Connectionists: Paper: Intracellular Dynamics of Virtual Place Cells.

[Sandro Romani]

Dear Colleagues,

I'd like to bring to your attention our recent paper on phase precession in
a
network model of the hippocampus.

The discovery of phase precession by O'Keefe and Recce (1) spurred a wealth
of theoretical and experimental studies addressing the possible mechanisms
and functions of temporal coding. In a recent experimental study,
Harvey et al (2) were able to record intracellularly in the hippocampus from
behaving rodents and observe the membrane potential correlates of
place fields and phase precession. The authors argued that their
observations
contradict existing network models of phase precession, a claim to
which we answer with the following contribution:


Romani S, Sejnowski T, Tsodyks M (2011) Intracellular Dynamics of Virtual
Place Cells. Neural Computation 23:651-655.

The pattern of spikes recorded from place cells in the rodent hippocampus is
strongly modulated by both the spatial location in the environment and the
theta rhythm. The phases of the spikes in the theta cycle advance during
movement through the place field. Recently intracellular recordings from
hippocampal neurons (Harvey, Collman, Dombeck, & Tank, 2009) showed an
increase in the amplitude of membrane potential oscillations inside the
place field, which was interpreted as evidence that an intracellular
mechanism caused phase precession. Here we show that an existing network
model of the hippocampus (Tsodyks, Skaggs, Sejnowski, & McNaughton, 1996)
can equally reproduce this and other aspects of the intracellular
recordings, which suggests that new experiments are needed to distinguish
the contributions of intracellular and network mechanisms to phase
precession.

http://www.mitpressjournals.org/doi/abs/10.1162/NECO_a_00087

(1) O’Keefe J, Recce ML (1993) Phase relationship between hippocampal place
units and the EEG theta rhythm. Hippocampus 3:317-330

(2) Harvey CD, Collman F, Dombeck DA, Tank DW (2009) Intracellular dynamics
of hippocampal place cells during virtual navigation. Nature 461:941-946.

Sincerely,

Sandro Romani, Terry Sejnowski & Misha Tsodyks
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