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Abstract
P300 event-related brain potentials (ERPs) were elicited using a simple discrimination
task in which participants discriminated two different equiprobable visual stimuli
with button-press responses (n = 20). A total of ten trial blocks were presented at
10-min intervals. P300 amplitude declined significantly, but peak latency did not
change reliably across trial blocks. P300 amplitude demonstrated a reliable cyclical
fluctuation across trial blocks, although P300 latency did not. Intra-trial block
ERP variability was assessed by computing the correlation coefficients between the
target and standard stimuli for amplitude and latency measures across participants
within each trial block. P300 amplitude correlations were weakest at the Fz electrode,
more strongly associated at Cz, and were most strongly correlated at Pz across trial
blocks. P300 latency correlations were somewhat weaker and similar in strength across
electrodes sites. The correlational patterns for both P300 amplitude and latency demonstrated
reliable cyclical variation. The N100 component produced strong and consistent correlations
for both amplitude and latency, whereas the P200 and N200 component measures evinced
cyclical correlational patterns similar to the P300 across trial blocks. These results
suggest that the stability of P300 and other component measures can vary appreciably
within and across trial blocks in a manner that reflects ultradian variation in arousal
level.