[Abstract Title]. - Society for Neuroscience

Poster
277. Voluntary Movement: Cortical Planning and Execution II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 277.8/KK34
Topic: D.17.b. Cortical planning and execution
Support: Patterson Trust
Princeton University
Title: Imaging the micro-representation of the motor repertoire with cellular resolution in the
cortex of awake mice
Authors: *D. A. DOMBECK 1,2 , D. W. TANK 1,2 ;
1 Mol Bio, 2 Princeton Neurosci. Inst., Princeton Univ., Princeton, NJ
Abstract: Intracortical micro-stimulation (ICMS) studies in mammalian motor cortex have
demonstrated that a macroscopic ethological organization exists in which subregions emphasize
different ethologically relevant categories of complex movements (Graziano, Ann. Rev.
Neurosci, 2006). Because in vivo microscopy can provide an unbiased view of the population
code within the cortical microcircuitry, we used our recently developed methods (Dombeck et.
al, Neuron, 2007) to investigate the representation of complex mouse movements at the
microscopic scale. We optically recorded the activity of layer 2/3 neurons in the forelimb motor
cortex (identified by ICMS) in mobile, head-restrained mice during two distinct complex
movements (running and grooming); the head-restrained mice remained mobile because their
limbs were resting on a spherical treadmill. Neural activity was monitored at cellular resolution,
during running and grooming, using two-photon microscopy measurements of calcium transients
from populations bolus loaded with Calcium Green-1-AM. The timing of the two movements,
recorded with a CCD camera, were converted into state vectors which were then cross-correlated
with the fluorescence traces from the ~100-200 neurons in the ~200-300 micron fields of view.
Different subpopulations of neurons were observed: those with activity patterns correlating
primarily to running, primarily to grooming, or to both movements. When the neurons within an
image were coded according to the magnitude of their movement correlations, the separate
subpopulations of neurons were found to be spatially ordered: movement correlated neurons
were more likely to be physically near neurons with the same movement correlation, with
neurons correlated to both movements mixed throughout the field. For example, grooming
correlated neurons were found to be physically closer to other grooming correlated neurons
rather than to running correlated neurons. Though sharp physical boundaries between the
subpopulations and purely homogeneous spatially ordered subpopulations were rarely observed,