Distortion Suppression in Neuromuscular Information Transmission Due to Interchannel Dispersion in Muscle Spindle Firing Thresholds

A mathematical multipath model of the flow of information within the afferent limb of the myotatic stretch reflex is reviewed and evaluated, with emphasis being placed on its multi-channel structure. The system is simulated, and the resultant output (alpha motoneuron transmembrane potential) is analyzed spectrally, with one single-tone input (muscle stretch) and a set of variations of different system parameters: (i) When all the channels are identical, the characteristics of the input signal are unrecognizable at the output, and can only be extracted by an ``unphysiological'' motoneuron. (ii) When the afferent conduction delays are distributed among the channels, the output is similarly distorted, and can only be improved by assuming an atypically long conduction path. (iii) When the muscle spindle firing thresholds are either varied among the channels or vary temporally within each channel, the distortion is dramatically reduced and the input signal is easily recoverable.