Detour problem-solving behavior in rats with early lesions to the “general learning system”

Abstract

Recent studies involving visual and nonvisual discrimination habits suggest that the components of the rodent’s general (nonspecific) learning system (a group of brain structures essential for normal acquisition of a wide range of laboratory tasks) include the regions of the globus pallidus, lateral thalamus, substantia nigra, midbrain central gray, median raphe, and pontine reticular formation. To determine whether these regions play a role in more complex kinds of learning, young rats previously subjected to selective lesions to these brain sites received five trials on each of three “climbing” detour problems. Performance on Trial 1 (a measure of response flexibility) as well as performance on Trials 2–5 (a measure of detour habit formation) of each problem was significantly impaired in those groups with damage to the globus pallidus, substantia nigra, median raphe, or pontine reticular formation. On the other hand, those groups with damage to the lateral thalamus or midbrain central gray failed to display consistent deficits in detour problem-solving behavior. This pattern of results suggests that the latter two structures can no longer be grouped with the globus pallidus, substantia nigra, median raphe, and pontine reticular formation as components of the rodent’s general learning system.