Now showing 1 - 4 of 4
ItemUsing long-wear electroencephalography to ascertain the variability of Lempel-Ziv Complexity (LZc) measures of consciousnessPatel, Giana Rose ( 2019)It has been recently claimed that measures of spontaneous electroencephalography (EEG) signal complexity, such as Lempel-Ziv Complexity (LZc), can provide an index of an individual’s level of consciousness. Research and clinical practice are currently limited to unreliable behavioural and physiological measures to indicate consciousness. Therefore, there is significant urgency for an objective, reliable, brain-based measure of consciousness. EEG complexity measures utilise algorithms from Information Theory to quantify the diversity in spontaneous EEG data. These are being used to measure the diverse neural activity which necessarily underlies conscious experience. LZc assesses the complexity of multi-channel EEG data using a compression algorithm. Studies of LZc typically involve comparing conditions of altered consciousness with periods of conscious wakefulness. These studies suggest that the change in complexity observed is reflective of the change in level of consciousness. However, very little is known about how LZc varies, either with or without a corresponding change in consciousness. The present study utilised portable long-wear EEG to record multi-day, continuous EEG data from two participants (a total of 8 days for Participant 1 and 4 days for Participant 2). Data from each participant was analysed independently. A LZc algorithm was used to compute a complexity value for every non-overlapping 10-second segment. Results demonstrated that, as with previous research, LZc during Wake (14-hours during the day, multiple days per participant) is, on average, higher than during sleep (Stage N1, Stage N2, Slow-Wave-Sleep, and REM sleep). However, there is considerable variation surrounding these means. Visualising LZc across Wake revealed a consistent but wide spread of variability around the mean, with a scattering of low LZc values reflected by a negative skew in the data. This also results in a wide range of possible mean LZc values made available from taking samples (between 1 and 120 minutes in duration) during this period. Although this variability reduces with larger samples sizes, even day-to-day, LZc can significantly differ within a person. Regardless of the source of this variability, its presence causes concern due to the overarching clinical motivations and potential practical applications of this measure. These results suggest that LZc may not be indicative of level of consciousness, as previously claimed. The issues raised and addressed in this study are not unique to LZc, but will apply to all complexity algorithms, current and future. With this study, we have shown that long-duration EEG is a successful framework for identifying variability in a complexity measure of consciousness. This information-rich dataset is uniquely capable of exposing and investigating complexity measures, with the additional insight of observing and analysing complexity across time. This study endeavours to redirect discussions of this field and promote the use of this framework to both acknowledge and empirically address all surrounding issues and assumptions. All complexity measures should undergo reliability testing as both a proof of concept and a proof of practice before being utilised in research or clinical applications.
ItemUsing single subject manual independent component analysis on resting-state fMRI dataParsons, Nicholas James ( 2019)It is important to understand the influence of common artefacts when processing fMRI data, and how best to remove these in order to produce reliable outcomes. This information affects clinicians and researchers. Little is known about functional connectivity in people with genetic generalised epilepsy at present, making it an ideal cohort to examine while using a quality data processing pipeline. The present thesis discusses individual artefactual contribution, and how to deal with artefact using single subject manual independent component analysis (SSM-ICA). A systematic review of the literature (Chapter two) found people with genetic generalised epilepsy to have reduced functional connectivity in the default mode and attention networks relative to healthy controls. A methods study (Chapter three) investigated functional connectivity in juvenile absence epilepsy, a subtype of genetic generalised epilepsy. Results showed reduced connectivity strength relative to controls. Further, incremental removal of artefacts using single subject manual independent component analysis showed fewer correlations breaching the .05 threshold. These areas were more confined to default mode and attention networks, suggesting most correlations derived without the use of SSM-ICA are spurious. Signal-to-noise ratios were also significantly higher in both incremental cleaning conditions.
ItemEarly maladaptive schemas associated with performance anxiety aetiology and phenomenology in classically-trained musiciansKirsner, Jennifer ( 2018)Music performance anxiety (MPA) is widespread amongst performing musicians, although research into developmental factors involved in its manifestation is minimal. The aim of this research was to explore the impact of childhood experiences with parents along with patterns of dysfunctional cognitive schemas that develop through childhood (‘Early Maladaptive Schemas’; EMSs) on the manifestation and severity of MPA in adulthood. Study 1 investigated the relationship between EMSs and MPA through online surveys. Study 2 then expanded on Study 1 by exploring childhood parenting experiences associated with the development of both EMSs and MPA through qualitative interviews. Study 1 employed 100 adult professional, amateur, and student classical musicians from across Australia (recruited via email and social media). Participants completed the Young Schema Questionnaire (Young, 2005) and the Kenny Music Performance Anxiety Inventory (Kenny, 2011). Factor analysis revealed four higher-order EMS factors, one of which was a significant predictor of MPA. This factor (entitled ‘Inadequacy/Impaired Autonomy’) comprised themes of failure, catastrophising, and incompetence/dependence. Study 2 included eight participants from Study 1, five of whom scored one standard deviation or more above the mean K-MPAI score and three of whom scored one standard deviation or more below the mean K-MPAI score. Participants were interviewed about experiences of parenting during childhood and adolescence, along with their experiences of MPA and musical training. Interpretative phenomenological analysis was used to explore themes in the interview data, which revealed three key parenting styles related to the development of MPA: Poor Parental Involvement and Availability, Unpredictable Parental Mood and Anger, and Parental Expectations and Overcontrol. Findings from both studies are discussed in light of clinical applications and interventions, and implications for both parents and music educators.
ItemA psychometric evaluation of the Temporal Experience of Pleasure Scales (TEPS)HO, PAUL ( 2014)A number of hypotheses for behaviour are built on the principle of “hedonic motivation”, the assumption that people are always motivated towards rewards that affords them with the greatest amount of pleasure. Current neurobiological studies have demonstrated that reward-motivational processes and hedonic processes are mediated by independent systems (Dillon et al., 2008). Salient rewards activate the production and attribution of incentive salience by the mesocorticolimbic dopaminergic system, which promotes reward-motivation or ‘wanting’ towards preferred rewards (Berridge, Robinson, & Aldridge, 2009). The attainment of rewards is marked by the experience of pleasure or ‘liking’, which is mediated by the attribution of hedonic gloss to this event by the forebrain opioidergic system (Pecina, Cagniard, Berridge, Aldridge, & Zhuang, 2003). The Incentive Salience Theory (IST) argues against the hedonic principle, maintaining that these two reward-related processes are dissociated, such that the loss or increase in reward ‘liking’ does not affect reward ‘wanting’, and vice-versa (Robinson & Berridge, 2001). The Temporal Experience of Pleasure Scales (TEPS; Gard, Gard, Kring, John, 2006) is the first self-report questionnaire that is designed to assess individual differences in the ability to experience dopaminergic-mediated anticipatory pleasure and opioidergic-mediated consummatory pleasure. However, the psychometric structure of the TEPS has not been fully evaluated, providing the goal of the current study to conduct a psychometric analysis consisting of a factor analysis and construct validation by a convergent-discriminant analysis. While the formation of two distinct subscales in the scale construction study and demonstrating predictive validity with schizophrenia (Gard, Kring, Gard, Horan, & Green, 2007), the two scales lacked clear dissociation and its relationship with schizophrenia has not been consistently observed (Strauss, Wilbur, Warren, August, & Gold, 2011). Two hundred and ninety-two university students in Australia (212 females, 80 males, Mage = 20.19 years, SD = 4.24, age range: 18-53) and 292 university students in the United Kingdom (226 females, 66males, Mage =20.96 years, SD = 4.72, age range: 18-44) completed the TEPS, which required the participant to report the amount of anticipation (anticipatory subscale) or in-the-moment pleasure (consummatory subscale) they would experience in response to hypothetical rewarding experiences. The Australian participants also completed a battery of conceptually-related self-report questionnaires. Given past lack of support, it was not surprising that the two-factor model of the TEPS was unsupported by the current factor analysis. On a similar note, construct validity was unsupported as the lack of discriminant validity with measures of reward-motivation and positive emotionality meant that the two subscales cannot be assumed to be dissociated measures of ‘wanting’ and ‘liking’. In light of these findings, it might be suggested that the assessment of these two reward-related processes by hypothetical self-report is difficult as humans may not be able to think of something pleasurable without also desiring it, and vice-versa (Berridge, 2007). Further limitations of self-reports include the fallibility of autobiographic memory and of affective forecasting (Wilson & Gilbert, 2005). Future studies should consider alternative assessment methods of ‘wanting’ and ‘liking’ that are less reliant on affective forecasting, such as ambulatory affective state assessments and implicit indexes whereas behavioural indexes are highly recommended for their proximity to reality and minimal reliance on conscious deliberation.