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Abstract:
We previously found that (1) attending to face identity vs.
location activated the ventral and dorsal visual processing
streams, respectively, (2) attending to identity vs. color
activated adjacent ventral regions, with relatively smaller
attention effects, (3) posterior polymodal areas were suppressed
across all attentional conditions (Clark et al. 1997). This
suggests that the magnitude of attentional change is inversely
proportional to the functional relatedness between a given brain
region and regions specialized for processing the attended feature.
The present study tested this hypothesis using stimuli comprised of
3 faces presented simultaneously for 1800 msec and three tones
presented in series. Subjects were instructed to match stimuli
along a single feature for each run, including ventral stream
(identity, color), dorsal stream (location, angle), and auditory
(pitch, duration) features. Attention blocks alternated with
sensorimotor control. Whole-brain gradient-echo EPI data were
collected from 20 subjects. In agreement with previous findings,
increased signal (attention > control) was found in areas
processing attended features. Attentional modulation of signal
change was generally larger for the comparison of features
processed between-modalities than between-streams. This was larger
in-turn than comparisons within-stream. Decreased signal (control
> attention) was principally found in areas processing
unattended modalities. These results confirm that the relative
magnitude of signal change with attention between features is
inversely proportional to the spatial proximity and functional
relatedness of brain regions that process those features.
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