Robert Goldstein

Attentional rigidity during exploratory and simultaneous discrimination behavior in septal lesioned rats

Abstract The temporal pattern of exploration displayed by rats with septal damage was found to be consistent and opposite to that of controls in two successive test environments (Experiment 1). Whereas the overall activity level of the controls decreased across days, the septals showed a substantial increase over this period. Within days, the controls exhibited marked decrements in activity; the lesioned animals, in contrast, manifested a sharp increment during Day 1. This positively sloped function gradually reversed itself over days until the final day when septal and control functions were similar (although differing in level). The animals were then tested for acquisition of an appetitively reinforced form discrimination in a T-maze under a noncorrection procedure, and although neither group solved the discrimination, the operated rats more rapidly developed persistent position preferences (Experiment 2). When the animals were given the identical problem under a modified self-correction procedure in a discrimination box (Experiment 3), an inability to shift attention readily actually aided those rats with anteroventral medial septal destruction in focussing on the relevant stimulus dimension and reaching criterion. In contrast, the normal plasticity exhibited by control animals paradoxically interfered with their ability to solve the discrimination. It was concluded that a strict somatomotor response inhibition or suppression model of septal function was inconsistent with the present results and related findings in the literature.

Effect of age, food deprivation and stress on gastric erosions in the rat☆☆☆

Abstract Two experiments were conducted in which rats were subjected to food deprivation and/or cold-restraint stress. In Experiment 1, 40- and 570-day old rats exhibited a significant degree of glandular gastric erosion due to the stress and to the deprivation. Both of these were attributable to the single condition wherein deprivation and stress were combined. No effect involving age was significant. In Experiment 2, 22-day old weanlings exposed to the same conditions evinced a significant glandular erosion effect of the deprivation, but neither the stress nor the interaction effects were significant. It was concluded that 3 hr of cold restraint in the sated mature rat has a relatively minor effect on the stomach. Forty-eight hours of food deprivation, also ineffective by itself in such animals, renders the stomach vulnerable to the effects of stress. In the weanling, in contrast, deprivation alone can cause glandular erosion but its potentiating effect is lacking. With respect to ruminal lesions, it was hypothesized that time without food rather than initial body weight or nutritional deficit is the critical variable.

Effect of deprivation duration and prefeeding on gastric stress erosions in the rat.

Abstract To assess the potentiating effects of food deprivation on gastric stress erosions, rats were food deprived for 9, 18, 48 or 144 hr and then subjected to cold-restraint. Comparison of each of these groups with a stressed, but nondeprived control group, revealed no significant differences in gastric erosions. It was suggested that many of the control animals, though not deprived, may not have had full stomachs during the stress and this may have masked the true potentiating effects of deprivation. In a second experiment, rats were divided into two groups and deprived, respectively, for 18 and 48 hr. These groups were subdivided and for 1 hr preceding stress, half were given food. This prefeeding significantly reduced glandular erosion scores, and there was a significant inverse relationship within the prefed groups between the amount of weight gained over the prefeeding hour and the subsequent erosion level. It was concluded that the potentiation of stress erosions by food deprivation occurs by virtue of the empty stomach associated with the deprivation rather than other concomitant changes. With respect to ruminal effects, nonstressed groups deprived for 48 and 144 hr allowed the conclusion that prolonged deprivation (144 hr) produces minor glandular effects but extensive damage to the rumen.

Lesion artifact in brain stimulation experiments.

Abstract Unstimulated rats with chronically implanted electrodes in the medial septal region exhibited a pattern of activity almost identical to electrolytically lesioned animals but significantly different from controls. Since the implantation procedure alone produced this effect, it constitutes a significant artifact in the interpretation of stimulation experiments.

Medial septal lesions and the frustration effect.

Abstract Rats with medial septal lesions and sham operates were run in a straight runway. After running stabilized, food was omitted on selected trials and the running speed on the following trial was observed for a frustration effect (FE). The septals exhibited a significantly greater increase in speed on this trial than controls. This enhanced FE in septals is at variance with predictions from frustration theory considering the greater resistance to extinction in septals and suggests a dissociation between the immediate and conditionable effects of frustration in such animals.

Effect of food deprivation on the approach and escape components of VMH self-stimulation ☆

Abstract Rats implanted with VMH electrodes were trained to control the temporal pattern of stimulation. Food deprivation did not affect stimulus duration but did decrease interstimulus time at the lower of 2 intensities. A subsequent stimulus bound feeding test was uniformly unsuccessful whereas stimulation invariably interfered with feeding. The disagreement between these effects and the reciprocal model of the VMH and LH was discussed.

Specificity of carbachol in the elicitation of drinking

Two studies were reported in which rats with hypothalamic cannulae were injected with carbachol. All animals exhibited drinking following injection. In the first study, this was demonstrated both prior to and following a series of test sessions, and in the second study, at the end only. During the test sessions themselves, only food was available. Animals displayed no tendency to increase their food intake upon carbachol administration during the 16 test sessions. This was contrasted with the ease with which such shifts have been demonstrated with electrical stimulation and suggests a specificity of function that can be detected with chemical but not electrical stimulation.