Research report Auditory responses in the HVC of anesthetized starlings Isabelle George * , Hugo Cousillas, Jean-Pierre Richard, Martine Hausberger Universite ´ de Rennes 1, UMR CNRS 6552, Campus de Beaulieu, ba ˆt.25, Ethologie-Evolution-Ecologie, 35042 RENNES Cedex, France Accepted 19 April 2005 Abstract The present study, using a systematic recording method that we recently developed, describes the behavior of the neurons of the vocal control nucleus HVC in response to a variety of acoustic stimuli in a songbird species with multiple song types, the European starling. Most neurons did not respond to any of the stimuli that were presented, and those neurons that did respond responded to a different number of stimuli and showed distinct response features. The latter were thus classified into 3 categories, according to the number of stimuli to which they responded. Although only intracellular data could unambiguously determine to which population the neurons we recorded belonged, these 3 categories might correspond to the 3 populations of neurons that have been previously described in the HVC. Interestingly, responsive neurons of the 3 categories appeared to mainly respond to stimuli that were not the bird’s own song. However, most of the stimuli to which the HVC neurons responded correspond to sounds that are important in the everyday social life of the starlings. We thus discuss our results in relation to the social life of these birds, to possible species differences in the processing of communicative signals, and to methodological issues. D 2005 Elsevier B.V. All rights reserved. Theme: Neural basis of behavior Topic: Neuroethology Keywords: Song system; HVC; Starlings; Auditory responses; Systematic recording; Urethane anesthesia 1. Introduction Birdsong represents a complex communication system that exhibits a number of parallels with human speech [12,41]. The production, perception, and learning of birdsong are subserved by a set of discrete brain nuclei called the song system. This song system has been described as a hierarchical network with one nucleus at its top [39]: namely, the HVC (used as proper name [49]). This vocal control nucleus appears to be a nexus for the flow of information through forebrain pathways and it is an important site of sensorimotor integration [37,42]. The HVC was first described by Nottebohm et al. [48] as a motor nucleus controlling the vocal production of the bird. The discovery of responses to noise and tone bursts in this nucleus [29] initiated a number of studies, and HVC auditory neurons were rapidly shown to be song-selective [35,36,54]. Since then, many studies have investigated the auditory responses of this nucleus, but, so far, they have often used sparse sampling of neurons which were preselected on the basis of their responsiveness to songs or to acoustic stimuli and have mainly focused on responses to the bird’s own song (e.g. [33,50]). Yet, it has been suggested that HVC may play a role in the auditory perception of conspecific songs [4,10,17], and several studies have mentioned a variety of responses to different auditory stimuli within the HVC [9,36]. However, no study has tried to describe such responses. The aim of the present study was to systematically sample HVC neurons and to describe their responses to a variety of stimuli, especially natural, behaviorally-relevant stimuli that play a crucial role in the social life of starlings (Sturnus vulgaris ). 0006-8993/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2005.04.047 * Corresponding author. Fax: +33 2 23 23 69 27. E-mail address: igeorge@netcourrier.com (I. George). Brain Research 1047 (2005) 245 – 260 www.elsevier.com/locate/brainres