Self\u2010reported quality of sleep is related to frontoparietal network connectivity in mild cognitive impairment

Background Sleep has been identified as a modifiable factor involved in both the development and progression of Alzheimer\u2019s disease (AD). Previous findings have suggested that poor sleep may be associated with increased risk of AD. Conversely, higher quality of sleep may slow progression of pathophysiological mechanisms in mild cognitive impairment (MCI) through functional connectivity reorganization of neural networks underlying higher cognitive functions. Method In clinic, 38 MCI patients and 38 age\u2010matched controls completed structural magnetic resonance imaging (MRI), resting\u2010state functional MRI (rs\u2010fMRI), and a cognitive test battery, covering memory, executive functions, and language. The Sleep Continuity in Alzheimer\u2019s Disease Scale (SCADS) was used to assess sleep quality. Patients were stratified into \u201cgood\u201d (n=20) and \u201cpoor\u201d (n=18) sleepers, using the median SCADS score as a cut\u2010point. Default mode (DMN) and left and right frontoparietal (FPN) networks were reconstructed through an independent component analysis approach. Differences in network connectivity across MCI groups were investigated with non\u2010parametric inference using FSL randomize (n=5000 permutations), corrected at a threshold\u2010free\u2010cluster enhancement level of pFWE < 0.025. Grey matter and sex were inserted as covariates in the analysis. The same model was implemented to investigate associations between connectivity and cognition in MCI. Finally, between\u2010network connectivity was assessed through partial correlation with sex as covariate. Result MCI good sleepers showed increased FPN connectivity compared to MCI poor sleepers. Increased FPN connectivity was positively associated with language performance in the former group. Finally, we found a positive coupling connectivity between DMN and FPN and between left and right FPN in MCI good sleepers, while this pattern was disrupted in MCI patients with lower quality of sleep. Conclusion These findings suggest a relationship between sleep quality and FPN connectivity in MCI, highlighting possible sleep\u2010induced compensatory mechanisms. Future studies in larger samples using longitudinal methods and objective measures of sleep will be necessary to confirm this finding. However, these results further support the concept that better sleep may be protective on the pathway to AD

Quality of sleep predicts increased frontoparietal network connectivity in patients with mild cognitive impairment

High quality of sleep may mitigate the impact of pathophysiological mechanisms in mild cognitive impairment (MCI) through functional connectivity reorganization of neural networks underlying higher cognitive functions. Thirty-eight patients with MCI stratified into high and low quality of sleep in accordance with a self-reported questionnaire for sleep habits, and 38 controls underwent resting-state functional magnetic resonance imaging. Independent component analysis was used to reconstruct the default mode network and frontoparietal network (FPN). High quality of sleep was associated with increased FPN connectivity among patients with MCI. Moreover, a positive coupling of connectivity between networks was found in MCI reporting high quality of sleep, congruently with the pattern observed in controls, whereas this coupling was disrupted in MCI with low quality of sleep. An association between FPN connectivity and language scores was observed in MCI. These findings suggest a relationship between sleep quality and FPN connectivity in MCI that may underlie compensatory mechanisms to overcome advancing neurodegeneration.status: publishe

Sleep&#8208;dependent association between atrophy and functional connectivity in mild cognitive impairment

The light-induced difference absorption spectra associated to the photo-accumulation of reduced pheophytin a were studied in the isolated D1–D2–Cyt b559 complex in the presence of variable methyl viologen concentrations and different illumination conditions under anaerobiosis. Depending on the methyl viologen/reaction centre ratio, the relative intensities of the spectral bands at 681.5±0.5, 667.0±0.5 and 542.5±0.5 nm were modified. The reduced pheophytin a located at the D1-branch of the complex absorbs at 681.7±0.5 nm, and at least two additional pigment species contribute to the Qy band of the difference absorption spectra with maxima at 667.0±0.5 and 680.5±0.5 nm. We propose the additional species correspond to a peripheral chlorophyll a and the pheophytin a located at the D2-branch of the complex, respectively. The blue absorbing chlorophyll at 667 nm is susceptible to chemical redox changes with a midpoint reduction potential of +470 mV. The Qx absorption bands of both pheophytins localised at the D2- and D1-branch of the D1–D2–Cyt b559 complex were at 540.7±0.5 and 542.9±0.5, respectively. The results indicated that the two pheophytin molecules can be photoreduced in the D1–D2–Cyt b559 complex in certain experimental conditions.Dirección General de Investigación Científica y Técnica PB98-163