Eye movement based metric serving as an on-site test metric for time awake

Eye movements can be used to study tiredness, lack of sleep as well as disturbances of attentiveness.

Prolonged time awake increases the need to sleep and causes sleepiness. It has been estimated that sleepiness causes 10–20 % of traffic accidents hence being a major identifiable and preventable cause of accidents. Even though the severity of sleepiness-related accidents and hazards have been recognized, there is no reliable on-site tester for estimating total time awake of a person. An objective and practical metrics for measuring sleepiness outside the laboratory is needed.

In her doctoral thesis Licentiate of Philosophy Kati Pettersson is presenting a novel approach to this and examines whether an eye movement based metric could serve as an on-site test metric for time awake.

Algorithm development & development of an eye movement based metric

The thesis consists of two parts. Algorithm development for electro-oculographic (EOG) feature extraction to enable effective and practical analyses of measurements conducted outside the laboratory, and development of an eye movement based metric to estimate prolonged time awake.

"The rationale for the studying the use of eye movements to estimate overall time awake is as follows: Different cognitive functions, especially attentional ones are vulnerable to sleepiness. The attentional and oculomotor processes share neuroanatomical networks in the brain and saccadic eye movements have been used to study attentional functions. Moreover, saccadic eye movements are sensitive to sleepiness," she says.

Cognitive performance comparable to alcohol intoxication

Increasing sleep drive induces rapid and uncontrolled sleep initiation leading to unstable cognitive performance which is comparable to alcohol intoxication.

Eleven healthy adults were tested during 60 hours of time awake

Saccadic eye movements were measured from eleven healthy adults every sixth hour with EOG in a 8-minute saccade task during 60 hours of prolonged time awake. The study finds that the saccade task performance, estimated as the number of saccades, decreased as a function of time awake on an individual level.

The saccadic performance differed between the participants but was stable within participants; this was tested with 5 participants.

The circadian rhythm affected the saccade task performance. Thus, the three process model of alertness (TPMA) was fitted to, and the circadian component was removed from the measured data. After removing the C-component, the linear model revealed a significant trend for six out of eleven participants.

Individual calibration is still needed

The results imply that saccades measured with EOG could be used as a time awake metric outside the laboratory. The metric needs individual calibration before the time awake of a person can be estimated.

"More research is needed to study individual differences, optimize the measurement duration, and stimulus parameters," Kati Pettersson says.

The doctoral thesis and the defence:

Kati Pettersson will defend the thesis entitled "Saccadic eye movements estimate prolonged time awake" in the Faculty of Science, University of Helsinki on Wednesday, September the 12th at noon. Professor Hans Van Dongen will serve as the opponent. The defence will take place at the Main building, Unioninkatu 34, Auditorium XII.

Lic. Phil. Pettersson has conducted the thesis work at the Finnish Institute of Occupational Health, under the supervision of Docent Kiti Müller (Nokia Bell Labs, Espoo & Department of Neurology, University of Helsinki) and Professor Edward Hæggström (Department of Physics, University of Helsinki).

The electronic thesis can be found here: https://helda.helsinki.fi/handle/10138/239934


Researcher Kati Pettersson, +358 40 533 7881, kati.pettersson@ttl.fi

Sleep and circadian rhythms

Kati Pettersson will defend her doctoral thesis "Saccadic eye movements estimate prolonged time awake" on Wednesday, September 12, at noon. Welcome to join the defence taking place in the Main building of the university!

Seminar on sleep circadian rhythms on Tuesday, September 11 at 14:30

The seminar is held at Kumpula Campus, Physicum auditorium E204, Gustaf Hällströmin katu 2. It is moderated by Prof. Edward Hæggström. Welcome!

14:40 – 15:20 Prof. Hans Van Dongen (Washington State University), Targeted metabolomics, peripheral oscillators, and metabolic health in shift work

Working night shifts increases the risk of obesity, diabetes, and other metabolic disorders, but why this happens is not known. It has been thought that metabolic disruption in shift workers is driven primarily by the brain's master clock (circadian pacemaker). However, it turns out that separate biological clocks (so-called peripheral clocks) in the liver, gut and pancreas play an important role as well. Prof. Van Dongen will discuss his group's recent research using targeted metabolomics, which showed that 24-hour rhythms in metabolites related to the digestive system shift much more rapidly than the brain’s master clock following night shift work.

15:20 – 16:00 Prof. Tiina Paunio (University of Helsinki and National Institute for Health and Welfare), Big Sleep

Big data is increasingly bringing new possibilities to unravel the mechanisms underlying complex human behavior, including aspects of sleep. Prof. Paunio will provide an integrated overview of how large-scale epidemiological studies, combined with analysis on interaction of the environment with genetic susceptibility in specific samples, helps us to understand risks, causes and consequences of insomnia.

@KumpulaScience @KumpulaPhysics #HelsinkiUni