Abstract
1. The motor cortex was stimulated electrically (vertex anode; cathode 6 cm lateral) in neurologically normal subjects undergoing surgery for scoliosis, and the evoked corticospinal volleys were recorded from the spinal cord using epidural electrodes. 2. Stimuli > 330 V produced a complex D-wave volley containing three separate peaks, with high-threshold components, 0.8 ms (D2) and 1.6 ms (D3), in advance of the lowest-threshold component (D1). As stimuli increased up to 1500 V, D3 replaced the later components completely, but there was no further latency 'jump'. 3. Brainstem stimulation using electrodes over each mastoid process produced a descending volley that had the same latencies as D3. At threshold, stimulation of the brainstem or spinal cord attenuated the D wave evoked by simultaneous cortical stimulation. 4. It is concluded that transcranial electrical stimulation of the motor cortex at high intensities can access corticospinal neurones at the pyramidal decussation, and that stimulation of the brainstem (and the spinal cord) preferentially accesses corticospinal axons. At threshold, motor cortex stimulation probably activates corticospinal neurones at or near the cerebral cortex.
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Selected References
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- Amassian V. E., Eberle L., Maccabee P. J., Cracco R. Q. Modelling magnetic coil excitation of human cerebral cortex with a peripheral nerve immersed in a brain-shaped volume conductor: the significance of fiber bending in excitation. Electroencephalogr Clin Neurophysiol. 1992 Oct;85(5):291–301. doi: 10.1016/0168-5597(92)90105-k. [DOI] [PubMed] [Google Scholar]
- Burke D., Hicks R. G., Stephen J. P. Corticospinal volleys evoked by anodal and cathodal stimulation of the human motor cortex. J Physiol. 1990 Jun;425:283–299. doi: 10.1113/jphysiol.1990.sp018103. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Burke D., Hicks R., Gandevia S. C., Stephen J., Woodforth I., Crawford M. Direct comparison of corticospinal volleys in human subjects to transcranial magnetic and electrical stimulation. J Physiol. 1993 Oct;470:383–393. doi: 10.1113/jphysiol.1993.sp019864. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Edgley S. A., Eyre J. A., Lemon R. N., Miller S. Excitation of the corticospinal tract by electromagnetic and electrical stimulation of the scalp in the macaque monkey. J Physiol. 1990 Jun;425:301–320. doi: 10.1113/jphysiol.1990.sp018104. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hicks R., Burke D., Stephen J., Woodforth I., Crawford M. Corticospinal volleys evoked by electrical stimulation of human motor cortex after withdrawal of volatile anaesthetics. J Physiol. 1992 Oct;456:393–404. doi: 10.1113/jphysiol.1992.sp019342. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Maccabee P. J., Amassian V. E., Eberle L. P., Cracco R. Q. Magnetic coil stimulation of straight and bent amphibian and mammalian peripheral nerve in vitro: locus of excitation. J Physiol. 1993 Jan;460:201–219. doi: 10.1113/jphysiol.1993.sp019467. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Thompson P. D., Day B. L., Crockard H. A., Calder I., Murray N. M., Rothwell J. C., Marsden C. D. Intra-operative recording of motor tract potentials at the cervico-medullary junction following scalp electrical and magnetic stimulation of the motor cortex. J Neurol Neurosurg Psychiatry. 1991 Jul;54(7):618–623. doi: 10.1136/jnnp.54.7.618. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Thompson P. D., Day B. L., Crockard H. A., Calder I., Murray N. M., Rothwell J. C., Marsden C. D. Intra-operative recording of motor tract potentials at the cervico-medullary junction following scalp electrical and magnetic stimulation of the motor cortex. J Neurol Neurosurg Psychiatry. 1991 Jul;54(7):618–623. doi: 10.1136/jnnp.54.7.618. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ugawa Y., Rothwell J. C., Day B. L., Thompson P. D., Marsden C. D. Percutaneous electrical stimulation of corticospinal pathways at the level of the pyramidal decussation in humans. Ann Neurol. 1991 Apr;29(4):418–427. doi: 10.1002/ana.410290413. [DOI] [PubMed] [Google Scholar]