Abstract
Birdsong is a learned behavior that is controlled by a group of identified nuclei, known collectively as the song system. The cortical nucleus HVC (used as a proper name) is a focal point of many investigations as it is necessary for song production, song learning, and receives selective auditory information. HVC receives input from several sources including the cortical area MMAN (medial magnocellular nucleus of the nidopallium). The MMAN to HVC connection is particularly interesting as it provides potential sensorimotor feedback to HVC. To begin to understand the role of this connection, we investigated the physiological relation between MMAN and HVC activity with simultaneous multiunit extracellular recordings from these two nuclei in urethane anesthetized zebra finches. As previously reported, we found similar timing in spontaneous bursts of activity in MMAN and HVC. Like HVC, MMAN responds to auditory playback of the bird's own song (BOS), but had little response to reversed BOS or conspecific song. Stimulation of MMAN resulted in evoked activity in HVC, indicating functional excitation from MMAN to HVC. However, inactivation of MMAN resulted in no consistent change in auditory responses in HVC. Taken together, these results indicate that MMAN provides functional excitatory input to HVC but does not provide significant auditory input to HVC in anesthetized animals. We hypothesize that MMAN may play a role in motor reinforcement or coordination, or may provide modulatory input to the song system about the internal state of the animal as it receives input from the hypothalamus.
Highlights
Songbirds are used as a model system to understand the neural basis for learned motor behaviors, vocalizations
The anterior forebrain pathway (AFP) is part of a basal ganglia forebrain loop that is primarily involved in song learning and plasticity, while the vocal motor pathway is required for song production
We found similar auditory responses in HVC and medial magnocellular nucleus of the nidopallium (MMAN), HVC was more selective for bird’s own song (BOS) over other songs than MMAN
Summary
Songbirds are used as a model system to understand the neural basis for learned motor behaviors, vocalizations. Learned vocalizations require the integration of auditory signals with appropriate motor output to shape the target sound. Maintenance of song requires feedback about the ongoing motor pattern, and the ability to modulate the motor pattern. The song system can be divided into two main pathways: the anterior forebrain pathway (AFP) and the vocal motor pathway. The AFP is part of a basal ganglia forebrain loop that is primarily involved in song learning and plasticity, while the vocal motor pathway is required for song production. This report begins to analyze the role of a thalamocortical pathway in maintenance of this complex learned behavior by first characterizing the impact of this pathway on a key vocal motor nucleus, HVC
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