Distinct and shared cerebral activations in processing innocuous versus noxious contact heat revealed by functional magnetic resonance imaging

Abstract

Whether innocuous heat (IH)-exclusive brain regions exist and whether patterns of cerebral responses to IH and noxious heat (NH) stimulations are similar remain elusive. We hypothesized that distinct and shared cerebral networks were evoked by each type of stimulus. Twelve normal subjects participated in a functional MRI study with rapidly ramped IH (38 degrees C) and NH (44 degrees C) applied to the foot. Group activation maps demonstrated three patterns of cerebral activation: (1) IH-responsive only in the inferior parietal lobule (IPL); (2) NH-responsive only in the primary somatosensory cortex (S1), secondary somatosensory cortex (S2), posterior insular cortex (IC), and premotor area (PMA); and (3) both IH- and NH-responsive in the middle frontal gyrus, inferior frontal gyrus (IFG), anterior IC, cerebellum, superior frontal gyrus, supplementary motor area, thalamus, anterior cingulate cortex (ACC), lentiform nucleus (LN), and midbrain. According to the temporal analysis of regions of interest, the IPL exclusively responded to IH, and the S2, posterior IC, and PMA were exclusively activated by NH throughout the entire period of stimulation. The IFG, thalamus, ACC, and LN responded differently during different phases of IH versus NH stimulation, and the NH-responsive-only S1 responded transiently during the early phase of IH stimulation. BOLD signals in bilateral IPLs were specifically correlated with the ratings of IH sensation, while responses in the contralateral S1 and S2 were correlated with pain intensity. These results suggest that distinct and shared spatial and temporal patterns of cerebral networks are responsible for the perception of IH and NH.

Brain response to thermal stimulation predicts outcome of patients with chronic disorders of consciousness

“…This pattern of activation is consistent with previous studies (Tracey et al, 2000;Laureys et al, 2002;Tseng et al, 2010). Most regions were activated bilaterally, but showed stronger activation on the side contralateral to the stimulus.…”

“…The stimulation temperature was kept at 42 ± 2°C and the baseline temperature was 21°C (room temperature). Thermal stimulation was carried out by putting a plastic bag containing warm water to the whole plantar surface of one of the subject's feet for 30 s. This ensured that each subject received abundant stimulation, but would suffer no adverse consequences (Moulton et al, 2005;Tseng et al, 2010).…”

Functional connectivity of the human insular cortex during noxious and innocuous thermal stimulation

“…Agreeing with the results from previous studies using PET (Casey et al, 1996;Craig et al, 2000), MEG (Maihofner et al, 2002) and fMRI (Davis et al, 1998;Seifert and Maihofner, 2007) we found a significant increased activation in brain areas belonging to the pain neuromatrix during painful stimulation (for review see Apkarian et al (2005) and ). Besides insular activations, the main finding of our factorial analysis results was a main effect of innocuous stimulation with increased activation of the parietal cortex as recently shown for innocuous contact-heat stimulation (Tseng et al, 2010). Regarding the insular cortex a main effect of pain with increased activation during noxious compared to innocuous stimuli was detected in bilateral aINS and contralateral pINS.…”

Imaging signatures of altered brain responses in small-fiber neuropathy

“…76 and controls in Ref. 78). There was no significant difference in age (P 5 0.38, Mann-Whitney U test) or gender (P 5 0.11, Fisher exact test) distribution between the patients and controls.…”