The Impact of Watch Keeping Schedules on Cognitive Performance and Physiology in Adults

INTERVENTION: Trained research assistants will deliver ten x 9 night lab study runs, monitoring participant adherence to the protocol at all times during the 10 day in‐laboratory visit which will be overseen by the chief investigators of the study. will be conducted, with 16 participants undergoing a two‐watch routine (2 conditions, 12h on and 12 off watch) 12) and 16 participants undergoing a three section watch routine (2 conditions, 8h on 16h off watch). On training day (day 1) participants will be talked through each neurobehavioral task and be given time to ask questions and familiarise themselves with the laboratory, followed by an 8h acclamation sleep. Participants will be given 6.5 hour sleep opportunities in each condition. The conditions differ in the timing of this sleep opportunity; A) 0930 to 1600, B) 0830 to 1230 and 2130 to 0000 C) 1800 to 0030, D) 0130 to 0800. On the 9th night participants will be given a 8h recovery sleep from 2300 to 0700. Neurobehavioural and physiological functioning will be measured in blocks simulating shifts; A) 0000 to 0900 and 1700 to 2100, B) 0000 to 0700 and 1300 to 1900, C) 0000 to 0500 and 1300 to 1700. D) 0900 to 1300 and 2100 to 0100. Variables that will be measured from the laboratory will be: a) Cognitive performance: Psychomotor Vigilance task (reaction time and errors), cognitive throughput (number correct), working memory (correct answers), vigilant attention (maintenance of performance), decision making (correct responses), inhibition (correct responses), CRUSE Submarine simulator (situation awareness) b) Team work task (COHESION task) c) Physiological state: heart rate, heart rate variability d) Eye tracking (desk mounted eye tracking device used during simulated drive) e) Salivary and blood cortisol and melatonin f) Sleep moni CONDITION: Cognitive performance and physiological changes in healthy adults experiencing circadian misalignment; ; Cognitive performance and physiological changes in healthy adults experiencing circadian misalignment Mental Health ‐ Studies of normal psychology, cognitive function and behaviour Neurological ‐ Studies of the normal brain and nervous system PRIMARY OUTCOME: Brain activity (sleep) measured using polysomnography (electrodes will be attached to participants' scalp, and the skin on their face, chin and chest) [Continuously during scheduled sleep periods and simulated drive] Cognitive performance as measured by Psychomotor Vigilance task[Measured at approximately 2‐hourly intervals during wake periods] Melatonin (circadian marker) measured by a saliva sample[Measured approximately 2‐hourly throughout wake periods.] INCLUSION CRITERIA: Healthy, young adults (18‐40 years) with normal sleep/wake behaviour (self reported). SECONDARY OUTCOME: Cognitive performance as measured by AusEd driving simulator task [Measured approximately once every 4h during the simulating shifts; A) 0000 to 0900 and 1700 to 2100, B) 0000 to 0700 and 1300 to 1900, C) 0000 to 0500 and 1300 to 1700. D) 0900 to 1300 and 2100 to 0000.] Cognitive performance as measured by Automated Neuropsychological Assessment Metrics (ANAM) (30 min battery of short (1‐3 min) cognitive tests[Measured approximately once every 4h during the simulating shifts; A) 0000 to 0900 and 1700 to 2100, B) 0000 to 0700 and 1300 to 1900, C) 0000 to 0500 and 1300 to 1700. D) 0900 to 1300 and 2100 to 0000.] Cognitive performance as measured by Cohesion test (15 min problem solving test)[Measured approximately once every 4h during the simulating shifts; A) 0000 to 0900 and 1700 to 2100, B) 0000 to 0700 and 1300 to 1900, C) 0000 to 0500 and 1300 to 1700. D) 0900 to 1300 and 2100 to 0000.] Cognitive performance as measured by CRUSE Submarine simulator (a 30min computer based console simulation.[Measured approximately once every 4h during the simulating shifts; A) 0000 to 0900 and 1700 to 2100, B) 0000 to 0700 and 1300 to 1900, C) 0000 to 0500 and 1300 to 1700. D) 0900 to 1300 and 2100 to 0000.] Cognitive performance as measured by Sternberg working a 20 min memory task[Measured approximately once every 4h during the simulating shifts; A) 0000 to 0900 and 1700 to 2100, B) 0000 to 0700 and 1300 to 1900, C) 0000 to 0500 and 1300 to 1700. D) 0900 to 1300 and 2100 to 0000.] Cortisol (stress marker) levels as measured by a saliva sample [Measured approximately 2‐hourly throughout wake periods] Heart rate variability measured using electrocardiography [Continuously during scheduled sleep periods and simulated drive] Subjective measure of cognitive performance measured by Visual Analogue Scale[Approximately 2‐hourly during wake periods of the experimental phase of the study] Subjective measures of sleepiness measured by the Karolinska Sleepiness Scale (KSS)[Measured at approximately 2‐hourly intervals during wake periods]