Scientific Understanding of Consciousness
Vocal Mirroring in Neurons
Nature 451, 305-310, 17 January 2008
Precise auditory–vocal mirroring in neurons for learned vocal communication
J. F. Prather, S. Peters, S. Nowicki, R. Mooney
Department of Neurobiology, Duke University Medical Center,
Department of Biology, Duke University, Durham, North Carolina 27710, USA
Brain mechanisms for communication must establish a correspondence between sensory and motor codes used to represent the signal. One idea is that this correspondence is established at the level of single neurons that are active when the individual performs a particular gesture [i.e., FAP] or observes a similar gesture performed by another individual. Although neurons that display a precise auditory–vocal correspondence could facilitate vocal communication, they have yet to be identified. Here we report that a certain class of neurons in the swamp sparrow forebrain displays a precise auditory–vocal correspondence. We show that these neurons respond in a temporally precise fashion to auditory presentation of certain note sequences in this songbird's repertoire and to similar note sequences in other birds' songs. These neurons display nearly identical patterns of activity when the bird sings the same sequence, and disrupting auditory feedback does not alter this singing-related activity, indicating it is motor in nature. Furthermore, these neurons innervate striatal structures important for song learning, raising the possibility that singing-related activity in these cells is compared to auditory feedback to guide vocal learning.
We focused our search in the telencephalic nucleus HVC, a structure necessary for singing and normal song perception and where high-level motor and auditory representations of birdsong have been detected. HVC contains two distinct populations of projection neurons, including one (HVCRA) that innervates song premotor neurons in the robust nucleus of the arcopallium (RA) and another (HVCX) that innervates a striatal region of the avian basal ganglia (area X) important to song learning and perception.
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