Corticospinal projections to upper limb motoneurones in humans.

摘要: 1. Magnetic stimulation was applied over the motor cortex in forty-five normal human subjects and peristimulus time histograms (PSTHs) of discharges single units were used to record changes firing probability individual spinal motoneurones contralateral upper limb muscles. Recordings obtained from 153 fourteen 2. For majority initial effect a short latency facilitation. The estimated central conduction velocities rise times underlying excitatory postsynaptic potentials (EPSPs) compatible with monosynaptic facilitation by fast corticospinal pathway. In some inhibition. Other showed no statistically significant probability. proportion tested each these categories depended on muscle. All sampled first dorsal interosseous (1DI) facilitation, as did forearm biceps brachii. More than half triceps brachii deltoid either or inhibited. 3. To compare net actions neurones activated magnetic various motoneurone pools, magnitude inhibition given unit normalized 1DI same subject at stimulus intensity, data pooled for number subjects. 4. received strong (estimated mean EPSP amplitude 2.9 +/- 0.2 mV), muscles weaker effect. 5. It is concluded that projections humans have distinct pattern which similar other primates.