ZENK protein regulation by song in the brain of songbirds

Abstract

When songbirds hear the song of another individual of the same species or when they sing, the mRNA levels of the ZENK gene increase rapidly in forebrain areas involved in vocal communication. This gene induction is thought to be related to long-term neuronal change and possibly the formation of song-related memories. We used immunocytochemistry to study the levels and distribution of ZENK protein in the brain of zebra finches and canaries after presentation of song playbacks. Birds that heard the playbacks and did not sing in response showed increased ZENK protein levels in auditory brain areas, including the caudomedial neostriatum and hyperstriatum ventrale, fields L1 and L3, the shelf adjacent to the high vocal center (HVC), the cup adjacent to the nucleus robustus archistriatalis (RA), and the nucleus mesencephalicus lateralis pars dorsalis (MLd). No ZENK expression was seen in song nuclei in these birds. Males that sang in response to the playbacks showed, in addition to auditory areas, increased ZENK protein in several song control nuclei, most prominently in HVC, RA, area X, and the dorsomedial nucleus (DN) of the intercollicular complex. The rise in ZENK protein followed that described previously for ZENK mRNA by a short lag, and the distribution of ZENK-labeled cells was in agreement with previous analysis of mRNA distribution. Thus, ZENK protein regulation can be used to assess activation of brain areas involved in perceptual and motor aspects of song. Possible implications of ZENK induction in these areas are discussed.

An Analysis of the Neural Representation of Birdsong Memory

“…Rectangles indicate the counting area for the NCM, CMHV, and hippocampus. Gray shaded areas are activated when birds hear song (Jarvis and Nottebohm, 1997;Mello and Ribeiro, 1998). Gray arrows connect nuclei of the conventional song system.…”

“…For each brain region, mean values of the two sections were used to determine the number of immunoreactive cells for the medial or lateral parts, respectively. Distance from the midline was assessed using the atlas of Vates et al (1996), Figure 3 of Mello and Ribeiro (1998), and an unpublished atlas of the zebra finch brain by A. M. Den Boer-Visser. Digital photographs of the brain areas were made with a Nikon (Tokyo, Japan) Coolpix 950 camera at 200ϫ magnification.…”

“…However, analysis of the expression of immediate early genes (IEGs), a measure of neuronal activation (Sagar et al, 1988;Tischmeyer and Grimm, 1999;Davis et al, 2003), has revealed that other parts of the brain are involved in song perception. These brain regions include the caudomedial neostriatum (NCM) [also known as the caudomedial nidopallium (Reiner et al, 2004)] and the caudomedial hyperstriatum ventrale (CMHV) (or caudomedial mesopallium in the new nomenclature of Reiner et al, 2004) (Mello et al, 1992;Mello and Clayton, 1994;Jarvis and Nottebohm, 1997;Mello and Ribeiro, 1998;Bolhuis et al, 2000) (Fig. 1).…”

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

“…The results of these studies suggest 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. Exposure of adult zebra finch males to conspecific song led to significantly increased expression of the IEG known as ZENK in the caudal part of the neostriatum (NCM) and of the hyperstriatum ventrale (cHV), but not in HVC, Area X, lMAN or RA, nor in Field L, a primary auditory projection area (14)(15)(16)(17)(18)(19)(20). The increase in ZENK expression did not occur after exposure to heterospecific song or to tone busts (14,15).…”

“…Recent studies have investigated the expression of immediate early genes (IEGs) (12,13) in adult zebra finch males after exposure to unfamiliar conspecific song (14)(15)(16)(17). Expression of IEGs is a measure of neuronal activation (12,13).…”