Neuropsychological deficits associated with small unilateral thalamic lesions

Neuropsychological deficits resulting from small, well demarcated, unilateral thalamic lesions were investigated in 13 right-handed patients. Fourteen patients with deep white matter lesions and 12 normal subjects served as controls. The performance of thalamic patients was generally worse than that of normals and patients with white matter lesions, although the lesions in the latter were significantly larger. There was no clear indication of a dichotomous lateralization of function at the level of the thalamus, although patients with left-sided lesions performed less well in almost all tests. There was some evidence of a rostrocaudal dichotomy, rostral thalamic lesions leading to memory deficits and caudal lesions to impairments of 'abstraction' and 'categorization'.