Contributions of post-learning REM and NREM sleep to memory retrieval

It has become clear that sleep after learning has beneficial effects on the later retrieval of newly acquired memories. The neural mechanisms underlying these effects are becoming increasingly clear as well, particularly those of non-REM sleep. However, much is still unknown about the sleep and memory relationship: the sleep state or features of sleep physiology that associate with memory performance often vary by task or experimental design, and the nature of this variability is not entirely clear. This paper describes pertinent features of sleep physiology and provides a detailed review of the scientific literature indicating beneficial effects of post-learning sleep on memory retrieval. This paper additionally introduces a hypothesis which attributes these beneficial effects of post-learning sleep to separable processes of memory reinforcement and memory refinement whereby reinforcement supports one's ability to retrieve a given memory and refinement supports the precision of that memory retrieval in the context of competitive alternatives. It is observed that features of non-REM sleep are involved in a post-learning substantiation of memory representations that benefit memory performance; thus, memory reinforcement is primarily attributed to non-REM sleep. Memory refinement is primarily attributed to REM sleep given evidence of bidirectional synaptic plasticity in REM sleep and findings from studies of selective REM sleep deprivation

Hyperarousal Is Associated with Socioemotional Processing in Individuals with Insomnia Symptoms and Good Sleepers

Despite complaints of difficulties in waking socioemotional functioning by individuals with insomnia, only a few studies have investigated emotion processing performance in this group. Additionally, the role of sleep in socioemotional processing has not been investigated extensively nor using quantitative measures of sleep. Individuals with insomnia symptoms (n = 14) and healthy good sleepers (n = 15) completed two nights of at-home polysomnography, followed by an afternoon of in-lab performance testing on tasks measuring the processing of emotional facial expressions. The insomnia group self-reported less total sleep time, but no other group differences in sleep or task performance were observed. Greater beta EEG power throughout the night was associated with higher intensity ratings of happy, fearful and sad faces for individuals with insomnia, yet blunted sensitivity and lower accuracy for good sleepers. Thus, the presence of hyperarousal differentially impacted socioemotional processing of faces in individuals with insomnia symptoms and good sleepers.Brock University Library Open Access Publishing Fun

Altered Sleep Mechanisms following Traumatic Brain Injury and Relation to Waking Function

Sleep difficulties are commonly reported following traumatic brain injury (TBI), but few studies have systematically examined the neurophysiological characteristics of sleep. Sleep EEG was quantified over multiple nights to examine mechanisms underlying sleep disruption in individuals who had sustained a TBI and to explore the relationship between sleep disruption and waking function. Sleep was recorded from 20 individuals with a TBI (18-64 years) and 20 age-matched controls over two uninterrupted nights, as well as during a night where auditory stimuli were delivered. All participants underwent neuropsychological testing and waking performance assessment. Compared to controls, the TBI group had subjective complaints of falling asleep, delayed sleep onset on polysomnography (PSG), less Slow Wave (< 1 Hz) and delta (1-4 Hz) EEG power in non-REM sleep, fewer spontaneous and evoked k-complexes, reduced periodicity of spontaneous k-complexes, and lower amplitude of evoked k-complexes. While for controls, the density, duration and periodicity of sleep spindles diminished with deepening of non-REM as typically observed, this pattern was disrupted in the TBI group with peak spindle presentation occurring in Stage 3 sleep. Night-to-night-stability of Stage 2 spindles was high for controls but absent for the TBI group. Greater injury severity was related to fewer evoked k-complexes and lower spindle density. Greater spindle production predicted better waking function in the TBI group. Taken together, these data demonstrate impairment in sleep regulatory and inhibitory mechanisms as factors underlying sleep complaints following a TBI. Spindle generation may be adaptive or a marker of resiliency following TBI

A Daytime Nap Enhances Visual Working Memory Performance and Alters Event-Related Delay Activity

Working memory (WM) is impaired following sleep loss and may be improved after a nap. The goal of the current study was to better understand sleep-related WM enhancement by: 1) employing a WM task that assesses the ability to hold and report visual representations as well as the fidelity of the reports on a fine scale, 2) investigating neurophysiological properties of sleep and WM capacity as potential predictors or moderators of sleep-related enhancement, and 3) exploring frontal and occipital event-related delay activity to index the neural processing of stimuli in WM. In a within-subjects design, thirty-six young adults (Mage = 20, 20 men, 16 women) completed a 300-trial, continuous-report task of visual WM following a 90-min nap opportunity and an equivalent period of wakefulness. Mixed-effect models were used to estimate the odds of successful WM reports and the fidelity of those reports. The odds of a successful report were approximately equal between nap and wake conditions at the start of the task, but by the end, the odds of success were 1.26 times greater in the nap condition. Successful WM reports were more accurate after a nap, independent of time on task. Neither WM capacity nor any of the sleep variables measured were found to significantly moderate the nap effect on WM. Lastly, amplitude of frontal and occipital delay activity was altered in the nap relative to the wake condition. The findings are discussed in relation to the role of sleep in sustained attention and contemporary models of visual WM

A Daytime Nap Enhances Visual Working Memory Performance and Alters Event-Related Delay Activity

Working memory (WM) is impaired following sleep loss and may be improved after a nap. The goal of the current study was to better understand sleep-related WM enhancement by: 1) employing a WM task that assesses the ability to hold and report visual representations as well as the fidelity of the reports on a fine scale, 2) investigating neurophysiological properties of sleep and WM capacity as potential predictors or moderators of sleep-related enhancement, and 3) exploring frontal and occipital event-related delay activity to index the neural processing of stimuli in WM. In a within-subjects design, thirty-six young adults (Mage = 20, 20 men, 16 women) completed a 300-trial, continuous-report task of visual WM following a 90-min nap opportunity and an equivalent period of wakefulness. Mixed-effect models were used to estimate the odds of successful WM reports and the fidelity of those reports. The odds of a successful report were approximately equal between nap and wake conditions at the start of the task, but by the end, the odds of success were 1.26 times greater in the nap condition. Successful WM reports were more accurate after a nap, independent of time on task. Neither WM capacity nor any of the sleep variables measured were found to significantly moderate the nap effect on WM. Lastly, amplitude of frontal and occipital delay activity was altered in the nap relative to the wake condition. The findings are discussed in relation to the role of sleep in sustained attention and contemporary models of visual WM

Further Analysis of Antecedent Interventions on Preschoolers' Compliance

Functional analyses were conducted to identify reinforcers for noncompliance exhibited by 3 young children. Next, the effects of three antecedent-based interventions—noncontingent access to a preferred item, a warning, and a high-probability instructional sequence—were examined. The high-probability instructional sequence was effective for 1 child. Antecedent interventions were ineffective and extinction was necessary for the other 2 children