On the Bulbospinal Locomotor Column in the Cat
Repetitive (30 to 60 pps) stimutation of the appropriate fibers at the medullary or spinal level elicits stepping. At both levels, there exist neurons which give synaptic responses even to single stimuli applied to the locomotor or stepping point. Most responses in the proximity of this stimulation site occur within 5–10 ms. Less than half of these responses are monosynaptic. This suggests the existence of strong excitatory interactions between neurons. Nevertheless the polysynaptic propagation of the activity evoked by a single stimulus was found to show a steep decrement and a significant temporal dispersion (up to 10 and even 30 ms). Further propagation of this activity is due to conduction along the fiber bundle.
Fibers of the stepping strip in the dorsolateral funiculus excite the stepping generator through the propriospinal neurons sending their axons into the ventrolateral funiculus.
Stepping can be elicited both by the direct bulbospinal pathway and via propriospinal neurons.
KeywordsSingle Stimulus Synaptic Response Cervical Segment Reticulospinal Neuron Step Point
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