Cortical Processing of Pain Perception in Humans: A Functional Magnetic Resonance Imaging Study

Abstract

There have been numerous studies of pain perception in humans using a variety of brain imaging methods. The majority of the past research has focused on the use of positron emission tomography (PET) as the primary imaging method. The present study examines the cortical mechanisms of pain perception in humans using a recently developed imaging technique called functional magnetic resonance imaging (fMRI). The primary interest in this study concerns how behavioural aspects of pain are reflected by cerebral cortical activity during noxious stimulation. As pain involves a combination of sensory, emotional, and cognitive responses, the extent and degree of activation in cortical areas associated with these responses can be affected. To address this issue, a behavioural experiment was first performed to assess the sensory, emotional, and cognitive components of tonic pain induced by a cold foam-pack (0°C). Subsequently, three subjects from the behavioural study pool participated in the imaging study of pain. In the imaging experiment, a cold foam-pack (0°C) and a non-cold foam-pack were applied to the left hands of these subjects. Activation produced by the noxious stimulus was compared with that produced by the innocuous stimulus. The results revealed inconsistencies in cortical activation among the three subjects and this could be related to each subject's behavioural measures. Individual and experimental variables may also account for the differences in results.