Visual Event-Related Potentials in Motor Disorders
Event-related potentials (ERPs) were recorded in 35 normal subjects and 43 patients with motor disorders (17 ataxic patients, 23 cases of Parkinson’s disease and 3 cases of progressive supranuclear palsy). P300 were evoked by two different tasks: Odd-ball paradigm and delayed matching S1-S2 paradigm. 20 out of 43 patients in Odd-ball paradigm and 24 out of 43 patients in S1-S2 paradigm showed prolonged latency, low amplitude or absentresponse. However, only 6 cases showed poor WAIS-R score below normal level. Visual ERPs may give sensitive information for subclinical or mild intellectual impairment in neurological disorders.
Many evidence showed that patients with Parkinson’s disease, progressive supranu-clear palsy and other neurodegenerative diseases not only have motor disorders, but also may have mental impairments (Raskin et al., 1990; Brown and Marsden, 1990; Bubois et al., 1988). This makes the studies on behavior and brain function such as RT (reaction time) difficult to differentiate the effect of motor disorders from the effect of mental deficts. Event-related potentials (ERPs) which is believed to reflect imformation processing of the brain independent of behavior may provide us some information about cognitive impairment. The most widely studied potential component of ERPs is P300 which was used as an electrophysiological index of cognitive processing. The latency of P300 is presummed to reflect the orientation, attention, stimulus evaluation and memory (Donchin, 1979; Naatanen et al.,1992; Kutas et al., 1977). The amplitude of P300 was found to be affected by the probability of response categories or the expectancy of the required response (Mecklinger and Ullsperger, 1995; Johnson, 1986). Although the liability of ERPs limited its clinical application, the abnormal changes of P300 can provide us useful information about cognitive changing.
P300 activity can be elicited by a lot of discrimination tasks. Perhaps auditory Odd-ball paradigm is the most simple and effective method. However, it may not be a sensitive one for the evaluation of slight cognitive changing. Therefore, we employed visual delayed matching paradigm (S1-S2 paradigm) and visual Odd-ball paradigm to elicit P300. The aim of the present study is: (1) to verify the usefullness of P300 in the evaluation of cognitive deficts; (2) to compare the results of P300 with neuropsychological test (WAIS-R test); (3) to study the probability of cognitive impairments in patients with some motor disorders.
KeywordsP300 Amplitude Progressive Supranuclear Palsy P300 Latency Motor Disorder Prolonged Latency
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