Striatal reward areas activated by implicit laughter induced by mimic words in humans: a functional magnetic resonance imaging study.

The neurobiological reward components of laughter induced by words were investigated. A functional magnetic resonance imaging-based brain imaging study demonstrated that visualization of mimic words and emotional facial expression words, highly suggestive of laughter, heard by the ear, significantly activate striatal reward centers, including the putamen/caudate/nucleus accumbens, prefrontal cortices, dorsal anterior cingulate cortex and the supplementary motor area, while non-mimic words under the same task that did not imply laughter do not activate these areas in humans. We tested a specific hypothesis that implicit laughter modulates the striatal dopaminergic reward centers by image formation of onomatopoeic words implying laughter and successfully confirmed the hypothesis.