Daniel P. Kimble

In utero taste/odor aversion conditioning in the rat

Rat fetuses exposed to a taste-odor stimulus and an aversive stimulus in utero showed an aversion to the taste/odor stimulus when tested 16 days postnatally. Fetuses which received various control treatments in utero did not show an aversion. These data show that rat fetuses at 20 days of gestation are capable of associative learning which can be demonstrated more than two weeks postnatally.

Possible inhibitory functions of the hippocampus

Abstract The mammalian hippocampus is proposed to constitute part of the neural machinery necessary for the generation of a brain process which is functionally equivalent to Pavlovian internal inhibition. Relevant neuroanatomical and electrophysiological data are presented in support of this proposal. The major behavioral effects of hippocampal lesions in situations in which internal inhibition is presumed to occur are discussed. These situations include habituation to novelty, discrimination reversal, overtraining, extinction and spontaneous alternation.

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.

Brightness discrimination and reversal in hippocampally-lesioned rats

Abstract Eleven albino rats with large bilateral hippocampal lesions, nine rats with bilateral lesions of the cortex overlying the hippocampus and 10 unoperated controls were trained on a brightness discrimination and tested on the reversal of the discrimination. The three groups did not differ in learning the discrimination, but the hippocampectomized rats were severely impaired in the reversal of the discrimination. Persistent positional responding during reversal characterized the behavior of the hippocampectomized rats. It is proposed that these results are best understood by postulating that hippocampal lesions produce a deficit in attentional processes.

Hippocampal lesions and delayed alternation in the rat

Rats were trained preoperatively on a delayed alternation task in which the delay period was increased until S accumulated four errors at a given delay interval. When the temporal limit for an S was thus determined, S was given either a bilateral hippocampal lesion or a bilateral cortical lesion. Postoperatively, the hippocampectomized Ss were totally unable to perform the delayed alternation task, even at extremely brief delays. The cortically damaged Ss showed no deficit, all improving on their preoperative temporal limit. These results confirmed and extended previous results with hippocampectomized monkeys.

The effect of hippocampal lesions on extinction and "hypothesis" behavior in rats.

Abstract The behavior of rats during the acquisition and extinction of a brightness discrimination was altered by bilateral hippocampal lesions. Lesions restricted to the neopallium overlying the hippocampus did not significantly affect behavior. While brain damage did not increase the number of trials required to reach the acquisition criterion, rats with hippocampal lesions did generate significantly longer position hypotheses during acquisition. During extinction, rats with hippocampal damage showed no increase in approach response latency and made significantly longer brightness, but not position hypotheses. These results, together with previous findings, strengthen the conclusion that the behavior of rats in low ratio reinforcement situations is particularly sensitive to the disruptive effects of hippocampal damage. Such damage may produce behavioral effects by altering the brain processes necessary for the shifts of attention which can be inferred to occur in normal animals in such situations.

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.

Avoidance and escape behavior following striatal lesions in the rat

Abstract The passive avoidance behavior of rats with bilateral lesions in either the corpus striatum or posterior neocortex was investigated on two tasks, one requiring the inhibition of a well-trained response, and the other the inhibition of a relatively untrained response. Additionally, the active avoidance behavior of rats with striatal, hippocampal, or posterior neocortical lesions was investigated. In the passive avoidance situation the rats with striatal lesions were impaired in the inhibition of a well-trained response, but not in the inhibition of a relatively untrained response. In the active avoidance situation those with striatal lesions were impaired in the acquisition of both avoidance and escape responses. It was suggested that the impaired performance of the experimental subjects was due to a deficit in the ability to make the necessary motor adjustments under stressful conditions.

Lesions of the limbic system: Their effects upon hypotheses and frustration

The behavior of animals with hippocampal destruction is compared with that of animals with damage to the neocortex and with the behavior of normal animals in several learning problems. An emphasis is given to the study of behavioral differences on an individual basis. As a result, new interpretations are made concerning the nature of behavioral effects of hippocampal destruction based upon abnormal transfer of training between learning experiences, hypothesis behavior, its perseveration, and the contribution of regulatory systems of the hypothalamus as normally modified by the hippocampus.

Further evidence for latent learning in hippocampal-lesioned rats

Rats with substantial dorsolateral lesions to the hippocampal formation showed significant latent learning of a complex spatial maze. Their overall maze performance, however, was characteristically impaired. Behavior during the pre-exposure phase of the experiment was useful in predicting test maze behavior. Three measures in particular had predictive value: entrances into the maze alley leading to the final choice point, behavior at that choice point, and goal box entries.