Functional connectivity of the secondary somatosensory cortex of the rat
Functional connectivity of the secondary somatosensory cortex of the rat
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DOI：
10.1002/ar.20696
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发表时间：
2008-08-01
影响因子：
2
通讯作者：
Yen, Chen-Tung
中科院分区：
文献类型：
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作者：
Liao, Chia-Chi;Yen, Chen-Tung
大鼠初级体感皮层（SI）和次级体感皮层（S2）的层级关系一直存在争议。从腹侧后外侧丘脑核（VPL）到S2的直接丘脑皮质投影的存在是决定S2在加工流中相对位置的关键因素。本研究采用神经解剖示踪和电生理方法研究了前肢和后肢表征在VPL、S1和S2中的相互联系。在示踪实验中，对VPL、S1和S2进行电生理鉴定，然后通过离子透入生物素化右旋糖酐胺（BDA，一种双向示踪剂）。在双标记实验中，将以下两种逆行示踪剂——bda、罗丹明葡聚糖（RD）和/或氟金（FG）——同时注射到同型前爪S1和S2中。在电生理研究中，比较了配对体诱发S1和S2的多单位反应。结果表明：(1)VPL前爪和后爪神经元以平行和体位的方式投射到相应的S1和S2区域；(2)双突起VPL神经元比例极低，表明前爪VPL到S1、S2的通路平行且独立；(3)前爪S1和S2对称、相互连接；(4) S1和S2多单元对前爪刺激的反应潜伏期呈直接平行通路。本研究为支持大鼠S1和S2在处理感觉信息过程中具有同等层次结构提供了进一步的证据。
The hierarchical relationship of the rat primary somatosensory cortex (SI) and secondary somatosensory cortex (S2) is controversial. The existence of a direct thalamocortical projection from ventral posterolateral thalamic nucleus (VPL) to S2 is a key factor in determining the relative position of S2 in the processing flow. In this study, the inter-connections of forepaw and hindpaw representations in VPL, S1, and S2 were examined by neuroanatomical tracing and electrophysiological approaches. In the tracing experiments, VPL, S1, and S2 were electrophysiologically identified, and then iontophoretically injected with biotinylated dextran amine (BDA, a bi-directional tracer). In the double-labeling experiments, two of the following retrograde tracers-BDA, Rhodamine dextran (RD), and/or Fluoro-Gold (FG)-were injected into homotypical S1 and S2 forepaw representations simultaneously. In the electrophysiological studies, paired somatic evoked multiunit responses in S1 and S2 were compared. Our results revealed that: (1) VPL forepaw and hindpaw neurons projected to corresponding S1 and S2 areas in a parallel and somatotopic manner; (2) very low percentage of double projecting VPL neurons were found, indicating parallel and independent pathways from forepaw VPL to S1 and S2; (3) forepaw S1 and S2 were symmetrically and reciprocally connected; (4) response latencies of the S1 and S2 multiunits to forepaw stimulation were in accordance with a direct and parallel pathway. This study provides further evidence to support the equivalent hierarchy of S1 and S2 in processing sensory information of the rat.