IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Speed cells in the medial entorhinal cortex
Autor/es:
EMILIO KROPFF; ERIC CARMICHAEL; EDVARD MOSER; MAY-BRITT MOSER
Lugar:
Washington
Reunión:
Conferencia; Society for Neuroscience Annual Meeting 2014; 2014
Institución organizadora:
Society for Neuroscience
Resumen:
Grid cells in the medial entorhinal cortex (MEC) have spatial maps
characterized by periodicity (Hafting et al, 2005). Their spatial code
applies to several places within an environment as well as across
environments (Fyhn et al, 2007), which suggests they could be the basis
of a path-integration representation of space (McNaughton et al, 2006). A
path integrator would receive a speed signal as an input and integrate
it along a short window of time to obtain the displacement of the
animal, using this result to update the spatial maps. Although weak
correlations with theta frequency (Jeewajee et al, 2008) or grid cell
firing (Sargolini et al, 2006; Wills et al, 2012) have been reported,
the local availability and nature of a speed signal in MEC is still
unclear. We recorded neural activity in the MEC and hippocampus of rats
in a 1mx1m open field and in the Flintstone car, a task designed to
control their speed. The car, which was ran by a computer along a 4m
track, had no floor, constraining rats to run by their own means at an
experimenter-determined speed in order to keep up and reach the end of
the track, where a food reward was delivered. We report that running
speed is coded in the firing rate of a large population of MEC cells,
representing around 10% of the overall cell count in all layers. The
firing of these speed cells is characterized by a positive-linear
relationship with running speed and low spatial and head-directional
information content. While other entorhinal populations (grid, head
direction and border cells) present large overlaps with each other,
their overlap with the population of speed cells is in all cases
significantly lower than expected by chance. In agreement with the
functional segregation of speed cells, when experimentally disentangling
speed and position we were unable to find any modulation by speed in
the grid cell population, and found only a weak modulation in
hippocampal place cells. Finally, MEC speed cells exhibited prospective
coding, anticipating the rats? movements around 60ms on average,
although in some selected examples the anticipation reached 200-300ms.
In turn, grid cells recorded in the same experiments behaved as if
guided by a prospective rather than a regular path integrator, as
evidenced by the anticipation of their firing position when acceleration
was positive as opposed to negative, an effect that was absent in
simultaneously recorded hippocampal place cells. This shift in firing
position was stronger in a) layer II and b) the last portion of the
theta cycle, not associated in grid cells with phase precession proper.
Put together, our results point to the coordinated involvement of MEC
grid cells and speed cells in path integration.