Pain perception: is there a role for primary somatosensory cortex?

McGill University and Université de Montréal, Montreal, Quebec, Canada H3A 1A1.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 08/1999; 96(14):7705-9. DOI: 10.1073/pnas.96.14.7705
Source: PubMed

ABSTRACT Anatomical, physiological, and lesion data implicate multiple cortical regions in the complex experience of pain. These regions include primary and secondary somatosensory cortices, anterior cingulate cortex, insular cortex, and regions of the frontal cortex. Nevertheless, the role of different cortical areas in pain processing is controversial, particularly that of primary somatosensory cortex (S1). Human brain-imaging studies do not consistently reveal pain-related activation of S1, and older studies of cortical lesions and cortical stimulation in humans did not uncover a clear role of S1 in the pain experience. Whereas studies from a number of laboratories show that S1 is activated during the presentation of noxious stimuli as well as in association with some pathological pain states, others do not report such activation. Several factors may contribute to the different results among studies. First, we have evidence demonstrating that S1 activation is highly modulated by cognitive factors that alter pain perception, including attention and previous experience. Second, the precise somatotopic organization of S1 may lead to small focal activations, which are degraded by sulcal anatomical variability when averaging data across subjects. Third, the probable mixed excitatory and inhibitory effects of nociceptive input to S1 could be disparately represented in different experimental paradigms. Finally, statistical considerations are important in interpreting negative findings in S1. We conclude that, when these factors are taken into account, the bulk of the evidence now strongly supports a prominent and highly modulated role for S1 cortex in the sensory aspects of pain, including localization and discrimination of pain intensity.


Available from: Jen-I Chen, Oct 23, 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: (1) Field potential study in conscious rats provides a convenient and effective animal model for pain mechanism and pharmacological research. However, the spatial-temporal character of nociception processing in cortex revealed by field potential technique in conscious rats remains unclear. (2) In the present study, multi-channel field potentials evoked by noxious laser stimulation applied to the hind paw of conscious rats were recorded through 12 chronically implanted skull electrodes. Independent component analysis (ICA) was used to remove possible artifacts and to extract the specific nociception-related component. (3) Two fast sharp responses and one slow blunt response were evoked by noxious laser stimulation. Systemic morphine (5 mg/kg, i.p.) preferentially attenuated the amplitude of the slow blunt response while had no significant effect on the first two sharp responses. ICA revealed that those responses came from activities of contralateral anterior parietal area, medial frontal area and posterior parietal area. A movement artifact was also detected in this study. Partial directed coherence (PDC) analysis showed that there were changes of information flows from medial frontal and posterior parietal area to anterior parietal area after noxious laser stimulation. (4) Characterization of the spatio-temporal responses to noxious laser stimulation may be a valuable model for the study of pain mechanisms and for the assessment of analgesia.
    Cellular and Molecular Neurobiology 09/2008; 28(5):671-87. DOI:10.1007/s10571-007-9216-3 · 2.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pain threshold and pain tolerance of heat noxious stimuli were assessed to determine whether they are equivalent when measured at three equidistant sites of both volar forearms. Heat pain threshold and tolerance were measured in 18 healthy volunteers using a standard stimulation device consisting of a thermode. Pain threshold and pain tolerance did not differ within and across forearm sites. Experimenters addressing heat pain threshold and tolerance in healthy volunteers may freely choose and change stimulation sites on both volar forearms, without the risk of confounding site effects on dependent variables. This data completes previous reports on side effects by analyzing the effect of site on the forearm for both heat pain threshold and tolerance. The absence of side and site effects may contribute to setting a more secure basis for assessments of laterality effects of painful stimulation.
    Neuroscience Letters 09/2008; 440(3):309-13. DOI:10.1016/j.neulet.2008.05.084 · 2.06 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Tactile, proprioceptive, and nociceptive information, including also chemosensory functions are expressed in the trigeminal nerve sensory response. To study differences in the processing of different stimulus qualities, we performed a study based on functional magnetic resonance imaging. The first trigeminal branch (ophthalmic nerve) was activated by (a) intranasal chemical stimulation with gaseous CO2 which produces stinging and burning sensations, but is virtually odorless, (b) painful, but not nociceptive specific cutaneous electrical stimulation, and (c) cutaneous mechanical stimulation using air puffs. Eighteen healthy subjects participated (eight men, 10 women, mean age 31 years). Painful stimuli produced patterns of activation similar to what has been reported for other noxious stimuli, namely activation in the primary and secondary somatosensory cortices, anterior cingulate cortex, insular cortex, and thalamus. In addition, analyses indicated intensity-related activation in the prefrontal cortex which was specifically involved in the evaluation of stimulus intensity. Importantly, the results also indicated similarities between activation patterns after intranasal chemosensory trigeminal stimulation and patterns usually found following intranasal odorous stimulation, indicating the intimate connection between these two systems in the processing of sensory information.
    Pain 07/2008; 139(2):376-88. DOI:10.1016/j.pain.2008.05.007 · 5.84 Impact Factor