Sleep restriction impairs visually and memory-guided force control

Abstract

Sleep loss is a common phenomenon with consequences to physical and mental health. While the effects of sleep restriction on working memory are well documented, it is unknown how sleep restriction affects continuous force control. The purpose of this study was to determine the effects of sleep restriction on visually and memory-guided force production magnitude and variability. We hypothesized that both visually and memory-guided force production would be impaired after sleep restriction. Fourteen men participated in an eleven-day inpatient sleep study and completed a grip force task after two nights of ten hours' time in bed (baseline); four nights of five hours' time in bed (sleep restriction); and one night of ten hours' time in bed (recovery). The force task entailed four 20-second trials of isometric force production with the thumb and index finger targeting 25% of the participant's maximum voluntary contraction. During visually guided trials, participants had continuous visual feedback of their force production. During memory-guided trials, visual feedback was removed for the last 12 seconds of each trial. During both conditions, participants were told to maintain the target force production. After sleep restriction, participants decreased the magnitude of visually guided, but not memory-guided, force production, suggesting that visual attention tasks are more affected by sleep loss than memory-guided tasks. Participants who reported feeling more alert after sleep restriction and recovery sleep produced higher force during memory-guided, but not visually guided, force production, suggesting that the perception of decreased alertness may lead to more attention to the task during memory-guided visual tasks.

Fig 1. Experimental timeline adapted with permission from Ness et. al., 2019.

White bars indicate time awake and black bars indicate time in bed. Participants completed motor task testing after 2 nights of 10-hours in bed (baseline condition); after four nights of 5-hours in bed (restriction condition); and for a third and final time after one night of 10-hours in bed (recovery condition).

Fig 2. Visually guided and memory-guided force paradigm.

A) The precision grip apparatus with load cells under the thumb and index finger; B) the experimental procedure was 130 s in length. Each block of 20 s of force was separated by 10 s of rest; C) the visual display contained two horizontal bars presented against a black background. The target bar (white) was stationary, and the red/green force bar provided real-time visual feedback. In the visually guided task, visual feedback was available for the duration of the trial. In the memory-guided task, the force bar disappeared for the last 12 s of the trial.

Fig 3. Force production as a percentage of maximum voluntary contraction (MVC) plotted by day and vision condition.

The red dashed line indicates the target force (25% MVC). A) Average force production over the last 12 s of each trial. The black bar indicates the visually guided condition, and the grey bar indicates the memory-guided condition. Error bars indicate the standard deviation of the mean. Open circles represent each individual participant’s mean force. ***p < 0.001; ** p < 0.01; *p < 0.05. B) Force production over the last 12 s of each trial. The dark black line indicates the visually guided condition, and the grey line indicates the memory-guided condition. Shaded areas represent the standard error of the mean.

Fig 4. Force production by day and vision condition as a percentage of maximum voluntary contraction (MVC), as related to Karolinska Sleepiness Scale (KSS) score.

The red dashed line indicates the target force (25% MVC). The black circles and lines indicate the visually guided condition, and the grey points and lines indicate the memory-guided condition. Each circle indicates a participants’ average force during each trial (4 trials per vision condition). Lines indicate the relationship between KSS score and force relative to MVC. Asterisks indicate difference in slopes between baseline and the respective day. ** p < 0.01; *p < 0.05.

Fig 5. Residuals of the final model across day and vision condition, demonstrating that residual variability in force production was higher in the memory-guided than the visually guided condition after sleep restriction and recovery sleep across participants.