Hippocampal Animals Research Articles

Factors affecting spontaneous activity in rats with limbic system lesions

Abstract Spontaneous activity was studied in rats with lesions of the septal area, hippocampus and cingulate cortex under conditions of deprivation and sensory stimulation. Cingulate animals were similar to controls throughout the experiment. Hippocampal animals were generally more active than controls, but were relatively unaffected by deprivation and stimulation. Septal animals displayed initially high activity levels which dropped well below control levels after 5 days. The septal group responded to conditions of food and water deprivation and auditory stimulation with an increase in total activity. An analysis of within-session activity measures indicated superior habituation rates for septal animals under normal conditions. However, habituation patterns were severely disrupted when deprivation or stimulation was imposed. This disruption did not occur in any of the other groups. It was suggested that spontaneous activity is a function of behavioral inhibition and facilitation, both mediated through the septum. Removal of the septum results in an exaggeration at both ends of the activity scale.

Effects of hippocampectomy on consummatory behavior and movement-inhibition in rats

Abstract The daily food and water intake of hooded rats with small and large, bilateral lesions of the hippocampus as well as neocortical and sham-operated controls was measured for 16 days preoperatively and 60 days postoperatively. These same subjects were then tested in a continuous-trial passive-avoidance task. The results indicated that the hippocampectomized subjects did not consume any more food or water than did the operated control groups. Moreover, the hippocampal animals were not deficient, relative to the control subjects, in withholding a prepotent approach tendency to avoid a noxious stimulus. These results caution against an unequivocal acceptance of prevailing views implicating the hippocampus in the regulation of food and water consumption as well as certain response-inhibition debilities.

Hippocampal lesions and spontaneous alternation behavior in the rat

Abstract Rats with hippocampal lesions and control animals were tested for spontaneous alternation behavior in a modified T-maze under three different stimulus conditions. When intra-maze stimuli (alley brightness) and spatial direction could be used simultaneously as cues for alternation, both groups alternated at rates significantly higher than chance. However, when intra-maze stimuli were opposed to spatial direction cues, the rats with hippocampal lesions alternated at chance levels while the controls continued to alternate spatial direction. The complexity of the phenomenon of spontaneous alternation itself and the locus and extent of the lesions employed were discussed as possible sources of the discrepancy between the results of this study and others investigating the role of hippocampus in spontaneous alternation behavior.

Behavior of hippocampal lesioned rats in home cage and novel situations☆

Abstract A time-sampling observation procedure was used to record behavior of hippocampal damaged and control rats in home cage and novel open field under both ad libitum and food deprivation conditions. In the home cage hippocampal animals slept less than controls under both conditions. There were no differences between groups during the day but hippocampal rats spent significantly more time sniffing and were more active during the night. In the novel open field containing food pellets, hippocampals were more active than controls in the ad libitum condition and habituated at the same rate, whereas, under deprivation hippocampal rats were more active early in the session but later spent more time than controls with the food. These results are interpreted as evidence for a motivational involvement of the hippocampus.

Effect of combined brain stimulation on gastric secretion, acidity and potassium concentration in cats

Hippocampectomized male rats were prepared, and the incidence as well as severity of gastric ulceration upon restraint were compared with those of normal control animals and controls with localized damage to the cortex over the hippocampus. In another experiment, observations on gastric ulceration were made without restraint in hippocampectomized animals, normal controls, controls with cortical damage, vagotomized animals and animals that received hippocampectomy as well as vagotomy.Both in restrained and unrestrained states, the incidence of animals with ulcer as well as the number and the total area of ulcers per stomach were significantly larger in the hippocampal animals than they were in the other animal groups. Vagotomy abolished the effect of hippocampectomy upon gastric ulceration in the unrestrained state.We infer that the hippocampus helps to protect the stomach from ulceration partly by controlling vagal activity.