Neural mechanisms of locomotion with special reference to its relationship with the spino-bulbo-spinal reflex

Abstract

Unit discharges of the reticular neurons and EMGs of extensors and flexors were recorded in the four limbs of thalamic cats during stepping on a motor driven treadmill to study the functional role of the spino-bulbo-spinal (SBS) reflex in locomotion.
Reticulospinal (RS) neurons showed increased spikes from the end of the stance to the beginnning of swing phase; in this period, flexor muscle EMGs were obtained. To analyze the relationship between the activity in RS neurons and that in flexor muscles, RS neuron spikes were used for triggering and post-spike were averaged. Averaged EMGs of the correlated EMGs flexor revealed 12 and 6 msec latencies for hind and fore-limbs, respectively. Most RS neurons elicited EMGs of flexor muscles of ipsilateral one leg, some elicited flexor EMGs of both the ipsilateral fore and hindlimbs, and a few had diagonal innervations of flexors in fore and hind-limbs.
The input and relay neurons of the reticular formation underlying the SBS reflex also showed alternative firing patterns during stepping.
The relationship among the activities of the 3 groups of reticular neurons was analyzed by the postor pre-spike averaging techniques and appropriate latency response were obtained.
The results indicate that flexor EMGs were excited reflexly in cats stepping on the treadmill. The role of the SBS reflex in locomotion is discussed.