Title

The Place-Specific Activity of Place Cells Does Not Require Signals From the Otolith Organs

Document Type

Poster Session

Presentation Date

11-19-2014

Conference Name

2014 Neuroscience Meeting Planner

Conference Location

Washington, DC

Abstract

Program No. 848.12/UU27

Hippocampal place cells represent perceived location within an environment, and are thought to contribute to spatial memory. This representation is typically controlled by visual information, but is abolished by damage or inactivation of the vestibular system. This vestibular contribution may originate in the semicircular canals or otolith organs, or both, but no studies have directly tested the contribution of each vestibular component to place cell function. We investigated the otolithic contribution to place cell function by recording hippocampal cells in freely moving tilted mice, which have dysfunctional otolith organs. Male homozygous tilted mice and their heterozygous littermates were implanted with 4 moveable tetrodes to record the activity of single neurons within the hippocampus. Following a 1-2 week recovery period, neuronal activity was recorded across 5 trials (1-Standard, 2-Cue Rotation, 3-Standard, 4-Darkness, 5-Standard), after which the electrode bundle was lowered ≈50μm to record a putatively different subset of cells on the following day. Single-neuron spike activity was isolated offline. For each isolated neuron, the position of the mouse at the time of each action potential was used to produce a Firing Rate X Place map of the arena. Spatial information content and coherence values were calculated for each rate map to determine whether that cell’s activity was significantly modulated by location under the different conditions. These measures, along with spatial correlation between trials, were used to determine whether place cell activity remained stable across trials or were differentially modulated by the conditions. Numerous place cells were identified in both control and tilted mice. Spatial information content and spatial coherence values did not change significantly across trials, and place field position was dominantly controlled by the visual cue card for both groups. Both groups also had many cells that maintained their place-specific activity in darkness. These results suggest that signals from the otolith organs are not necessary for the location-specific activity of hippocampal place cells in light or in darkness.

Keywords

Vestibular, Place Cells, Spatial Orientation

Disciplines

Psychology

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