Bio-Imaging Lab, University of Antwerp, B-2020 Antwerp, Belgium.
J Comp Neurol. 2010 May 1;518(9):1442-59. doi: 10.1002/cne.22281.
Neuron recruitment has been implicated in morphological and functional plasticity in the adult brain. Whereas mammals restrict neuron recruitment specifically to two regions of known plasticity, the hippocampus and olfactory bulb, newborn neurons are found throughout the forebrain of adult songbirds. In order to study the area-specificity of the widespread proliferation and recruitment in the songbird brain, six adult male canaries received repetitive intraperitoneal injections of the mitotic marker BrdU (5-bromo-2-deoxyuridine) and were sacrificed after 24 hours to study proliferation or after 38 days to study recruitment. Migration and incorporation of new neurons was apparent throughout many but not all parts of the canary forebrain and was quantitatively related to mitotic levels in the most closely associated proliferative zones. Surprisingly, some areas of the vocal control system sensitive to plastic changes, such as nucleus higher vocal center (HVC) and area X, recruited similar numbers of new neurons as their surrounding brain tissues, employing no specific directional mechanisms. The distribution pattern in and around HVC could best be described by a random displacement model, where cells originating from the overlying lateral ventricle can move independently in any direction. Other plastic song control areas, such as the medial magnocellular nucleus of anterior nidopallium and the robust nucleus of arcopallium, were specifically avoided by migrating neurons, while migration toward the olfactory bulb showed high specificity, similar to the mammalian rostral migratory stream. Thus, different mechanisms appear to organize area-specific neuron recruitment in different recipients of the adult songbird brain, unrelated to global plasticity of brain regions.
神经元募集与成年大脑的形态和功能可塑性有关。哺乳动物将神经元募集仅限于两个已知具有可塑性的区域，即海马体和嗅球，而新生神经元则存在于成年鸣禽的前脑的各个区域。为了研究鸣禽大脑中广泛增殖和募集的区域特异性，六只成年雄性金丝雀接受了有丝分裂标记物 BrdU（5-溴-2-脱氧尿苷）的重复腹腔内注射，并在 24 小时后用于研究增殖，或在 38 天后用于研究募集。新神经元的迁移和整合在许多但不是所有的金丝雀前脑区域都很明显，并且与最密切相关的增殖区域中的有丝分裂水平呈定量关系。令人惊讶的是，一些对可塑性变化敏感的发声控制系统区域，如高音中心核（HVC）和区域 X，招募了与周围脑组织相似数量的新神经元，而没有采用特定的定向机制。HVC 内和周围的分布模式可以通过随机位移模型来最好地描述，其中源自上覆侧脑室的细胞可以独立地向任何方向移动。其他可塑性鸣禽控制区域，如前脑的大细胞核和 arcopallium 的坚固核，被迁移的神经元特异性地回避，而向嗅球的迁移则表现出高度的特异性，类似于哺乳动物的前向迁移流。因此，不同的机制似乎在成年鸣禽大脑的不同接受者中组织了区域特异性神经元募集，与大脑区域的整体可塑性无关。
