Auditory synapses to song premotor neurons are gated off during vocalization in zebra finches

Songbirds use auditory feedback to learn and maintain their songs, but how feedback interacts with vocal motor circuitry remains unclear. A potential site for this interaction is the song premotor nucleus HVC, which receives auditory input and contains neurons (HVC(X) cells) that innervate an anterior forebrain pathway (AFP) important to feedback-dependent vocal plasticity. Although the singing-related output of HVC(X) cells is unaltered by distorted auditory feedback (DAF), deafening gradually weakens synapses on HVC(X) cells, raising the possibility that they integrate feedback only at subthreshold levels during singing. Using intracellular recordings in singing zebra finches, we found that DAF failed to perturb singing-related synaptic activity of HVC(X) cells, although many of these cells responded to auditory stimuli in non-singing states. Moreover, in vivo multiphoton imaging revealed that deafening-induced changes to HVC(X) synapses require intact AFP output. These findings support a model in which the AFP accesses feedback independent of HVC. DOI:http://dx.doi.org/10.7554/eLife.01833.001