Physiological investigation of pain perception in humans

我们研究了CO_2激光刺激下的疼痛相关体感诱发电位(Pain SEPs)，以阐明人类痛觉的机制。我们用痛觉诱发电位计算了痛觉上行的有髓小纤维和脊丘脑束的传导速度，两者的传导速度都在10m/s左右。同时对手指施加振动刺激和主动运动可显著减少和延长疼痛SEP，但持续降温并不能。这一发现与门控理论(Melzack&Wall)一致。疼痛SEP也因脚部等偏远区域的自愿和被动活动而显著减弱。这一发现不是由没有主动运动的肢体的振动或运动想象产生的。因此，疼痛感知和运动相关的皮质活动之间的相互作用必须发生在大脑的某些区域，而不能缓解疼痛。我们研究了各种神经系统疾病患者的疼痛SEP，如周围神经病、脊髓空洞症、多发性硬化症(MS)和HTLV-I相关脊髓病(HAM)。疼痛SEP结果显示疼痛程度与损伤程度显著相关。此外，疼痛SEP可以在MS和HAM中检测到临床下的损害。Pain SEP对临床测试非常有用，特别是当我们记录和分析疼痛SEP和传统的电刺激SEP时。

We investigate pain-related somatosensory evoked potentials follwing CO_2 laser stimulation (pain SEPs) to elucidate the mechanisms of pain perception in humans. We caluculated conduction velocity (CV) of small myelinated fibers (Adelta) and the spinothalamic tract which pain sensation ascends through by using pain SEPs.CV of both of them were about 10 m/sec.We investigated machanisms of change of pain perception induced by various modalities of sensation in normal subjects. Concurrently applied vibratory stimuli to and active movements of fingers significantly reduced and prolonged pain SEPs, but continuous cooling did not. The findings were consistent with gate control theory (Melzack & Wall). Pain SEPs were also significantly attenuated by voluntary and passive movements of remote areas such as the foot. This finding was not produced by vibration or movement imagery of the limbs without active movement. Therefore, interactions between pain perception and movement-related cortical activities must take place in some areas of the brain without relieving pain.We studied pain SEPs in patients with various neurological diseases such as peripheral neuropathies, syringomyelia, multiple sclerosis (MS) and HTLV-I-associated myelopathy (HAM). Results of pain SEps showed a significant correlation with a degree of pain impairment. In addition, subclnical lesions could be detected by pain SEPs in MS and HAM.Pain SEPs were very useful for clinical testing, particularly when we recorded and analyzed both pain SEPs and conventional electrically-stimulated SEPs.