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Abstract:
This study investigated mechanisms underlying diminished
exploratory behavior following frontal lobe damage. Nine patients
with infarctions in prefrontal cortex (PFC) and 20 matched normal
controls (NCs) participated in an ERP study in which they viewed a
series of drawings that included repetitive background, infrequent
target, and infrequent novel stimuli. They controlled viewing
duration by a button press that served as a measure of exploratory
behavior, and responded to targets by a foot pedal. PFC damage
markedly reduced the amplitude of the novelty P300 and the viewing
duration of novel stimuli. The novelty P300 amplitude explained
much of the variance associated with viewing duration of novel
relative to background stimuli. After controlling for the effect of
viewing duration, there continued to be a strong relationship
between PFC damage and diminished P300 amplitude to novel events.
However, after controlling for the influence of P300 amplitude,
there was no association between PFC injury and reduced viewing
duration on novel stimuli. PFC patients did not differ from NCs in
terms of target P300 amplitude, viewing duration of targets, or
reaction time. We conclude that PFC damage leads to diminished
visual exploration through its disruption of neural processes
indexed by the novelty P300. These processes appear to regulate the
allocation of attentional resources and exploratory behaviors, and
are not limited to immediate orienting responses.
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