Responses of the supra-sylvian (SII) cortex in humans to painful and innocuous stimuli -: A study using intra-cerebral recordings

In this study we compare the intrinsic characteristics and localization of nociceptive CO2 laser evoked potential (LEP) and non-nociceptive electrical EP (SEP) sources recorded by deep electrodes (one to two electrodes per patient, 10-15 contacts per electrode) directly implanted in the supra-sylvian cortex of 15 epileptic patients. Early CO2 laser (N140-P170) and electrical (N60-P90) evoked potentials were recorded by all of the electrodes implanted in the supra-sylvian cortex contralateral to stimulation. SEPs and LEPs had similar waveforms and interpeak latencies. The LEPs appeared 84 +/- 15 ins later and were, on average, 14.2 +/- 22.2 muV smaller than the SEPs. These differences may be accounted for by the characteristics and the sizes of the different peripheral fibers (A delta vs. A beta) activated by the two types of stimuli. The stereotactic Talairach coordinates of the SEP and LEP sources covered the pre- and post-rolandic upper bank of the sylvian fissure, and were not significantly different for noxious and non-noxious stimuli. The spatial distribution of these contralateral responses fits with that of the modeled sources of scalp CO2 LEPs, magneto-encephalographic studies, and PET data from pain and vibrotactile activation studies. These results pert-nit us to define the SII cortex as a cortical integration area of non-nociceptive and nociceptive inputs. This is supported by: (i) anatomical data reporting that the SII area receives inputs from both posterior columns and spino-thalamic pathways conveying the nonnoxious and noxious information, respectively, and (ii) single cell recordings in monkeys, demonstrating that the SII area contains both nociceptive-specific neurons and wide-dynamic-range neurons receiving convergent input from nociceptive and non-nociceptive somatosensory afferents. (C) 2001 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved.