INTEGRATIVE RESEARCH REVIEW OF THE IMPACTS OF UNILATERAL HAND CLENCHING ON BEHAVIOR: CLINICAL IMPLICATIONS

"Manipulations differentially activating the left or right cerebral hemisphere influence behavior in ways congruent with known theories of hemispheric lateralization of function. For example, rightward eye gaze increases positive mood via left hemisphere activity, and left unilateral nostril breathing increases right hemisphere spatial task performance. Determining under what conditions, and to what extent, simple techniques can be used to alter mental and emotional state holds considerable appeal because methods might be used as adjuncts to other tactics to mitigate negative affect in clinical situations, or to improve cognition in neurocognitive impairment. One method demonstrating promise for altering cognition and emotion, and that could be used in home-settings, is sustained unilateral hand clenching. The goal of the present paper was to analyze the literature to examine i. typical methods used for this manipulation; ii. in what manner such movements alter cognition and/or emotion; iii. whether one versus the other hemisphere, is particularly affected by manipulation. A literature search was conducted using relevant search terms, resulting in 24 articles. Across the literature, a wide range of domains was examined, including memory, decision making, creativity, language, emotion, and social perception, with many examining more than one domain. Nine included neurophysiological measures. Overall, 4 studies reported an impact of only unilateral right-hand clenching and 5 of only unilateral left-hand clenching, on behavior. Twelve reported an impact of both hand clenching conditions. Three reported no impact of hand clenching on performance. Future work should examine unilateral hand clenching in clinical populations."