20 and 40 c/sec power functions in the visual, motor, and auditory cortices of the cat during three levels of performance in a successive visual discrimination task
Hix, Lyllian Blaine
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The electrical activity in 5 frequency bands in the arousal spectrum was studied in the primary visual cortex, motor cortex, and primary auditory cortex of one cat during prestimulus (PS) and stimulus periods at 3 levels of performance in a successive visual discrimination task. The task involved pressing a bar to obtain milk only in the presence of a 10 c/sec flashing light as the SD and inhibiting during an S-delta period of a 3 c/sec light. EEG records representing the poorest, an intermediate, and the best behavioral performance, based on SD/S-delta ratios, in the visual discrimination task were computer analyzed to give average continuous power functions at 1/3 octave frequency bands with center frequencies of 20, 25, 31.5, 40, and 50 c/sec. The trials in the task on each tape were divided into as many as six behavioral categories, depending on the availability of trials within each category, as follows: PS, SD, and S-delta concomitant with a response (PSR, SDR, S-delta R, respectively) and PS, SD, and S-delta in which no response occurred (PSNR, SDNR, respectively). Initiation of computation was contingent upon a response, either behavioral or artificial and either with or without a delay, so that the averaged band powers in a period of time prior and subsequent to the response could be accurately ascertained. The analysis epoch was divided into two periods of time, one in which the electrical activity was assumed to be response related, the other assumed to be sufficiently removed in time from the response that the electrical activity was little affected by the response. The results were: 1. At all three levels of performance the 40 c/sec activity in visual I and motor cortex, but not in auditory I, was consistently higher during SDR than during the other behavioral conditions studied. 2. The 40 c/sec electrical activity in visual I coincident with a reinforced response increased as performance improved, although the 40 c/sec activity with intermediate performance appeared to be more similar to that occurring with superior performance than to that concomitant with poor performance. The 40 c/sec electrical activity in the motor cortex with a reinforced response varied little with performance level. 3. A marked peaking of the 40 c/sec activity and a marked decrease in 20 c/sec activity occurred coincident with a reinforced response in both visual I and motor cortex, but not in auditory I. These phenomena were particularly evident with intermediate and superior performance in visual I, 4. Graphic data indicated an inverse relationship between the 20 c/sec and 40 c/sec activity in the visual and motor cortices during SDR and S-deltaNR. The 20 c/sec activity was higher during S-deltaNR than during SDR and the 40 c/sec was higher during SDR than during S-deltaNR. Statistical analysis was not possible because of the small N (N=3). 5. A marked peaking of the 20 c/sec activity in auditory I occurred approximately 2 to 2 1/2 sec following a reinforced response during "lapping" behavior. At the same time, significant but very small decreases in the 40 and 50 c/sec bands occurred. The 20 c/sec activity was consistently higher during lapping than it was following a response that was not reinforced or during a prestimulus period. 6. Since 40 c/sec activity was observed in association with facllitatory or arousal behavior and the 20 c/sec with behavioral inhibition, a tentative hypothesis was advanced that the 40 c/sec activity is an electrical correlate of the orienting response and that the 20 c/sec activity is an electrical correlate of the inhibition of the orienting response.