Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
Department of Physiology, Kansai Medical University, 2-5-1 Shin-machi, Hirakata City, Osaka, 573-0101, Japan.
Eur J Neurosci. 2019 Mar;49(5):672-686. doi: 10.1111/ejn.14202. Epub 2018 Nov 8.
Many visual objects are attached with values which were created by our long rewarding history. Such stable object values attract gaze. We previously found that the output pathway of basal ganglia from caudal-dorsal-lateral portion of substantia nigra pars reticulata (cdlSNr) to superior colliculus (SC) carries robust stable value signal to execute the automatic choice of valuable objects. An important question here is whether stable value signal in basal ganglia can influence on other inner processing such as perception, attention, emotion, or arousal than motor execution. The key brain circuit is another output path of basal ganglia: the pathway from SNr to temporal and frontal lobes through thalamus. To examine the existence of stable value signal in this pathway, we explored thalamus in a wide range. We found that many neurons in the medial thalamus represented stable value. Histological examination showed that the recorded sites of those neurons included ventral anterior nucleus, pars magnocellularis (VAmc) which is the main target of nigrothalamic projection. Consistent with the SNr GABArgic projection, the latency of value signal in the medial thalamus was later than cdlSNr, and the sign of value coding in the medial thalamus was opposite to cdlSNr. As is the case with cdlSNr neurons, the medial thalamus neurons showed no sensitivity to frequently updated value (flexible value). These results suggest that the pathway from cdlSNr to the medial thalamus influences on various aspects of cognitive processing by propagating stable value signal to the wide cortical area.
许多视觉对象都带有我们长期奖励历史所创造的价值。这种稳定的对象价值吸引了我们的注意力。我们之前发现，来自网状部腹外侧部黑质（cdlSNr）到上丘（SC）的基底神经节输出通路携带强大的稳定价值信号，以执行有价值物体的自动选择。这里的一个重要问题是，基底神经节中的稳定价值信号是否会影响其他内部处理，如感知、注意力、情感或觉醒，而不仅仅是运动执行。关键的大脑回路是基底神经节的另一个输出路径：来自 SNr 到通过丘脑的颞叶和额叶的通路。为了检查该通路上是否存在稳定的价值信号，我们广泛探索了丘脑。我们发现，丘脑内侧的许多神经元都代表着稳定的价值。组织学检查显示，这些神经元的记录部位包括腹前核、大细胞部（VAmc），这是黑质丘脑投射的主要靶点。与 SNr 的 GABArgic 投射一致，内侧丘脑的价值信号潜伏期晚于 cdlSNr，并且内侧丘脑的价值编码信号与 cdlSNr 相反。与 cdlSNr 神经元一样，内侧丘脑神经元对频繁更新的价值（灵活的价值）没有敏感性。这些结果表明，来自 cdlSNr 到内侧丘脑的通路通过向广泛的皮层区域传播稳定的价值信号来影响认知处理的各个方面。
