Intracortical and Thalamocortical Connections of the Hand and Face Representations in Somatosensory Area 3b of Macaque Monkeys and Effects of Chronic Spinal Cord Injuries
Intracortical and Thalamocortical Connections of the Hand and Face Representations in Somatosensory Area 3b of Macaque Monkeys and Effects of Chronic Spinal Cord Injuries
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DOI：
10.1523/jneurosci.2069-15.2015
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发表时间：
2015-09-30
影响因子：
5.3
通讯作者：
Jain, Neeraj
中科院分区：
文献类型：
--
作者：
Chand, Prem;Jain, Neeraj
颈椎水平慢性脊髓背柱损伤成年猴的大脑经历了大规模的重组。重组导致完整的下巴输入扩大，重新激活初级躯体感觉皮质(3b区)、丘脑腹后核和脑干楔状核中非传入手部代表的神经元。这种大规模可塑性的一个可能机制是穿过手脸边界的轴突发芽。在这里，我们确定了这种萌发是否发生在3b区。我们首先确定了手和面部在正常区域3b的固有皮质连接的程度。在靠近电生理决定的手面部边界的这些表示中注入了少量的神经解剖学示踪剂。标记神经元的位置根据详细的电生理躯体定位图和组织学确定的手脸边界绘制，显示在平坦的皮质髓鞘染色的部分中。结果表明，跨越手面部边界的皮质内投射很少。在背柱慢性单侧损伤和下巴代表扩大的猴子中，跨越手面部边界的连接与正常猴子没有什么不同。丘脑皮质从手和面部代表的腹后核至3b区的连接在损伤后也保持不变。结果表明，在3b区或丘脑皮质传入的内在联系的萌发并不有助于大脑皮层的大规模可塑性。
Brains of adult monkeys with chronic lesions of dorsal columns of spinal cord at cervical levels undergo large-scale reorganization. Reorganization results in expansion of intact chin inputs, which reactivate neurons in the deafferented hand representation in the primary somatosensory cortex (area 3b), ventroposterior nucleus of the thalamus and cuneate nucleus of the brainstem. A likely contributing mechanism for this large-scale plasticity is sprouting of axons across the hand-face border. Here we determined whether such sprouting takes place in area 3b. We first determined the extent of intrinsic corticocortical connectivity between the hand and the face representations in normal area 3b. Small amounts of neuroanatomical tracers were injected in these representations close to the electrophysiologically determined hand-face border. Locations of the labeled neurons were mapped with respect to the detailed electrophysiological somatotopic maps and histologically determined hand-face border revealed in sections of the flattened cortex stained for myelin. Results show that intracortical projections across the hand-face border are few. In monkeys with chronic unilateral lesions of the dorsal columns and expanded chin representation, connections across the hand-face border were not different compared with normal monkeys. Thalamocortical connections from the hand and face representations in the ventroposterior nucleus to area 3b also remained unaltered after injury. The results show that sprouting of intrinsic connections in area 3b or the thalamocortical inputs does not contribute to large-scale cortical plasticity.