High-resolution functional magnetic resonance imaging revealed distinct and shared nociceptive heat and innocuous tactile processing networks within posterior parasylvian region of monkeys.
Emerging evidence supports an important role of posterior parasylvian areas in both pain and touch processing. Whether there are separate or shared networks for these sensations remains controversial. The present study compared spatial patterns of brain activation in response to unilateral nociceptive heat (47.5°C) or innocuous tactile stimulation (8-Hz vibration) to digits through high-resolution functional magnetic resonance imaging (fMRI) in squirrel monkeys. In addition, the temporal profile of heat-stimulus-evoked fMRI Blood Oxygenation Level Dependent (BOLD) signal changes was characterized. By examining high-resolution fMRI and histological measures at both the individual and the group levels, we found that both nociceptive heat and tactile stimuli elicited activation in bilateral secondary somatosensory and ventral parietal areas (S2/PV) and in ipsilateral ventral somatosensory areas (VS) and retroinsula (Ri). Bilateral posterior insular cortex (pIns) and area 7b responded preferentially to nociceptive heat stimulation. Single voxels within each activation cluster showed robust BOLD signal changes during each block of nociceptive stimulation. Across animals (n = 11), nociceptive response magnitudes of contralateral VS and pIns and ipsilateral Ri were significantly greater than corresponding areas in the opposite hemisphere. In sum, both distinct and shared areas in regions surrounding the posterior sylvian fissure were activated in response to nociceptive and tactile inputs in nonhuman primates.
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Department of Radiology and Radiological Science, Vanderbilt University, Nashville, TN, USA
Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
*Corresponding author. Address: AA 1105 MCN, 1161 21st Avenue South, Nashville, TN 37027, USA. Tel.: +1 615 9367069; fax: +1 615 3220734.
Article history: Received 31 May 2011; Received in revised form 6 September 2011; Accepted 4 October 2011.