RESUMO
Effects of electrical stimulation of OFC (gyrus proreus, gyrus orbitalis, gyrus sigmoideus anterior) on MD unitary activity were studied. Acute preparations, curarized and unanesthetized or anesthetized with chloralose or barbiturates, were used. Steel microelectrodes were used for recording. Single rectangular pulses (0.5 msec and 0.1-0.5 ma) or short duration trains of stimuli were delivered. 479 neurons were tested and 244 (50.9 percent) responsive cells were revealed. Responses patterns: Type I, excitatory in nature. The discharge was composed of one or more spikes (latencies below 100 msec). Type II, characterized by the suppression or diminution of spontaneous activity during variable periods of time. Type III, defined by the appearance of burst activity (latencies above 150 msec). Values up to 1500-2000 msec were not rare. Type II and III responses have clearly prevailed. The g. proreus stimulation gave the higher MD responsive values. Successive stimulations of the five cortical areas were made to study convergence phenomena. The largest degree of convergence was found with stimulation interplay at the two zones of g. proreus. In a small group of neurons, the convergence of cortical and peripheral natural stimulation was also observed. A hypothesis has been proposed for long latency response generation and the inhibitory effect of cortical stimulation on the nuclear activity has been emphasized.
