Abstract
The ability to focus on a task while disregarding irrelevant information is an example of selective attention. The perceptual-load hypothesis argues that the occurrence of early or late selection mechanisms is determined by task-relevant perceptual load. Additionally, evidence shows that pupil size serves as proxy of locus coeruleus-norepinephrine (LC-NE) activity, a system associated with cognitive and attentional mediation. Here, we assessed pupil baseline (and pupil dilation) as predictors of load-related early and late selection performance. Participants were asked to search for a target in conditions of high and low perceptual load, while ignoring irrelevant stimuli. The results showed that pupil baseline size, measured prior trial onset, significantly predicted the upcoming search efficiency only in low perceptual load, when—according to the perceptual-load hypothesis—all perceptual information receives attentional resources. In addition, pupil dilation was linked to the time course of perceptual processing and predicted response times in both perceptual load conditions, an association that was enhanced in high load. Thus, this study relates attentional selection mechanisms, as defined by the perceptual-load theory, with pupil-related LC-NE activity. Because pupil baseline predicted attentional performance in low load but not in high load, this suggests that different attentional mechanisms are involved, one in which the LC-NE system plays a key role (low load) and one in which it is less relevant (high load). This suggests that the degree with which LC-NE influences behavioral performance is related to the perceptual load of the task at hand.
Highlights
Attention and pupil sizeWhen a person is engaged in studying, playing sports, or focused on reading this article, that individual is likely to become simultaneously unaware of events happening in the surroundings
Pupil baseline predicted response times only in low load, whereas taskevoked pupil dilation predicted response times both in low and high load, this relationship was enhanced in high load
We focused on pupil baseline measures as predictors of visual selection performance in conditions of high and low visual perceptual load
Summary
Attention and pupil sizeWhen a person is engaged in studying, playing sports, or focused on reading this article, that individual is likely to become simultaneously unaware of events happening in the surroundings. Fluctuations in pupil size have been associated with the time course of perceptual processing (de Gee et al, 2014) and decision-making (Einhauser et al, 2010; Oliva & Anikin, 2018) This relationship arises because under isoluminance conditions, pupil dilation is largely caused by norepinephrine (NE) release from the locus coeruleus (LC) (Joshi et al, 2016). The LC sends inputs to different prefrontal brain areas involved in control functions and attentional processing (Foote et al, 1991; Joshi et al, 2016) Norepinephrine release on these target areas is believed to act by increasing neural gain (Aston-Jones & Cohen, 2005), which enhances the signal-to-noise ratio in the processing of sensory input (Sara & Bouret, 2012b; Mather et al, 2016a; Arnsten & Rubia, 2012). When a target is detected, the LC produces a phasic activation that is subsequently accompanied by a task-evoked pupil response
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