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Abstract:
Abstract: In rapid streams of visual stimuli, identification
of a first target interferes with identification of a second target
presented during the next second (the Attentional Blink, AB). The
AB resembles another interference effect known as the Psychological
Refractory Period (PRP), except that in the PRP effect targets are
not masked. This study compared the neuroanatomical substrates of
both phenomena using fMRI. Two white targets (T1, T2) were embedded
in streams of black letters (25ms duration, 10/s) presented
centrally on a monitor. T2 followed T1 by either 100 or 600 ms. Two
conditions were examined: 1) streams of 9 letters producing the AB
effect; 2) streams of 7 letters in which the distractors
immediately following T1 and T2 were removed to produce a PRP
effect. When compared to a baseline (fixation point), all
conditions activated the perirolandic, lateral premotor, and
anterior cingulate regions primarily on the left. Compared to the
long delay, the short delay showed decreased activation in ventral
prefrontal and ventral premotor regions. Compared to the AB task,
the PRP task produced increased activations in the left medial
prefrontal region. Common activations confirm premotor and
cingulate involvement in attention tasks, whereas delay effects may
be linked to loss of processing efficiency observed in these
interference effects. Finally, the task differences observed
suggest that medial prefrontal activity may be linked to the added
masking interference of the AB effect.
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