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Maturational influences on perseveration of avoidance and reversal learning after selected brain damage in rats
Insights
Age at the time of brain injury significantly impacts recovery of avoidance behavior in rats. Lesion location and age interact, with older subjects showing greater perseveration after prefrontal cortex or hippocampal damage.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Cognitive Neuroscience
Background:
- Age at the time of central nervous system damage is a critical factor influencing behavioral recovery.
- Understanding the interplay between age, lesion location, and behavioral deficits is crucial for developing effective interventions.
Purpose of the Study:
- To investigate the influence of age at the time of lesion on the recovery of avoidance behavior in rats.
- To examine the effects of dorsomedial prefrontal cortex, ventrolateral prefrontal cortex, and hippocampal lesions on perseverative responding.
- To assess the impact of combined lesions and varying recovery periods on behavioral outcomes.
Main Methods:
- Experiment I: Weanling and adult male rats received bilateral electrolytic lesions to the prefrontal cortex or hippocampus, followed by step-up avoidance task acquisition, reversal, and extinction.
- Experiment II: Replicated Experiment I with combined lesions (dorsomedial prefrontal cortex plus caudate nucleus) and varied recovery periods (7 or 60 days).
- Behavioral measures included trials to criteria, errors, and latencies during initial training and after a 30-day interval.
Main Results:
- Age significantly affected initial avoidance learning, with age effects becoming more dominant after 30 days post-lesion.
- Hippocampal and ventrolateral prefrontal cortex lesions resulted in the most significant response perseveration.
- In Experiment II, all independent variables were significant during acquisition, but only age was significant during extinction.
Conclusions:
- Age at the time of brain damage profoundly influences the recovery of avoidance behavior.
- The location of the lesion interacts with age to determine the extent of behavioral deficits and perseveration.
- Recovery patterns differ based on lesion type and the duration of the recovery period.
Abstract:
In Experiment I, 18 weanling and 18 adult male rats received bilateral electrolytic lesions of the dorsomedial or ventrolateral prefrontal cortex, or the hippocampus, while 12 additional pups and adults served as nonoperated controls (n = 6/group). Subjects were observed for perseverative responding in acquisition of a stepup avoidance task, followed by reversal training and extinction. Thirty days later, subjects were retrained and tested in the same manner. During initial training, the numbers of trials to criteria, errors, and latencies on the last 5 trials all indicated significant effects from age, primarily, and surgery, secondarily. After 30 days, surgical effects assumed a more dominant role, with hippocampal and ventrolateral damage producing the greatest extent of response perseveration. Experiment II replicated the essential procedural sequence as Experiment I, but included damage from combined lesions. 24 weanlings and 24 adults received bilateral lesions to the dorsomedial prefrontal cortex, the dorsomedial prefrontal cortex plus caudate nucleus, or sham lesions. Subjects from this experiment were trained after 7 days or 60 days recovery (n = 6/group). The acquisition results indicated that all independent variables were significant, but only the age effect attained significance in the extinction data. Both experiments point to the profound influence of age at the time of damage in accounting for recovery of avoidance behavior.