PSYCHOLOGICAL FUNCTIONS IN RELATION TO LESION SIZE AND SITE IN CRYOTHALAMECTOMY FOR PARKINSONISM

Summa~y.-The relationship of number or size and site of unilaterally and bilaterally induced thalamic lesions to psychological changes in parkinsonians was assessed by means of quantifiable tests of cognition, perception, and recent memory. In no instance was lesion size or site, within the confines of the venttolateral nucleus of the thalamus, significantly or differentially related to cognitive or perceptual changes. These findings were discussed in terms of possible roles of thalamic nuclei in psychological functions. The "law of physiological safety," the role of functional compensation, and the presence of reladvely small lesions within a larger bilateral thalamic zone were considered in interpreting the results. Clinical implications were noted with regard to patient selection for placement of multiple lesions. The presence of wide individual differences in a brain's tolerance of lesion infliction was emphasized also.