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Neurophysiological markers of the control and deployment of attention

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(Thesis) Ph.D.
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It is well established that voluntarily shifting attention to the expected location of an impending target will improve the perception of that stimulus once it occurs there. However, the neural mechanisms that underlie this ability to voluntarily deploy attention to spatial locations are still poorly understood. Here, I present four studies that aim to identify reliable neurophysiological markers of the control and deployment of attention in space and to deliniate the sequence of neural activities that enables the attentional enhancement of perception. Using scalp-recorded electroencephalography (EEG), I examined electrophysiological responses elicited by cues that directed attention to spatial locations in preparation for an impending target. In the first two studies, I focused on lateralized event-related potential (ERP) components observed over anterior (chapter 1) and posterior (chapter 2) scalp sites that have previously been interpreted as reflecting attentional control activity in the frontal lobes and anticipatory biasing of sensory cortex, respectively. The anterior ERP activity was found to be unnecessary for attentional control and highly dependant on task parameters. The posterior ERP activity was also found to be dependent on task parameters, whereas posterior alpha-band EEG activity was a reliable indicator of anticipatory biasing of sensory cortex. In the final two studies, I used beamformer spatial filtering to estimate the neural generators of theta-band EEG activity involved in the control of attention in the visual (chapter 3) and auditory (chapter 4) modalities. The observed activities in parietal, frontal, and sensory cortices were highly predictive of the attentional enhancement of target processing. Furthermore, the sequence of theta-band activities and gamma-band synchronization between these theta sources revealed the patterns of communication in the functional network responsible for deploying our attention to locations in space. Combined, these studies indicate that the investigation of EEG in the time-frequency domain may be more advantageous for the identification of reliable neurophysiological markers of the control and deployment of attention than the traditional method of examining lateralized ERPs. In addition, the results of studies 3 and 4 give rise to a new model of the functional network that enables us to voluntarily deploy our attention in space.
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