![]() ![]() ![]() We conducted six trials per individual, alternating infusion of saline (vehicle) or the GABA A agonist muscimol into this brain region. We then implanted guide cannulas to target the PAG for neurochemical manipulation in these males. We castrated male canaries and implanted them with SILASTIC implants that continuously release T, ensuring high singing rates. In the present study, we examine the role of PAG in the control of singing. Furthermore, DOPAC, a metabolite of dopamine, in PAG has been found to correlate with song production ( Heimovics et al., 2011). Neural activity in PAG also appears to be tied to activity in POM, as European starlings with lesions to POM have decreased expression of the immediate early gene ZENK in the PAG ( Alger et al., 2009). In addition, PAG sends dopaminergic projections to several nuclei in the song control system, HVC, the robust nucleus of the arcopallium (RA), and area X ( Lewis et al., 1981 Appeltants et al., 2000, 2002 Castelino et al., 2007). There are reciprocal projections between PAG and POM ( Riters and Alger, 2004). One potential pathway for transmission of T-modulated activity in POM to the song control system is via the periaqueductal gray (PAG). However, it is not yet known how T in POM can induce such changes in song behavior. In addition, partially lesioning the POM has the inverse effect, causing male European starlings ( Sturnus vulgaris) to sing less frequently ( Riters and Ball, 1999 Alger et al., 2009). This effect of T on the motivation to sing appears to occur via activity in the medial preoptic nucleus (POM), since implantation of T specifically in this region in castrated male canaries increases the number of songs per minute and the percentage of time spent singing ( Alward et al., 2013). It is this increase in T that leads to a heightened motivation to sing, in addition to a variety of other effects on song quality ( Ball et al., 2003). At this time, males also have increased plasma testosterone (T Ball et al., 2002 Leitner et al., 2003 Ball and Balthazart, 2017). Appropriately, in seasonally breeding songbird species such as the canary ( Serinus canaria), the motivation to sing increases during the breeding season, when attracting a mate is particularly important ( Voigt and Leitner, 2008). While song can have a variety of functions, one of its key utilities is in mate attraction ( Catchpole and Slater, 2008). Songbirds are an ideal model for addressing this problem, as they rely on vocal communication to relay biologically significant information, and have a vocal learning process with many parallels to that of humans ( Doupe and Kuhl, 1999 Kuhl, 2000, 2003 Konishi, 2004). Currently, the neural circuits and molecular mechanisms underlying this motivation are largely unknown. Therefore, individuals that live in social groups must be motivated to engage in vocal communication. However, having the ability to communicate verbally is useless if one does not actually do so. Without the ability to communicate, the benefits of living in a social group, such as coordinated food gathering, collective defense of self and territory, mating, and caring for young, are unattainable. Other song features were however not affected.įor social species, communication between individuals is essential for forming bonds and promoting survival. 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. Muscimol infusion into the PAG, but not nearby regions, increased the latency to sing post-injection. The order of injection type was randomized and counterbalanced between individuals. Each bird received multiple infusions of both muscimol and saline with a 48-h washout period between treatments. ![]() Through this guide cannula, we transiently inactivated PAG with injections of the GABA A agonist, muscimol. 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. One potential mechanism is via modulation of dopaminergic input into song control nuclei by the periaqueductal gray (PAG). 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. During the breeding season when T is high, males sing at a higher rate compared with males with low T. 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). ![]()
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