Dissociation of Subjective and Objective Alertness During Prolonged Wakefulness

Figures & data

Figure 1 Protocol for PVT performance, physiological and subjective tests. During habitual bedtime, participants kept awake for 6 hours (shown in shadow). Participants completed a 10-min PVT (indicated by circles,

) and subjective ratings (indicated by triangles,

) every two hours. The physiological tests were conducted within each hour (indicated by asterisks,

).

Figure 2 Psychomotor vigilance test (PVT) task.

Table 1 Results of Absolute Values of Objective, Subjective, and Physiological Outcome Metrics Over the Course of Time (0:00, 2:00, 4:00, and 6:00 Am)

Outcome Metrics		0:00	2:00	4:00	6:00	χ^2/F	P
PVT	Number of lapses	5.18±7.91	7.08±7.24	11.76±12.59	20.16±13.85	49.822***	<0.001
	Mean 1/RT (ms−^Citation1)	2.90±0.35	2.74±0.43	2.56±0.58	1.84±0.80	72.474***	<0.001
Subjective	Sleepiness	5.71±1.16	6.53±1.29	7.03±1.30	8.08±1.02	79.917***	<0.001
	Fatigue	3.71±1.20	4.55±1.48	5.16±1.55	6.24±1.73	74.146***	<0.001
Physiological	Temperature (°C)	36.48±0.33	36.32±0.34	36.29±0.38	36.23±0.35	12.559***	<0.001

Notes: ***p < 0.001. Values are shown as mean±SD. The test statistic of number of lapses, mean 1/RT, sleepiness, and fatigue is χ², and the test statistic of temperature is F.

Figure 3 The time courses of the subjective, objective, and physiological outcome metrics from 0:00 to 6:00 am. (A) Number of lapses, (B) Mean 1/RT, (C) Sleepiness, (D) Fatigue, (E) Body temperature. Asterisks indicate significant differences, *p < 0.05. In each plot, the mean ± SEM is shown.

Table 2 Results of Relative Values of ∆objective, ∆subjective, and ∆physiological Outcome Metrics Over Time

Outcome Metric		2:00–0:00	4:00–2:00	6:00–4:00	χ^2	P
PVT	∆Number of lapses	1.89±6.27	4.68±9.53	8.39±11.76	11.651**	0.003
	∆Mean 1/RT (ms−^Citation1)	−0.16±0.25	−0.18±0.33	−0.71±0.70	23.211***	<0.001
Subjective	∆Sleepiness	0.82±0.95	0.50±0.89	1.05±1.14	4.049	0.132
	∆Fatigue	0.84±0.89	0.61±1.10	1.08±1.15	3.907	0.142
Physiological	∆Temperature (°C)	−0.16±0.21	−0.04±0.25	−0.06±0.25	2.080	0.353

Notes: **p < 0.01, and ***p < 0.001. The magnitudes of the relative changes in the adjacent time marked as ∆subjective (∆fatigue and ∆sleepiness), ∆objective (∆number of lapses and ∆mean 1/RT), and ∆physiological (∆temperature) outcome metrics. Values are shown as mean±SD.

Table 3 Correlation Analysis Results: Association of ∆temperature with ∆PVT and ∆subjective Outcome Metrics

		PVT				Subjective
		∆Number of Lapses		∆Mean 1/RT		∆Sleepiness		∆Fatigue
		r	p	r	p	r	p	r	p
∆Temperature	0:00–2:00	0.236	0.154	−0.062	0.713	0.159	0.340	−0.061	0.714
	2:00–4:00	−0.048	0.773	−0.016	0.924	0.044	0.792	−0.168	0.313
	4:00–6:00	−0.374*	0.021	0.372*	0.021	−0.174	0.297	−0.289	0.078

Notes: *p < 0.05. The magnitudes of the relative changes in the adjacent time marked as ∆subjective (∆fatigue and ∆sleepiness), ∆objective (∆number of lapses and ∆mean 1/RT), and ∆physiological (∆temperature) outcome metrics.

Figure 4 The correlations of the changes of subjective ratings/objective performance with the changes of body temperature during the period of prolonged wakefulness. (A) ∆Number of lapses between 4:00 and 6:00, (B) ∆Mean 1/RT between 4:00 and 6:00.

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