Department of Psychology and Biology, and Helmholtz Institute, Utrecht University, 3584 CH Utrecht, The Netherlands.
Proc Natl Acad Sci U S A. 2012 Jul 31;109(31):12782-7. doi: 10.1073/pnas.1207207109. Epub 2012 Jul 16.
Unlike nonhuman primates, songbirds learn to vocalize very much like human infants acquire spoken language. In humans, Broca's area in the frontal lobe and Wernicke's area in the temporal lobe are crucially involved in speech production and perception, respectively. Songbirds have analogous brain regions that show a similar neural dissociation between vocal production and auditory perception and memory. In both humans and songbirds, there is evidence for lateralization of neural responsiveness in these brain regions. Human infants already show left-sided dominance in their brain activation when exposed to speech. Moreover, a memory-specific left-sided dominance in Wernicke's area for speech perception has been demonstrated in 2.5-mo-old babies. It is possible that auditory-vocal learning is associated with hemispheric dominance and that this association arose in songbirds and humans through convergent evolution. Therefore, we investigated whether there is similar song memory-related lateralization in the songbird brain. We exposed male zebra finches to tutor or unfamiliar song. We found left-sided dominance of neuronal activation in a Broca-like brain region (HVC, a letter-based name) of juvenile and adult zebra finch males, independent of the song stimulus presented. In addition, juvenile males showed left-sided dominance for tutor song but not for unfamiliar song in a Wernicke-like brain region (the caudomedial nidopallium). Thus, left-sided dominance in the caudomedial nidopallium was specific for the song-learning phase and was memory-related. These findings demonstrate a remarkable neural parallel between birdsong and human spoken language, and they have important consequences for our understanding of the evolution of auditory-vocal learning and its neural mechanisms.
与非灵长类动物不同，鸣禽学习发声非常类似于人类婴儿学习口语。在人类中，额叶的布洛卡区和颞叶的韦尼克区分别在言语产生和感知中起着至关重要的作用。鸣禽有类似的大脑区域，这些区域在发声和听觉感知和记忆之间表现出类似的神经分离。在人类和鸣禽中，都有证据表明这些大脑区域的神经反应存在侧化现象。当人类婴儿接触到言语时，他们的大脑激活已经表现出左侧优势。此外，在 2.5 个月大的婴儿中，已经证明了韦尼克区对言语感知的特定记忆的左侧优势。听觉-发声学习可能与半球优势有关，而这种关联是通过鸣禽和人类的趋同进化而产生的。因此，我们研究了鸣禽大脑中是否存在类似的与歌曲记忆相关的侧化现象。我们让雄性斑马雀接触导师或不熟悉的歌曲。我们发现，在幼年和成年雄性斑马雀的布洛卡样大脑区域（HVC，基于字母的名称）中，神经元激活存在左侧优势，而与呈现的歌曲刺激无关。此外，幼年雄性在类似于韦尼克区的大脑区域（尾侧中脑背侧核）中对导师歌曲表现出左侧优势，但对不熟悉的歌曲没有表现出左侧优势。因此，尾侧中脑背侧核的左侧优势是特定于歌曲学习阶段的，与记忆有关。这些发现展示了鸟类歌声和人类口语之间令人瞩目的神经平行现象，并对我们理解听觉-发声学习及其神经机制的进化具有重要意义。
