An fMRI study of the anterior cingulate cortex and surrounding medial wallactivations evoked by noxious cutaneous heat and cold stimuli

The anterior cingulate cortex (ACC) and adjacent regions in the medial wall have been implicated in sensory, motor and cognitive processes, including pain. Our previous functional magnetic resonance imaging (fMRI) studies hav e demonstrated pain-related activation of the posterior portion of the ACC during transcutaneous electrical nerve stimulation (TENS) and variable patt erns of cortical activation with innocuous and noxious thermal stimuli in i ndividual subjects. The present study represents the companion paper to our recent study of pain-and thermal-related cortical activations with the aim to use fMRI to delineate the activations in the ACC and surrounding region s of the medial wall during application of innocuous and noxious thermal st imuli as well as during performance of a motor task in individual subjects. Ten normal subjects were imaged on a conventional 1.5 T GE 'echospeed' sys tem. Functional images were obtained from sagittal sections through each he misphere centered at approximately 3-5 and 7-9 mm from midline. Each subjec t was imaged during innocuous (cool, warm) and noxious thermal (cold, hot) stimulation of the thenar eminence, and execution of a motor (sequential fi nger-thumb opposition) task. Task-related activations were mostly confined to contralateral and medial ipsilateral images. Although the present result s demonstrate intersubject variability in the task-related activations, som e general modality-specific patterns were apparent: (i) innocuous thermal-r elated activations were located mainly in the anterior ACC; (ii) noxious th ermal-related activations were primarily located in the anterior ACC, the v entral portion of the posterior ACC, and the supplementary motor area (SMA) ; (iii) motor-related activations were primarily located in the SMA and dor sal portion of the posterior ACC. These results indicate that specific spat ial patterns of activation exist within the ACC and surrounding regions of the medial wall for innocuous and noxious thermal stimuli, and that noxious thermal- and motor-related activations appear to be segregated within the ACC. Therefore, we propose a segregation of the ACC into an anterior non-sp ecific attention/arousal system and a posterior pain system. (C) 2000 Inter national Association for the Study of Pain. Published by Elsevier Science B .V. All rights reserved.