AbstractSwallowing is a complex neurophysiological process involving the activation of several components of the central nervous system with bilateral but asymmetric representations of swallowing musculature in the motor cortex. Difficulty in swallowing (dysphagia) in stroke patients has been reported by up to 50% of victims, and can increase morbidity and mortality in this population due to the development of aspiration pneumonia and malnutrition. One of the common factors that predispose patients to dysphagia after a stroke is believed to be the reduced sensory awareness in the oropharyngeal area, which affects the swallowing process. The uses of diet modification to reduce thin liquid aspiration have gained interest but are often unpalatable or have limited success. Carbonated liquid have shown some beneficial effects in swallowing behaviour. However, there is very little evidence to support this intervention. Therefore, the aim of this thesis is to investigate the neurophysiological and behavioural effects of carbonated liquids on swallowing in healthy volunteers.The effects of carbonated solutions on swallowing performance compared to non-carbonated solutions (still water) was investigated in a pilot study and (still water and citric acid) in the main study using reaction time task (chapter 2). Carbonation appears to alter swallowing performance compared to other liquids by improving complex tasks. In addition, beneficial neurophysiological effects of carbonated liquids were evident after 10 minutes of carbonated liquid swallowing compared to still water and citric acid solution in healthy volunteers (chapter 3).In chapter 4, the response of the healthy swallowing motor cortex to carbonated liquids following application of a virtual lesion compared to still water and saliva swallowing, was investigated. Carbonated liquids were able to reverse the inhibitory effect induced by 1 Hz rTMS to the dominant pharyngeal motor representation. Moreover, the beneficial effects of carbonated liquids on swallowing performance, measured with a swallowing reaction times task after application of a virtual lesion was observed in a pilot investigation in healthy volunteers (chapter 5). These data demonstrate that carbonated liquids have beneficial neurophysiological and swallowing performance effects and support notion that the chemical properties of carbonated liquids may provide the required peripheral sensory information that alter the brain swallowing function, which leads to an improvement in the swallowing performance of stroke dysphagic patients. These data lay the foundation for considering the use of carbonation as facilitating stimuli in dysphagic patients.