Long-term potentiation within the cat motor cortex.

Synaptic plasticity in the motor cortex of anesthetized cats was examined using intracellular recording and labeling techniques. Intracortical microstimulation (ICMS) was delivered in the superficial layers and recordings were made from cells in layer V. When the neuron responded to ICMS with an excitatory postsynaptic potential (EPSP), tetanic ICMS (100-200 Hz, 10-20 s) was delivered to the same site. Five of 19 cells which were examined and labeled with biocytin showed long-term potentiation (LTP) of the EPSP, and 12 cells showed post-tetanic potentiation (PTP) following the tetanic stimulation. All the examined cells were pyramidal neurons. These results demonstrate that plasticity exists within the intracortical connection of the motor cortex that may be involved in motor learning.