Birdsong is a hierarchically patterned learned motor behavior controlled by a nearly serially connected stream of nuclei. This pathway is bilaterally organized, with anatomically indistinguishable structures in each hemisphere. Little is known regarding the nature, or organization, of song features that are encoded by these structures. In the present proposal, we use a number of complimentary experimental techniques (single- and multi-unit recording, stimulation and lesions) to investigate the organization of song feature encoding in HVc, a key telencephalic song control nucleus. These studies will be performed in singing adult zebra finches (Taeniopygia guttata) under normal and perturbed sensory feedback conditions. ? ? In AIM 1, we exploit interhemispheric coordination of song motor activity in HVc to study the relationship between premotor activity and song output. We hypothesize that analysis of neural patterns recorded simultaneously in both hemispheres will provide insight into the hierarchical encoding of song features. We propose that patterns of coincident activity across hemispheres will specify key song timing features such as syllable, and possibly note, onset and offset. Sensory feedback perturbations cause long-term changes in song output of adult songbirds. It is not known how such perturbations affect song premotor neural patterns in HVc.
AIM 2 will compare neural activity patterns in HVc before and directly after cutting the tracheosyringeal (ts) nerve, a manipulation that alters both acoustic and proprioceptive feedback. We will use multiunit recording to initially characterize the effect of such perturbations on the HVc population response. We will then use single-unit recordings to identify neuronal cell types that are affected by sensory feedback manipulation. ? ? Finally, AIM 3 will investigate how perturbations of HVc network activity, either by microlesions or stimulation, affect the normally stereotyped song output of adult zebra finches. To eliminate the possibility of compensatory activity in the intact contralateral HVc, spatially restricted manipulations will be performed in birds forced to sing with only one song system hemisphere. The proposed studies directly address the spatial and temporal organization of song feature encoding in HVc. ? ?
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