Normal cognitive function requires that humans selectively attend to important or relevant elements of their environment while ignoring irrelevant or distracting information. The alternative, whereby all information in the sensory domain is processed to the level of consciousness, does not allow for normal function and is a core deficit in certain neural disorders such as autism, schizophrenia and attention deficit disorder. While the majority of studies to date have focused on how selective processing itself is affected by attention, the current research proposal concentrates on the neural mechanisms by which selective attentional states are first established in anticipation of attentionally relevant stimuli. That is, when the brain is involved in attentionally demanding tasks, it is of considerable advantage to direct attention to the relevant stimulus to be attended, prior to its arrival and to disengage attention from locations or sensory modalities that may contain potentially confusing information. This proposal is designed to specifically address the processes by which attentionally irrelevant information in the environment is ignored or inhibited during selective attention tasks. Recent studies have shown that selective inhibition of potentially distracting information may be subserved by oscillatory brain rhythms in the 8-14 Hz alpha frequency-band. By using trial-by-trial cueing to direct subjects' attention selectively between competing information channels and assessing the brain activity in the intervening period between the rue' and the subsequent imperative stimulus (S2), the brain mechanisms involved in establishing and maintaining selective attentional states are examined. Two convergent methodologies, high-density mapping of event-related potentials (ERPs) and event-related functional magnetic resonance imaging (fMRI) are employed to assess the brain regions that are involved in setting up and maintaining selective attentional states. Spectral analyses are performed to examine the role of alpha-oscillations in this process.
The specific aims of this proposal are: 1) to examine the relationship of alpha-inhibitory mechanisms to attentional load and 2) to establish the anatomy of these anticipatory attentional mechanisms using the high spatial resolution of event-related fMRI.
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