Burke D, Hicks R, Stephen J
Department of Clinical Neurophysiology, Prince Henry Hospital, Little Bay, NSW, Australia.
Brain. 1992 Oct;115 ( Pt 5):1497-508. doi: 10.1093/brain/115.5.1497.
In 18 neurologically normal subjects the corticofugal volleys evoked by anodal and cathodal electrical stimulation of the motor cortex were recorded using epidural electrodes at the high-thoracic and low-thoracic regions of the spinal cord during surgery for scoliosis. At and just above threshold, anodal and cathodal stimulation of the upper-limb area and motor cortex produced a D wave that propagated to the low-thoracic region. The stimulus intensity required to produce D waves was significantly lower with anodal stimulation. I waves were recorded at higher stimulus intensities than the D wave but not more readily with cathodal stimulation. There was no significant difference in the extent to which stimulus intensity had to be increased above D-wave threshold to produce I waves with the two stimulus polarities, and the number of I waves was the same when the stimulus was increased by the same amount above D-wave threshold. After withdrawal of isoflurane, I waves could not be recorded when the stimulus intensity was below D-wave threshold with either stimulus polarity. Anodal stimulation over the upper-limb area remained more effective than cathodal stimulation in producing both D and I waves. These results indicate that, at threshold, regardless of anaesthesia, anodal and cathodal stimuli access upper-limb corticospinal neurons directly at a similar site, the anodal stimuli being more effective. In addition, the results suggest that some corticospinal neurons in the upper-limb area of motor cortex have projections to lumbar segments.
在18名神经功能正常的受试者中，在脊柱侧弯手术期间，使用硬膜外电极在脊髓的高胸段和低胸段记录运动皮层阳极和阴极电刺激诱发的皮质下行冲动。在阈值及略高于阈值时，上肢区域和运动皮层的阳极和阴极刺激产生了一个向低胸段传播的D波。阳极刺激产生D波所需的刺激强度明显更低。I波在比D波更高的刺激强度下记录到，但阴极刺激时I波出现得并不更容易。两种刺激极性下，将刺激强度提高到高于D波阈值以产生I波所需增加的程度没有显著差异，当刺激强度在高于D波阈值的基础上增加相同量时，I波的数量相同。停用异氟烷后，当刺激强度低于D波阈值时，无论哪种刺激极性都无法记录到I波。上肢区域的阳极刺激在产生D波和I波方面仍然比阴极刺激更有效。这些结果表明，在阈值时，无论麻醉状态如何，阳极和阴极刺激在相似部位直接作用于上肢皮质脊髓神经元，阳极刺激更有效。此外，结果表明运动皮层上肢区域的一些皮质脊髓神经元投射到腰段。
