Functional MRI Study of Brain Activation With Observation of Facial Expressions

Objectives: The purpose of this study is to identify areas of brain activation during the urge to yawn. Little is known about how yawning is suppressed, or why yawning often occurs in response to seeing another person yawn (contagious yawning). Contagious yawning is similar to other contagious motor programs, such as the greater urge Tourette subjects feel to tic when seeing repetitive movements or other subjects' tics, the urge to scratch when discussing itching and scratching, or the urge to urinate when hearing running water. Hypothetically, the urge or the suppression of this urge is modulated by a common cortical circuit implicated in Tourette syndrome. We plan to use functional magnetic resonance imaging (fMRI) to identify the pattern of blood oxygenation level-dependent (BOLD) activation in the brain when normal volunteers feel the urge to yawn.

Study Population: We intend to study 25 normal, right-handed, healthy volunteers.

Study Design: Using an event-related design, we will scan subjects, using the same 3T fMRI scanner, while showing a video of a person yawning, gaping, coughing, or doing nothing. Each of these four action stimuli will last for four seconds, with varying interstimulus intervals. Each video set will contain all actions displayed ten times pseudorandomly. Two data sets will be collected from each subject and will be separated by a brief rest period. Subjects will be instructed before the scan to watch a videotaped person perform various behaviors, without detailing the specific actions. So as not to influence their natural response to the yawning stimulus, we will instruct them only to keep their head still. The variable of interest will be the activation during urge-generation, contrasted with other control stimuli. A survey will be administered for informational purposes following the scan to assess the subjects' general impression of their susceptibility to yawning, whether they yawned in the scanner, whether they suppressed the urge to yawn, and if the urge to yawn increased or decreased with the repetition of the yawning segment.

Outcome Measures: The primary outcome of this study is the activation of brain structures in response to viewing another person yawning. In particular, we are interested in the activation of the anterior cingulate cortex, parietal operculum, insula, supplementary motor area, and dorsolateral prefrontal cortex as these are areas implicated in the urge to move in response to either internal (as in Tourette syndrome) or external (as in itching from histamine injection) states. Since the urge to yawn is the process of interest, suppression of yawning is not relevant to the fMRI analysis.