Potential dementia biomarkers based on the time-varying microstructure of sleep EEG spindles

Proceedings of the 29th Annual International Conference of the IEEE EMBS Cité Internationale, Lyon, France August 23-26, 2007The time-varying microstructure of sleep EEG spindles may have clinical significance in dementia studies. In this work, the sleep spindle is modeled as an AM-FM signal and parameterized in terms of six parameters, three quantifying the instantaneous envelope (IE) and three quantifying the instantaneous frequency (IF) of the spindle model. The IE and IF waveforms of sleep spindles from patients with dementia and normal controls were estimated using the time-frequency technique of Complex Demodulation (CD). Sinusoidal curve-fitting using a matching pursuit (MP) approach was applied to the IE and IF waveforms for the estimation of the six model parameters. Specific differences were found in sleep spindle instantaneous frequency dynamics between spindles from dementia subjects and spindles from controls

Sleep in Frontotemporal Dementia is Equally or Possibly More Disrupted, and at an Earlier Stage, When Compared to Sleep in Alzheimer's Disease

Background: Conversely to other neurodegenerative diseases (i.e., Alzheimer's disease, AD), sleep in frontotemporal dementia (FTD) has not been studied adequately. Although some evidence exists that sleep-wake disturbances occur in FTD, very little is known regarding sleep macrostructure and/or primary sleep disorders. Objective: To investigate these issues in this population and compare them to similar issues in AD and in healthy elderly (HE). Methods: Twelve drug-naïve behavioral-variant FTD (bvFTD) patients (7 men/5 women) of mean age 62.5 ± 8.6 years were compared to seventeen drug-naïve AD patients (9 men/8 women) of mean age 69.0 ± 9.9 years and twenty drug-naïve HE (12 men/8 women) of mean age 70.2 ± 12.5 years. All participants were fully assessed clinically, through a sleep questionnaire, an interview, and video-polysomnography recordings. Results: The two patient groups were comparably cognitively impaired. However, compared to FTD patients, the AD patients had a statistically significant longer disease duration. Overall, the sleep profile was better preserved in HE. Sleep complaints did not differ considerably between the two patient groups. Sleep parameters and sleep macrostructure were better preserved in AD compared to FTD patients, regardless of primary sleep disorders, which occurred equally in the two groups. Conclusions: With respect to AD, FTD patients had several sleep parameters similarly or even more affected by neurodegeneration, but in a much shorter time span. The findings probably indicate a centrally originating sleep deregulation. Since in FTD patients sleep disturbances may be obvious from an early stage of their disease, and possibly earlier than in AD patients, physicians and caregivers should be alert for the early detection and treatment of these symptoms

Data driven optimal filtering for phase and frequency of noisy oscillations: application to vortex flowmetering

A new method for extracting the phase of oscillations from noisy time series is proposed. To obtain the phase, the signal is filtered in such a way that the filter output has minimal relative variation in the amplitude (MIRVA) over all filters with complex-valued impulse response. The argument of the filter output yields the phase. Implementation of the algorithm and interpretation of the result are discussed. We argue that the phase obtained by the proposed method has a low susceptibility to measurement noise and a low rate of artificial phase slips. The method is applied for the detection and classification of mode locking in vortex flowmeters. A novel measure for the strength of mode locking is proposed.Comment: 12 pages, 10 figure

Sleep disturbances in relation to fatigue in major depression

Objective: This study aimed to investigate the independent correlations of subjective sleep disturbances (insomnia and daytime sleepiness) with the severity of fatigue in patients with major depression. Methods: Eighty-one currently depressed patients (70 females and 11 males), aged between 23 and 65 years, with a DSM-IV diagnosis of major depressive disorder were studied. Patients with physical diseases or other conditions associated with prominent fatigue were excluded. The 17-item Hamilton Depression Rating Scale (HDRS), the Athens Insomnia Scale (AIS), and the Epworth Sleepiness Scale (ESS) were used for the cross-sectional assessment of the severity of depression, insomnia, and sleepiness, respectively. Severity of fatigue was measured with the Fatigue Severity Scale (FSS). Pearson's and Spearman's coefficients were used in bivariate correlations between FSS score and the independent variables (age, gender, inpatient/outpatient status, HDRS score, AIS total score, AIS individual item scores, and ESS score). A stepwise multiple regression analysis was then performed, with FSS score as the dependent variable. Results: The severity of fatigue was significantly correlated with female sex, HDRS score, AIS total score, awakenings during the night (AIS item 2), compromised sleep quality (AIS item 5), and ESS score. Sleep quality (AIS item 5) and daytime sleepiness (ESS) were the only significant predictors of the severity of fatigue in the multiple regression analysis. Conclusions: Both sleep quality and daytime sleepiness correlate independently with fatigue severity, as measured with the FSS, in patients with major depression. The FSS does not appear to be a 'pure' measure of fatigue in depressed patients, a finding with potential implications for the choice of appropriate fatigue measures in this population. © 2009 Elsevier Inc. All rights reserved

EEG-based investigation of brain connectivity changes in psychotic patients undergoing the primitive expression form of dance therapy: a methodological pilot study

Primitive expression (PE) is a form of dance therapy (DT) that involves an interaction of ethologically and socially based forms which are supplied for re-enactment. There exist very few studies of DT applications including in their protocol the measurement of neurophysiological parameters. The present pilot study investigates the use of the correlation coefficient (ρ) and mutual information (MI), and of novel measures extracted from ρ and MI, on electroencephalographic (EEG) data recorded in patients with schizophrenia while they undergo PE DT, in order to expand the set of neurophysiology-based approaches for quantifying possible DT effects, using parameters that might provide insights about any potential brain connectivity changes in these patients during the PE DT process. Indication is provided for an acute potentiation effect, apparent at late-stage PE DT, on the inter-hemispheric connectivity in frontal areas, as well as for attenuation of the inter-hemispheric connectivity of left frontal and right central areas and for potentiation of the intra-hemispheric connectivity of frontal and central areas, bilaterally, in the transition from early to late-stage PE DT. This pilot study indicates that by using EEG connectivity measures based on ρ and MI, the set of useful neurophysiology-based approaches for quantifying possible DT effects is expanded. In the framework of the present study, the causes of the observed connectivity changes cannot be attributed with certainty to PE DT, but indications are provided that these measures may contribute to a detailed assessment of neurophysiological mechanisms possibly being affected by this therapeutic process. © 2014, Springer Science+Business Media Dordrecht