Abstract
A surface-negative (s-N), depth-positive (d-P) premovement potential was recorded by electrodes implanted on the surface and at a 2.0-3.0 mm depth in areas 5 and 7, and in the premotor, motor and somatosensory cortices in monkeys on self-paced hand movements. The monkeys were also tasked with visuo-initiated hand movements. Cortical field potentials were recorded by the above-mentioned electrodes while they were learning to accomplish the movements, and then analyzed. It was found that in the early learning period (association of stimulus with movement), an s-N, d-P potential, at about 80 ms latency from stimulus, appeared in the left prefrontal cortex and a few days later also in the left area 7, both potentials gradually increased in amplitude. On the other hand, in the late learning period (making movement quicker and more appropriate), an s-N, d-P potential appeared in the motor cortex, and also in the somatosensory cortex and area 5 at a longer latency from that in the motor cortex, in all cases contralateral to the operating hand, and these potentials gradually increased in amplitude. Aligning the data by movement onset indicated that these s-N, d-P potentials in the motor and somatosensory cortices and in area 5 were premovement potentials related to motor execution, but this was not the case in area 7. It is suggested that area 7 is related to different functions: visual processing or selective attention on visuo-initiated hand movements and motor functions on self-paced hand movements. [Jpn J Physiol 55 Suppl:S179 (2005)]
