| Abstract: | Responses of neurons in the medulla and cervical segments of the spinal cord to simultaneous repetitive stimulation (50 pps) of two locomotor points (LP) that exceed the threshold for evoking walking by one to two times were investigated in mesencephalic cats. In most cases a neuron responsed to stimulation of only one LP. Stimulation of a second LP usually enhanced the firing index of that response, if it was low. Or it decreased the firing index if it was high, and it had no effect if the firing index was about 0.1. Some of the neurons responded to stimulation of one LP by increasing the baseline activity, though the pulses were not locked to individual stimuli. The effect of stimulation of the second LP on this increase in activity depended on the size of the increase. Data were also obtained on the convergence of effects on single neurons from the ipsi- and contralateral LPs of the midbrain and medulla. Possible mechanisms of the summation of subthreshold excitation of a pair of LPs during the initiation of locomotion are discussed.Institute of Information Transmission Problems, Russian Academy of Sciences, Moscow. Translated from Neirofiziologiya, Vol. 24, No. 4, pp. 471–481, July–August, 1992. |
