The hierarchical development of the primate visual cortex and associated streams remains somewhat of a mystery. While anatomical, physiological, and psychological studies have demonstrated the early maturation of the dorsal "where"/"how" or motion cortical stream, little is known about the circuitry responsible. The influence of the retinogeniculostriate pathway has been investigated, but little attention has been paid to the role of two more recently described disynaptic retinothalamic projections to the middle temporal (MT) area, an early maturing dorsal stream cortical field, and which bypass the primary visual cortex (V1). These pathways are via the koniocellular layers of the lateral geniculate nucleus (LGN) and the medial portion of the inferior pulvinar (PIm). Both have been demonstrated in the adult nonhuman primate, but their influence during the maturation of the visual cortex is unknown. We used a combination of neural tracing and immunohistochemistry to follow the development of LGN and PIm inputs to area MT in the marmoset monkey. Our results revealed that the early maturation of area MT is likely due to the disynaptic retinopulvinar input and not the retinogeniculate input or the direct projection from V1. Furthermore, from soon after birth to adulthood, there was a dynamic shift in the ratio of input from these three structures to area MT, with an increasing dominance of the direct V1 afference.

译文

灵长类视觉皮层和相关流的分层发展仍然是一个谜。尽管解剖学,生理学和心理学研究表明背侧 “where”/“how” 或运动皮质流的早期成熟,但对负责的电路知之甚少。已经研究了视网膜原肌纹状体途径的影响,但很少关注两个最近描述的双突触视网膜丘脑投射对中颞 (MT) 区域的作用,即早熟的背流皮层场,并且绕过了初级视觉皮层 (V1)。这些途径是通过外侧膝状核 (LGN) 和下牙髓 (PIm) 的内侧部分的细胞层。两者都已在成年非人类灵长类动物中得到证实,但它们在视觉皮层成熟过程中的影响尚不清楚。我们使用神经追踪和免疫组织化学的组合来跟踪LGN和PIm输入到mar猴中MT区域的发育。我们的结果表明,区域MT的早期成熟可能是由于非突触视网膜的输入,而不是视网膜的输入或来自v1的直接投影。此外,从出生后不久到成年,这三个结构的输入与区域MT的比率发生了动态变化,直接V1传入的优势越来越大。

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