Neural control of vocal pitch production in humans

点击翻译按钮获取中文摘要

People constantly modulate the pitch of the voice when they speak and when they sing. Modulation of vocal pitch is critical for the expression of meanings and emotions. For example, a rise of pitch, such as during a question, conveys a sense of uncertainty, whereas a drop in pitch conveys a sense of consensus or resolution. However, very little is known about how the human brain controls the modulation of pitch when people vocalize, and so I am interested in investigating this process using brain imaging techniques, most especially the method known as fMRI, or functional magnetic resonance imaging. One thing that is well understood is that the pitch of the voice is controlled by a group of muscles that influence the tension of the vocal cords. When the vocal cords are tensed, the pitch of the voice rises, and when the vocal cords are made to relax, the pitch drops. Hence, the control of vocal pitch involves a kind of push-pull mechanism between opposing muscles in the larynx (i.e., voice box) that affect the tension of the vocal cords. A first step towards examining pitch control in the brain is to compare the patterns of brain activation when people are asked to either raise or lower the pitch of their voice. Are there separate brain areas that control these two processes? My colleagues and I recently identified a part of the motor cortex of the human brain that controls the function of the larynx and hence vocal pitch. An analysis of the neuroimaging literature on speech and song shows that this area is the major vocal centre of the human brain. Having established the general importance of this area for vocal control, I would like to probe this area further and investigate how pitch is regulated by tasks that bias the system towards either rises or falls in pitch. This work has important implications not only for speech and singing but for speech disorders. Many neurological diseases, such as Parkinson's disease or amyotrophic lateral sclerosis, have devastating effects on the voice. In addition, fluency disorders such as stuttering are thought to have a definite neural basis. Therefore, an understanding of how the brain controls the voice has important applications to a host of diseases that affect the functioning of the voice.