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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Sleep dependent learning

Huyton, Clare Louise January 2008 (has links)
Research evidence has indicated an important role for sleep in processes of learning and memory. Evidence has shown that a night of sleep in adults can lead to procedural task performance improvements that are not matched during similar periods awake. This thesis further examines the relationship between sleep and processes of leaming and memory, and investigates sleep and cognitive fiinction in various clinical disorders.
2

Arousal from sleep : mechanisms and cardiovascular consequences

O'Driscoll, Denise Marie January 2006 (has links)
No description available.
3

Stereological investigation of specific brain regions in a developmental model of chronic intermittent hypoxia

Tadtayev, Sergiy January 2006 (has links)
No description available.
4

The EEG as a biomarker for individual differencesin the physiology and pharmacology of sleep-wake regulation

Arbon, Emma Louise January 2013 (has links)
There are prominent individual differences in sleep pattel11s and some of these can be observed within the EEG. In order to determine whether the EEG can effectively serve as a biomarker for individual differences and in order to establish whether such differences constituted trait-like individual differences, we assessed the stability and robustness of sleep and the sleep EEG in physiological and pharmacological studies. The spectral composition of the EEG and PSG derived sleep measures were assessed for trait- like inter-individual variability by calculating ICCs in 1) a study investigating the effects of sleep extension, sleep restriction and total sleep deprivation on sleep and the EEG and the contribution of the PER3 polymorphism to individual differences 2) a study investigating the effects of polychromatic light mixtures on the EEG and 3) a study investigating the effects of prolonged-release melatonin, temazepam and zolpidem on sleep and the EEG. Absolute power density values derived from the spectral composition of the EEG werc particularly stable and robust and the ICCs were rated as 'moderate' to 'almost perfect' for NREM and REM sleep across the studies. ICCs for PSG measures were more variable. ICCs were also calculated on relative data in order to assess the stability and robustness of the response to sleep-wake manipulations in the first study; however, these ICCs were very low in comparison to those obtained for absolute data. The PER3 polymorphism differentially affected the some PSG measures and the EEG in our study population. In conclusion, we have provided further evidence for trait-like individual differences within sleep and the EEG, and as such the EEG does effectively serve as a biomarker for individual differences. However, whether these individual differences relate only to phenomena of the EEG or whether they relate to individual differences in sleep-wake regulation needs further investigation.
5

Polymorphisms in the human Period genes

Carpen, Jayshan D. January 2007 (has links)
No description available.
6

The pre-frontal cortex : links between neuropsychological performance and the sleep and wake EEG

Anderson, Clare January 2003 (has links)
The Pre-Frontal Cortex (PFC) has one of the highest Cerebral Metabolic Rates (CMR) during wakefulness (Braun et al., 1997, Maquet et al., 1990) and the lowest CMR during Slow Wave Sleep (SWS) at night (Maquet, 2000) .Inasmuch that the PFC is a focus for low frequency delta activity (e g. Werth et al., 1996, 1997), generated directly by the cortex (Steriade et al., 1993a-c), it is argued, here, that this serves a localised function of sleep and is thus reflective of enhanced recovery. Given the PFC-delta activity link, Clark et al. (1998) assessed daytime regional cerebral blood flow (rCBF) and found increased 'brainwork' during the day resulted in increased delta activity at night, specifically in the (left) PFC.
7

Psychopharmacological aspects of sleep in adults : primary focus on older adults

Diaper, Alison Marie January 2004 (has links)
It is suggested that older adults have more difficulty maintaining sleep than younger adults, and that sleep also becomes more fragmented with increasing age. The aim of this thesis was to assess sleep patterns in older adults, and to investigate some pharmacological agents taken by older adults as sleep aids. A survey of 5846 older adults identified sleep complaints and methods of alleviation. Results supported previous findings, and pain and nocturia were found to be the main reasons for nocturnal awakenings. Respondents reported the use of hypnotics, antidepressants, over-the-counter preparations and herbal remedies as sleep aids. Respondents also used whisky, hot milky drinks and reading at bedtime to aid sleep. Three placebo-controlled clinical trials were implemented to assess the effects of a herbal remedy (valerian), three hypnotics (loprazolam, zopiclone and zolpidem), and two antidepressants (dothiepin and moclobemide) on sleep and daytime performance. Results showed few advantageous effects of an acute dose of valerian. Loprazolam, zopiclone and zolpidem were given to younger adults to assess these treatments without the confounds of old age. These treatments were found to be effective hypnotics from the first night of use, but there were more residual sedative effects under loprazolam than zopiclone or zolpidem. Neither dothiepin nor moclobemide were found to be suitable for use as sleep aids, also using a younger population. Findings indicate most older adults do not have sleep complaints, but those who do are likely to have sleep problems due to physical reasons. More research is necessary into the duration of valerian use and doses for efficacy. Residual sedative effects under loprazolam may increase the risk of accidents, and shorter acting hypnotics, such as zopiclone and zolpidem, may reduce this risk. Dothiepin showed more sedative effect than moclobemide, but there was little evidence of improved sleep. Further research is necessary to establish the causes of poor sleep in old age, and to assess the suitability of other sleep aids in this age group.
8

Συνδετικότητα εγκεφάλου στο ηλεκτροεγκεφαλογράφημα ύπνου

Σακελλαρίου, Δημήτριος 16 May 2014 (has links)
Η συνδετικότητα εγκεφάλου αφορά σε πρότυπα δικτύων τόσο ανατομικών, όσο στατιστικά ή και αιτιακά συσχετισμένων συνδέσεων διακριτών μονάδων του νευρικού συστήματος του εγκεφάλου. Στην εργασία αυτή μελετάται τόσο η απόδοση όσο και η φυσιολογική ερμηνεία μετρικών υπολογισμού της στατιστικής καθώς και αιτιακής συνάφειας χρονοσειρών. Οι χρονοσειρές αφορούν σε καταγραφές περιοχών/ηλεκτροδίων του ηλεκτροεγκεφαλογραφήματος ύπνου φυσιολογικών ανθρώπων. Πιο συγκεκριμένα, οι μέθοδοι υπολογισμού της συνδετικότητας εφαρμόζονται μεταξύ περιοχών του εγκεφάλου και σε χρονικές στιγμές όπου λαμβάνουν χώρα μικρογεγονότα του ύπνου, όπως υπνικές άτρακτοι (sleep spindles) και K-συμπλέγματα (K-complexes), με απώτερο σκοπό την κατανόηση του ρόλου αυτών των γεγονότων στον ύπνο. / During Non-Rapid Eye Movement (NREM) sleep brain is considered to be relatively disconnected from the environment. Also connectedness between brain areas has been found decreased, although we do not know the role played in this by specific elements of sleep microstructure. We developed a method with millisecond time resolution appropriate for assessing brain connectivity during NREM sleep spindles, the φ-coherence. It is based on the observation by Nolte (2008) that when the phase between two signals is zero, the coherence value can be attributed to volume conduction rather than functional neuronal connection. So φ-coherence excludes this value. The new method counts among the effective connectivity measures as advantageous in (a) its superb time resolution (b) ability to study events clustered from different time periods or subjects (c) simultaneous study of any choice from all possible combinations of EEG electrodes and display their φ-coherence in time-frequency topological maps and (d) parameterization of all the plots included in the maps regarding frequency, time and φ-coherence threshold. Preliminary results from 360 fast spindles recorded in whole night sleep of two healthy volunteers the use of φ-coherence indicated a prevailing connectivity pattern of causal interactions mostly from centroparietal regions (C3, Cz, C4, Pz, P3, P4) to right frontotemporal regions (F8, T4). The study aims to help our understanding of the role played by spindles not only in sleep maintenance but also in memory consolidation and in several neuropsychiatric disorders.
9

Εγκεφαλογραφική μελέτη της τοπογραφίας των υπνικών ατράκτων

Δαμάσκος, Γιώργος 30 May 2012 (has links)
Οι υπνικές άτρακτοι είναι χαρακτηριστικές κυματομορφές του ηλεκτροεγκεφαλογραφήματος (ΗΕΓ) του σταδίου 2 του ήσυχου (NREM) ύπνου, που έχουν υπναγωγικό ρόλο και σχετίζονται με διαδικασίες μνήμης και μάθησης. Μια υπνική άτρακτος είναι ομάδα ρυθμικά επαναλαμβανόμενων κυρίως αρνητικών κυμάτων με πλάτος που σταδιακά αυξάνεται και στη συνέχεια, σταδιακά μειώνεται, εντός της ζώνης συχνοτήτων 12-15 Hz (ζώνη συχνοτήτων ρυθμού σίγμα) και με διάρκεια μεταξύ 0.5 και 2 δευτερολέπτων. Η απεικόνιση, για μια κορυφή της ατράκτου, της κατανομής καποιας ηλεκτροεγκεφαλογραφικής μεταβλητής (π.χ. του ηλεκτρικού δυναμικού) στο πεδίο των ηλεκτροδίων καλείται τοπογραφία της κορυφής αυτής. Σκοπός της μελέτης ήταν να διερευνηθεί η τοπογραφία των ταχέων υπνικών ατράκτων κατά μέσο όρο, έτσι από ένα σύνολο 1449 γρήγορων ατράκτων επιλέχθηκαν προς ανάλυση 843 οι οποίες εμφανίζονταν σποραδικά και τουλάχιστον 3 δευτερόλεπτα μακριά από άλλα εμφανή εγκεφαλογραφικά συμβάντα που θα μπορούσαν να τις επηρεάσουν. Οι υπνικές άτρακτοι σημαδεύτηκαν πάνω στο ΗΕΓ οπτικά στην πρώτη, στην μεσαία και στην τελευταία αρνητική κορυφή τους, ακολούθησε προ-επεξεργασία, αποθορυβοποίηση των δεδομένων και εν συνεχεία μεσοποίηση τους στο πεδίο του χρόνου και των συχνοτήτων. Από την ανάλυση προκύπτει ότι η μέση τοπογραφία των ατράκτων στην αρχή, στη μέση και στο τέλος μεγιστοποιείται κεντρικά της κεφαλής και είναι σχετικά σταθερή και στις τρεις περιπτώσεις με μικρή τάση μετατόπισης προς τα εμπρός καθώς το φαινόμενο εξελίσσεται. Ομως, οι μεμονωμένες άτρακτοι εμφανίζουν μεγάλη ποικιλία προτύπων κίνησης του σημείου μεγίστης ισχύος η οποία δεν αποτυπώνεται στο μέσο όρο αλλά γίνεται αντιληπτή εξετάζοντας την τοπογραφία ενός μεγάλου αριθμού ατράκτων πριν τη μεσοποίηση. / Sleep spindles are characteristic waveforms of NREM sleep stage 2 electroencephalogram (EEG) which are involved in the generation and preservation of sleep as well as learning and memory processes. A sleep spindle is a group of rhythmic waves with gradually increasing and then decreasing amplitude (crescendo decrescendo morphology) within the frequency band 11-15 Hz and duration from 0.5 to 2 seconds. The voltage map of all electrodes for a spindle’s peak is called topography of the peak (power distribution visualization). The purpose of this study was to investigate the topography of fast spindles average thus, from a set of 1449 fast spindles, 843 were at least 3 seconds away from other EEG notable events which could affect them and were chosen for the average study. Sleep spindles were marked on EEG signal visually at first, middle and last negative peak, the next steps were preprocessing and denoising and finally averaging in time and in frequency domains. After the analysis we conclude that the average topography of the spindles at their start, middle and end is relatively stable and maximizes at the center of the head with a little tension to move forward as the phenomenon evolves. However, individual spindles show a great variety of movement patterns of the point of maximal electrical potential which patterns are not depicted in their average but can be understood by examining a large number of spindles before averaging.
10

Ανίχνευση βραδέων και ταχέων ατράκτων στο εγκεφαλογράφημα ύπνου

Τσιντώνη, Ασημίνα 26 July 2013 (has links)
Οι διάφορες δραστηριότητες του εγκεφάλου συχνά χαρακτηρίζονται από ειδικούς ρυθμούς στο ηλεκτροεγκεφαλογράφημα (ΗΕΓ). Το 2ο στάδιο του ύπνου χωρίς ταχείες οφθαλμικές κινήσεις (στάδιο NREM) χαρακτηρίζεται από τις ατράκτους που σηματοδοτούν την ουσιαστική έναρξη του ύπνου. Αποτελούν 0.5-1 δευτερόλεπτα ρυθμικής διαδοχής κύρια αρνητικών κυμάτων γενικευμένα στο ΗΕΓ τα οποία παρουσιάζουν προϊούσα αύξηση και μετά μείωση του πλάτους τους. Οι άτρακτοι συμμετέχουν σε διάφορες σημαντικές λειτουργίες του εγκεφάλου. Η κατανόηση του πολύπλευρου και πολύ σημαντικού ρόλου των ατράκτων έχει αποτελέσει αφορμή ώστε να γίνουν προσπάθειες εντοπισμού των υπεύθυνων για τη γένεσή τους εγκεφαλικών κυκλωμάτων. Σκοπός της προτεινόμενης μεθόδου είναι η εφαρμογή της μεθόδου εντοπισμού σημάτων σε πολυκαναλικές καταγραφές χρησιμοποιώντας περιορισμούς που στηρίζονται στο πεδίο του χώρου (spatial constraints) και το πεδίο της συχνότητας (frequency constraints) χρησιμοποιώντας την τεχνική ανάλυσης σε ανεξάρτητες συνιστώσες (ICA). Η μέθοδος εφαρμόστηκε για την ανάλυση βραδέων και ταχέων ατράκτων σε εγκεφαλογραφήματα ύπνου. Στο εργαστήριο Φυσιολογίας έχουν γίνει ΗΕΓ καταγραφές ολονύκτιου ύπνου με καταμέτρηση πολλών εκατοντάδων ατράκτων οι οποίες χρησιμοποιήθηκαν για την ανάπτυξη της παραπάνω μεθόδου αυτομάτου ανίχνευσης και εντοπισμού των ατράκτων. / Several brain activities are characterized by specific rhythms in electroencephalogram (EEG). The non rapid eye movement (NREM) stage of sleep is characterized by sleep spindles signaling the beginning of sleep. Spindles are rhythmic generalized negative waves in EEG with progressively increasing and gradually decreasing amplitude lasting 0.5-1 sec. Spindles are involved in several brain functions. The comprehension of the significance and multilateral role of spindles has driven efforts to detect the brain circuits involved in their generation. The purpose of this study is the introduction of a signal detection method in multichannel records, using Independent Component Analysis with spatial and frequency constraints. This automatic detection method was applied to the analysis of fast and slow spindles in sleep EEG, obtained from whole-night sleep recording in the laboratory of Physiology Department at University of Patras.

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