Robert L. Isaacson

The development of food search behavior by rats: the effects of hippocampal damage and haloperidol.

Food deprived rats were required to locate four pellets of food located in 4 of 16 holes in an enclosed arena. Three groups of animals were studied in 11 testing sessions: rats with bilateral hippocampal damage; rats with bilateral neocortical damage; and an unoperated group. Half of each group received haloperidol and half received saline injection 20 min before Sessions 4 through 10. No injections were given on the first three sessions or on the final, 11th session. Animals with hippocampal lesions visited more nonfood holes than control animals and did not develop consistent sequences of food-hole visits. The administration of haloperidol reduced the number of consistent sequences of food seeking behaviors by intact animals without significantly affecting the efficiency of performance as measured by the number of nonfood holes visited. Haloperidol reduced the number of visits to nonfood holes of animals with hippocampal lesions.

Olfactory lesions, emotionality and activity ☆

Abstract Female rats with bilateral or unilateral lesions of the olfactory bulbs were rated for emotionality and tested on several measures of spontaneous activity. Bilateral lesions resulted in hyperemotionality similar in kind, and in some cases degree, to the rage produced by septal lesions. Except for some effects which were probably due to emotionality, the spontaneous behavior of rats with olfactory lesions was well within a normal range, and distinctly different from that of septally lesioned rats.

Task dependent recovery after early brain damage

Lesions of the hippocampus and overlying neocortex were produced in cats of varying ages to determine whether the age at which the damage occurred would be related to the behavioral deficits observed. The behavioral deficits obtained depended upon the age of the animal at the time of surgery and on the particular task and response measure being considered. For animals suffering either hippocampal or neocortical damage reduced deficits on the DRL tasks, were obtained if the brain lesions were produced at, or before 4 months of age, in the extinction of a runway response, animals with lesions made early in life were unimpaired, while animals receiving lesions at 6 weeks of age, or later, were significantly impaired. Cats receiving hippocampal destruction at 6 weeks of age, or later, were deficient on the reversal of a brightness discrimination, while cats with neonatal lesions were not significantly different from controls. Animals with hippocampal lesions made at any age were impaired on the passive avoidance task and also had similar degrees of response fixation in the reversal of the brightness discrimination task. An unexpected result of the present study was the similarity found in behavioral effects of neocortical and hippocampal lesions in several problems.

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.

Hippocampal destruction in man and other animals

Abstract Reports of patients in whom a “recent memory” deficit have been observed following bilateral or unilateral temporal lobe removal were reviewed. These reports were compared with the results of investigations using animals in which the hippocampus had been destroyed surgically. The hypothesis was advanced that the disease processes responsible for the conditions leading to temporal lobe surgery in man, especially those of an epileptic nature, may play a part in determining the differences between the human and animal observations. Studies of the behavioral effects produced by the establishment of artificial epileptogenic foci in the brains of otherwise normal animals tend to provide support for this hypothesis.

Learning of food and water positions by hippocampus damaged rats

Abstract Hippocampus damaged, neodecorticate, and normal control rats were tested in a Maier three table situation. One goal was baited with food, the other with water. The animals were food or water deprived on alternate days and trained to run to the appropriate goal. After reaching criterion, reversal learning was begun. The results showed that neodecorticate and normal rats switched responses to obtain appropriate rewards but hippocampal rats were deficient in learning this. The hippocampal group had high total errors and a strikingly high proportion of such errors were committed consecutively. Upon reversal, both hippocampal and neodecorticate rats initially had high error scores. On the seventh day of reversal learning the hippocampal group still had a mean of 3 errors while the others had 1 error. The results were discussed in terms of perseverative tendencies and a lack of attention to relatively minor but crucial stimuli.

The effect of a twenty-four hour intertrial interval on the acquisition of spatial discrimination by hippocampally damaged rats

Abstract Rats with either aspiration- or penicillin-induced (irritative) lesions of the hippocampus or overlying neocortex and normal rats were trained on a spatial discrimination in a T-maze after being tested for spontaneous alternation. Animals were given only one trial per day (24 hr ITI). Only the animals with aspiration lesions of the hippocampus were impaired in acquiring the spatial discrimination. Animals with either hippocampal or neocortical lesions alternated at reduced rates.

Repeated intraventricular injections of ACTH 1-24: the effects of home or novel environments on excessive grooming.

Rats implanted with cannulas in the intraventricular foramen were tested after repeated daily injections of ACTH 1–24 or saline. Animals were either observed in their home cages or transported to an experimental room and observed in a “novel” Plexiglas chamber. Animals treated with the ACTH peptide evidenced an excessive, natural-type grooming which did not differ in the two experimental situations. No sign of adaptation of the ACTH-induced grooming was found over 10 consecutive days of testing. Saline-treated animals evidenced more grooming in the novel experimental chambers than when observed in their home cages. Some suggestion of adaptation of the grooming response was found in the saline-treated animals tested in the novel chambers. The results suggest that ACTH 1–24 induces a specific grooming response that is not dependent on being tested in a novel environment.

Activity changes related to the location of lesions in the hippocampus

Studies were made of the effects of dorsal or ventral hippocampal lesions, as related to extent of damage to cytoarchitectural fields, on open field activity. Rats with dorsal, ventral, or near-total hippocampal damage, animals with lesions restricted to the neocortex, and operated control animals without damage to the brain were given daily 5-min open-field activity tests in nine postoperative testing sessions. Rats with dorsal or near-total hippocampal damage had significantly more destruction of CA1 fields than rats with ventral hippocampal damage. In contrast, rats with ventral or near-total hippocampal damage had significantly more damage to CA3 fields than rats with dorsal damage and were significantly more active than the other groups. However, the results of within-group correlational analyses indicate that differential CA field destruction was not correlated with open field activity.

Naloxone and haloperidol reduce grooming occurring as an aftereffect of novelty.

When the grooming of rats is scored in a novel environment it is substantially increased compared to that observed in familiar home cages. Rats pretreated with naloxone (0.2, 1.0, or 2.0 mg/kg) or haloperidol (0.2 mg/kg exhibited less grooming than controls scored after handling and transported to a novel environment. Later, the same rats were pretreated with these doses of naloxone or haloperidol and tested in an open field hole board. Locomotion, exploration, and rearing scores of the drug-treated animals were not different from those of control animals. In another experiment, animals were tested in their home cages in their familiar colony room after the moderate stress of handling, transport, and ip injection. The stress-enhanced grooming was blocked by naloxone (2.0 mg/kg). It was concluded that mild to moderate stress may induce grooming without novelty per se, and that this effect is likely mediated by ACTH acting in an agonist fashion on an opiate-sensitive system.