The effect of resections of the inferotemporal cortex or the amygdala on visual orienting and habituation.

Visual orienting and its habituation were studied by means of an eye-camera technique in monkeys with bilateral inferotemporal or amygdala resections. The number of observing responses emitted was increased by inferotemporallesions and drastically curtailed by amygdalectomy. By contrast, the change in the distribution of observing responses when the orienting stimulus was displayed was no different in iDferotemporally lesioned monkeys and in the controls but orienting was abolished by amygdalectomy. These results are discussed in terms of an analysis of attention into a selective and an intensive comppnent. IN A RECENTLY published report we analyzed, by means of an eye camera, MACKWORTH [1], the observing responses of monkeys with bilateral inferotemporal cortex resections. These animals, who are severely impaired in visually guided instrumental behavior, PRIBRAM [2], were no different from unoperated controls in the proportion of eye fixations directed to stimulus figures. rather than to background. However, selective observation of one figure out of two on the basis of differential reinforcement was absent in these brainoperated monkeys. The presen~ study reports an additional analysis of the observing responses of monkeys with partial ablations of the temporal lobe. With regard to lesions of the inferotemporal cortex the question is asked whether such ablations affect the visual selection of one of a group of figures when selection does not depend on differential reinforcement. A situation was chosen in which visual orienting and its habituation could be measured, MACKWORTH and OTTO [3]. Additionally, the opportunity was taken to include investigation of the effects of another temporal lobe lesion, bilateral resection of the amygdala, on visual orienting. This opportunity was welcome because in our laboratory amygdalectomy had been shown to interfere in a complex fashion with orienting and its habituation. GSR and cardiac orienting reactions are depressed, BAGSHAW, KIMBLE and PRIBRAM [4]; BAGSHAW and BENZIES [5] while behavioral indicators of orienting (and certain aspects of the EEG) ;t, while present, fail to habituate in the time course shown by control subjects, BAGSHAW and I· BENZIES [5].