The neurological basis of many common speech and language disorders remains elusive, largely because very little is known about how vocal motor patterns are generated in the brain. One of the key questions yet to be addressed is how speech patterns come to be seamlessly interweaved with breathing patterns. Where and how in the brain speech and breathing interact remains unknown. Breathing patterns must be altered to accommodate the highly variable speech patterns utilized by a speaking or singing human, yet the temporal flow of speech is naturally constrained by the need to breath regularly. This process betrays the presence of a complex neural substrate that regulates the descending flow of vocal motor commands into the central respiratory rhythm centers using current information obtained from pulmonary and laryngeal somatosensory feedback. Although human speech is uniquely complex, echolocating bats compare favorably within the context of vocal-respiratory dynamics. Echolocation behavior relies upon a precise, yet highly dynamic set of distinct respiratory modes which can be selectively evoked in the lab by computer-generated auditory stimuli. This application will combine in vivo electrophysiological methods with computer-generated auditory stimuli to investigate the role of a newly discovered neuronal subtype in the lateral region of the parabrachial nucleus that appears essential for the normal changes in breathing patterns associated with vocalizing. It is hypothesized that these vocal-respiratory integration neurons are responsible for creating phase-shifts in breathing rhythms to accommodate vocalizing. If so, these neurons would represent an important interface between the vocal motor pathway and the neural circuitry regulating respiratory rhythms. The parabrachial nucleus is a highly conserved region of the vertebrate brain known to possess profound influences over breathing patterns, and is considered an essential component of the vocal motor pathway in mammals. Any pathological or developmental disruption of the vocal-respiratory integration mechanisms would unavoidably degrade the normal flow of speech. Thus, a more thorough understanding of how and where in the brain this is achieved could reveal the neurological basis of some human speech disorders, such as stuttering, disarthria and apraxia. ? ? ?
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