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Abstract:
Abstract: We examined the hypothesis that distractibility is
a characteristic sequela of mild closed head injury (MHI).
Event-related potentials and behavioral measures (reaction time,
hit rate) were studied in patients with MHI (N = 20), patients with
frontal lobe damage (N = 14), and healthy controls (N = 20) during
a three-tone oddball task. The stimulus sequence consisted of rare,
equiprobable target (2000 Hz) and distractor (500 Hz) tones that
were randomly interspersed in a train of frequently occuring
standard tones (1000 Hz). Subjects were instructed to press a
button when detecting the target tone, and to ignore the other
deviant. Results showed that all groups distinguished targets from
distractors as indicated by the larger P3 amplitude to target
relative to distractor tones. In addition to significantly longer
reaction time to targets, the MHI group had smaller target-evoked
P3 amplitude compared with frontal patients, and smaller amplitude
to distractors relative to frontal patients as well as controls. In
conclusion, the distractibility hypothesis was not confirmed, as
MHI patiens were capable of differential allocation of processing
resources to task relevant and irrelevant events. The prolonged
reaction time and attenuated ERP amplitudes to both classes of
deviants, suggest limited availability or access to the attentional
resources needed for adequate task performance.
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