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Abstract:
Divided-attention tasks invoke the "Central Executive" - a
division of attentional resource to deal with scheduling. In
contrast, when a single task is made more difficult, one must
increase focused attention. Both situations require increased
attentional resources and therefore may involve frontal and
parietal attentional systems. We used EEG coherence to investigate
whether communication between sites in the dorsal frontal and
parietal lobes during divided attention is the same as during
increased focused attention. EEG activity was recorded from 27
scalp sites while 57 undergraduate participants performed an
auditory oddball vigilance task at two levels of stimulus
difficulty (discriminating 100 and 150 ms tones versus 100 and 125
ms tones) first alone and then simultaneously with a digit
detection working memory task. Response times and number of errors
increased significantly when participants were faced with
performing the harder discrimination (RT=681, 718 ms; errors=21.9,
32.2) and when they were required to perform the dual task (RT=636,
763 ms; errors=24.1, 30.1). Frontal-parietal beta band coherence
showed a significant reduction with greater stimulus difficulty
(p=.026) and significant increase with the dual task (p=.002), with
no interaction between difficulty and task. These results suggest
that different brain processes are involved when the brain must
divide its cognitive resources (i.e., central executive) from when
the brain is required to focus attentional resources.
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