De Ryck M, Van Reempts J, Duytschaever H, Van Deuren B, Clincke G
Department of Neuropsychopharmacology, Janssen Research Foundation, Beerse, Belgium.
Brain Res. 1992 Feb 21;573(1):44-60. doi: 10.1016/0006-8993(92)90112-m.
The present study was aimed at delineating the neocortical substrate of tactile/proprioceptive limb placing reactions in rats by means of behavioral tests that excluded the participation of facial stimuli in limb function. Using a photochemical technique, we made unilateral focal lesions in the frontal and parietal neocortex. Fore- and/or hindlimb placing deficits resulted from damage to a fronto-parietal region lying between the medial agranular cortex and the primary somatosensory (whisker barrel field) cortex. When the antero-posterior coordinate was varied from 4 mm anterior to 1 mm posterior to bregma, tactile/proprioceptive forelimb dysfunction was more pronounced after damage to the parietal forelimb area, but lesions confined to the frontal lateral agranular cortex also yielded clear-cut forelimb placing deficits. Damage to either area alone allowed for partial recovery of forelimb function. However, following combined, total destruction of both frontal and parietal forelimb areas, forelimb deficits did not recover. This resembled the irreversible hindlimb deficits after near-total destruction of the parietal hindlimb area. Damage to the medial agranular cortex left limb placing intact. Likewise, for as long as the medial edge of lesions to the whisker barrel field did not come closer than 3 mm to the midline, thus remaining outside the parietal hindlimb area, limb placing remained normal. This sharp medial and lateral delineation of the cortical substrate subserving tactile/proprioceptive limb placing coincides with the borders of a thick, dense subfield of large pyramidal neurons in the deeper parts of layer V. Limb placing remained intact when medial agranular cortex lesions damaged only 30% of that subfield, whereas 70% destruction of that layer following more laterally placed lesions in the parietal hindlimb area produced irreversible hindlimb dysfunction. The severity of hindlimb placing deficits was related to the amount of incursion by whisker barrel field lesions into the subfield of deep layer V large pyramidal neurons. Finally, very large lesions of the occipital cortex did not affect tactile/proprioceptive limb placing. We discuss the neocortical areal and laminar specificity of tactile/proprioceptive limb function in the context of recent neuroanatomical and electrophysiological findings, and their relevance to normal cortical function, recovery from neocortical stroke (including diaschisis), and age-related cortical dysfunction.
本研究旨在通过行为测试来描绘大鼠触觉/本体感觉肢体放置反应的新皮质基质，这些行为测试排除了面部刺激对肢体功能的影响。我们使用光化学技术在额叶和顶叶新皮质制作单侧局灶性损伤。位于内侧无颗粒皮质和初级躯体感觉（触须桶状区）皮质之间的额顶叶区域受损导致前肢和/或后肢放置缺陷。当前后坐标从前囟前4毫米变化到前囟后1毫米时，顶叶前肢区域受损后触觉/本体感觉前肢功能障碍更为明显，但仅限于额叶外侧无颗粒皮质的损伤也会产生明显的前肢放置缺陷。单独损伤任何一个区域都能使前肢功能部分恢复。然而，额叶和顶叶前肢区域联合完全破坏后，前肢缺陷并未恢复。这类似于顶叶后肢区域几乎完全破坏后不可逆的后肢缺陷。内侧无颗粒皮质损伤后肢体放置功能保持完整。同样，只要触须桶状区损伤的内侧边缘距离中线不小于3毫米，即仍位于顶叶后肢区域之外，肢体放置功能就保持正常。支持触觉/本体感觉肢体放置的皮质基质的这种清晰的内侧和外侧界限与V层较深部分大锥体神经元的一个厚而密集的子区域的边界相吻合。当内侧无颗粒皮质损伤仅破坏该子区域的30%时，肢体放置功能保持完整，而在顶叶后肢区域更外侧放置的损伤导致该层70%的破坏则产生不可逆的后肢功能障碍。后肢放置缺陷的严重程度与触须桶状区损伤侵入深层V大锥体神经元子区域的程度有关。最后，枕叶皮质的非常大的损伤不影响触觉/本体感觉肢体放置。我们结合最近的神经解剖学和电生理学发现，讨论触觉/本体感觉肢体功能的新皮质区域和层特异性，以及它们与正常皮质功能、新皮质中风（包括远隔性机能障碍）恢复和年龄相关皮质功能障碍的相关性。
