Date of Award

Summer 2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Communication Sciences and Disorders

Advisor(s)

Christy Ludlow

Abstract

The purpose of this study was to evaluate the effectiveness of two types of non-invasive, sensory stimulation on increasing the rate of swallowing and for inducing cortical activity associated with swallowing. The types of stimulation investigated were vibrotactile stimulation to the external throat area surrounding the laryngeal tissues and oral air puff stimulation to the anterior faucial pillars. A functional near infrared spectroscopy (fNIRS) system measured relative changes in the concentration of oxygenated hemoglobin (HbO) in cortical sensorimotor regions as an indirect measure of brain activity. The experiment included 16 healthy adult participants between the ages of 28 and 60 years of age with no reported history of swallowing problems. Results indicated a significant difference between stimulation types on the frequency of swallowing. A significant change in the number of swallows was found between the air puff stimulation and control periods, while no difference was found between the vibrotactile stimulation and control periods. A significant main effect of type of stimulation (p ≤ .0005) indicated that the two stimuli also differed in the effects on changes in blood oxygenation in the brain. Reduced concentration of HbO, particularly in the right sensory region, was seen during air puff stimulation compared to the control period. There was no overall difference in concentration of HbO in the cortical somatosensory and motor regions between the vibrotactile stimulation and control periods. Data recorded from fNIRS suggest an increased concentration of HbO in some participants during vibrotactile stimulation in the right sensory region which was positively related to the degree of increase in swallowing rate. The findings of an inverse blood oxygenation level at the cortex would suggest that although air pressure stimulation of the faucial pillars is upregulating swallowing at the brainstem level, it might interfere with cortical activation for swallowing when applied concurrently. The potential for cortical activation seen by vibrotactile device is important. If the vibrotactile device activates the cortex, the device could be used in targeted interventions aimed at enhancing voluntary swallowing control.

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