Singing with and without words: hemispheric asymmetries in motor control.

Singing is relatively preserved and can even improve the language production of aphasic patients who have lesions of the left hemisphere but an intact right hemisphere. In contrast, singing is impaired following lesions or anesthesia of the right hemisphere, suggesting a right hemisphere role in singing. To assess the influence of singing upon hemispheric control of articulatory output in normal subjects, we measured lip opening asymmetry by single-frame photographic analysis. Spontaneous speech, reciting the words of a song, and singing with words all showed right-side lip opening superiority, revealing a major left hemisphere role in control of verbal articulation. Singing without words, on the other hand, did not show asymmetric facial motor activation, suggesting that the right hemisphere also participates in singing. In addition, we assessed auditorily perceivable differences in articulation when lip movement on one side of the mouth was artificially restricted (hemibuccal speech). Articulation quality was higher when speaking from the right side of the mouth.