Abstract
The current fMRI study investigated cortical processing of electrically induced painful tooth stimulation of both maxillary canines and central incisors in 21 healthy, right-handed volunteers. A constant current, 150% above tooth specific pain perception thresholds was applied and corresponding online ratings of perceived pain intensity were recorded with a computerized visual analog scale during fMRI measurements. Lateralization of cortical activations was investigated by a region of interest analysis. A wide cortical network distributed over several areas, typically described as the pain or nociceptive matrix, was activated on a conservative significance level. Distinct lateralization patterns of analyzed structures allow functional classification of the dental pain processing system. Namely, certain parts are activated independent of the stimulation site, and hence are interpreted to reflect cognitive emotional aspects. Other parts represent somatotopic processing and therefore reflect discriminative perceptive analysis. Of particular interest is the observed amygdala activity depending on the stimulated tooth that might indicate a role in somatotopic encoding.
Highlights
Brain structures consistently activated by noxious stimuli are: anterior cingulate cortex (ACC), insula, secondary somatosensory cortex (SII), lentiform nuclei, cerebellum, and thalamus
According to gender related differences, we found a trend in the interaction gender × stimulus intensities (F = 2.74, η2 = 0.13, p = 0.051) but no interaction according to the gender × rating interaction with F = 0.87, η2 = 0.04, and p = 0.46
Focusing on significantly activated cingulate cortex subdivisions (PCC, pMCC, aMCC, pregenual ACC (pACC), and sACC) we found a left hemispheric lateralization in the pACC and a trend toward left-lateralization in the aMCC, but no lateralization in the more posterior divisions
Summary
Brain structures consistently activated by noxious stimuli are: anterior cingulate cortex (ACC), insula, secondary somatosensory cortex (SII), lentiform nuclei, cerebellum, and thalamus. Activation related to nociception has been reported for primary somatosensory cortex (SI), motor cortex (M1), premotor areas, and subcortical structures (Treede et al, 1999; Petrovic et al, 2000; Peyron et al, 2000; Bingel et al, 2002; Farrell et al, 2005) These areas have been divided into a lateral and medial pain system and substantial evidence has emerged in support of this model (Albe-Fessard et al, 1985; Bushnell et al, 1999; Tracey and Mantyh, 2007), alternative hypotheses have been put forward (Apkarian et al, 2005; Craig, 2005; Mouraux and Iannetti, 2009). The current study aimed at elucidating cortical spatial representation and hemispheric lateralization in response to dental nociception
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