THE ROLE OF THE MEDIAL PERIAQUEDUCTAL GRAY AND CATECHOLAMINES IN THE REGULATION OF BIRDSONG

Abstract

Vocal communication is fundamental to the success of many social species, as it aids in coordinated activities such as gathering food, defense, and rearing young – all of which increase rates of survival and reproductive success. However, having the ability to communicate acoustically is useless unless it is utilized properly. Consequently, appropriate regulation of the motivation to engage in vocal communication is essential for individuals in a social species.One species that relies heavily on vocal communication is the canary (Serinus canaria). This songbird displays seasonal changes in motivation to communicate – sing – that are instigated by, and depend on, the action of the steroid-hormone testosterone (T) in the brain. The medial preoptic nucleus (POM) is a key site for this change, as canaries with T only in the POM sing at high rates. However, we do not yet understand the mechanism through which this occurs. In this dissertation, we investigate the possibility that this change is regulated by the medial periaqueductal gray (PAG), which has reciprocal connections with the POM and sends fibers containing the catecholamine dopamine into song control nuclei including HVC and Area X. First, we temporarily inhibited PAG, finding an increased latency to sing. Next, we demonstrated aromatase expression in POM-PAG projection neurons and showed that PAG-HVC projection neurons actively produce dopamine during song. Then we infused dopamine receptor agonists and antagonists into HVC, demonstrating that D1 receptor activation increases song latency and alters song structure. Finally, we established that cells in HVC receiving dopaminergic input are excitatory, and likely projection neurons, compared to Area X cells, which are likely medium spiny neurons. This research provides valuable insight into how PAG affects song production, providing greater understanding of the neural mechanisms necessary for the motivation to engage in communication and a role of dopamine in motivated, goal-directed behavior.