A series of functional MRI studies will be presented designed to (a) dissociate different processes of visuospatial attention, and (b) characterize the effects of nicotine thereon. Parametric manipulation of bottom-up and top-down processes of attentional resource allocation revealed distinct networks of brain regions engaged by these functions. A different analysis approach based on trial-by-trial variation in reaction time identified rostral anterior and posterior cingulate cortices as activated with faster responding under conditions of stimulus unpredictability. These structures are part of the “default” network that is active in the absence of goal-directed activity, and appear to subserve a broad and spontaneous information gathering function. Nicotine improved attentional performance and enhanced task-induced deactivation of such default activity. Greater performance enhancement was associated with greater default deactivation, controlling for nicotine plasma levels. Control experiments did not suggest any confounds by non-specific vascular effects of nicotine.

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