Abstract
Interaction with the outside world is guided by the ability to switch and maintain attention. While top-down attention drives object selection, bottom-up influences can interfere, causing an individual to switch their focus to another target. Top-down modulation of alpha power (8-14 Hz) has been reported in cued attention paradigms, but has rarely been examined during tasks involving dynamic stimuli. In this study, the neural representation of top-down and bottom-up interactions was explored during three visual selective attention tasks. All three tasks involved two competing sequences of flashing arrows to the left and right of a central fixation point. In each sequence, arrow orientations changed over time, resulting in different trajectories. Subjects were cued to attend either the left or right target sequence and report its trajectory. Passive trials, requiring no action, were included as a control. Tasks had zero, one, or six flashing distractor arrows at locations separate from the two target sequences. All arrow timings were staggered, allowing association of event-related neural activity with individual arrow onsets. In order to obtain alpha power measurements, EEG was recorded simultaneously in 64 channels. Modulation of alpha power was observed in parieto-occipital channels contralateral to the cued sequence. With no distractors, alpha desynchronization, or power decrease, occurred at each onset in the cued sequence only. A similar, but weaker, desynchronization pattern was observed in the one-distractor task. In the six-distractor task, however, desynchronization no longer occurred at target onsets, but at distractor onsets for all trials. An overall difference in power between active and passive trials was observed throughout both zero-and one-distractor tasks, but not in the six-distractor task. These results suggest that while top-down attention exerts strong modulation of alpha power, bottom-up attention can interfere, strengthening the response to non-targets while weakening the response to targets.
Meeting abstract presented at VSS 2017