Learning-related neuronal activation in the zebra finch song system nucleus HVC in response to the bird's own song.

Like many other songbird species, male zebra finches learn their song from a tutor early in life. Song learning in birds has strong parallels with speech acquisition in human infants at both the behavioral and neural levels. Forebrain nuclei in the 'song system' are important for the sensorimotor acquisition and production of song, while caudomedial pallial brain regions outside the song system are thought to contain the neural substrate of tutor song memory. Here, we exposed three groups of adult zebra finch males to either tutor song, to their own song, or to novel conspecific song. Expression of the immediate early gene protein product Zenk was measured in the song system nuclei HVC, robust nucleus of the arcopallium (RA) and Area X. There were no significant differences in overall Zenk expression between the three groups. However, Zenk expression in the HVC was significantly positively correlated with the strength of song learning only in the group that was exposed to the bird's own song, not in the other two groups. These results suggest that the song system nucleus HVC may contain a neural representation of a memory of the bird's own song. Such a representation may be formed during juvenile song learning and guide the bird's vocal output

Localized neuronal activation in the zebra finch brain is related to the strength of song learning

Songbirds (Oscines) learn their songs from a tutor. It is not known where in the brain the memories of these learned sounds are stored. Recent evidence suggests that song perception in songbirds involves neuronal activation in brain regions that have not traditionally been implicated in the control of song production or song learning, notably the caudal part of the neostriatum (NCM) and of the hyperstriatum ventrale. Zebra finch males (Taeniopygia guttata castanotis) were reared without their father and exposed to a tape-recorded song during the sensitive period for song learning. When, as adults, they were reexposed to the tutor song, the males showed increased expression of the protein products of the immediate early genes egr-1 (ZENK) and c-fos in the NCM and caudal hyperstriatum ventrale, but not in the conventional “song-control nuclei.” The strength of the immediate early gene response (which is a reflection of neuronal activation) in the NCM correlated significantly and positively with the number of song elements that the birds had copied from the tutor song. These results show localized neural activation in response to tutor song exposure that correlates with the strength of song learning

Correlation coefficients of the relationship between the number of elements copied from the tutor song and Zenk expression in the HVC, RA and Area X for groups of birds exposed to the tutor song (TUTOR), bird’s own song (BOS), or novel conspecific song (NOVEL).

a<p>NS, Not Significant; p-values <0.05 were considered significant.</p

Scatter plots of mean number of Zenk immunoreactive cell nuclei per mm² in the song system nucleus HVC, in relation to the percentage of song elements copied from the tutor song (song similarity) for groups of birds exposed to (A) tutor song (TUTOR), (B) bird’s own song (BOS) or (C) novel conspecific song (NOVEL).

<p>Note that y-axis has a log scale.</p

Schematic diagrams of composite views of parasagittal sections of the songbird brain.

<p>A. Diagram of a songbird brain giving approximate positions of nuclei and brain regions involved in auditory perception and memory. Yellow areas represent brain regions that show increased neuronal activation when the bird hears song. B. Diagram of a songbird brain giving approximate positions of nuclei and brain regions involved in vocal production and sensorimotor learning. Orange nuclei in the song system show increased neuronal activation when the bird is singing. Abbreviations: CLM, caudal lateral mesopallium; CMM, caudal medial mesopallium; DLM, nucleus dorsolateralis anterior, pars medialis; HVC, acronym used as a proper name; L1, L2, L3, subdivisions of Field L; LMAN, lateral magnocellular nucleus of the anterior nidopallium; NCM, caudal medial nidopallium; nXIIts, tracheosyringeal portion of the nucleus hypoglossus; RA, robust nucleus of the arcopallium. Modified and reproduced, with permission, from references <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041556#pone.0041556-Bolhuis5" target="_blank">[9]</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041556#pone.0041556-Moorman2" target="_blank">[60]</a>, copyright 2010 Nature Publishing Group. All rights reserved.</p

Mean (± SEM) number of Zenk-positive nuclei per mm² in the song system brain nuclei (A) HVC, (B) RA and (C) Area X, for groups of male zebra finches exposed to tutor song (TUTOR), bird’s own song (BOS) or novel conspecific song (NOVEL).

<p>Mean (± SEM) number of Zenk-positive nuclei per mm² in the song system brain nuclei (A) HVC, (B) RA and (C) Area X, for groups of male zebra finches exposed to tutor song (TUTOR), bird’s own song (BOS) or novel conspecific song (NOVEL).</p