Parvocellular and magnocellular visual processing in spinocerebellar degeneration and Parkinson's disease: an event-related potential study

Objective: We recorded event-related potentials (ERPs) using appropriate vi sual stimuli to establish a non-invasive method that separately investigate s the parvocellular (P) and magnocellular (M) visual functions, and to eval uate the visual function in spinocerebellar degeneration (SCD) and Parkinso n's disease (PD). Methods: Eight SCD and 10 PD patients were compared with 11 age-matched con trol subjects. In the P-task, subjects were required to discriminate equilu minant red (frequent) and green (rare) random dots. In the M-task, moving r andom dots on a rotating cylinder (frequent) and those moving irregularly ( rare) were discriminated. Results: Control subjects showed an endogenous positive component at 400 ms (P400(p)) with an early exogenous negative potential (N160(p)) in the P-ta sk. In the M-task, N160(m) and P400(m) were recorded. A deuteranope lacked P400(p) with normal P400(m). In SCD, P400(p) latency and N160(p)-P400(p) in terval were increased with normal N160(p) latency. N160(m) latency was also increased while N160(m)-P400(m) interval was normal. In PD, there were no significant changes in the P-task but P400(m) latency was increased with no rmal N160(m) latency. Conclusions: SCD patients may have not only abnormal higher processing in t he P-pathway but abnormal fundamental processing in the M-pathway. PD may h ave impaired higher processing of the M-pathway with the preserved P-functi on. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.