Abstract
Recent brain imaging studies using functional magnetic resonance imaging (fMRI) have implicated a frontal-parietal network in the top-down control of attention. However, little is known about the timing and sequence of activations within this network. To investigate these timing questions, we used event-related electrical brain potentials (ERPs) and a specially designed visual-spatial attentional-cueing paradigm, which were applied as part of a multi-methodological approach that included a closely corresponding event-related fMRI study using an identical paradigm. In the first 400 ms post cue, attention-directing and control cues elicited similar general cue-processing activity, corresponding to the more lateral subregions of the frontal-parietal network identified with the fMRI. Following this, the attention-directing cues elicited a sustained negative-polarity brain wave that was absent for control cues. This activity could be linked to the more medial frontal–parietal subregions similarly identified in the fMRI as specifically involved in attentional orienting. Critically, both the scalp ERPs and the fMRI-seeded source modeling for this orienting-related activity indicated an earlier onset of frontal versus parietal contribution (∼400 versus ∼700 ms). This was then followed (∼800–900 ms) by pretarget biasing activity in the region-specific visual-sensory occipital cortex. These results indicate an activation sequence of key components of the attentional-control brain network, providing insight into their functional roles. More specifically, these results suggest that voluntary attentional orienting is initiated by medial portions of frontal cortex, which then recruit medial parietal areas. Together, these areas then implement biasing of region-specific visual-sensory cortex to facilitate the processing of upcoming visual stimuli.
Highlights
At every moment of our lives, we are deluged with sensory stimuli coming at us from multiple directions and through our various sensory modalities—much more information than we can fully process
Recent functional neuroimaging studies have indicated that a network of brain areas in frontal and parietal cortex is involved in directing our attention to specific locations in our visual field
Our results indicate that visual-spatial attentional control is initiated in frontal brain areas, joined shortly afterwards by parietal involvement
Summary
At every moment of our lives, we are deluged with sensory stimuli coming at us from multiple directions and through our various sensory modalities—much more information than we can fully process. The critical function of attention allows us at each moment to continuously select and extract the most important information from this flood of sensory inputs in order to provide those stimuli with fuller processing. Previous brain imaging and electrophysiological studies [3,4,5,6,7,8] have shown that this behavioral improvement is associated with increased evoked brainactivity responses in early visual sensory areas for stimuli that occur at the attended location. The directing of visual-spatial attention is associated with increased activity in a network of mainly dorsal frontal and parietal cortical brain areas [8,9,10,11,12,13,14,15,16]. It is thought that this frontal–parietal network may facilitate a biasing of the system in advance toward task-relevant information by enhancing baseline activity in feature-specific visual areas that will be processing the visual stimuli [7,17,18,19,20,21,22]
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