Lesions of the anterior thalamic nuclei and intralaminar thalamic nuclei: place and visual discrimination learning in the water maze
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Medial thalamic damage produces memory deficits in humans (e.g., Korsakoff’s syndrome) and experimental animals. Both the anterior thalamic nuclei (ATN) and rostral intralaminar plus adjacent lateral thalamic nuclei (ILN/LT) have been implicated. Based on the differences in their main connections with other neural structures, we tested the prediction that ATN lesions would selectively impair acquisition of spatial location discrimination, reflecting a hippocampal system deficit, whereas ILN/LT lesions would impair acquisition of visual pattern discrimination, reflecting a striatal system deficit. Half the rats were first trained in a spatial task in a water maze before switching to a visual task in the same maze, while the remainder were tested with the reverse order of tasks. Compared with sham-operated controls, (1) rats with ATN lesions showed impaired place learning, but normal visual discrimination learning, (2) rats with ILN/LT lesions showed no deficit on either task. Rats with ATN lesions were also hyperactive when their home cage was placed in a novel room and remained more active than ILN/LT or SHAM rats for the subsequent 21 h, especially during the nocturnal phase. These findings confirmed the influence of ATN lesions on spatial learning, but failed to support the view that ILN/LT lesions disrupt striatal-dependent memory.
KeywordsAnterior thalamic nuclei Hippocampus Intralaminar thalamic nuclei Spatial memory Striatum Visual pattern memory Water maze
The authors are grateful to O. Bildstein, G. Edomwony and O. Egesi for their help in animal care. They also acknowledge research funds from the University of Strasbourg and the CNRS. J.C.D-A. has been supported during his stay in Strasbourg as an invited professor by University of Strasbourg. M.W. was supported by a Lavoisier post-doctoral fellowship from the French Government (when he was at Christchurch) and a 1-year fellowship by the Fondation pour la Recherche Médicale. A 3-year PhD fellowship was awarded to J.L. from the French Ministère de l’Enseignement Supérieur et de la Recherche. Finally, L.L. contributed to the current work while being a post-doctoral fellow supported by the French A.N.R. (ANR-06-NEURO-027-04).
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