Unit responses in the "locomotor strip" of the cat hindbrain to microstimulation

Synaptic responses of single units in the "locomotor strip" of the hindbrain were recorded extracellularly. Short-latency responses appeared in neurons of the rostral part of the strip to stimulation of the "locomotor region" of the mesencephalon. Neurons of the caudal part of the strip responded to microstimulation of its other regions, including rostral. If the distance between the neuron and point of stimulation was under 2-3 mm, short-latency (1.2-1.6 msec) responses could be observed. The thresholds and latent periods of the responses increased when the distance apart increased. Polysynaptic responses with a latent period of 3-4 msec could be potentiated by an increase in the frequency of stimulation up to 30-40 Hz. It is suggested that axons of the "locomotor strip" are oriented in the rostrocaudal direction for a distance of 2-3 mm and give off collaterals which run toward neighboring neurons. The strip may be an integrative center, "intercalated" between the rostral portions of the brain stem and spinal cord.