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  • Inter hemispheric differences in power spectrum appeared dur

    2018-11-15

    Inter-hemispheric differences in power spectrum appeared during both monaural and binaural stimulation, suggesting a dependence on factors other than the stimulated side, e.g., hemispheric dominance or other processes that are happening simultaneously. Even though the major changes in power spectra and coherence were observed in the temporal region, which is part of the auditory cortex, we also found changes in frontal regions. Changes in temporal and frontal regions have also been found in patients with intra-cochlear implants during sleep [22] and wakefulness [23]. Coexistence of frontal and temporal changes is not surprising since there is functional synergy between these areas. In spite of new methods of quantitative analysis of electrical activity in the brain, the power spectrum remains the most used for providing information about the topographic distribution of energy in the EEG. Coherence techniques can be used to assess the functional relationship between cortical regions by quantifying the degree of cortical synchronization between areas within frequency bands [24]. Our coherence analysis showed that the Deforolimus changed during sound stimulation. We observed that increase or decrease in coherence depended on the frequency band and stage of sleep. However, the variability of the results indicates that unknown factors are also in play. Increased coherence has previously been reported during rhythmic auditory stimulation in both waking and slow wave sleep [25]. It has been shown that intra-hemispheric coherence changes during the transition from wakefulness to sleep, being higher in the dominant hemisphere; the inter-hemispheric coherence asymmetry tends to disappear as the EEG progresses into sleep [26,27]. Cantero et al (1999) [28] also demonstrated that the same EEG activity can show different coherence pattern depending on the brain state. The lateralization for speech, music and pitch processing is widely accepted [29]. However, cortical responses are not known for sounds like those used in tinnitus treatment with customized sounds.
    Acknowledgments
    Partially supported by ANII (National Agency of Innovation and Research, Uruguay) and Cedar Sinai Medical Center, USA.
    Introduction Few epidemiological studies have evaluated the pattern of sleep-wake cycle in the general population. Questionnaires or sleep logs, in addition to the objective evaluation of sleep-wake patterns by actigraphs, are typically used in these studies [1–5]. It is important to note that the results of actigraphic recording as an instrument to investigate sleep pattern has been compared with polysomnography, which is considered the gold standard for objective evaluation of sleep, showing good correlation [6,7]. Deforolimus Previous studies have shown that duration and quality of sleep, which have consequences for health, are strongly associated with race, gender, and socioeconomic status [1]. It has also been demonstrated that the self-reported sleep duration is longer than the sleep duration objectively evaluated using an actigraph [2] and that morningness/eveningness preference is largely independent of ethnicity, gender, and socioeconomic status, indicating that this preference may be better explained by endogenous factors [3]. However, past studies with young adults showed female had significantly stronger tendency toward the morningness preference, and the authors considered the role of social-cultural factors in the existence of gender differences [4,5]. Depending on the evaluated population, the sleep-wake cycle is influenced by external cues that can greatly change the quality of life and cause significant consequences to the health of the individual and collective. Many cultural, environmental and social stimuli are related to an increase in light intensity to which the individual is subjected. Depending on time of the day that these stimuli occur, they can act on the circadian system and cause a phase delay or advance [8,9]. We should propose that the characterization of the sleep-wake cycle of a population is not trivial because exogenous and endogenous characteristics influence the habits of sleeping and waking. In this context, the aim of this study was to characterize the temporal pattern of sleep and wakefulness in a sample of the adult subjects from São Paulo city. The study was based on questionnaire and actigraphic data.