ELECTROPHYSIOLOGICAL EVIDENCE FOR VISUOCOGNITIVE DYSFUNCTION IN YOUNGER NON CAUCASIAN PATIENTS WITH PARKINSONS-DISEASE

A study of ''primary'' (VEPs) and ''cognitive'' (ERPs) visual evoked p otentials was carried out in a group of non-demented Afro-American Par kinson's disease (PD) patients, Current studies suggest that differenc es exist in the clinical manifestations of PD in Caucasian and non-Cau casian populations, Two horizontal sinusoidal gratings differing in sp atial frequency, i.e., 1 and 4 cycles per degree (cpd), were presented in an ''odd-ball'' paradigm to 17 patients with PD and 17 age-matched control subjects. While the 1 cpd stimulus, is not expected to reveal retinal dopaminergic deficency, but only visuocognitive deficits, the 4 cpd may give direct information of both ''retinal'' and ''cognitive '' visual deficits, We measured the latencies and amplitudes of N70, P 100 and P300 components, and derived the ''normalized'' measures of P3 00-N70 latency difference (Central Processing Time-CPT70), the P300-P1 00 latency difference (CPT100) and the P300 amplitude responses normal ized to either N70 and P100 amplitude (Amplitude Ratios AR70 and AR100 ). Our results do show that cognitive electrophysiological deficits in younger PD patients exist in non-Caucasians, perhaps to an even great er degree than in Caucasians, and confirm that absolute and normalized ERP amplitude and latency abnormalities are a distinguishing feature of younger PD patients from controls, In particular P300 measures are abnormal for 1 cpd pattern. A negative correlation exists between P300 amplitude and the motor score, By comparing the results for 1 and 4 c pd stimuli it can be concluded that ''primary'' and ''cognitive'' visu al abnormalities are independently affected in PD, implying that visuo -cognitive abnormalities are not passively determined by retinal dopam inergic deficiency.