1,720,975 research outputs found
Sonno, apprendimento e funzioni intellettive: revisione della letteratura ed ipotesi interpretative
No full textNon-linear EEG measures during sleep: effects of the different sleep stages and cyclic alternating pattern
No full textThe objective of this work was to study the non-linear aspects of sleep EEG, taking into account the different sleep stages and the peculiar organization of its phasic events in ordered sequences CAP by applying a series of new non-linear measures non-linear cross prediction or NLCP , which appear more reliable for the detection and characterization of non-linear structures in experimental data than the commonly used correlation dimension. Eight healthy subjects aged 18-20 years participated in this study. Polysomnography was performed in all subjects; signals were sampled at 128 Hz and stored on hard disk. The C3 or C4 derivation was used for all the subsequent computational steps, which were performed on EEG epochs 4096 data points selected from sleep stage 2 S2 and slow-wave sleep SWS , in both CAP and non-CAP NCAP conditions. Also, epochs from sleep stage 1 S1 , REM
and wakefulness preceding sleep were recorded. The dynamic properties of the EEG were assessed by means of the
non-linear cross-prediction test, which uses three different ‘model’ time series in order to predict non-linearly the original data set Pred, Ama, and Tir . Pred is a measure of the predictability of the time series, and Ama and Tir are measures of asymmetry, indicating non-linear structure. The non-linear measures applied in this study indicate that sleep EEG tends to show non-linear structure only during CAP periods, both during S2 and SWS. Moreover, during CAP periods, non-linearity can only be detected during the phase A1 subtypes and partially A2 of CAP. The A3 phases show characteristics of non-stationarity and bear some resemblance to wakefulness. Based on the results of this study, sleep might be considered as a dynamically evolving sequence of different states of the EEG, which we could track by detecting non-linearity, mostly in association with CAP. Our results clearly show that detectable non-linearity in the EEG is closely related to the occurrence of the phase A of CAP
Sleep patterns of Down's syndrome children: effects of butoctamide hydrogen succinate (BAHS) administration.
No full textSeveral investigators have described the altered sleep patterns in Down's syndrome subjects. The most relevant findings have been a reduction in percentage of REM sleep, a prolonged latency to the first REM episode, an increase in undifferentiated sleep, and a reduced ratio of the oculomotor frequencies. Because it is of interest to identify new drugs able to increase the percentage of REM sleep in mentally retarded subjects, we studied the effects of butoctamide hydrogen succinate (BAHS) on nocturnal sleep in eight young institutionalized Down's syndrome subjects. BAHS produced a significant increase in the percentage of REM sleep as well as a decrease in undifferentiated sleep and latency to the first RE
Cyclic alternating pattern and spectral analysis of heart rate variability during normal sleep
No full textThe natural arousal rhythm of non-rapid eye movement (NREM) sleep is known as the cyclic alternating pattern (CAP), which consists of arousal-related phasic events (Phase A) that periodically interrupt the tonic theta/delta activities of NREM sleep (Phase B). The complementary condition, i.e. non-CAP (NCAP), consists of a rhythmic electroencephalogram background with few, randomly distributed arousal-related phasic events. Recently, some relation between CAP and autonomic function has been preliminarily reported during sleep in young adults by means of spectral analysis of heart rate variability (HRV). The present study was aimed at analysing the e ects of CAP on HRV in a group of normal children and adolescents. Six normal children and adolescents (age range 10.0–17.5 y) were included in this study. All-night polygraphic recordings were performed after adaptation to the sleep laboratory. Six 5-min epochs were selected from sleep Stage 2 and six from Stages 3 and 4 (slow-wave sleep), both in CAP and NCAP conditions. From such epochs, a series of parameters describing HRV was then calculated, in both time and frequency domains, on the electrocardiographic R–R intervals. Statistical comparison between CAP and NCAP epochs revealed a significant di erence for most of the frequency domain parameters (increase of the low-frequency band, increase of the low-frequency/high-frequency ratio and decrease in the high-frequency band during CAP) both in Stage 2 and in slow-wave sleep. Our results demonstrate that the physiological fluctuations of arousal during sleep described as CAP are accompanied by subtle, but significant, changes in balance between the sympathetic and
vagal components of the autonomic system
Object recognition impairment in Fmr1 knockout mice is reversed by amphetamine: involvement of dopamine in the medial prefrontal cortex.
No full textFragile X syndrome is an X-linked form of mental retardation including, among others, symptoms such as stereotypic behaviour, hyperactivity, hyperarousal, and cognitive deficits. We hypothesized that hyperactivity and/or compromised attentional, cognitive functions may lead to impaired performance in cognitive tasks in Fmr1 knockout mice, the most widely used animal model of fragile X syndrome, and suggested that psychostimulant treatment may improve performance by acting on one or both components. Since hyperactivity and cognitive functions have been suggested to depend on striatal and prefrontal cortex dopaminergic dysfunction, we assessed whether amphetamine produced beneficial, positive effects by acting on dopaminergic corticostriatal systems. Our results show that Fmr1 knockout mice are not able to discriminate between a familiar object and a novel one in the object recognition test, thus showing a clear-cut cognitive impairment that, to date, has been difficult to demonstrate in other cognitive tasks. Amphetamine improved performance of Fmr1 knockout mice, leading to enhanced ability to discriminate novel versus familiar objects, without significantly affecting locomotor activity. In agreement with behavioural data, amphetamine produced a greater increase in dopamine release in the prefrontal cortex of Fmr1 knockout compared with the wild-type mice, while a weak striatal dopaminergic response was observed in Fmr1 knockout mice. Our data support the view that the psychostimulant ameliorates performance in Fmr1 knockout mice by improving merely cognitive functions through its action on prefrontal cortical dopamine, irrespective of its action on motor hyperactivity. These results indicate that prefrontal cortical dopamine plays a major role in cognitive impairments characterizing Fmr1 knockout mice, thus pointing to an important aetiological factor in the fragile X syndrome
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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