Relationship between sustained unilateral hand clench, emotional state, line bisection performance, and prefrontal cortical activity: A functional near-infrared spectroscopy study

ABSTRACT

Sustained unilateral hand clenching alters perceptual processing and affective/motivational state, with these alterations presumed to reflect increased hemispheric activity contralateral to the side of motor movement. However, data from electroencephalographic and imaging studies are contradictory regarding the relationship between sustained hand clenching and brain activity. In order to investigate the relationship between brain activity, sustained unilateral hand clenching, and changes in affect and perceptual processing, frontal hemispheric activity was measured via functional near-infrared spectroscopy (fNIRS), using derived O₂Hb prior to, during, and post-sustained unilateral hand clench. Participants’ mood and spatial perception were recorded pre- and post-clenching. Sustained unilateral hand clenching altered brain activity and mood, but not spatial perception. Results revealed increased O₂Hb bilaterally following sustained unilateral hand clenching, relative to baseline, regardless of hand. In agreement with previous fNIRS studies, sustained unilateral hand clenching resulted in greater ipsilateral, compared with contralateral, O₂Hb. An interaction between side of hand clench and change in mood was in the direction predicted by theories of hemispheric lateralization of emotion: Following left-hand clenching, individuals became more affectively negative, and following right-hand clenching, they became more affectively positive.

KEYWORDS:

• fNIRS
• frontal cortex
• emotion
• hand clench

Acknowledgements

The authors would like to thank Mark Zuppichini for participant recruitment and literature compilation. We also thank Ryan King and Alexa Decker for data entry. The funding source had no involvement in any aspect of study design, data collection, or decision to submit the article for publication.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

R.E.P. received a Defense University Research Instrumentation Grant [grant number W911NF-13-1-0312] from the U.S. Army Research Office.