Lesions of anterior thalamic nuclei impair acquisition of new and changing of preoperatively learnt active avoidance stereotypes.
Six-month-old male Long-Evans rats reproduced their preoperatively learnt active avoidance responses (CAR) in a Y-maze and in a jump test box after bilateral symmetric lesions of thalamic anterior ventral (AV) and anterior medial (AM) nuclei without significant changes. However, when the test sequence was changed in a way that transitions from high success probability (low error probability) to low success probability (high error probability) were taken into account, then problems with time limit and increased punishments were not overcome by lesioned rats. Transitions in the opposite direction were better mastered. All AV-AM rats were unable to acquire a new CAR stereotype in a W-like maze in which the first phase had a low success probability. Rats without lesions were rarely influenced by various test sequences. The lesioned rats showed purely arrest behaviour and did not develop learned helplessness in successless sessions and were transiently hyperactive in the open field test. The data support the hypothesis that the anterior thalamic nuclei as part of the Papez circuit participate in the analysis of success probability and preferent consolidation of correct responses, when stereotype behaviour has to be changed.
Klingberg
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Paul Flechsig Institute for Brain Research, Department of Neurophysiology, Karl Marx University, Leipzig, GDR.
Klingberg
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D000818:Animals; D001362:Avoidance Learning; D004192:Discrimination, Psychological; D008297:Male; D009928:Organ Specificity; D051381:Rats; D012016:Reference Values; D013239:Stereotyped Behavior; D013787:Thalamic Nuclei / Q000502:physiology*