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Abstract:
This study examined the effects of task relevance and task
difficulty on P300 amplitude and latency during a continuous
auditory attention task. Subjects were presented with degraded and
undegraded syllables under two task relevant conditions. In the
motor attention condition (MA), subjects made a bilateral button
press to target stimuli. In the listen attention condition (LA),
subjects listened for target stimuli without counting or
vocalizing. Analysis of amplitude effects for targets yielded a
significant Condition X Lead (Fz, Cz, Pz) interaction (p < .01).
P300 amplitude during both MA and LA showed the expected
anterior-posterior scalp topography, with the highest amplitude at
Pz. However, amplitude across all leads was higher for MA than LA,
with the smallest difference at Fz. P300 latency effects for
targets revealed a significant Condition X Lead X Task Difficulty
(degraded, undegraded) interaction (p < .01). P300 latency was
longer for degraded than undegraded targets at Pz for MA, and at Fz
for LA. Analysis of P300 amplitudes between targets and nontargets
yielded significant differences in both MA and LA conditions (p
< .01). MA and LA targets produced higher amplitudes than
nontargets. The findings suggest that P300 amplitude is most
affected by task relevance; whereas P300 latency is most affected
by task difficulty.
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