Abstract
Attentional performance depends on an individual's level of alertness, which refers to a state of responsiveness that enables the organisms to process stimuli faster and more efficiently (Posner & Petersen, 1990). A phasic, short-lived increase of alertness can be induced by an external warning cue signaling the imminent occurrence of a stimulus. Alertness states are assumed to be controlled by a distributed neuronal network involving frontal and parietal lobes, thalamic and brain stem areas (Sturm & Wilms, 2001). Which aspects of attentional processing are affected by phasic alertness, and the neural mechanisms underlying the effects, however, are only poorly investigated. In this study, we measured performance and EEG of 20 young participants in a partial letter report task with an auditory alerting manipulation. Report accuracy was modeled based on the computational "Theory of Visual Attention" (Bundesen, 1990), and we estimated several, independent parameters of visual attention performance: Sensory effectiveness (= the total available processing capacity), spatial bias (relative weighting of right-vs. left-hemifield stimuli), and distractibility (relative weighting of target and distracter stimuli). We computed visual event-related lateralizations (ERLs), which reflect contra-vs.-ipsilateral differences in sensory processing of laterally presented stimuli, and mark amplification of stimulus-related processing by selective attention (Hillyard et al., 1998). We found that phasic alerting increased sensory effectiveness significantly, which was accompanied by an increased lateralized N1 in response to unilaterally presented stimuli. By contrast, spatial weighting and distractibility, and the parameters' ERL correlates (Wiegand et al., in prep.), were not affected by the phasic alerting manipulation. The results indicate that in young, healthy participants, phasic alerting increases the total attentional processing capacity that is allocated to a stimulus, but not how capacity is divided between multiple stimuli in the visual field depending on their spatial position or task-relevance.
Meeting abstract presented at VSS 2016