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Abstract:
Abstract: Introduction. The present study investigated the
effect of focused versus divided attention for auditory stimuli in
a dichotic listening situation. Subjects. Twelve healthy intact
males between 20-30 years of age. Methods. Subjects listened to
lists of consonant-vowel syllables, or short musical instrument
passages, with the task of detecting a "target" syllable or musical
instrument by pressing a button. The subjects were instructed to
either divide attention between the ears, or to focus attention on
the left or right ear stimulus. Brain activation was measured with
15 O-PET, and significant changes in regional normalized counts
(rNC) were evaluated using statistical parametric mapping (SPM96)
software. Results. During divided attention, significant activation
was seen bilaterally in the superior temporal gyrus. Focusing of
attention significantly decreased activity in the temporal lobe, at
the expense of an increased activation in the posterior inferior
parietal lobe. The CV-syllables also activated areas corresponding
to the classic language areas of Broca and Wernicke. The musical
instrument stimuli mainly activated areas in visual association
cortex, cerebellum, and the hippocampus. Conclusion. Attention has
a facilitory effect on auditory processing, causing reduced
activation in the primary auditory cortex when attention is
explicitly recruited. The observed activations in the parietal lobe
during the focused attention conditions could be part of modality
non-specific "attentional network".
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