Title Page Introduction

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). Preceding 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 sub areas L2b, L3 and L, and in the rostral part of the higher order auditory area NCM. Temporal BOLD response clustering revealed rostral and caudal clusters that we defined as ‘cluster Field L’ and ‘cluster NCM’ respectively. However, since 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 only significant for 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. Page 2 of 41