To estimate the potential contributions of PIC (Persistent Inward Current) activation and synaptic input patterns to
motor unit discharge patterns, we examined the responses of a set of cable
motoneuron models to different patterns of excitatory and inhibitory
The models were first tuned to approximate the current- and
voltage-clamp responses of low- and medium-threshold spinal motoneurons
studied in decerebrate cats and then driven with different patterns of
excitatory and inhibitory inputs.
The responses of the models to excitatory
inputs reproduced a number of features of human motor unit
However, the pattern of rate modulation was strongly influenced
by the temporal and spatial pattern of concurrent inhibitory inputs.
Thus, even though PIC activation is likely to exert a strong influence on
firing rate modulation, PIC activation in combination with different
patterns of excitatory and inhibitory synaptic inputs can produce a wide
variety of motor unit discharge patterns."
Powers RK, Elbasiouny SM, Rymer WZ, Heckman CJ (2012) Contribution of Intrinsic Properties and Synaptic Inputs to Motoneuron Discharge Patterns: A Simulation Study. J Neurophysiol 107(3):808-23 [PubMed]