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Abstract:
Abstract: Fast spiral gradient-echo fMRI (36 axial slices of
whole brain acquired in 2 seconds) was used to study 16
right-handed subjects (6 females, 10 males, 19-44 years) as they
performed a 2-factor spatially-directed auditory attention task.
The first factor, the stimulus train itself, had two levels: blocks
of standard tones (1000 Hz, 100 ms duration, 800 ms inter-stimulus
interval), and blocks of standard tones pseudorandomly intermixed
with deviant ones (1300 Hz, same duration, 0.15 probability), both
delivered dichotically via earphones. The second, attentional
factor had three levels: subjects were instructed to ignore all
tones; to press a button when a deviant tone is detected by the
left ear; and similarly for the right ear. Conditions were
intermixed and balanced; data were analyzed by multiple regression.
Switching attention from the right ear to the left generated in
every subject a larger pattern of BOLD activation in the left
temporal lobe, as well as additional activations in the right
temporal, prefrontal, and cingulate cortices. The larger activation
possibly reflects a greater degree of effort when attending with
the left ear. If so, it would comprise evidence of a right-ear
advantage in attending to non-linguistic stimuli, in addition to
that usually reported for linguistic stimuli.
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