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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

Exploring the Neural Correlates of Auditory Awareness / Utforskning av neurala korrelat inom auditivt medvetande

Gerdfeldter, Billy January 2018 (has links)
Neural correlates of consciousness (NCCs) represent the physiological processes related to consciousness and awareness. Consciousness is theorized as a recurrent process of integration between separate but specialized brain areas. Previous research has used electroencephalography (EEG) to locate NCCs of sensory awareness in vision through event-related potentials (ERPs). Two ERP components thought to represent visual awareness are the visual awareness negativity (VAN) and late positivity (LP). VAN and LP have been extensively studied, yet little research has been conducted in other sensory modalities. In this study, the presence of an auditory awareness negativity (AAN) and associated LP is investigated in 23 subjects using EEG. To avoid false positives in data analysis, two research hypotheses were preregistered. The results indicate that auditory LP does occur, but that AAN does not, in hypothesized intervals. However, the data suggest that AAN may occur at a later interval. Possible attributes of the later interval are discussed. In sum, the data provide results consistent with recurrent theories of sensory awareness.
2

Separating Post-perceptual Processes From Auditory Awareness : An Electrophysiological Study With a No-response Task

Fjordstig, Andréas January 2019 (has links)
Two theories of consciousness have different ideas about when consciousness happens and what neural processes enable conscious experience. The recurrent processing theory supports an early onset of consciousness caused by recurring loops of information between sensory areas. Contrary to this belief, the global workspace theory claims that consciousness appears later, through global recurrent loops of information between sensory and higher order brain areas such as the visual cortex and frontoparietal areas. Electrophysiological studies have found an event-related negativity arising in primary visual areas around 200 ms that correlates to awareness. This activity suits the predictions of an early onset of consciousness made by the recurrent processing theory. It is followed by a later positive amplitude appearing around 400 ms. This activity is in line with predictions made by the global workspace theory. The current study transition from visual to auditory awareness research in order to find the neural correlates of consciousness in audition. A sound detection task with tones calibrated to each participants threshold value was used in the experiment and two electrophysiological measurements of auditory awareness were found. An auditory awareness negativity that appears around 200 ms after stimulus onset and a late positivity appearing around 400 ms. Researchers disagree about if these event-related potentials correlate with awareness or unrelated cognitive mechanisms. In order to solve this problem, the current experiment was devised to test if they were affected by response conditions. A no-response paradigm with reversed response conditions was used to separate pre- and post-conscious mechanisms from the auditory awareness negativity and the late positivity. Results showed that auditory awareness negativity was independent of response condition and thus free from post-perceptual processes. The late positivity amplitude seems to be dependent on response condition but the result was inconclusive.

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