Studies on central nervous mechanisms concerning cognitive functions

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Field potentials were recorded with electrodes implanted in various cortical areas while a monkey was learning reaction-time hand movements with complex tone. When cortical surface-negative, depth-positive (s-N,d-P) potential (at a latency of about 80 ms after stimulus) appeared in the rostral bank of the inferior limb of the arcuate sulcus of the left cerebral hemisphere, and became gradually larger, the monkey began to respond to stimulus with movement (recognition learning). As the potential in the prefrontal cortex and the cerebellar-mediated potential in the motor cortex gradually increased with further training, the movement became quicker and more skillful. Three monkeys achieved the movement with complex tone in shorter training days than the movement with pure tone. Cortical field potentials were recorded during learning processes of visuo-initiated hand movements, and analized. It was found that as-N,d-P potential (at about 80 ms after stimulus) in the rostral bank of the inferior limb of the arcuate sulcus of the left cerebral hemisphere was related to recognition learning, and that a s-N,d-P potential (at a latency of about 80 ms after stimulus) in the rostral bank of the arcuate sulcus in the right cerebral hemisphere was motivation-dependent activity. A s-N,d-P potential (at about 70 ms after stimulus) was also recorded in the rostral bank of the inferior limb of the arcuate sulcus of the left cerebral hemisphere in audio-initiated vocalization. There facts suggest that dorsolateral prefrontal cortex is involved in motivational functions as well as in cognitive functions.The cortical activity related to recognition learning is s-N,d-P potential, and is considered to be a superficial thalamo-cortical response. Morphological studies suggest that the VAmc thalamic nuclei are related to initiation of the activity. There was hardly any change in the activity before and after cerebellectomy or basal ganglia cooling.