A comparative fMRI study of cortical representations for thermal painful, vibrotactile, and motor performance tasks

Abstract

Cortical activity due to a thermal painful stimulus applied to the right hand was studied in the middle third of the contralateral brain and compared to activations for vibrotactile and motor tasks using the same body part, in nine normal subjects. Cortical activity was demonstrated utilizing multislice echo-planar functional magnetic resonance imaging (fMRI) and a surface coil. The cortical activity was analyzed based upon individual subject activity maps and on group-averaged activity maps. The results show significant differences in activations across the three tasks and the cortical areas studied. The study indicates that fMRI enables examination of cortical networks subserving pain perception at an anatomical detail not available with other brain imaging techniques and shows that this cortical network underlying pain perception shares components with the networks underlying touch perception and motor execution. However, the thermal pain perception network also has components that are unique to this percept. The uniquely activated areas were in the secondary somatosensory region, insula, and posterior cingulate cortex. The posterior cingulate cortex activity was in a region that, in the monkey, receives nociceptive inputs from posterior thalamic medial and lateral nuclei that in turn are targets for spinothalamic terminations. Discrete subdivisions of the primary somatosensory and motor cortical areas were also activated in the thermal pain task, showing region- dependent differences in the extent of overlap with the other two tasks. Within the primary motor cortex, a hand region was preferentially active in the task in which the stimulus was painful heat. In the primary somatosensory cortex most activity in the painful heat task was localized to area 1, where the motor and vibratory task activities were also coincident. The study also indicates that the functional connectivity across multiple cortical regions reorganizes dynamically with each task.