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UBC Theses and Dissertations

Brain network dynamics of auditory change detection and working memory in recreational cannabis users Rumak, Samuel P.


There are concerns that cannabis use leads to increased risk of mental illness and neurocognitive impairment. However, empirical findings into the deleterious effects of cannabis use on cognition have been mixed and the underlying brain processes are poorly understood. The present research examined auditory cognitive processes putatively related to psychosis and cannabis use. Groups of cannabis users (CU) and non-users (NU) are compared on two novel tasks that examine electroencephalographic (EEG) measures of early somewhat pre-attentional (MMN) and later attentional (P300) auditory change detection and P300 response in auditory working memory. Additionally, sophisticated EEG source localization was used to interrogate underlying oscillatory activity and brain network connectivity. Chapter 2 introduced the novel roving dual oddball task, and revealed an asymmetry between easy and difficult task conditions, possibly due to increased attentional demands as evidenced by an interplay between dorsal and ventral attentional systems. Chapter 3 compared CU and NU on the same dual oddball task and revealed slower response times and increased P300 latency for CU on the more difficult condition. Theta-band network connectivity suggested that CU engaged in a stimulus driven strategy that became less effective in the more difficult condition due to a breakdown of fronto-temporal connectivity. Groups did not differ in early auditory processes (MMN). Chapter 4 unexpectedly revealed CU to have superior performance on working memory for basic auditory features (pitch and pattern), which was partially reflected in larger P300 amplitudes. Theta connectivity revealed different patterns of brain connectivity. Chapter 5 combined data from Chapters 3 and 4 to examine a local MMN effect across a larger sample along with measures putatively related to impairments associated with heavy cannabis use and psychosis. Again, CU did not show reduced MMN and showed only small differences on various measures. As a whole, this research suggests that proposed auditory impairments due to heavy cannabis use may not generalize to all subsets of cannabis users, and additional research is needed before any definitive conclusions can be reached regarding the impact of frequent cannabis use on cognitive processes.

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