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Publication Date

Fall 2018

Degree Type

Thesis - Campus Access Only

Degree Name

Master of Science (MS)

Department

Industrial and Systems Engineering

Advisor

Sean Laraway

Keywords

Circadian Rhythm, Constant Routine, Eye Tracking, Light, Pupil, Sleep Deprivation

Subject Areas

Neurosciences; Psychobiology

Abstract

Pupil responses to light, also known as the pupillary light reflex (PLR), were used in previous studies as an indirect measure of sleep deprivation and circadian status (Bonmati-Carrion et al., 2016; Münch, Léon, Crippa, & Kawasaki, 2012). However, most studies only looked at single data points of the response such as peak velocity and not the timecourse of the response itself. Also, the dilation phase of the PLR was often ignored. In the current study, we set out to observe the response dynamics of the PLR for a holistic evaluation of the human sleep-wake cycle. Twelve healthy subjects participated in a constant routine protocol where three baseline daytime and 7-9 nighttime measurements of pupillary performance were collected for each subject. The PLR was induced using a sequence of two square-wave pulses of background white light presented on a 144-Hz monitor and pupil size was monitored using a custom 250-Hz video-based eye tracking system. Nine metrics of pupillary performance were developed to assess pupillary dynamics, steady-state performance, and extrema characteristics of pupil kinematics. Significant effects of time awake were observed in constriction latency, peak velocity, and the dilation time constant. Dilation dynamics can be used as a biomarker for melatonin, whereas the extrema metrics and steady-state pupil size can be used as biomarkers of cortisol levels and phase. Future studies can use the unique signatures of each of these metric families to quantify the chronobiological status of the individual.

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