Noradrenergic Deficits Alter Processing of Communication Signals in Female Songbirds

During acoustic communication, animals must attend to sounds from a particular source while simultaneously rejecting intrusion from other sources. One possible candidate mechanism for this process is the noradrenergic system. Noradrenaline is a neuromodulator that tunes sensory processing systems and regulates attention. We examined whether pharmacological degradation of the noradrenergic system using N-(2-chloroethyl)-N-2-bromobenzyl-amine hydrochloride (DSP-4) modifies processing of species-typical auditory signals in female canaries (Serinus canaria). We measured auditory responses to conspecific and heterospecific songs using ZENK protein expression within the caudomedial nidopallium (NCM) and the mesopallium caudomedial (CMM). Song-induced ZENK expression in these auditory forebrain areas is typically higher in birds exposed to conspecific songs as opposed to heterospecific songs. Our results reveal that this differential ZENK induction is abolished specifically within dNCM and CMM in female canaries treated with DSP-4. Furthermore, in DSP-4-treated birds, conspecific song-induced ZENK expression is significantly reduced when compared to saline-treated birds. This suggests that the noradrenergic system modifies auditory processing by enhancing neuronal responses to signals relevant to survival and reproduction rather than inhibiting neuronal responses to signals that are less relevant. Overall, our results reveal that noradrenaline plays a significant neuromodulatory role during the reception of species-typical communication signals. Copyright (C) 2008 S. Karger AG, Basel