Florence S L, Kaas J H
Department of Psychology, Vanderbilt University, Nashville, Tennessee 37240, USA.
J Neurosci. 1995 Dec;15(12):8083-95. doi: 10.1523/JNEUROSCI.15-12-08083.1995.
Reorganization of somatosensory cortex after peripheral nerve damage typically has been attributed to cortical plasticity. Here we provide evidence that much of the large-scale cortical reorganization that occurs after a major loss of peripheral inputs reflects the sprouting or expansion of afferents from the remaining forelimb into deprived territories of the spinal cord and brainstem. We examined sensory afferent terminations in the spinal cord and brainstem, and determined the somatotopic organization of cortical area 3b in three adult monkeys with previous hand or forearm amputation, as veterinary treatment of forelimb injuries. In each monkey, the distribution of labeled sensory afferent terminations from the remaining parts of the fore-limb was much more extensive than the normal distribution of inputs from the forelimb, and extended into portions of the dorsal horn of the spinal cord and the cuneate nucleus of the brainstem related to the amputated hand. In the same animals, tactile stimulation of the forelimb activated much of the deprived hand representation in area 3b of cortex; the lateral portion of the deprived region in area 3B appeared to be reactivated by inputs from the face. These data provide important new evidence that one of the mechanisms subserving large scale reorganization in cortex is a relay of topographic changes that occur subcortically. Presumably, the expanded primary sensory inputs activate postsynaptic neurons that are normally driven by inputs from the hand so that the neurons now have receptive fields on the forearm. Since the topographic representation of the body is greatly magnified in the relay to cortex, the subcortical changes can result in dramatic cortical map changes.
周围神经损伤后体感皮层的重组通常被归因于皮层可塑性。在此，我们提供证据表明，在大量外周输入丧失后发生的许多大规模皮层重组反映了来自剩余前肢的传入神经纤维向脊髓和脑干的剥夺区域的发芽或扩张。我们检查了脊髓和脑干中的感觉传入终末，并确定了三只因前肢损伤接受兽医治疗而先前进行过手部或前臂截肢的成年猴子的皮层3b区的躯体定位组织。在每只猴子中，来自前肢其余部分的标记感觉传入终末的分布比前肢正常输入分布广泛得多，并延伸到与截肢手相关的脊髓背角和脑干楔状核的部分区域。在同一批动物中，前肢的触觉刺激激活了皮层3b区中许多被剥夺的手部代表区；3B区被剥夺区域的外侧部分似乎被来自面部的输入重新激活。这些数据提供了重要的新证据，表明皮层中支持大规模重组的机制之一是皮层下发生的地形变化的中继。据推测，扩大的初级感觉输入激活了通常由手部输入驱动的突触后神经元，因此这些神经元现在在前臂上有感受野。由于身体的地形表征在向皮层的中继中被大大放大，皮层下的变化可导致显著的皮层图谱变化。
