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Replication was achieved of previous demonstrations that sensory stimuli involving continuous environmental input decelerate heart rate even in the presence of increased sympathetic tonus as measured by skin resistance. Systolic blood pressure and pulse pressure were not found to change, indicating that the bradycardia was not induced by baroreceptor effects. On the other hand, noxious stimuli and a conceptual task resulted in heart rate acceleration, increased systolic blood pressure, peripheral vasoconstriction, and decreased skin resistance. This evidence is taken to be consistent with a conceptual scheme which considers cardiovascular activity as instrumental in enhancing, or rejecting, environmental inputs.

RECENT experimental studies have demonstrated that extensive ablation of the preoccipital cortex in monkeys (Broadmann's Areas 18 and 19) does not affect their visual status (Lashley,1 Chow,* Riopelle and associates4). Animals with such a lesion have normal visual abilities, such as acuity, depth perception, visual field, object recognition, etc., and show good retention of learned visual discriminations. In clinical literature this cortical sector has been considered as a visual integrative center, the damage of which causes severe visual symptoms, notably the various types of visual agnosia (Nielsen5). Beside the possibility of a species difference, the discrepancy between animal experimentation and clinical cases may be due to a difference in the nature of brain injury. It has been suggested that pathological brain tissue may create more irritation and disruption of neural functions than the clean removal of that tissue alone (Hebb6). In animal work, the ablated prestriate

This experiment was intended to evaluate further an hypothesis in which perceptual and sensory-motor performances were considered to be influenced by autonomic processes via autonomic regulation of cortical activity. For this purpose, lability and level measures of sudomotor activity and heart rate were obtained during rest and performance in 54 male Ss. The hypothesis was consistently supported in 7 significant or near-significant correlations out of a possible 14. Faster performance time on the sensory-motor task was found with Ss having low resting heart rate, increased heart-rate variability during performance, and low levels of skin resistance. Faster performance time on the perceptual task was found in Ss with a high frequency of GSR activity during performance. Also, an interaction effect was suggested between some of the autonomic measures, being most pronounced in the perceptual task.

On five subjects, skin resistance levels and galvanic skin response were recorded unilaterally and simultaneously from each side of the body for between 24 and 36 days. Reliable differences in skin resistance were found in three subjects and in galvanic skin response in two subjects. The magnitude of the skin resistance difference was significantly reduced in four subjects during stimulation.