Muriel H. Bagshaw

The GSR of monkeys during orienting and habituation and after ablation of the amygdala, hippocampus and inferotemporal cortex ☆

Abstract In an effort to locate within the brain those systems essential for orienting and habituation, monkeys with lesions in the temporal lobe were tested for galvanic skin responses to a repeated pure tone stimulus and to a novel tone. Normal animals showed habituation of the GSR within 30 trials with distinctive reoccurrence of response to the novel tone. Animals with bilateral amygdalectomy had decreased GSR reactivity to both tones, whereas those with hippocampectomy and inferotemporal isocortex lesions had normal records. Consideration of this result in light of previous findings of a defect in behavioral habituation after amygdalectomy leads to the suggestion that the orienting reaction is involved not in the generation of reaction to novelty but, rather, in its registration in the central nervous system.

Multiple measures of the orienting reaction and their dissociation after amygdalectomy in monkeys

Abstract In an earlier study we proposed that amygdalectomy results in the dissociation of the orienting reaction. One component of this reaction, the galvanic skin response (GSR) disappears after amygdalectomy and we made the hypothesis that failure to habituate was closely linked to this failure in the orienting GSR. We called this GSR component an indicator of “registration”. The present study was undertaken to discover what other measures of orienting could be classified with the GSR as indicators of registration. Accordingly, six bilaterally amygdalectomized and four shamoperated rhesus monkeys were given 50 irregularly repeated presentations of a pure tone while GSR, heart rate, respiratory rate, EEG, and ear movements were recorded. Amygdalectomized monkeys failed to show the GSR, heart-rate, and respiratory-rate components of the orienting reaction while EEG activation and ear movement-orienting responses remained essentially intact.

The GSR of monkeys during orienting and habituation after selective partial ablations of the cingulate and frontal cortex

Abstract A previous report of depression of the galvanic skin response component of the orienting reaction after amygdalectomy despite behavioral deficits in habituation, prompted this study. Two frontal lobe lesions were investigated for effect on GSR reactivity to tones. The lateral frontal cortex lesion was found to depress the GSR orienting reaction whereas the medial-frontal-anterior cingulate lesion did not. Additional analysis of the control records in terms of lability-stability ratings showed that the lateral frontal Ss maintained a level of reaction lower than that of initially stabile or “rerun” stabilized controls. The conclusion of the previous report, i.e. that autonomic indicators of orienting may serve as a registration component of the behavioral reaction to novelty is supported and extended.

Effect of amygdalectomy on stimulus threshold of the monkey.

Abstract To determine whether the apparent loss of fear of amygdalectomized monkeys is due to a loss of sensitivity, stimulus-threshold measurements were made using the galvanic skin response. Amygdalectomized subjects were found to have a lower threshold than normal monkeys. In addition they failed to respond differentially to different intensities of stimulus.

THE EFFECT OF RESECTIONS OF THE INFEROTEMPORAL CORTEX OR THE AMYGDALA ON VISUAL ORIENTING AND HABITUATION

Abstract 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 inferotemporal lesions 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 inferotemporally 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 component.

Galvanic skin response conditioning deficit in amygdalectomized monkeys

Abstract Amygdalectomized monkeys have depressed galvanic skin responses during tests of the orienting reaction to repeated presentation of simple tones. An effort to condition the galvanic skin response (GSR) with electric stimulation of skin was instituted. No evidence of conditioning of a weak conditional stimulus (light off) was obtained from the amygdalectomized monkeys in a differential classical situation, despite normal GSR to skin stimulation. Normal monkeys were found conditionable.