Hood, Bernadett Marian (1996) Information processing in narcolepsy. PhD thesis, Victoria University of Technology.

Abstract

Narcolepsy is a disorder of excessive daytime sleepiness. Previous attempts to investigate the relationship between this sleepiness and everyday cognitive fimction have been limited by both the ability of narcoleptics to contain their sleepiness for brief testing periods and the potential lack of sensitivity of routine performance tasks to sleepiness induced changes. The first study reported in this thesis developed a research protocol which allowed subjects with narcolepsy to express states of sleepiness and non sleepiness and to then compare the performance of subjects with narcolepsy to age, gender, and IQ matched controls on tasks evaluating automatic, attentional and complex cognitive fiinctioning. The results indicate that at high arousal subjects with narcolepsy performed as well as controls on automatic tasks. This suggests that the capacity to perform for narcolepsy is not restricted by physiological factors but is secondary to the effects of sleepiness. Comparison of both the within subject effects for narcolepsy subjects of the transition between high and low arousal states, and the between subject effects of low arousal for narcolepsy subjects compared to controls, indicate that complex cognitive tasks are the most sensitive to arousal fluctuation. The second study compared the effects of low arousal for narcoleptic subjects, on selected performance tasks, with the effects of 32 hours of sleep deprivation for non pathologically sleepy subjects. The previously noted decrement for complex processing tasks secondary to low arousal in narcoleptic subjects was not demonstrated for the sleep deprived population. These differential performance outcomes for narcoleptic and sleep deprived controls are evaluated within a theoretical model of the interaction between sleepiness and performance. The third study reported in this thesis evaluated the subjective impressions of narcoleptic subjects of diminished memory fimction associated with the disorder. Previous evaluations have been non specific, requiring subjects to simply provide a global rating of subjective memory fiinction. The current study formalised this subjective analysis of memory function using the Metamemory in Adulthood Instrument to compare aspects of subjective memory dysfunction between narcoleptic subjects,subjects with excessive daytime sleepiness not associated with narcolepsy, and controls. The analysis indicates narcoleptics have significantly diminished self efficacy for memory function, in comparison to the reference groups, despite demonstrating equivalent levels of memory knowledge. In addition an integrated model is developed that illustrates the postulated role of affective dysfunction and sleepiness in narcolepsy in contributing to both cognitive difficulties and dysfunction on complex processing tasks.

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