Στην εργασία αυτή θα γίνει μελέτη και εφαρμογή της μεθόδου Ανάλυσης Ανεξάρτητων Συνιστωσών πάνω σε σήματα ηλεκτροεγκεφαλογραφημάτων. Το πρώτο κεφάλαιο αποτελείται από μια εισαγωγή στις ιδιότητες και την προέλευση των ηλεκτροεγκεφαλικών σημάτων, καθώς και στη μεθοδολογία, τον σκοπό και τη χρησιμότητα των ΗΕΓ. Στη συνέχεια παρουσιάζονται τα προβλήματα που αντιμετωπίζει η ανάλυση σημάτων όταν εφαρμόζεται στα ΗΕΓ, καθώς και οι μέχρι στιγμής χρησιμοποιούμενες λύσεις. Στο δεύτερο κεφάλαιο της εργασίας παρουσιάζονται τα αποτελέσματα της βιβλιογραφικής έρευνας πάνω στην ανάλυση ανεξάρτητων συνιστωσών. Επίσης θα δοθεί το μαθηματικό υπόβαθρο και η αιτιολόγηση της επιλογής ενός συγκεκριμένου αλγορίθμου, του FastICA. Στο τρίτο κεφάλαιο γίνεται η εφαρμογή της μεθόδου ΑΑΣ πάνω σε καταγεγραμμένα σήματα ηλεκτροεγκεφαλογραφημάτων, μέσω του περιβάλλοντος Matlab. Πραγματοποιείται η ανάλυση σε συνιστώσες, αναγνωρίζονται και αφαιρούνται τα σήματα μη εγκεφαλικής προέλευσης και τελικά χρησιμοποιείται μέθοδος απεικόνισης των πηγών εγκεφαλικής δραστηριότητας ως ισοδύναμα ηλεκτρικά δίπολα. Το τέταρτο και τελευταίο κεφάλαιο συνοψίζει τα αποτελέσματα και τα συμπεράσματα που εξήχθησαν κατά τη διάρκεια της εκπόνησης αυτής της διπλωματικής. / -

No description available.

Real-world decision making is challenging due, in part, to changes in the underlying reward structure: the best option last week may be less rewarding today. Determining the best response is even more challenging when feedback validity is low. Presented here are the results of two experiments designed to determine the degree to which midbrain reward processing is responsible for detecting reward contingency changes when feedback validity is low. These results suggest that while midbrain reward systems may be involved in detecting unexpected uncertainty in non-stationary environments, other systems are likely involved when feedback validity is low – namely, the locus-coeruleus-norepinephrine system. Finally, a computational model that combines these systems is described and tested. Taken together, these results downplay the role of the midbrain reward system when feedback validity is low, and highlight the importance of the locus-coeruleus-norepinephrine system in detecting reward contingency changes.

We have designed a system suitable for auditory electroencephalographic (EEG) experiments, with the objective of enabling studies of auditory motion. This thesis details the perceptual cues involved in spatial auditory experiments, and compares a number of spatial panning algorithms while examining their suitability to this purpose. A behavioural experiment involving perception of static auditory objects was used in an attempt to differentiate these panning algorithms. This study was used to inform the panner choice used in an auditory EEG experiment. This auditory EEG experiment involved the effects of discontinuity in velocity and position, and their affects on object perception. A new event related potential (ERP) component – the lateralized object related negativity (LORN) – was identified, and we consider its significance. libnetstation, a library for connecting with the NetStation (EEG) system has been developed, and released as open source software. / viii, 61 leaves : ill. ; 29 cm

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Many athletes and spectators believe that experiencing and controlling psychological momentum is a critical component to achieving success in sport (Perreault, Vallerand, Montgomery, & Provencher, 1998; Stanimirovic & Hanrahan, 2004). Despite this, little is known regarding why some individuals perceive momentum differently than others. This study was designed to determine if optimistic thinking has a relationship with psychological momentum perceptions. Female Division I NCAA volleyball players (N = 68) completed the Life Orientation Test – Revised (Scheier, Carver, & Bridges, 1994), the Sport Attributional Style Scale - Short (Hanrahan & Grove, 1990b), and a psychological momentum survey. The results indicated that attributional style constructs intentionality and globality were significant predictors of psychological momentum perceptions. Also, participants had greater disagreement regarding the momentum value of early and late points in a set than those in between. Neither dispositional optimism nor sport-specific optimistic attributional style were correlated with psychological momentum perceptions. Future attempts to measure psychological momentum perceptions should consider a mixed methods approach along with more ecologically valid assessment protocols. / Department of Psychological Science

The incidence of stroke is increasing and is expected to continue to increase with the aging population, escalating rates of obesity and physical inactivity, and the rising prevalence of heart failure. Stroke is a leading cause of long-term disability, which includes approximately half of survivors that experience cognitive impairment. It is accepted that aerobic exercise can improve physical health in both healthy and stroke populations. Evidence also suggests aerobic exercise may positively affect cognitive function among healthy adults; however, whether there are similar beneficial effects among stroke survivors remains unclear. The purpose of this thesis was to examine whether a single session of moderate intensity aerobic exercise acutely improves cognitive function, specifically executive function, in comparison to a rest control among people with chronic stroke. Our first objective was to determine whether aerobic exercise alters cortical processing, as measured by P300 amplitude and latency during a modified Eriksen Flanker task. The second objective was to investigate whether aerobic exercise influences behavioral measures of response time and accuracy during a modified Eriksen Flanker task. Finally, the third objective was to examine the time course of effects up to 40 minutes after exercise cessation. In our sample, participants had shorter P300 latency and larger P300 amplitude 20 to 40 minutes after exercise cessation in comparison to rest. There were no significant behavioural changes. These findings suggest that aerobic exercise may enhance, or at least maintain cognitive processing speed and attention 20 to 40 minutes after exercise cessation, which otherwise deteriorated in the rest condition. Although results should be viewed cautiously due to a small sample size, these findings have potential implications for stroke rehabilitation. Our results suggest that aerobic exercise may be able to improve attentional focus during subsequent rehabilitation exercises for up to 40 minutes or more. Future research should examine whether the effects of various exercise doses and whether paired exercise and rehabilitation improves clinical outcomes.

Frontal electroencephalographic (EEG) alpha (α) asymmetry may index the activation of lateralized affect and motivation systems in humans. Resting EEG activation was measured and its relationship to Iowa gambling task (IGT) performance was evaluated. No effects were found for α power asymmetry. However, beta (β) power asymmetry, an alternative measure of resting EEG activation, was associated with the number of risky decisions made in the early portion of the task. Additionally, IGT deck selection patterns suggest there are at least three distinct performance styles in healthy individuals. Interestingly, β power asymmetry contradicts performance predictions based on accepted frontal asymmetry affect and motivation models.

Increasing evidence supports the use of physical activity for modifying brain activity and overall neurological health (Hillman et al, 2008). Specifically, aerobic exercise appears to improve cognitive efficacy with regards to decisional oddball tasks shown through the P300, whose amplitude and latency is augmented (Magnié et al., 2000). Furthermore, the effects of an acute bout of aerobic exercise on cardiovascular function are well established and are sustained following exercise cessation. Based on these findings, we proposed that (1) an acute bout of exercise may modulate movement-related cortical excitability within motor areas and (2) that transient effects would be sustained as long as heart rate (HR) remained elevated. Subjects (n=23) were placed in a soundproof booth and instructed to perform a self-paced unimanual ballistic wrist extension every 3-6 seconds of the right wrist while holding a moveable handle. The motion involved a brisk contraction followed by relaxation and positional reset, collected continuously for approximately 8 minutes. Electroencephalography was used to measure movement-related cortical activity of the Bereitschaftspotential (BP) time-locked to onset of muscle activity associated with movement. The BP is a slow negative self-paced movement related cortical potential that precedes movement by approximately 1500ms. Current work commonly separates the BP into 3 main components early, late, and re-afferent Potentials. The early BP is representative of motor preparation of supplementary motor area (SMA) activity while the late component is representative of motor execution from primary motor cortex (M1). Early and late components are often distinguished by a a characteristic change in slope; where the early BP is a slow negative rise and the late components a steeper negative deflection beginning approximately 500ms prior to movement onset. Broken down further the late component consists of a portion of negative slope before giving rise to a peak approximately 100ms after movement onset known as the motor potential (MP). Following baseline measures, subjects performed 20 minutes of aerobic exercise at a moderate intensity (70% of age-predicted maximum heart rate) on a recumbent cycle ergometer. After the cessation of exercise, BP measures were recorded at two time points: immediately post-exercise (Post) and following a return to iv baseline HR (Post[Rest]) and two additional measures separated by 15 minutes each (Post[Rest2] and Post[Rest3]) which was, on average, 45 minutes after the cessation of exercise. Electromyography (EMG) was employed over the extensor carpi radialis muscle belly to describe muscle burst activity and onset characteristics. Results determined that Early but not Late BP was influenced by aerobic exercise. This early movement related cortical adaptation is indicative of enhanced processing within supplementary motor area. Moreover, this effect was sustained for up to an hour and 15 minutes following exercise cessation. This data is suggestive that aerobic exercise influences on motor related cortical excitability is not driven by an aerobic exercise effect and is more indicative of a delayed neurotransmitter effect.

We are capable of effortlessly parsing a complex scene presented to us. In order to do this, we must segregate objects from each other and from the background. While this process has been extensively studied in vision science, it remains relatively less understood in auditory science. This thesis sought to characterize the neuroelectric correlates of auditory scene analysis using electroencephalography. Chapter 2 determined components evoked by first-order energy boundaries and second-order pitch boundaries. Chapter 3 determined components evoked by first-order and second-order discontinuous motion boundaries. Both of these chapters focused on analysis of event-related potential (ERP) waveforms and time-frequency analysis. In addition, these chapters investigated the contralateral nature of a negative ERP component. These results extend the current knowledge of auditory scene analysis by providing a starting point for discussing and characterizing first-order and second-order boundaries in an auditory scene. / x, 90 leaves : col. ill. ; 29 cm