The organization of frontoparietal cortex in the tree shrew (Tupaia belangeri): II. Connectional evidence for a frontal‐posterior parietal network

Abstract

Tree shrews are small squirrel-like mammals that are the closest living relative to primates available for detailed neurobiological study. In a recent study (Remple et al. [2006] J. Comp. Neurol. 497:133-154), we provided anatomical and electrophysiological evidence that the frontoparietal cortex of tree shrews has two motor fields (M1 and M2) and five somatosensory fields (3a, 3b, S2, somatosensory caudal area [SC], and parietal ventral area [PV]). In the present study, we injected anatomical tracers into M1, M2, 3a, 3b, SC, and posterior parietal cortex to establish the ipsilateral cortical connections of these areas. The results provide evidence for a number of new cortical areas including medial motor and somatosensory areas (MMA and MSA), three posterior parietal areas (PPd, PPv, and PPc), and an area ventral to temporal inferior cortex (TIV). Ml receives topographic projections from M2, MMA, 3a, and PPv, and nontopographic connections from the temporal anterior and dorsal areas (TA and TD), PPc, TIV, and MSA. The connections of M2 are similar to those of M1, except that M2 receives denser projections from TIV, PPc, and dorsal frontal cortex and sparser input from M1. Areas 3a, 3b, and SC receive dense topographic projections from each other, S2, and PV and sparser connections from PPd and PPv. Area 3a receives additional input from posterior parietal and temporal regions and from M1 and MMA. Overall, the frontoparietal connections of tree shrew cortex are most similar to those of prosimian primates and quite different from those of more distant relatives such as rats.

Cortical neural responses to previous trial outcome during learning of a directional choice task

“…However, agreement has not been reached for a clear homology between the rat's AGm and the primate's counter parts. Since the rat's AGm projects to the spinal cord, it is adequately identified as one of the nonprimary motor areas in primates (Donoghue and Wise 1982;Remple et al 2007) while leaving the specific identifications of the rat's AGm conjectural. On the other hand, the rat's AGl has been considered homologous to the primary motor cortex (Donoghue and Wise 1982;Donoghue and Parham 1983) and is connected reciprocally with AGm (Reep et al 1987(Reep et al , 1990Ueta et al 2013).…”

“…The medial agranular cortex (AGm) is a well differentiated field from AGl. Even though it is suggested by some as a part of the prefrontal area (Uylings et al 2003;Dalley et al 2004), its dense and direct projection to spinal cord makes it look similar to one of the nonprimary motor areas but not prefrontal (Neafsey and Sievert 1982;Donoghue and Wise 1982;Passingham et al 1988;Remple et al 2007;Erlich et al 2011). In addition to its neurons involved in predicting trial outcomes, lesions of AGm cause an increase in reaction time, which suggests an involvement in movement preparation (Smith et al 2010).…”

The evolution of the complex sensory and motor systems of the human brain

“…As in squirrels, the superior colliculus is large. Somatosensory cortex includes S1, S2, PV, SC and SR of other mammals [34]. The representation of the forepaw is enlarged in S1, and the forepaw is used for manipulating objects.…”

Morphological characteristics and cryodamage of Chinese tree shrew (<I>Tupaia belangeri chinensis</I>) sperm

“…树鼩是一种昼行、树栖的小型哺乳动物, 曾被 定义为攀鼩目、 灵长目 (Liu et al, 2001;Wong & Kaas, 2009), 目前对树鼩的分类地位仍然存在争议。但无 论如何, 树鼩是最接近于灵长类的小型哺乳动物, 具有许多灵长类动物共有的特征 (Poonkhum et al, 2000)。 树鼩在人类医学及生物学研究方面具有重要 地位, 如神经生物学 (Remple et al, 2007)、人类肝炎 病毒感染 (Xu et al, 2007;Li et al, 2008)、视觉系统发 育 (Poveda & Kretz, 2009)及群体阶层应激 (Kozicz et al, 2008;Zambello et al, 2010)等。目前, 有关雄性树 鼩生殖生物学研究的报道较少 (Collins et al, 2007)。 Collins et al 于 1982 年报道了雄性树鼩生殖道的解 剖学特征和生理功能 (Collins et al, 1982); 随后, 有 研究报道了雄性树鼩从出生到性成熟过程的生殖 器官生长与发育 (Collins & Tsang, 1987); 精子细胞 在睾丸内的成熟过程 (Maeda et al, 1998); 雄性树鼩 精子的形成和染色质凝聚 (Suphamungmee et al, 2008) 等结果。然而, 树鼩睾丸、精子形态结构特性的研 究仍然很有限。我们曾报道树鼩精子可以被冷冻保 存 (Ping et al, 2011), 但是精子冷冻后的超微结构变 化尚不清楚。为此, 本研究分析树鼩的睾丸、附睾 精子的形态学结构特征, 以及树鼩精子冷冻复苏后 的结构变化。 1 材料和方法…”