Files in this item
|(no description provided)|
|Title:||Neural substrates of avoidance behavior: The afferent limb|
|Author(s):||Poremba, Amy Lynn|
|Doctoral Committee Chair(s):||Gabriel, Michael|
|Department / Program:||Psychology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||During avoidance conditioning, the rabbit sitting in a large activity wheel was presented with two tones. One tone the positive conditional stimulus (CS+), predicted a mild foot-shock, the other tone (CS$-$) did not. The rabbit could learn to avoid the footshock by locomoting in the running wheel. Using a neuronal circuit model of discriminative active avoidance conditioning, sources of afferent input to critical learning-related limbic structures were examined for their influence on neuronal activity and behavior.
The current experiments were designed to answer whether the amygdala and the medial geniculate nucleus (MGN) provide critical input to the limbic system for learning the avoidance behavior. In Experiment 1, electrolytic and ibotenic acid lesions of the medial geniculate nucleus severely impaired learning of the avoidance behavior. Additionally, all training-induced activity (TIA) was blocked in the limbic thalamus and cingulate cortex indicating that the MGN afferent input is critical for the development of TIA.
Experiment 2 concerned the effects of temporary inactivation of the amygdala at different times during acquisition and maintenance of the avoidance behavior.
Temporary inactivation of the amygdala on the first day of training blocked acquisition of the avoidance behavior and development of TIA in the neurons of medial division of the MGN (mMGN) and anterior ventral (AV) thalamic nucleus. On the second day of training, when the amygdala was not inactivated, there were no indications of retention for the first day's learning experience. Performance of the avoidance behavior was impaired after three sessions of overtraining and TIA was decreased in the AV thalamic neurons and increased in the mMGN and medial dorsal (MD) thalamic neurons. However, after an additional seven sessions of overtraining or seven days of rest there were no significant impairment of the avoidance behavior and no changes in TIA. Temporary inactivation of the amygdala on the first training day had long reaching consequences and blocked the normal development of TIA in all of the structures recorded from (except MD thalamic nucleus), and significantly reduced conditioned response performance during the session of criterion.
These findings indicate that the MGN and the amygdala are both critical links in the afferent pathway important for the acquisition of the avoidance behavior.
|Rights Information:||Copyright 1996 Poremba, Amy Lynn|
|Date Available in IDEALS:||2011-05-07|
|Identifier in Online Catalog:||AAI9625181|