Aging and sleep in Williams syndrome: accelerated sleep deterioration and decelerated slow wave sleep decrement

Fundamentals of sleep regulation: Model and benchmark values for fractal and oscillatory neurodynamics

Homeostatic, circadian and ultradian mechanisms play crucial roles in the regulation of sleep. Evidence suggests that ratios of low-to-high frequency power in the electroencephalogram (EEG) spectrum indicate the instantaneous level of sleep pressure, influenced by factors such as individual sleep-wake history, current sleep stage, age-related differences and brain topography characteristics. These effects are well captured and reflected in the spectral exponent, a composite measure of the constant low-to-high frequency ratio in the periodogram, which is scale-free and exhibits lower interindividual variability compared to slow wave activity, potentially serving as a suitable standardization and reference measure. Here we propose an index of sleep homeostasis based on the spectral exponent, reflecting the level of membrane hyperpolarization and/or network bistability in the central nervous system in humans. In addition, we advance the idea that the U-shaped overnight deceleration of oscillatory slow and fast sleep spindle frequencies marks the biological night, providing somnologists with an EEG-index of circadian sleep regulation. Evidence supporting this assertion comes from studies based on sleep replacement, forced desynchrony protocols and high-resolution analyses of sleep spindles. Finally, ultradian sleep regulatory mechanisms are indicated by the recurrent, abrupt shifts in dominant oscillatory frequencies, with spindle ranges signifying non-rapid eye movement and non-spindle oscillations - rapid eye movement phases of the sleep cycles. Reconsidering the indicators of fundamental sleep regulatory processes in the framework of the new Fractal and Oscillatory Adjustment Model (FOAM) offers an appealing opportunity to bridge the gap between the two-process model of sleep regulation and clinical somnology.

Oxidative Stress in Down and Williams-Beuren Syndromes: An Overview

Oxidative stress is the result of an imbalance in the redox state in a cell or a tissue. When the production of free radicals, which are physiologically essential for signaling, exceeds the antioxidant capability, pathological outcomes including oxidative damage to macromolecules, aberrant signaling, and inflammation can occur. Down syndrome (DS) and Williams-Beuren syndrome (WBS) are well-known and common genetic conditions with multi-systemic involvement. Their etiology is linked to oxidative stress with important causative genes, such as SOD-1 and NCF-1, respectively, of the diseases being primarily involved in the regulation of the redox state. Early aging, dementia, autoimmunity, and chronic inflammation are some of the main characteristics of these conditions that can be associated with oxidative stress. In recent decades, there has been a growing interest in the possible role of oxidative stress and inflammation in the pathology of these conditions. However, at present, few studies have investigated these correlations. We provide an overview of the current literature concerning the role of oxidative stress and oxidative damage in genetic syndromes with a focus on Down syndrome and WBS. We hope to provide new insights to improve the management of complications related to these diseases.

An EEG investigation of alpha and beta activity during resting states in adults with Williams syndrome

Background

Williams syndrome (WS) is neurodevelopmental disorder characterised by executive deficits of attention and inhibitory processing. The current study examined the neural mechanisms during resting states in adults with WS in order to investigate how this subserves the attention and inhibitory deficits associated with the syndrome.

Method

Adopting electroencephalography (EEG) methodology, cortical electrical activity was recorded from eleven adults with WS aged 35 + years during Eyes Closed (EC) and Eyes Open (EO) resting states, and compared to that of thirteen typically developing adults matched for chronological age (CA) and ten typically developing children matched for verbal mental ability (MA). Using mixed-design analyses of variance (ANOVA), analyses focused on the full alpha (8–12.5 Hz), low-alpha (8–10 Hz), upper-alpha (10–12.5 Hz), and beta (13–29.5 Hz) bands, as these are thought to have functional significance with attentional and inhibitory processes.

Results

No significant difference in alpha power were found between the WS and CA groups across all analyses, however a trend for numerically lower alpha power was observed in the WS group, consistent with other developmental disorders characterised by attentional/inhibitory deficits such as Attention Deficit Hyperactivity Disorder (ADHD). In contrast, comparable beta power between the WS and CA groups during both EC/EO conditions suggests that their baseline EEG signature is commensurate with successful attentional processing, though this needs to be interpreted with caution due to the small sample size. Analyses also revealed an unusual trend for low variability in the EEG signature of the WS group, which contradicts the heterogeneity typically observed behaviourally.

Conclusions

This novel finding of low variability in the EEG spectra in the WS group has been previously associated with poor behavioural performance in ADHD and is highly informative, highlighting future research needs to also consider how the role of low variability in the EEG profile of WS manifests in relation to their behavioural and cognitive profiles.

Psychopharmacology of Williams syndrome: safety, tolerability, and effectiveness

Introduction: Williams syndrome (WS) is a neurogenetic disorder characterized by a hyper-social personality, intellectual disability, and multiple medical co-morbidities. Psychiatric co-morbidities are also common. Since medical co-morbidities are common in this population, the risk-benefit of the use of psychiatric medications must be carefully considered and monitoring for safety and tolerability is needed.Areas covered: We review the cognitive profile and common medical co-morbidities in WS. We then discuss the common presentations of psychiatric disorders and review the available evidence on the use of psychiatric medications in WS. No prospective psychiatric medication trials have been conducted. We highlight the side effect profile of common psychiatric medications as they pertain to WS.Expert opinion: Psychiatric disorders can have a major effect on the quality of life of individuals with WS. The lack of long-term safety data and high likelihood of medical co-morbidities in WS make the judicious use of psychiatric medications more challenging; however, they can play an important role in decreasing distress and improving functioning. We provide recommendations for first- and second-line classes of medications based on our clinical experience and consideration of adverse effect profiles, as well as safety monitoring parameters at baseline and periodically.

Increased overall cortical connectivity with syndrome specific local decreases suggested by atypical sleep-EEG synchronization in Williams syndrome

Williams syndrome (7q11.23 microdeletion) is characterized by specific alterations in neurocognitive architecture and functioning, as well as disordered sleep. Here we analyze the region, sleep state and frequency-specific EEG synchronization of whole night sleep recordings of 21 Williams syndrome and 21 typically developing age- and gender-matched subjects by calculating weighted phase lag indexes. We found broadband increases in inter- and intrahemispheric neural connectivity for both NREM and REM sleep EEG of Williams syndrome subjects. These effects consisted of increased theta, high sigma, and beta/low gamma synchronization, whereas alpha synchronization was characterized by a peculiar Williams syndrome-specific decrease during NREM states (intra- and interhemispheric centro-temporal) and REM phases of sleep (occipital intra-area synchronization). We also found a decrease in short range, occipital connectivity of NREM sleep EEG theta activity. The striking increased overall synchronization of sleep EEG in Williams syndrome subjects is consistent with the recently reported increase in synaptic and dendritic density in stem-cell based Williams syndrome models, whereas decreased alpha and occipital connectivity might reflect and underpin the altered microarchitecture of primary visual cortex and disordered visuospatial functioning of Williams syndrome subjects.

Capacity to improve fine motor skills in Williams syndrome

BACKGROUND

Individuals with Williams syndrome (WS) are known to have difficulties in carrying out fine motor movements; however, a detailed behavioural profile of WS in this domain is still missing. It is also unknown how great the capacity to improve these skills with focused and extensive practice is.

METHOD

We studied initial performance and learning capacity in a sequential finger tapping (FT) task in WS and in typical development. Improvement in the FT task has been shown to be sleep dependent. WS subjects participating in the current study have also participated in earlier polysomnography studies, although not directly related to learning.

RESULTS

WS participants presented with great individual variability. In addition to generally poor initial performance, learning capacity was also greatly limited in WS. We found indications that reduced sleep efficiency might contribute to this limitation.

CONCLUSIONS

Estimating motor learning capacity and the depth of sleep disorder in a larger sample of WS individuals might reveal important relationships between sleep and learning, and contribute to efficient intervention methods improving skill acquisition in WS.