Abstract
Pupil dilation is classically associated with increase in cognitive load in humans. Here, we studied the potential link between human pupil dilation and meaning integration effort as indexed by event-related brain potentials (ERPs). We recorded pupil size variation and ERPs simultaneously while participants were presented with matching or unrelated picture–word pairs. Whilst relatedness in meaning between spoken words and pictures typically modulated ERPs, pupil size was also affected quickly after picture onset. Moreover, during the time-window associated with meaning integration, greater pupil dilation correlated with less negative N400 amplitudes elicited by unrelated pictures. Since pupil dilation has been linked to activity of the locus coeruleus–norepinephrine (LC–NE) system, these findings may provide new insights into the suggested link between human high-level cognitive function and activity of the LC–NE system.
Highlights
Dilation of the pupil has been associated with ongoing cognitive processes in the human brain (Loewenfeld, 1958; Beatty, 1982b)
By correlating pupil size with event-related brain potentials (ERPs) amplitude from stimulus onset, we investigated whether pupil dilation is associated with the cognitive processes reflected in ERPs
The time-step t-tests on 50 ms long bins were performed every millisecond for ERPs and every 16 ms for pupil dilation records according to their sampling rate
Summary
Dilation of the pupil has been associated with ongoing cognitive processes in the human brain (Loewenfeld, 1958; Beatty, 1982b). As shown in studies involving in vivo stimulation or recording of LC neurons’ activity in monkeys or rodents performing sensory and memory tasks, increasing phasic LC–NE system activity is associated with increasing task performance and stimulus processing efficiency (Usher et al, 1999; Berridge and Waterhouse, 2003; Aston-Jones and Cohen, 2005; Samuels and Szabadi, 2008b). An increasing number of studies have used stimulus evoked pupil dilation as an indirect measure of phasic activity of the human LC–NE system in the absence of intracranial recordings of human LC neural activity (e.g., Einhauser et al, 2008; Gilzenrat et al, 2010; Gabay et al, 2011; Jepma and Nieuwenhuis, 2011)
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