Population coding of arm-movement-related neurons in and below the superior colliculus of Macaca mulatta

It has been shown for the motor cortex of primates, that an arm trajectory is coded as a population vector formed by many neurons with activities correlated with arm movements. Recently, neurons in the primate superior colliculus that also display activities related to arm movements have been described. In the present paper we show that a subpopulation of this type of neuron is able to code for limb movement by the population vector. However, the cosine function cannot describe these neurons adequately. Rather the Fisher distribution yields a much better description of arm-movement-related cells in the superior colliculus.