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 visual stimuli to establish a non-invasive method that separately investigates the parvocellular (P) and magnocellular (M) visual functions, and to evaluate the visual function in spinocerebellar degeneration (SCD) and Parkinson's disease (PD).


METHODS
Eight SCD and 10 PD patients were compared with 11 age-matched control subjects. In the P-task, subjects were required to discriminate equiluminant red (frequent) and green (rare) random dots. In the M-task, moving random 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-task. 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) interval 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 normal N160(m) latency.


CONCLUSIONS
SCD patients may have not only abnormal higher processing in the P-pathway but abnormal fundamental processing in the M-pathway. PD may have impaired higher processing of the M-pathway with the preserved P-function.
Arakawa
K
K
Department of Neurology, National Center of Neurology and Psychiatry, Tokyo, Japan. arakawa@neuro.med.kyushu-u.ac.jp
Tobimatsu
S
S
Kato
M
M
Kira
J
J
D000368:Aged; D003118:Color Perception / Q000502:physiology; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D005829:Geniculate Bodies / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology; D010300:Parkinson Disease / Q000503:physiopathology*; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation; D013132:Spinocerebellar Degenerations / Q000503:physiopathology*; D014795:Visual Pathways / Q000502:physiology*