Multiple Running Speed Signals in Medial Entorhinal Cortex

James R. Hinman, Mark P. Brandon, Jason R. Climer, G. William Chapman, Michael E. Hasselmo

Abstract:

Grid cells in medial entorhinal cortex (MEC) can be
modeled using oscillatory interference or attractor
dynamic mechanisms that perform path integration,
a computation requiring information about running
direction and speed. The two classes of computational models often use either an oscillatory frequency or a firing rate that increases as a function
of running speed. Yet it is currently not known
whether these are two manifestations of the same
speed signal or dissociable signals with potentially
different anatomical substrates. We examined coding of running speed in MEC and identified these
two speed signals to be independent of each other
within individual neurons. The medial septum (MS)
is strongly linked to locomotor behavior, and removal
of MS input resulted in strengthening of the firing
rate speed signal, while decreasing the strength of
the oscillatory speed signal. Thus, two speed signals
are present in MEC that are differentially affected by
disrupted MS input.