Abnormal learning and forgetting of individual spatial reversal problems in brain-damaged rats

Abstract

Except for amygdaloid lesions and cortical cerebellar ablations, selective destruction of virtually any part of the tel-, di-, mes-, or metencephalon was found to impede spatial reversal learning in the rat. (These data contrast sharply with those reported in recent studies on visual reversal learning in the rat.) Test trials given after learning each reversal problem disclosed significant (or marginally significant) deficits in retention only in those groups sustaining damage to the cingulate cortex, ventral hippocampus, rostral caudoputamen, lateral supraoptic hypothalamus, posterolateral hypothalamus, lateral thalamic complex, mediodorsal thalamus, ventromedial thalamus, parafascicular nucleus, substantia nigra, interpeduncular-central tegmental area, pontomesencephalic reticular formation, or pontine reticular formation. It is proposed that there may be at least three classes of learning (amnesic) disorders observed on any given task: (1) a learning impairment only, (2) a retention impairment only, and (3) both a learning and retention impairment.Huppert and Piercy (1979) have presented evidence suggesting that there may be at least two classes of learning (amnesic) disorders in braindamaged patients. In one, learning is impaired, but retention over time of what has been learned is unimpaired. The second is characterized by an impairment (or no impairment) in learning, but retention over time of what has been learned is impaired.

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

“…However, it would be premature to conclude that the solution of our detour problems requires the same cognitive abilities as those required for the solution of maze habits and spatial reversal tasks. This is shown by the findings that rats with occipital ablation s or lateral thalamic lesions are virtually indistinguishable from the controls in learning Problem A (Thompson et al, 1984a; present study), but are significantly impaired in learning maze habits (Lashley, 1929; and spatial reversal tasks (Thompson, 1983a).…”

Detour problem-solving behavior in rats with neocortical and hippocampal lesions: A study of response flexibility

“…This would follow from the fact that the latter would also disrupt hippocampal function to the extent that the hippocampus would be deprived of certain kinds of sensory input necessary to transact its comparator role. This account would seem to explain the similar disturbances observed in neocortically and hippocampally damaged rats on such tasks as complex mazes (Foreman & Stevens, 1982;Thompson, 1979), position reversals (Thompson, 1983), and active and passive avoidance responses (Thompson, 1978b).…”

“…However, it must be recognized that neocortical lesions produce impairments on maze, position reversal, and active and passive avoidance responses that cannot be satisfactorily explained in terms of sensory privation (Dale & Goodale, 1979;Lashley, 1929;Thompson, 1979Thompson, , 1982Thompson, , 1983. These data would suggest that the role of the hippocampus in behaviors that are disorganized by neocortical lesions may not necessarily be dependent upon sensory information from the neocortical receiving areas.…”

“…Rats with similarly localized corticallesions are known to be deficient in place learning, as gauged by performance on simple (Lashley, 1929;Thompson, 1983) and complex (Lashley, 1929;Thomas & Weir, 1975;Thompson, 1979) maze habits. Furthermore, an extensive series of experiments comparing the effects of occipital lesions with those of hippocampal lesions on a wide variety of laboratory tasks led to the conclusion that the nonvisual function of the former was closely associated with the spatial functions of the latter (Thompson, 1982), a conclusion that must be revised in light of the present findings.…”

Learning ability of young rats is unaffected by repeated exposure to a static electromagnetic field in early life

“…The learning task consisted of the repeated reversal of a position habit in a single unit T-maze adapted for the use of escape-avoidance of mild foot shock as a motive [see Thompson, 1983, for a complete description of the apparatus and procedure]. On the first day, each animal was trained to choose the right (correct) arm and avoid the left (incorrect) arm of the T (reversal problem 0).…”