Neurotoxic lesions of the dorsomedial thalamus impair the acquisition but not the performance of delayed matching to place by rats: a deficit in shifting response rules.
This study examined the acquisition of a T-maze matching to place task by rats with neurotoxic lesions of the thalamic nucleus medialis dorsalis. This test of spatial working memory also entails learning a task rule that is contrary to the animals' innate preference. The rats next performed the same matching task over different retention delays. Finally, they were trained on a reversal of the task rule, i.e., to nonmatch to place. Although the lesions produced a clear acquisition impairment on the matching task, there was no evidence of a loss of working memory. A series of control tasks found no appreciable effect on a conditioned cue preference task or on open field activity. The pattern of results shows that medialis dorsalis lesions lead to a selective increase in perseverative behavior that can retard task acquisition. This perseverative deficit closely resembles that observed after prefrontal damage in rats, strongly indicating dysfunction in a common system.
Hunt
P R
PR
Medical Research Council Cambridge Centre for Brain Repair, University of Cambridge, Cambridge, CB2 2PY, United Kingdom.
Aggleton
J P
JP
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D003213:Conditioning, Psychological / Q000502:physiology; D008297:Male; D018782:Maze Learning / Q000502:physiology; D008570:Memory, Short-Term / Q000502:physiology*; D009498:Neurotoxins; D017397:Prefrontal Cortex / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013028:Space Perception / Q000502:physiology*; D013788:Thalamus / Q000502:physiology*
D009498:Neurotoxins