Emotional working memory during sustained wakefulness

Alternated emotional working memory in individuals with subclinical insomnia disorder: An electrophysiological study

The deleterious effects of sleep loss on sleep-dependent memory and emotional function have been documented in the current literature. Yet, the effects of insomnia-induced chronic sleep disturbance on emotional short-term memory have been scarcely investigated. Twenty-one participants with subclinical insomnia disorder (SID) and 20 healthy participants (healthy control, HC) performed a delayed recognition task of emotional faces, and event-related potentials (ERPs) involved in memory encoding, retention, and retrieval of faces across different emotional valences were assessed. Behavioral findings revealed that participants in the SID group had a larger response bias, being more likely to perceive negative faces as "old" faces presented in the retrieval phase than those in the HC group. ERP findings revealed that emotional faces in the SID vs. HC group induced significantly smaller P1 and late P3b and larger N170 amplitudes in the encoding phase and smaller negative slow wave (NSW) in the retention phase. In retrieval phase, the interaction between Sleep group and Valence were revealed for P1 and early P3b amplitudes, but no group differences were found after Bonferroni correction. These findings suggested that insomnia induced chronic sleep disturbance would influence performance on emotional working memory and induced processing phase specific regulation of neurophysiology in emotional working memory regardless of valence.

A systematic review of sleep deprivation and neurobehavioral function in young adults

AIM

To examine the effect of sleep deprivation (total and partial) on neurobehavioral function compared to a healthy sleep opportunity (7-9 h) in young adults 18-30 years.

BACKGROUND

More than one-third of young adults are sleep deprived, which negatively affects a range of neurobehavioral functions, including psychomotor vigilance performance (cognitive), affect, and daytime sleepiness.

METHODS

A systematic review of randomized controlled trials (RCTs) on sleep deprivation and neurobehavioral function. Multiple electronic databases (Cochrane Central Registry of Controlled Trials [CENTRAL], PubMed, PsycINFO, CINAHL, and Web of Science) were searched for relevant RCTs published in English from the establishment of each database to December 31, 2020.

RESULTS

Nineteen RCTs were selected (N = 766, mean age = 23.7 ± 3.1 years; 44.8% female). Seven were between-person (5 were parallel-group designs and 2 had multiple arms), and 12 were within-person designs (9 were cross over and 3 used a Latin square approach). Total sleep deprivation had the strongest detrimental effect on psychomotor vigilance performance, with the largest effects on vigilance tasks in young adults in the included studies.

CONCLUSION

Acute sleep deprivation degrades multiple dimensions of neurobehavioral function including psychomotor vigilance performance, affect, and daytime sleepiness in young adults. The effect of chronic sleep deprivation on the developing brain and associated neurobehavioral functions in young adults remains unclear.

The effect of 5 nights of sleep restriction on empathic propensity

Literature supports the existence of a significant relationship between sleep quality/quantity and empathy. However, empathic ability and empathic propensity are distinct constructs. Expression of empathic propensity depends on the subjective cognitive costs attributed to the empathic experience. Studies on the effects of the experimental reduction in sleep duration on empathic behaviour are still lacking. Therefore, we investigated the consequences of 5 consecutive nights of sleep restriction on empathic propensity. A total of 42 university students (mean [SEM] age 24.09 [0.65] years; 22 females) underwent a cross-over design consisting of 5 consecutive nights of regular sleep and 5 consecutive nights of sleep restriction with a maximum of 5 hr sleep/night. After each condition, all participants were evaluated using the Empathy Selection Task, a new test assessing the motivated avoidance of empathy for its associated cognitive costs. The results showed different effects of sleep restriction depending on the habitual way of responding in the empathic context. Participants with baseline high levels of empathic propensity reduced their empathic propensity after prolonged sleep restriction. Differently, participants who tended to avoid empathising already in the habitual sleep condition maintained their empathic behaviour unchanged after sleep curtailment. In conclusion, inter-individual variability should be taken into account when evaluating the effects of sleep restriction on empathic propensity. People with habitual higher tendency to empathise could choose to avoid empathic experience following several consecutive nights of inadequate sleep.

Total sleep deprivation reduces top-down regulation of emotion without altering bottom-up affective processing

Sleep loss is reported to influence affective processing, causing changes in overall mood and altering emotion regulation. These aspects of affective processing are seldom investigated together, making it difficult to determine whether total sleep deprivation has a global effect on how affective stimuli and emotions are processed, or whether specific components of affective processing are affected selectively. Sixty healthy adults were recruited for an in-laboratory study and, after a monitored night of sleep and laboratory acclimation, randomly assigned to either a total sleep deprivation condition (n = 40) or a rested control condition (n = 20). Measurements of mood, vigilant attention to affective stimuli, affective working memory, affective categorization, and emotion regulation were taken for both groups. With one exception, measures of interest were administered twice: once at baseline and again 24 hours later, after the sleep deprived group had spent a night awake (working memory was assessed only after total sleep deprivation). Sleep deprived individuals experienced an overall reduction in positive affect with no significant change in negative affect. Despite the substantial decline in positive affect, there was no evidence that processing affectively valenced information was biased under total sleep deprivation. Sleep deprived subjects did not rate affective stimuli differently from rested subjects, nor did they show sleep deprivation-specific effects of affect type on vigilant attention, working memory, and categorization tasks. However, sleep deprived subjects showed less effective regulation of negative emotion. Overall, we found no evidence that total sleep deprivation biased the processing of affective stimuli in general. By contrast, total sleep deprivation appeared to reduce controlled processing required for emotion regulation.

Impaired emotional memory and decision-making following primary insomnia

Previous studies have indicated that sleep plays an important role in emotional memory and decision-making. However, very little attention has been given to emotional memory and decision-making in patients with primary insomnia (PI). We investigated whether PI influences the accuracy of emotional memory and social decision-making.We examined 25 patients with PI and 20 healthy controls (HC) using an emotional picture memory task and the Iowa Gambling Task (IGT). In the emotional picture memory task, participants completed two testing sessions: an emotional picture evaluation and a delayed recognition phase. During the emotional picture evaluation phase, participants were presented with 48 pictures with different valence (16 positive, 16 neutral, and 16 negative), which they had to evaluate for emotional valence and arousal. During the recognition phase, participants were asked to make a yes/no memory assessment of a set of pictures, which contained the 48 target pictures intermingled with 48 non-target pictures.The performance of the participants with PI was the same as that of the HC in the emotional picture evaluation task. However, the PI group showed worse recognition of the positive and neutral pictures than did the HC group, although recognition of negative pictures was similar in the 2 groups. In the IGT, participants in the PI group more frequently selected cards from the risky decks as the game progressed and selected more disadvantageous cards than did participants in the HC group after the first block.Our findings suggest that insomnia had different effects on memory, depending on the valence of the memory. Specifically, memory performance was impaired for positive and neutral items, but the recognition of negative stimuli seemed to be more resistant to the effects of insomnia. Our results also suggest that decision-making, which is known to be mediated by the ventromedial prefrontal cortex, including decision-making under conditions of uncertainty, may be vulnerable in PI.

Effect of sleep deprivation on emotional working memory

The emotional dysregulation and impaired working memory found after sleep loss can have severe implications for our daily functioning. Considering the intertwined relationship between emotion and cognition in stimuli processing, there could be further implications of sleep deprivation in high‐complex emotional situations. Although studied separately, this interaction between emotion and cognitive processes has been neglected in sleep research. The aim of the present study was to investigate the effect of 1 night of sleep deprivation on emotional working memory. Sixty‐one healthy participants (mean age: 23.4 years) were either sleep deprived for 1 night (n = 30) or had a normal night’s sleep (n = 31). They performed an N‐back task with two levels of working memory load (1‐back and 3‐back) using positive, neutral and negative picture scenes. Sleep deprivation, compared with full night sleep, impaired emotional working memory accuracy, but not reaction times. The sleep‐deprived participants, but not the controls, responded faster to positive than to negative and neutral pictures. The effect of sleep deprivation was similar for both high and low working memory loads. The results showed that although detrimental in terms of accuracy, sleep deprivation did not impair working memory speed. In fact, our findings indicate that positive stimuli may facilitate working memory processing speed after sleep deprivation.

Sleep and emotional processing

A growing body of literature suggests that sleep plays a critical role in emotional processing. This review aims at synthesizing current evidence on the role of sleep and sleep loss in the modulation of emotional reactivity, emotional memory formation, empathic behavior, fear conditioning, threat generalization and extinction memory. Behavioral and neurophysiological evidence suggesting that rapid-eye movement (REM) sleep plays an important role in emotional processing is also discussed. Furthermore, we examine the relations between sleep and emotions by reviewing the functional neuroimaging studies that elucidated the brain mechanisms underlying these relations. It is shown that sleep supports the formation of emotional episodic memories throughout all the stages that compose memory processing. On the contrary, sleep loss deteriorates both the encoding of emotional information and the emotional memory consolidation processes. Research is also progressively providing new insights into the protective role of sleep in human emotional homeostasis and regulation, promoting adaptive next-day emotional reactivity. In this respect, evidence converges in indicating that lack of sleep significantly influences emotional reactivity. Moreover, notwithstanding some contradictory findings, the processing of emotionally salient information could mainly benefit from REM sleep. However, some crucial aspects of sleep-dependent emotional modulation remain unclear.

The effect of sleep deprivation on retrieval of emotional memory: a behavioural study using film stimuli

Although the deleterious effects of sleep deprivation on memory consolidation are well documented, it is still unclear how the facilitating effect of emotions on memory consolidation processes could be modulated by the lack of sleep. In this study, we investigated the effects of sleep deprivation on episodic memory using emotional and non-emotional film stimuli. Forty-eight healthy subjects, divided into a sleep group (SG) and a sleep-deprived (SD) group, completed an Encoding and a Recall phase. Participants in the SD group were sleep deprived the night immediately following the Encoding phase, whereas the control group slept at home. The Recall phase was administered to all subjects 48 h after the Encoding. During the Encoding phase, six film clips of different valence (two positive, two neutral and two negative) were presented to the participants. During the Recall phase, episodic memory was assessed by a recognition task. Results showed that the SD group had a lower discrimination memory performance for all stimuli compared to the SG, confirming the deleterious effect of sleep deprivation on episodic memory consolidation. Therefore, lack of sleep severely impairs the consolidation of both emotional and neutral memories, as valence-related effects on memory consolidation were not observed after sleep deprivation.

The effect of sleep deprivation on the encoding of contextual and non-contextual aspects of emotional memory

Sleep loss affects emotional memory, but the specific effects on its contextual and non-contextual aspects are unknown. In this study we investigated the possible differential influence of one night of sleep deprivation on the encoding and subsequent recall of these two aspects of emotional information. Forty-eight healthy subjects, divided in a sleep deprivation (SD) and a well-rested group (WR), completed two testing sessions: the encoding session took place after one night of sleep for the WR and after one night of sleep deprivation for the SD group; the recall session after two nights of recovery sleep for both groups. During the encoding session, 6 clips of films of different valence (2 positive, 2 neutral and 2 negative) were presented to the participants. During the recall session, the non-contextual emotional memory was assessed by a recognition task, while the contextual emotional memory was evaluated by a temporal order task. The SD group showed a worst non-contextual recognition of positive and neutral events compared to WR subjects, while recognition of negative items was similar in the two groups. Instead, the encoding of the temporal order resulted deteriorated in the SD participants, independent of the emotional valence of the items. These results indicate that sleep deprivation severely impairs the encoding of both contextual and non-contextual aspects of memory, resulting in significantly worse retention two days later. However, the preserved recognition of negative non-contextual events in sleep deprived subjects suggests that the encoding of negative stimuli is more "resistant" to the disruptive effects of sleep deprivation.

Emotional memory processing is influenced by sleep quality

OBJECTIVE

The recall of emotional memory is enhanced after sleep and is hindered by sleep deprivation. We used an emotional memory task to assess whether poor sleep quality, as well as sleep deprivation, may influence the accuracy of memory recognition, but also the affective tone associated with the memory.

METHODS

Seventy-five subjects, divided into poor sleeper (PS), good sleeper (GS), and sleep deprivation (SD) groups, completed two recall (R) sessions: R1, 1 h after the encoding phase; and R2, after one night of sleep for PS and GS groups and after one night of sleep deprivation for the SD group. During the encoding phase, the participants rated valence and arousal of 90 pictures. During R1 and R2, the participants first made a yes/no memory judgment of the 45 target pictures intermingled with 30 non-target pictures, then rated valence and arousal of each picture.

RESULTS

Recognition accuracy was higher for the PS and GS groups compared to the SD group for all pictures. Emotional valence of the remembered pictures was more negative after sleep deprivation and poor quality sleep, while it was preserved after a good sleep.

CONCLUSIONS

These results provide the first evidence that poor sleep quality negatively affects emotional valence of memories, within the context of preserved emotional memory consolidation. It is suggested that low sleep quality and lack of sleep may impose a more negative affective tone to memories. The reported effects are not to be ascribed to depressive mood, but to a specific influence of poor sleep quality.