Bioelectric activity of the brain in 3-4 years old children in eyes-open resting state

Background. Electroencephalography is the main technique for assessing the functional state of the brain. Indications for EEG are diagnosis of paroxysmal states, prediction of the outcome of a pathological state, evaluation of bioelectrical activity if brain death is suspected. Up to 90 % of the native EEG in calm wakefulness in healthy individuals is occupied by “alpha activity”. In children in active wakefulness, the EEG pattern depends to a great extent on their age.Objective. The aim of the work was to assess EEG parameters in children aged 3–4 years in eyes-open resting state. Design and methods. 31 healthy participants aged 3–4 years were enrolled. EEG was registered for 30 minutes in a state of passive wakefulness in the supine position with open eyes. Average values of the power of the spectra for the alpha-rhythm, delta-rhythm and theta-rhythm in the frontal and temporal leads, as well as the ratio of the average power of alpha/theta and alpha/delta rhythms in the frontal and temporal leads were calculated.Results. Average power of the alpha-rhythm was significantly higher over the right frontal lobe than over the right frontal-temporal area, as well as average amplitude of it was significantly higher in F3-A1 than F7-A1, F4-A2 than F8-A2, which is associated with the articulatory praxis. Average alpha-rhythm power was significantly higher in T5-A1 than T3-A1 and T6-A2 than T4-A2, which corresponds to the recognition and naming of objects optically. Significant differences according to the total average power of the alpha- and theta-rhythms above the frontal and frontal-temporal regions reflect the relationship between the frontal cortex temporal lobes and the premotor zones, i.e. arcuate bundle, responsible for the “speech system”.Conclusion. The identified patterns can reflect the characteristics of the state of active wakefulness in a 3–4-year-old child and can be used for comparison in the future (both in the course of behavioral experiments and observation of patients with certain pathological processes).

The Dynamics of Affect Across the Wake-Sleep Cycle: From Waking Mind-Wandering to Night-Time Dreaming

Affective experiences occur across the wake-sleep cycle—from active wakefulness to resting wakefulness (i.e., mind-wandering or daydreaming) to sleep (i.e., dreaming). Yet, we know little about the dynamics of affective experiences across these states. Here, we investigated the within-person fluctuations in the prevalence and valence of affect experienced during mind-wandering and night-time dreaming. We compared the affective ratings of 328 mind-wandering and 529 dream episodes from 32 healthy adults. In a sub-sample, we additionally analysed the affective ratings of 548 waking episodes from 15 participants. Results showed that mind-wandering was more positively valenced than dreaming, and that both mind-wandering and dreaming were more negatively valenced than active wakefulness. We also compared participants’ self-ratings of affect with external ratings of affective experiences described in verbal reports regarding the same episodes. With self-ratings all the episodes were predominated by positive affect. However, the affective valence of verbal reports changed from positively valenced waking reports to affectively balanced mind-wandering reports to negatively valenced dream reports. Together, the findings show that (1) the positivity bias (i.e., more positive than negative affect) characteristic to waking experiences decreases across the wake-sleep continuum, and (2) conclusions regarding the affective nature of subjective experiences depend on whether self-ratings of affect or the verbal reports describing these experiences are analysed. These findings contribute to our understanding of the nature and possible function of affective experiences across different states of consciousness and call for more integration between the fields of emotion research, mind-wandering research, and dream research.

Sleep is more than rest for plasticity in the human cortex

Sleep promotes adaptation of behavior and underlying neural plasticity in comparison to active wakefulness. However, the contribution of its two main characteristics, sleep-specific brain activity and reduced stimulus interference, remains unclear. We tested healthy humans on a texture discrimination task, a proxy for neural plasticity in primary visual cortex, in the morning and retested them in the afternoon after a period of daytime sleep, passive waking with maximally reduced interference, or active waking. Sleep restored performance in direct comparison to both passive and active waking, in which deterioration of performance across repeated within-day testing has been linked to synaptic saturation in the primary visual cortex. No difference between passive and active waking was observed. Control experiments indicated that deterioration across wakefulness was retinotopically specific to the trained visual field and not due to unspecific performance differences. The restorative effect of sleep correlated with time spent in NREM sleep and with electroencephalographic slow wave energy, which is thought to reflect renormalization of synaptic strength. The results indicate that sleep is more than a state of reduced stimulus interference, but that sleep-specific brain activity restores performance by actively refining cortical plasticity.

0108 Brief Periods of Sleep and Quiet Rest Equivalently Benefit Memory Consolidation

Introduction Past research has demonstrated that sleep benefits the consolidation of memories. However, more recent studies have suggested that quiet rest could have similar benefits for memory. Here, we examined the effect of a brief period of sleep, quiet rest, or active wakefulness on declarative and procedural memory. We hypothesized that sleep and quiet rest would equally benefit memory, compared to a period of active wakefulness. Methods After completing a declarative (Icelandic-English word pairs) and procedural memory task (the Motor Sequence Task (MST)), participants began a 30-min retention period with PSG monitoring, in which they either slept (n=24), quietly rested with their eyes closed (n=22), or completed a distractor task (n=28). Following the retention period, participants were tested on the same memory tasks they completed earlier. Results Percent improvement on the MST from the end of training to the end of the test session differed by condition, F(2, 73)=4.21, p=.019. Sleep and quiet rest led to nearly identical improvement (p=.95), with improvement in both of these conditions being significantly greater than in active wake (sleep vs. active wake: p=.01; quiet rest vs. active wake: p=.02). Similarly, retention of the Icelandic-English word pairs differed by condition (F(2, 73)=5.68, p=.005), with sleep and quiet rest demonstrating nearly identical memory change over time (p=.81), and retention in both of these conditions being significantly higher than in active wake (sleep vs. active wake: p=.007; quiet rest vs. active wake: p=.004). Conclusion These data suggest that sleep and quiet rest can exert an equivalent effect on memory consolidation for both declarative and procedural memory, at least across very brief retention durations. Therefore, neurobiology specific to sleep might not be necessary to induce offline improvement in memory across short intervals. Support This research was supported by National Institutes of Health Award R15MH107891.

A longitudinal study of Caenorhabditis elegans larvae reveals a novel locomotion switch, regulated by Gαs signaling

Despite their simplicity, longitudinal studies of invertebrate models are rare. We thus sought to characterize behavioral trends of Caenorhabditis elegans, from the mid fourth larval stage through the mid young adult stage. We found that, outside of lethargus, animals exhibited abrupt switching between two distinct behavioral states: active wakefulness and quiet wakefulness. The durations of epochs of active wakefulness exhibited non-Poisson statistics. Increased Gαs signaling stabilized the active wakefulness state before, during and after lethargus. In contrast, decreased Gαs signaling, decreased neuropeptide release, or decreased CREB activity destabilized active wakefulness outside of, but not during, lethargus. Taken together, our findings support a model in which protein kinase A (PKA) stabilizes active wakefulness, at least in part through two of its downstream targets: neuropeptide release and CREB. However, during lethargus, when active wakefulness is strongly suppressed, the native role of PKA signaling in modulating locomotion and quiescence may be minor.