Vierck C J
Department of Neuroscience, University of Florida College of Medicine, Gainesville 32610-0244, USA.
Somatosens Mot Res. 1998;15(2):157-63. doi: 10.1080/08990229870880.
Transection of the dorsal spinal column in monkeys has been previously shown to spare detection, localization and a variety of discriminations between spatial attributes of tactile stimuli. In contrast, performance on certain tests involving stimulus sequences is substantially impaired, such as tactile direction sensitivity and frequency discrimination. The present study extends these findings to show that a repetitive cutaneous stimulus is undetectable following complete interruption of the ipsilateral dorsal column. Macaca arctoides monkeys were trained to discriminate between different durations of 10 Hz indentation of the glabrous skin of one foot. Preoperatively, these animals could discriminate reliably between three pulses (the standard stimulus duration of 200 ms) and comparison trains of six or more pulses (500 ms or more). Following incomplete interruption of the ipsilateral dorsal column of one monkey, discrimination of the duration of stimulation was unimpaired. However, complete lesions of the ipsilateral dorsal column eliminated performance above the criterion of 75% correct responses for approximately 1 year of postoperative testing of three monkeys. Comparison stimuli of as many as 38 pulses (3.7 s) were utilized during postoperative testing. The inability to detect repetitive stimulation is hypothesized to be related to abnormal intracortical inhibition that has been demonstrated to occur within the primary somatosensory cortex (SI) of monkeys after interruption of the contralateral dorsal column.
先前的研究表明，猴子的脊髓背柱横断后，触觉刺激的空间属性的检测、定位及各种辨别能力仍可保留。相比之下，某些涉及刺激序列的测试表现则会大幅受损，如触觉方向敏感性和频率辨别。本研究扩展了这些发现，表明在同侧背柱完全中断后，重复性皮肤刺激无法被检测到。对熊猴进行训练，使其能够辨别一只脚无毛皮肤以10赫兹频率压痕的不同持续时间。术前，这些动物能够可靠地区分三个脉冲（标准刺激持续时间为200毫秒）与六个或更多脉冲（500毫秒或更长）的比较序列。在一只猴子的同侧背柱不完全中断后，刺激持续时间的辨别能力未受影响。然而，在对三只猴子进行术后约一年的测试中，同侧背柱的完全损伤消除了高于75%正确反应标准的表现。术后测试中使用了多达38个脉冲（3.7秒）的比较刺激。无法检测到重复性刺激被推测与异常的皮质内抑制有关，这种抑制已被证明在对侧背柱中断后的猴子初级体感皮层（SI）内会发生。
