Browsing by Author "McCracken, Heather"

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    Attention-Deficit/Hyperactivity Disorder (ADHD) and the influence of multisensory processes and sensorimotor integration on motor performance
    (2022-07-01) McCracken, Heather; Yielder, Paul; Murphy, Bernadette
    This thesis sought to investigate how adult Attention-Deficit/Hyperactivity Disorder (ADHD) influences processes relating to motor learning, sensory integration, and somatosensory processing. ADHD is associated with difficulties in motor control, including alterations to neural structure and function. However, it is unknown how these characteristics may influence motor control in adulthood. Results from study one suggests that those with ADHD exhibit an attenuation of neural activity in Brodmann area (BA) 2, right-hemispheric parietal lobe, in response to multisensory input. This may be reflective of alterations related to attentional resources and sensory processing when multiple simultaneous inputs are presented, as is the case during a multisensory condition. Differing activation within BA 2 provides important insight into the functioning of audiovisual multisensory processing in adults with ADHD. The second study, which utilized short-latency median nerve somatosensory evoked potentials (SEPs) paired with a novel visuomotor paradigm, yielded results of differing N18 and N30 SEP peak responses in those with ADHD. This suggests alterations to olivary-cerebellar-M1 processing and SMI when acquiring new motor skills, particularly those that are dependent on visuomotor input. Study three employed a novel force-matching motor paradigm and median nerve SEPs. Results indicated differential changes in the N18 SEP peak response after performing the novel force-matching task, suggesting a reduction in olivary-cerebellar-M1 inhibition. Finally, study 4 used source localization techniques to assess neural generator activity in response to median nerve stimulation after both visuomotor and force-matching motor paradigms. The ADHD group exhibited greater activation within BA 31 at post measures after performing the force-matching task, when compared to their baseline activity. This increased activity at post-measure may reflect activation of the Default Mode Network (DMN) and attentional changes, both of which are noted to be implicated in ADHD. As a whole, these findings provide a further understanding of the neurophysiological characteristics associated with ADHD, and their implications for motor control.
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    Audiovisual multisensory integration in young adults with and without a diagnosis of Attention-Deficit/Hyperactivity Disorder
    (2018-08-01) McCracken, Heather; Yielder, Paul; Murphy, Bernadette
    Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder with behavioural and neurophysiological characteristics. Several cortical structures that are altered in ADHD are involved in the process of multisensory integration (MSI). MSI is a fundamental form of sensory processing involved in many everyday tasks. Therefore, it is important to know whether those with ADHD experience altered MSI. Two different paradigms were used to assess MSI in adults with a diagnosis of ADHD. First, a simple response time (RT) task was completed. Electroencephalography (EEG) analysis revealed that those with ADHD had MSI occur, while there were significant differences in brain activity between groups. Study two employed a two-alternative forced-choice discrimination task. Those with ADHD responded faster than controls. EEG analysis revealed that those with ADHD have enhanced MSI. Activity differences were found in brain regions that are structurally altered in those with ADHD, indicating that structural alterations in ADHD may promote sensory processing.