Disentangling linear and nonlinear brain responses to evoked deep tissue pain

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• 作者：Marco L. Loggia ; Robert R. Edwards ; Jieun Kim ; Mark G. Vangel ; Ajay D. Wasan ; R ; y L. Gollub ; Richard E. Harris ; Kyungmo Park ; Vitaly Napadow
• 关键词：Cuff pain algometry ; Psychophysics ; Neuroimaging ; BOLD fMRI ; Default mode network ; Human
• 刊名：Pain
• 出版年：2012
• 出版时间：October, 2012
• 年：2012
• 卷：153
• 期：10
• 页码：2140-2151
• 全文大小：1405 K

文摘

Pain stimuli evoke widespread responses in the brain. However, our understanding of the physiological significance underlying heterogeneous response within different pain-activated and -deactivated regions is still limited. Using functional magnetic resonance imaging, we evaluated brain responses to a wide range of stimulus intensity levels (1 innocuous, 7 painful) in order to estimate region-specific stimulus-response functions, which we hypothesized could illuminate that region¡¯s functional relationship to pain. Linear and nonlinear brain responses to pain were estimated through independent Legendre polynomial transformations of pain ratings within a general linear model. This approach identified at least 5 different, regionally specific activity profiles in the brain. Linearly increasing (eg, primary somatosensory/motor cortex, insulae) and intensity-independent (eg, secondary somatosensory cortex) activation was noted in traditional pain-processing areas, potentially reflecting sensory encoding and all-or-none salience responses, respectively. Multiple activity profiles were seen in areas of the default mode network (DMN): intensity-independent deactivation (eg, posterior cingulate cortex), linearly decreasing (eg, contralateral inferior parietal lobule), and quadratic (U-shaped; eg, medial prefrontal cortex). The latter observation suggests that: (1) different DMN subregions exhibit functional heterogeneity and (2) some DMN subregions respond in a percept-related manner to pain, suggesting closer linkage between the DMN and pain processing than previously thought. Future studies should apply a similar approach using innocuous stimuli of multiple intensities to evaluate whether the response profiles reported here can also be generalized to nonpainful somatosensory processing.