Browsing by Author "Mughal, Simran"

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    Cerebellar Contributions to Rapid Cross-Modal Attention in Visual-Tactile Processing
    (University of Waterloo, 2024-08-28) Mughal, Simran
    Clinical, functional connectivity, and behavioral studies have provided growing evidence for the involvement of the right lateral cerebellar hemisphere in cognition, especially attention. The presence of contralateral connections between the cerebellum and cerebrum via the thalamus provides the groundwork for cerebellar involvement in cognition and lateralization of function. At any given time, the brain is subjected to multiple relevant stimuli. While we cannot divide our attention between these stimuli, we can rapidly shift our focus. If these rapid attentional shifts occur in close temporal proximity between two target stimuli (T1 and T2), there is a decrease in accurately reporting the second target (T2). This phenomenon is termed attentional blink (AB). Studies combining continuous theta burst stimulation (cTBS) with visual AB tasks have shown that inhibiting the right cerebellar hemisphere enhances visual attentional blink. However, the exact physiological mechanisms underlying cerebellar influence on attentional networks during sensory processing remain unclear. It is also uncertain whether the cerebellum impacts sensory processing when presented with two relevant targets in different sensory modalities compared to unimodal conditions, and whether lateralization of function is conserved in this process. The aim of this study was to investigate the cerebellar involvement in cross-modal attentional processes and its impact on rapid attentional shifts when integrating cross-modal information presented within short time intervals. Hypothesizing that cross-modal AB would be enhanced following right cerebellar stimulation, 26 healthy participants underwent two sessions consisting of pre and post-cTBS cross-modal AB tasks targeting either the left or right cerebellar hemisphere. The task involved presenting either a visual or tactile stimulus (T1), followed by a stimulus of the opposite modality (T2), and then a mask of the same modality as T2. After stimulus presentation, participants were prompted to indicate the perceived side for both stimuli. Our results demonstrated that after transiently depressing the right cerebellar hemisphere, there was a significant reduction in extracting T2 tactile targets from the mask. Furthermore, there was an overall reduction in reporting T2 in the AB condition within the visual-tactile block type. There was no significant change in performance in either condition after stimulating the left cerebellar hemisphere. These results imply the cerebellum’s role as a sensory modulator in a hemisphere- specific way. Given our results, we conjecture that during complex tasks which require attentional control, the right cerebellum is recruited to manage bottom-up processing of the mask (distractors) via sensory gating. This allows top-down processes to effectively integrate T2 (target) after processing T1. We put forward the “Sensory Balance Model”, offering insights into the neurophysiological mechanisms underlying cerebellar involvement in attentional modulation.