied to Medicine > B140 Neuroscience
G Mathematical and Computer Sciences > G730 Neural Computing
Divisions:College of Science > School of Computer Science
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ID Code:27715
Deposited On:03 Jul 2017 13:38

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