Pearson P P, Arnold P B, Oladehin A, Li C X, Waters R S
Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee Health Science Center, 855 Monroe Avenue, Memphis, TN 38163, USA.
Exp Brain Res. 2001 May 1;138(1):8-25. doi: 10.1007/s002210100678.
Physiological mapping of the body representation 1 month or longer after forelimb removal in adult rats revealed new pockets of shoulder representation in the forepaw barrel subfield (FBS) in the first somatosensory cortex (SI). These "new" shoulder representations have longer evoked response latencies than sites in the shoulder representation within the trunk subfield, hereafter referred to as the "original" shoulder representation. We postulated that the "new" shoulder representations in the FBS were relayed from the "original" shoulder representation. We investigated this hypothesis by studying anatomical connectivity between the "original" shoulder representation and the FBS in intact control and forelimb deafferented adult rats using Phaseolus vulgaris leucoagglutinin (PHA-L), biocytin, and biotin dextran-amine (BDA) as anterograde tracers. The retrograde tracer cholera toxin beta subunit (CT-B) injected into the FBS was also used to study connectivity between the "original" shoulder representation and the FBS. Using these anatomical tracing techniques, we were unable to show the existence of a direct corticocortical connection between the "original" shoulder representation in the trunk subfield and the FBS in either intact or deafferented rats. Functional connectivity between the two cortical regions was studied by ablating the "original" shoulder representation alone or in combination with the shoulder representation in the second somatosensory cortex (SII) while recording evoked responses in the FBS following electrical stimulation of the shoulder. Both ablations failed to eliminate the evoked responses at the "new" shoulder sites in the FBS, suggesting that SI and SII are not necessary for "new" shoulder input in the FBS. It is suggested that subcortical sites may play a major role in large-scale cortical reorganization. Results of projections from the "original" shoulder representation to parietal medial (PM), parietal lateral (PL), SII, parietal ventral (PV), and parietal rhinal (PR) sensory fields and agranular lateral (AgL) and agranular medial (AgM) motor fields are also described.
成年大鼠前肢切除1个月或更长时间后身体表征的生理图谱显示，在第一体感皮层（SI）的前爪桶状亚区（FBS）出现了新的肩部表征区域。这些“新的”肩部表征区域的诱发反应潜伏期比躯干亚区内肩部表征区域（以下称为“原始”肩部表征区域）的位点更长。我们推测，FBS中的“新的”肩部表征是从“原始”肩部表征中继而来的。我们通过使用菜豆白细胞凝集素（PHA-L）、生物素和生物素葡聚糖胺（BDA）作为顺行示踪剂，研究完整对照成年大鼠和前肢去传入成年大鼠中“原始”肩部表征与FBS之间的解剖学连接，来探究这一假设。将逆行示踪剂霍乱毒素β亚基（CT-B）注入FBS，也用于研究“原始”肩部表征与FBS之间的连接。使用这些解剖学追踪技术，我们无法证明在完整或去传入大鼠中，躯干亚区内的“原始”肩部表征与FBS之间存在直接的皮质-皮质连接。通过单独切除“原始”肩部表征或联合切除第二体感皮层（SII）中的肩部表征，同时记录肩部电刺激后FBS中的诱发反应，来研究两个皮质区域之间的功能连接。两种切除均未能消除FBS中“新的”肩部位点的诱发反应，这表明SI和SII对于FBS中“新的”肩部输入并非必需。提示皮层下位点可能在大规模皮层重组中起主要作用。还描述了从“原始”肩部表征到顶叶内侧（PM）、顶叶外侧（PL）、SII、顶叶腹侧（PV）和顶叶鼻周（PR）感觉区以及颗粒外外侧（AgL）和颗粒外内侧（AgM）运动区的投射结果。
