Psychiatry - Research Publications

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Author: Harding, Ian × Author: Harrison, Benjamin × Author: Pantelis, Christos × Type: Journal Article ×

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    The neural cascade of olfactory processing: A combined fMRI-EEG study
    Masaoka, Y ; Harding, IH ; Koiwa, N ; Yoshida, M ; Harrison, BJ ; Lorenzetti, V ; Ida, M ; Izumizaki, M ; Pantelis, C ; Homma, I (ELSEVIER SCIENCE BV, 2014-12-01)
    Olfaction is dependent on respiration for the delivery of odorants to the nasal cavity. Taking advantage of the time-locked nature of inspiration and olfactory processing, electroencephalogram dipole modeling (EEG/DT) has previously been used to identify a cascade of inspiration-triggered neural activity moving from primary limbic olfactory regions to frontal cortical areas during odor perception. In this study, we leverage the spatial resolution of functional magnetic resonance imaging (fMRI) alongside the temporal resolution of EEG to replicate and extend these findings. Brain activation identified by both modalities converged within association regions of the orbitofrontal cortex that were activated from approximately 150-300 ms after inspiration onset. EEG/DT was additionally sensitive to more transient activity in primary olfactory regions, including the parahippocampal gyrus and amygdala, occurring approximately 50 ms post-inspiration. These results provide a partial validation of the spatial profile of the olfactory cascade identified by EEG source modeling, and inform novel future directions in the investigation of human olfaction.
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    Functional Connectivity in Brain Networks Underlying Cognitive Control in Chronic Cannabis Users
    Harding, IH ; Solowij, N ; Harrison, BJ ; Takag, M ; Lorenzetti, V ; Lubman, DI ; Seal, ML ; Pantelis, C ; Yuecel, M (NATURE PUBLISHING GROUP, 2012-07)
    The long-term effect of regular cannabis use on brain function underlying cognitive control remains equivocal. Cognitive control abilities are thought to have a major role in everyday functioning, and their dysfunction has been implicated in the maintenance of maladaptive drug-taking patterns. In this study, the Multi-Source Interference Task was employed alongside functional magnetic resonance imaging and psychophysiological interaction methods to investigate functional interactions between brain regions underlying cognitive control. Current cannabis users with a history of greater than 10 years of daily or near-daily cannabis smoking (n=21) were compared with age, gender, and IQ-matched non-using controls (n=21). No differences in behavioral performance or magnitude of task-related brain activations were evident between the groups. However, greater connectivity between the prefrontal cortex and the occipitoparietal cortex was evident in cannabis users, as compared with controls, as cognitive control demands increased. The magnitude of this connectivity was positively associated with age of onset and lifetime exposure to cannabis. These findings suggest that brain regions responsible for coordinating behavioral control have an increased influence on the direction and switching of attention in cannabis users, and that these changes may have a compensatory role in mitigating cannabis-related impairments in cognitive control or perceptual processes.