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Perturbing the Pathway: The Impact of Lollipops and Lidocaine on Supramarginal Gyrus Activity During Reading Tasks
Poster D122 in Poster Session D, Wednesday, October 25, 4:45 - 6:30 pm CEST, Espace Vieux-Port
Mitchell G Holmes1, Jacqueline Cummine1, Daniel Aalto1,2, Amberley Ostevik1, Caroline C Jeffery1,2; 1University of Alberta, 2Covenant Health, Edmonton, Canada
Introduction: The universal print-to-speech framework describes a tight coupling between auditory (i.e., superior temporal gyrus) and somatosensory (i.e., supramarginal gyrus) feedback systems during various reading tasks. And, while much evidence has outlined the consequences of auditory perturbations on subsequent reading performance, comparatively little work has examined the impacts of somatosensory perturbations on reading. Surprisingly, recent work from our lab showed that somatosensory perturbations (i.e., lollipops and/or lidocaine in the mouth) facilitated reading performance in typical readers. However, the neural consequences of these perturbations remain unknown. The current study investigates the effects of mouth perturbations on the activity of the supramarginal gyrus, the brain region understood to play an important role in the somatosensory feedback system. Specifically, we examine whether lidocaine, known for numbing sensory receptors, suppresses activity, while large lollipops enhance activity in the supramarginal gyrus during reading tasks. This research will act to further our understanding of a universal print-to-speech framework. Methods: Participants proficient in English completed two reading tasks: an Orthographic Lexical Decision Task (OLDT; “does the letter string spell a real word, yes or no?”) and a Phonological Lexical Decision Task (PLDT; “does the letter string sound like a real word, yes or no?”) under three conditions: no perturbation, a lollipop perturbation (i.e., a large lollipop held in the mouth), and a lidocaine perturbation (i.e., a topical lidocaine solution swished in the mouth). Functional Near-Infrared Spectroscopy (fNIRS) was used to measure cortical hemodynamic responses during each task. Results: Behavioural data indicated enhancements in reading performance for both perturbation conditions compared to the control condition. Additionally, there was a marked increase in brain activity within the supramarginal gyrus during the lollipop condition compared to control and lidocaine conditions. Conversely, the lidocaine condition exhibited decreased brain activity compared to control and lollipop conditions. Conclusion: Our findings demonstrate that the lollipop perturbation increased supramarginal gyrus activity, while the lidocaine perturbation decreased activity. These results support our hypothesis that somatosensory perturbations in the mouth modulate the activity of the supramarginal gyrus during reading tasks and shed light on the neural underpinnings involved in the print-to-speech framework.
Topic Areas: Reading,