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Abstract

The P300 complex was derived from the electroencephalogram (EEG) as subjects mentally counted infrequent large checkerboard visual stimuli, presented randomly among frequent small checkerboard stimuli. Use of low contrast (10%) stimuli and four midline scalp electrodes, facilitated separation of cognitive and sensory components and enabled the P300 complex to be resolved into three distinct components--N200, P3a, and P3b. In 20 healthy adult subjects normative data were established and the P3a and P3b components were shown to depend on cognitive function. In 19 age-matched cirrhotic patients without overt hepatic encephalopathy (HE) the EEG and visual evoked potentials (VEPs) were normal, but latencies of P3a and/or P3b were prolonged in 9. Prolonged latencies were not associated with an abnormal number connection test. Ten additional age-matched cirrhotic patients without overt HE, who were alcohol, drug, and caffeine free, were randomized to receive flumazenil (1 mg) and placebo intravenously, double-blind. After flumazenil or placebo, latencies of P3a and P3b and psychometric test results did not change significantly. These findings suggest that in cirrhotic patients without overt HE (i) impaired cognitive sensory function may occur in the absence of abnormalities of a standard psychometric test, the EEG, or VEPs, and (ii) increased latencies of P3a and P3b may constitute a component of subclinical HE, which is not mediated by increased brain levels of central benzodiazepine receptor agonist ligands.

Event-related evoked potential versus clinical tests in assessment of subclinical cognitive impairment in chronic hepatitis C virus

“…Ciećko-Michalska [ 31 ] suggested that ERPs are a more sensitive method than psychometric tests in detecting early changes in the brain function of patients with cirrhosis. In partial agreement, Jones et al [ 32 ] had also found in the visual ERP study that the prolongation of P300 latency in cirrhotic patients without overt hepatic encephalopathy (HE) may occur in the absence of abnormalities of a standard psychometric test.…”

Performance of a Self-Paced Brain Computer Interface on Data Contaminated with Eye-Movement Artifacts and on Data Recorded in a Subsequent Session

“…This forms preliminary evidence that the system's performance remains robust although event-related potentials may change over time [25–27]. More research, however, is needed to verify the stability of the system's performance over long time periods.…”