Daytime variations in central nervous system activation measured by a pupillographic sleepiness test

Abstract

Pupil size is regulated exclusively by the autonomic nervous system, and in darkness is proportional to the level of central sympathetic tone. Spontaneous pupillary movements, while at rest in darkness and quiet, were recorded for a period of 11 min, using infrared video pupillography. Thirteen young adults took part in a 30‐h experiment lasting from 08.00 h to 14.00 h on the following day. Pupillographic testing and completion of a self‐rated scale for the estimate of sleepiness were repeated every two hours. Pupillary unrest index (PUI), as a measure of pupil size instability associated with daytime sleepiness, showed the lowest values at 09.00 h, when pupil size was found to be maximal, and 23.00 h. During the course of the day, amplitude spectrum ≤0.8 Hz and PUI showed increasing values during the afternoon hours, followed by a decrease during the evening. Daytime variations in the pupillary unrest index in healthy normal subjects were found to be positively correlated with the level of alertness. These findings are similar to the daytime variations found by the MSLT (multiple sleep latency test) in young adults.

Pupillary correlates of lapses of sustained attention

“…There was a main effect of block, F(4, 140) = 3.75, MSE = .04, p < .01, partial η 2 = .10, and a significant linear trend, F(1, 35) = 9.30, MSE = .01, p < .01, partial η 2 = .21. Overall, the decrease in pupil diameter and the increase in pupil variability are consistent with increases in pupillary unrest as time on task increases, suggesting that as time on task increased participants alertness and arousal decreased (Morad et al, 2000;Wilhelm et al, 2001).…”

The effect of chewing gum on physiological and self-rated measures of alertness and daytime sleepiness

“…It has been argued that pupillary fatigue oscillations are a result of decreases in sympathetic nervous system (SNS) activation of the Edinger Westphal nuclei and decreases in the parasympathetic nervous system (PSNS) inhibition of the Edinger Westphal nuclei [13]. Since both systems are part of the peripheral nervous system (PNS), it is possible that gum chewing is only affecting PNS changes in arousal and not the central nervous system (CNS).…”

“…For example, mint flavour has been associated with increased alertness. Norrish and Dwyer [12] employed the Pupillograpy Sleepiness Test (PST) and demonstrated that exposure to a peppermint odour can attenuate pupillary unrest (an inverse correlate of self-rated alertness [13]). …”

“…The PST measures fluctuations in the size of the pupil's diameter (pupillary oscillations), with darknessinduced changes in pupillary oscillations correlating significantly with self-rated alertness [13]. The pupillary oscillations in darkened conditions are determined by the inter-relation of sympathetic nervous activity matched with central parasympathetic inhibition (see [12,13,16] for reviews).…”

“…The pupillary oscillations in darkened conditions are determined by the inter-relation of sympathetic nervous activity matched with central parasympathetic inhibition (see [12,13,16] for reviews). Reductions in alertness are associated with decreases in both sympathetic nervous activity and central parasympathetic inhibition of the Edinger-Westphal nuclei; such reductions inhibit dilator and sphincter muscle control of the pupil diameter resulting in greater fluctuations of pupil size ( [13]). This task provides both baseline and test pupillary unrest index (PUI) scores.…”