Psychological test results of subjects with known cerebral lesions and Parkinson's disease as compared to controls.

In the study of Parkinson's disease, motor deficits have received primary attention because of their limiting influence on over-all adaptive abilities. Certain other factors such as emotional depression and inertia have been commented upon as playing an important role in the individual's over-all manner of adjustment. There has been some indication in the literature (Talland, 1962; Levita, et ai., 1964) that these patients have essentially intact intellectual functioning and any decrease in abilities which may be noted in this population is due primarily to aging and its attendant effects. A recent study (Reitan & Boll, in press) has shown that, when patients suffering from Parkinson's disease were evaluated over a wide variety of motor, perceptual-motor, cognitive. problemsolving, and sensory tasks, these patients showed a degree of deficit that signif~canrlp exceeded the decline in adaptive abilities normally seen in persons of comparable age and of no known neurological impairment. This type of evidence does not, in itself, however, provide definitive proof that the basis for the impairment was some faulg cerebral functioning. It is a rather widely held notion that emotional lethargy causes these patients to do generally less well and to put forth less effort on all tasks, and therefore generalized lowering in excellence of performance would be expected. In an attempt to evaluate this hypothesis the present study was designed to compare the functioning of Parkinsonian Ss with Ss of similar age and background with diagnosed disorders of the cerebral hemispheres. A rank-difference correlation coefficient was computed to determine whether or not tests which differentiated normal from known brain-damaged Ss were the same tests which differentiated normal from Parkinsonian Ss. If the same tests were equally effective in differentiating normal from Parkinsonian as they were in differentiating normals from patients with known cerebral damage, then further support would be lent to the hypothesis that the generalized impairment of adaptive abilities demonstrated by Parkinsonian patients is indeed due to impairment of cerebral functioning rather than merely to a motor inability or a generalized emotional disinterest of one sort or another. The ranking of effectiveness of 29 tests discriminatin normal from braindamaged Ss was obtained from a study by Reed and Reitan (19f3) while the ranking of these tests discriminating normals from Parkinsonian Ss was obtained from a study by Reitan and Boll (in press). In each instance ranks were assigned according to the size of t ratio generated when data beween brain-damaged or Parkinsonian and control Ss were compared. The Spearman rank-difference correlation coefficient was ,547 (# = .01). This suggests that tests which best discriminate normal Ss from Ss who have identifiable cerebral pathology tend to be the same ones that differentiate normal Ss from those with Parkinson's disease, supporting the hypothesis that impaired cerebral functioning is a significant factor in producing psychological deficit in both groups.