Evidence that a Singing Impediment is Caused by Impaired Interhemispheric Coordination of Brain Activity

The neural network that mediates learned vocalizations in oscine songbirds provides a useful animal model for understanding the neural mechanisms mediating certain aspects of human speech. We studied the song impairment in zebra finches caused by unilateral lesion of nucleus Uvaeformis (Uva), a thalamic nucleus important for song production, as a model for the human speech impediments that can arise after brain injury. We observed an immediate degradation of singing premotor neural activity in the HVC (a brain nucleus encoding higher‐order features of song) after unilateral Uva lesion, as well as a loss of coordination of singing premotor activity across the hemispheres. To establish a more direct link between interhemispheric coordination of brain activity and the quality of song syllables produced, we compared HVC neural activity in lesioned birds during production of the most consistently formed song syllables (“Good”) vs the most poorly formed syllables (“Evil”). We discovered a significant difference in time‐specific synchronizing signals between Good and Evil syllables. This provides some of the most conclusive evidence that impairment of interhemispheric coordination is the physiological basis for some vocal impediments. Supported by the Howard Hughes Medical Institute through the Undergraduate Science Education Program, the ASU School of Life Sciences and the Barrow Neurological Foundation.