Functional Magnetic Resonance Imaging in Zebra Finch Discerns the Neural Substrate Involved in Segregation of Conspecific Song From Background Noise

1 Bio-Imaging Lab and 2 Vision Lab, University of Antwerp, Antwerp, Belgium; 3 Sensory Ecology and Neuroethology Lab ENES EA3988, Université Jean Monnet, Saint-Etienne & Laboratoire Traitement du Signal Instrumentation, Centre National de la Recherche Scientifique, Unité Mixte de Recherche (CNRS UMR) 8620, Université Paris XI, Orsay, France; and 4 Hubert Curien Lab CNRS UMR 5516, Université Jean Monnet, Saint-Etienne, France Submitted 29 April 2007; accepted in final form 18 September 2007 Recently, fMRI was introduced in a well-documented animal model for vocal learning, the songbird. Using fMRI and conspecific signals mixed with different levels of broadband noise, we now demonstrate auditory-induced activation representing discriminatory properties of auditory forebrain regions in anesthetized male zebra finches ( Taeniopygia guttata ). Earlier behavioral tests showed comparable calling responses to the original conspecific song stimulus heard outside and inside the magnet. A significant fMRI response was elicited by conspecific song in the primary auditory thalamo-recipient subfield L2a; in neighboring subareas L2b, L3, and L; and in the rostral part of the higher-order auditory area NCM (caudomedial nidopallium). Temporal BOLD response clustering revealed rostral and caudal clusters that we defined as "cluster Field L" and "cluster NCM", respectively. However, because the actual border between caudal Field L subregions and NCM cannot be seen in the structural MR image and is not precisely reported elsewhere, the cluster NCM might also contain subregion L and the medial extremes of the subregions L2b and L3. Our results show that whereas in cluster Field L the response was not reduced by added noise, in cluster NCM the response was reduced and finally disappeared with increasing levels of noise added to the song stimulus. The activation in cluster NCM was significant for only two experimental stimuli that showed significantly more behavioral responses than the more degraded stimuli, suggesting that the first area within the auditory system where the ability to discern song from masking noise emerges is located in cluster NCM. Address for reprint requests and other correspondence: T. Boumans, University of Antwerp, Bio-Imaging Lab, Groenenborgerlaan 171, B-2020 Antwerp, Belgium (E-mail: Tiny.Boumans{at}ua.ac.be )