Abstract
Male canaries (Serinus canaria) display seasonal changes in the motivation to sing which have been found to be dependent on the action of testosterone (T). During the breeding season when T is high, males sing at a higher rate compared to males with low T. The effect of T on song rate is known to be mediated by the medial preoptic nucleus (POM); however, it is unclear how T-signaling in POM impacts song production. One potential mechanism is via modulation of dopaminergic input into song control nuclei by the periaqueductal gray (PAG). In order to test the role of PAG in T-mediated song production, we treated male canaries with peripheral T implants and implanted a guide cannula targeting the PAG. Through this guide cannula, we transiently inactivated PAG with injections of the GABAA agonist, muscimol. Each bird received multiple infusions of both muscimol and saline with a 48-hour washout period between treatments. The order of injection type was randomized and counterbalanced between individuals. Muscimol infusion into the PAG, but not nearby regions, increased the latency to sing post-injection. These results support the hypothesis that PAG is involved in the production of song, potentially mediating the motivation to sing or alternatively interfering with the pre-motor activity of nucleus RA. Other song features were however not affected.
SIGNIFICANCE STATEMENT Communication is essential for social species relying on coordinated behavior for survival and reproduction. However, the neural mechanisms underlying the motivation to engage in vocal communication are currently unknown. Here, we show that inhibition of the periaqueductal gray (PAG) increases the latency for male canaries to sing, but does not influence features of song quality once they resume singing. These results indicate that the PAG is involved in regulating the motor initiation or the underlying motivation of the complex, learned behavior of singing but not of innate vocalizations, such as calls. Our findings suggest that the PAG is likely involved in transmitting preoptic signals to the song control system, probably via dopaminergic projections from this region to song control nuclei.
Footnotes
Authors report no conflict of interest.
This work was supported by NINDS 1 R01 NS104008-01. Chelsea Haakenson’s contribution to this research was supported, in part, by NSF award DGE-1632976.
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
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