Pupil dilation reflects the temporal evolution and content of a perceptual decision J W de Gee, T H J Knapen, T Donner |
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Psychology Department, University of Amsterdam, Netherlands
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| Pupil dilation at constant illumination has long been used as an index of mental effort and arousal. More recently, pupil dilation has been linked to perceptual decision-making, though the exact nature of this link has remained unknown. Here, we asked (i) whether decision-related pupil dilation is driven only by the final commitment to a choice, or also by the preceding evidence integration process; and (ii) whether its amplitude reflects the final choice, or the correctness of the choice. We measured pupil dilation in four subjects (each ~2400 trials) during a yes-no visual contrast detection task (free response paradigm), in which the target pattern was embedded in dynamic noise, provoking prolonged temporal integration (range of median RT: 1439-2440 ms). Linear system analysis of the pupil diameter time course revealed significant transient components at stimulus onset and choice, and a significant ramping component during decision formation. The overall amplitude of pupil dilation was bigger for hits and false alarms than for misses and correct rejects. The pattern of results replicates in a bigger sample of subjects. Our results suggest that the autonomic systems mediating pupil dilation are continuously driven by ongoing decision processes and informed about the contents of decision outcomes. |
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