Both singing and speaking are vocal motor acts, but they are qualitatively very different in their goals: In both cases, pitch production is required, but in speaking, pitch is a means to achieving a goal (communicating the desired message), while in singing, pitch is the goal itself. To what extent do these different vocal behaviors differ in the neural substrates underlying their control? Tomorrow, at Sensorimotor Journal Club, Naomi Kort will present a paper describing an fMRI study that attempted to address this question:
Ozdemir, E., A. Norton, et al. (2006). Shared and distinct neural correlates of singing and speaking. Neuroimage 33(2): 628-635. (link to pdf of article)
Using a modified sparse temporal sampling fMRI technique, we examined both shared and distinct neural correlates of singing and speaking. In the experimental conditions, 10 right-handed subjects were asked to repeat intoned ("sung") and non-intoned ("spoken") bisyllabic words/phrases that were contrasted with conditions controlling for pitch ("humming") and the basic motor processes associated with vocalization ("vowel production"). Areas of activation common to all tasks included the inferior pre- and post-central gyrus, superior temporal gyrus (STG), and superior temporal sulcus (STS) bilaterally, indicating a large shared network for motor preparation and execution as well as sensory feedback/control for vocal production. The speaking more than vowel-production contrast revealed activation in the inferior frontal gyrus most likely related to motor planning and preparation, in the primary sensorimotor cortex related to motor execution, and the middle and posterior STG/STS related to sensory feedback. The singing more than speaking contrast revealed additional activation in the mid-portions of the STG (more strongly on the right than left) and the most inferior and middle portions of the primary sensorimotor cortex. Our results suggest a bihemispheric network for vocal production regardless of whether the words/phrases were intoned or spoken. Furthermore, singing more than humming ("intoned speaking") showed additional right-lateralized activation of the superior temporal gyrus, inferior central operculum, and inferior frontal gyrus which may offer an explanation for the clinical observation that patients with non-fluent aphasia due to left hemisphere lesions are able to sing the text of a song while they are unable to speak the same words.