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Title: Social isolation in rats and the role of the septo-hippocampal system
Author: Dalrymple-Alford, J. C.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1983
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The behavioural effects of social isolation in the rat were examined to assess their complexity and their possible neural mediation by changes in the septo-hippocampal system. A comprehensive review (including the data presented in this thesis) of non-social behaviour, behaviour in learning tasks and social behaviour supported the viewpoint that the wide effects of social isolation do not have a unitary aetiology and thus have more than one neural representation. Two general categories were distinguished. Firstly, 'permanent' effects of isolation depend on isolation imposed at weaning (hyperactivity and many learning effects which are loosely indicative of "behavioural disinhibition"). Secondly, reversible effects are found after isolation at several ages (responses to 'noxious' stimuli; social behaviours). However, a comparison of social isolation with the syndromes following lesions to the septum and the hippocampus demonstrated a close resemblance between these treatments in terms of the 'permanent' effects of isolation-rearing. In the experimental studies, isolates were found to show both lower initial ambulation and subsequent hyperactivity in the open field; the hyperactivity was also found for rearing responses and for non-specific activity. Inhibited ambulation and increased emergence latencies were not apparent under low levels of stimulation. Hyperactivity, increased resistance to extinction and poorer maze learning were dependent on isolation-rearing; inhibited activity and slower running during alley training were found irrespective of the age at isolation. Isolation produced facilitated shuttle-box avoidance but did not affect spontaneous alternation. A study of open-field activity, passive avoidance and shuttle-box avoidance found that group-reared rats were susceptible to the effects of later dorsal hippocampal lesions, but isolation-reared rats were generally unaffected by these lesions; these findings question the generality of the idea that impoverished animals are more affected by CNS injury. Finally, isolates were not impaired in the reversal of a spatial habit, in responses to satiation or in the acquisition of a simultaneous brightness discrimination, but isolates showed perseverative 'hypothesis behaviour' during the extinction of the latter task without a significant impairment of running responses. Although the effects of isolation-rearing and the effects of damage to the septo-hippocampal system clearly differ (eg. spontaneous alternation; open-field rearing), several effects of isolation-rearing may reflect changes in septo-hippocampal function and/or in related pathways. The possible contributions of the frontal cortex, the amygdala and the ventromedial hypothalamus were also considered.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available