Hampton Cara M, Sakata Jon T, Brainard Michael S
Keck Center for Integrative Neuroscience, University of California, San Francisco, CA 94143-0444, USA.
J Neurophysiol. 2009 Jun;101(6):3235-45. doi: 10.1152/jn.91089.2008. Epub 2009 Apr 8.
Behavioral variability is important for motor skill learning but continues to be present and actively regulated even in well-learned behaviors. In adult songbirds, two types of song variability can persist and are modulated by social context: variability in syllable structure and variability in syllable sequencing. The degree to which the control of both types of adult variability is shared or distinct remains unknown. The output of a basal ganglia-forebrain circuit, LMAN (the lateral magnocellular nucleus of the anterior nidopallium), has been implicated in song variability. For example, in adult zebra finches, neurons in LMAN actively control the variability of syllable structure. It is unclear, however, whether LMAN contributes to variability in adult syllable sequencing because sequence variability in adult zebra finch song is minimal. In contrast, Bengalese finches retain variability in both syllable structure and syllable sequencing into adulthood. We analyzed the effects of LMAN lesions on the variability of syllable structure and sequencing and on the social modulation of these forms of variability in adult Bengalese finches. We found that lesions of LMAN significantly reduced the variability of syllable structure but not of syllable sequencing. We also found that LMAN lesions eliminated the social modulation of the variability of syllable structure but did not detect significant effects on the modulation of sequence variability. These results show that LMAN contributes differentially to syllable versus sequence variability of adult song and suggest that these forms of variability are regulated by distinct neural pathways.
行为变异性对运动技能学习很重要，但即使在熟练掌握的行为中也会持续存在并受到积极调控。在成年鸣禽中，两种类型的鸣叫变异性会持续存在，并受到社会环境的调节：音节结构的变异性和音节序列的变异性。这两种成年变异性的控制在多大程度上是共享的还是不同的仍不清楚。基底神经节-前脑回路的输出，即LMAN（前巢核外侧大细胞核），与鸣叫变异性有关。例如，在成年斑胸草雀中，LMAN中的神经元积极控制音节结构的变异性。然而，尚不清楚LMAN是否对成年音节序列的变异性有贡献，因为成年斑胸草雀鸣叫中的序列变异性很小。相比之下，白腰文鸟在成年后仍保留音节结构和音节序列的变异性。我们分析了LMAN损伤对成年白腰文鸟鸣叫的音节结构和序列变异性以及这些变异性形式的社会调节的影响。我们发现，LMAN损伤显著降低了音节结构的变异性，但没有降低音节序列的变异性。我们还发现，LMAN损伤消除了音节结构变异性的社会调节，但未检测到对序列变异性调节的显著影响。这些结果表明，LMAN对成年鸣叫的音节与序列变异性有不同的贡献，并表明这些变异性形式由不同的神经通路调节。
