Figure 1.
The timing of events in each laboratory session occurred as shown in the figure. Baseline assessment preceded the 6.5 hour night time sleep episode, which was followed by the sleep inertia assessment conducted during a four hour light exposure as shown in the top right box of the figure. The the timing and order of administration of the cognitive tasks in both baseline and sleep inertia assessments occurred as shown in the bottom left rectangle. The light box measuring 138 x 80 x 90 cm and painted white on the inside, contained two top-mounted commercially available fluorescent tubes (Philips T5 24W lamps 827: 2700K light; Activiva Active: 17000K light with a Color Rendering Index > 80). A diffuser covered the tubes to yield a diffuse relatively homogeneous light distribution within the box. Consent to publish the photograph of the light box was obtained.
Figure 2.
Sleep inertia in subjective alertness and cognition.
Values shown here are the actual means +/- 1 SEM from the data. Baseline performance is shown to the left of the sleep episode while sleep inertia performance is shown to the right of it. (A) The effect of sleep inertia on subjective alertness as measured by the Karolinska Sleepiness Scale (KSS). The open circles depict alertness levels before a cognitive assessment (KSS1), while the closed circles depict half-hourly levels starting with the end of the first sleep inertia cognitive assessment (KSS2). (B) Mean response time (RT) and the variability of the mean RT on the PVT. (C) Lapses (number of RT’s > 500 msecs) and the inverse mean of the slowest 10% of RT’s on the PVT. (D) Cognitive throughput as measured with accuracy (percentage correct responses during a 2 minute period) and speed (number of responses during a two minute period) in the add task.
Panels E, F, G and H show the effect of sleep inertia on working memory as measured by the 1-back and 3-back tasks. (E) Aprime on the 1-back and 3-back tasks. (F) Average RT on the match and non-match combined in the 1-back and 3-back tasks. (G) RT on the match trials in the two tasks. (H) RT on the non-match trials in the two tasks.
Figure 3.
(A) A comparison of the acute effect of sleep inertia across the cognitive processes using Cohen’s d, computed with the mean and standard deviations on a student’s t-test between baseline (2 hours before bed-time) and initial sleep inertia assessments. The magnitude effect of sleep inertia appeared stronger alertness and in tasks primarily driven by lower order processes such as attention. (B) A comparison of the dissipation of sleep inertia across cognitive processes using implied f2 computed with the numerator and denominator degrees of freedom of the F statistic from the mixed-model ANOVA. The effect of sleep inertia appeared stronger in alertness and performance in tasks primarily mediated by attention.
Figure 4.
Comparison of the illuminance and spectral profiles of the experimental white-light mixtures and the white-light at home.
(A) Double plot of the average 24-h profile of activity (upper plot) and Illuminance (lower plot) in the home environment of the participants The range of dawn and dusk during the study period ([October- December inclusive] 51°14'07.44"N latitude) are shown in the lower plot as black and red vertical reference lines, respectively. The black and red vertical reference lines represent the range of dawn and dusk respectively. Each data point in the two plots is an hourly average of 1 minute sampling, first computed for each participant and then averaged across the participants. (B) Double plot of the average 24-h profile of illuminance in the home environment of the participants. The black and red vertical reference lines represent the range of dawn and dusk respectively (C) Average morning illuminance while living at home and during the light exposure laboratory sessions. The Box-Plots show the 5th, 25th, median, 75th and 90th percentiles. (D) Double plot of the average 24-h profile of irradiance in the home environment of the participants. The black and red vertical reference lines represent the range of dawn and dusk respectively. (E) The average irradiance in the home environment of the participants just before wake time and during the morning hours corresponding to the laboratory light exposure session. (F) Average red, green and blue irradiance during the evening hours while living at home and during the laboratory light exposure sessions.
Figure 5.
The effect of white light conditions on sleep inertia in working memory.
Values shown here are the actual means +/- 1 SEM from the data. (A) RT on the match trials in the 1-back task. (B) RT on the match trials in the 3-back task. (C) RT on the non-match trials in the 1-back task. (D) RT on the non-match trials in the 3-back task. There was a significant light x time interaction only on the match trials in the 3-back task, as shown in the inset in panel B. The inset figure shows the RT’s from the first and last sleep inertia assessments; a significant difference was found in the Blue-Enhanced and Bright Blue-Enhanced conditions in the 3-back task.