The facilitatory and depressive effects of iontophoretically applied acetylcholine on different components of neuron responses in the motor cortex of the cat during performance of a conditioned paw positioning reflex.

Iontophoretic application of acetylcholine to neurons in the motor cortex of cats during performance of a conditioned reflex consisting of placing the paw on a support increased neuron excitability and facilitated "extrinsic" connections, resulting in increases in primary responses to electrical stimulation of the parietal region of the cortex, and which was independent of the first effect of suppression, which was seen only in relation to the long-latency components of the response. The functional significance of the differently directed effects of acetylcholine application is indicated by the statistically significant changes in motor reaction times seen in some experiments, which were in the same direction as changes in neuronal responses in the same experiments.