Kinematic features of passive forelimb movements and rat cuneate neuron discharges

We examined the role of main and external cuneate nuclei neurons in processing sensory information during forelimb passive movement. We recorded activity of neurons using circular and figure-eight trajectories, at different speeds, in anaesthetized rats. A multivariate regression analysis was performed to correlate neural discharge to movement direction and speed, the two components of the velocity vector. We found that the activity of the majority of cuneate neurons related to passive movement velocity and that the directional component of the velocity vector accounted for a larger fraction of the variability in the firing rate than the scalar component (speed). These results indicate that cuneate cells can process whole limb afferent information to elaborate a representation of the movement velocity vector.