| Abstract: | The activity of single neurons of the visual cortex in the initial state and upon presentation of a certain program of stimuli, which included a series of modality-specific (light flashes, continuous light) and nonspecific (clicks, tone) stimuli used separately and in combination, was recorded extracellularly by glass electrodes in unanesthetized and uncurarized white rats restrained in a stall. The responses of the neurons to flashes and clicks were analyzed by the poststimulus histogram method. The regular shifts of neuronal activity in response to light flashes (with a frequency of one per second) in the form of an increase or decrease of firing rate were noted not only during the first 150–200 msec (short-latent responses — SLR) but also later, after 700–800 msec (long-latent responses — LLR). The LLR differed from the SLR also by greater variability (decrease or increase upon repeating the stimuli) and by pronounced interaction with the modality-nonspecific stimuli, which had a weak effect on the SLR and by themselves very rarely evoked responses of the visual cortex neurons. The neuron could demonstrate several LLR with a different latent period. The independent nature of each LLR was indicated by the relative independence of its dynamics. All these data permit the consideration that one and the same neuron in one cycle of its activity can be included in different functional systems of the brain, which evidently provide direct reception of information arriving over specific sensory conductors and its subsequent processing. Therefore, neurons, which made up more than half of those investigated, can be regarded as polyfunctional.N. I. Grashchekov Laboratory of Problems of Controlling Functions in Man and Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 3, pp. 242–250, May–June, 1970. |
