Medina L, Veenman C L, Reiner A
Department of Anatomy and Neurobiology, College of Medicine, The University of Tennessee, Memphis 38163, USA.
J Comp Neurol. 1997 Jul 21;384(1):86-108.
In the present study, we investigated whether a dorsal thalamic region comparable to the motor part of the mammalian ventral tier (the ventral anterior nucleus, the ventral lateral nucleus, and the oral ventroposterolateral nucleus) exists in pigeon. With this aim, we reinvestigated the projections of the pigeon dorsal pallidum to the dorsal thalamus by using 1) injections of the anterogradely transported form of biotinylated dextran amine (BDA; 10,000 molecular weight) in the pigeon dorsal pallidum (paleostriatum primitivum) and 2) injections of the retrogradely transported form of BDA (3,000 molecular weight) in the pigeon dorsal thalamus. Our results indicate that the dorsal pallidum in pigeons projects to three areas of the dorsal thalamus: the dorsointermediate posterior nucleus, the ventrointermediate area, and the nucleus subrotundus. Only the projection to the dorsointermediate posterior nucleus was described previously (Karten and Dubbeldam [1973] J. Comp. Neurol. 148:61-90; Kitt and Brauth [1982] Neuroscience 6:1551-1566). To investigate whether any of the dorsal thalamic nuclei receiving pallidal input project to a motor cortical field, injections of the retrograde tracer Fluoro-Gold were placed into the rostral Wulst. This is an avian cortical field that appears to contain a region comparable to mammalian primary somatomotor cortex (Karten [1971] Anat. Rec. 169:353; Wild [1992] J. Comp. Neurol. 287:1-18). Our results indicate that neurons in the rostral ventrointermediate area, but not in the nucleus subrotundus, the dorsointermediate posterior nucleus, or the intermediate or caudal parts of the ventrointermediate area, project to the rostral Wulst. In addition to the input from the dorsal pallidum, the avian ventrointermediate area also receives input from the lateral substantia nigra and the lateral and internal cerebellar nuclei (present results). Our results suggest the existence in birds of a pallidothalamocortical loop similar to the pallidoventral tier-motor cortex loop of mammals and suggest that the avian ventrointermediate area is comparable to the motor part of the mammalian ventral tier in both location and connections. If this is confirmed by physiological experiments, then it would indicate that basal ganglia control of movement mediated by a pallidothalamocortical loop may have evolved with the stem reptiles.
在本研究中，我们探究了鸽子是否存在与哺乳动物腹侧层运动部分（腹前核、腹外侧核和嘴侧腹后外侧核）相当的背侧丘脑区域。出于这一目的，我们通过以下两种方法重新研究了鸽子背侧苍白球向背侧丘脑的投射：1）将生物素化葡聚糖胺（BDA；分子量10,000）的顺行运输形式注入鸽子背侧苍白球（原纹状体）；2）将BDA（分子量3,000）的逆行运输形式注入鸽子背侧丘脑。我们的结果表明，鸽子的背侧苍白球投射至背侧丘脑的三个区域：背中间后核、腹中间区和圆核。之前仅描述了其向背中间后核的投射（卡滕和杜贝尔丹[1973]《比较神经学杂志》148:61 - 90；基特和布劳思[1982]《神经科学》6:1551 - 1566）。为了研究接受苍白球输入的任何背侧丘脑核是否投射至运动皮层区域，将逆行示踪剂氟金注入嘴侧古纹状体粗核。这是一个鸟类皮层区域，似乎包含与哺乳动物初级躯体运动皮层相当的区域（卡滕[1971]《解剖学记录》169:353；怀尔德[1992]《比较神经学杂志》287:1 - 18）。我们的结果表明，嘴侧腹中间区的神经元，而非圆核、背中间后核或腹中间区的中间或尾侧部分的神经元，投射至嘴侧古纹状体粗核。除了来自背侧苍白球的输入外，鸟类腹中间区还接受来自黑质外侧部以及小脑外侧核和内侧核的输入（当前结果）。我们的结果提示，鸟类存在与哺乳动物苍白球 - 腹侧层 - 运动皮层环路类似的苍白球 - 丘脑 - 皮层环路，并提示鸟类腹中间区在位置和连接上与哺乳动物腹侧层的运动部分相当。如果这一点得到生理学实验的证实，那么这将表明由苍白球 - 丘脑 - 皮层环路介导的基底神经节对运动的控制可能在爬行类祖先中就已演化形成。
