Data processing in the cat motoneuron system: averaging functions and rate limitation

The variability in instantaneous frequency of cat motoneurons in response to various degrees of regularity and synchronization of input is used to examine several forms of data processing occurring in the cat motoneuron system. A theoretical basis is presented which distinguishes between spatial averaging and time averaging of information from muscle afferents and which suggests realizable experiments for assessing their relative strengths. The results of the experiments demonstrate spatial averaging to be a strong form of processing in the motoneuron system; time averaging is found to be much less so. Thus, temporal information is preserved to a greater extent by the motoneuron than is spatial information. Also, an inherent source of motoneuron variability is identified and linked with the process of rate limitation.