Pupillary fluctuation amplitude before target presentation reflects short-term vigilance level in Psychomotor Vigilance Tasks

• Published in: PloS one Vol. 16; no. 9; p. e0256953
• Main Authors: Yamashita, Jumpei, Terashima, Hiroki, Yoneya, Makoto, Maruya, Kazushi, Koya, Hidetaka, Oishi, Haruo, Nakamura, Hiroyuki, Kumada, Takatsune
• Format: Journal Article
• Language: English
• Published: San Francisco Public Library of Science 17.09.2021; Public Library of Science (PLoS)
• Subjects: Amplitudes; Biology and Life Sciences; Communication; Evaluation; Fluctuations; Informatics; Information science; Laboratories; Locus coeruleus; Medicine and Health Sciences; Monitoring; Norepinephrine; Physiological aspects; Reaction time; Reaction time task; Social Sciences; Task analysis; Vigilance; Vigilance (Psychology); Japan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0256953

Our daily activities require vigilance. Therefore, it is useful to externally monitor and predict our vigilance level using a straightforward method. It is known that the vigilance level is linked to pupillary fluctuations via Locus Coeruleus and Norepinephrine (LC-NE) system. However, previous methods of estimating long-term vigilance require monitoring pupillary fluctuations at rest over a long period. We developed a method of predicting the short-term vigilance level by monitoring pupillary fluctuation for a shorter period consisting of several seconds. The LC activity also fluctuates at a timescale of seconds. Therefore, we hypothesized that the short-term vigilance level could be estimated using pupillary fluctuations in a short period and quantified their amplitude as the Micro-Pupillary Unrest Index (M-PUI). We found an intra-individual trial-by-trial positive correlation between Reaction Time (RT) reflecting the short-term vigilance level and M-PUI in the period immediately before the target onset in a Psychomotor Vigilance Task (PVT). This relationship was most evident when the fluctuation was smoothed by a Hanning window of approximately 50 to 100 ms (including cases of down-sampled data at 100 and 50 Hz), and M-PUI was calculated in the period up to one or two seconds before the target onset. These results suggest that M-PUI can monitor and predict fluctuating levels of vigilance. M-PUI is also useful for examining pupillary fluctuations in a short period for elucidating the psychophysiological mechanisms of short-term vigilance.