Representation of nociceptive stimuli in primary sensory cortex

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Abstract
USING fMRI, we observed cortical activity associated with nociceptive hot and cold sensations applied to hand and foot that are not spatially restricted to the corresponding regions of the primary somatosensory cortex (SI). Hot (55–57°C) and cold (0–2°C) tactile stimuli were applied separately to the right hand and foot of eight right-handed subjects. Although somatotopic mapping of hand and foot was observed as expected based on the Penfield homunculus, activations associated with hot during both hand and foot stimulation and subsequently, cold, activated regions unique to each thermal modality irrespective of the body part. This distributed system for thermal information is present at both nociceptive and more neutral thermal intensities (i.e. warm and cool sensations) indicating the presence of distributed sensory processing associated with thermal-related sensations in human primary sensorimotor cortex.