Previous neuroimaging studies have shown brain activity during not only the application of noxious stimuli, but also prior to stimulation. The functional significance of the anticipatory response, however, has yet to be explored. Two theoretical responses involve either a decrease or an increase in sensitivity of the nociceptive system. In a functional magnetic resonance imaging (fMRI) study, brainstem responses during anticipation and processing of thermal noxious stimuli were investigated. Twelve healthy subjects were warned prior to and then received noxious stimulation to their left hand. Behavioral data showed a positive correlation between the intensity of anticipation and pain. FMRI data revealed brainstem activation in the PAG during the anticipation period. When correlated with individual anticipation ratings, activation during anticipation included significant clusters within the entorhinal cortex and ventral tegmental area (VTA). During receipt, activation within the brainstem included the PAG, VTA, rostral ventromedial medulla (RVM), and the parabrachial nucleus (PB), all elements of descending pain pathways. Using a backward model approach, we explored the functional significance of the anticipatory neural response for subsequent pain processing. Results of this regression analysis revealed that insula activity during receipt was predicted by activity in both the entorhinal cortex and VTA during anticipation. We suggest that activation in both regions before and during pain may underlie anticipation and subsequent pain modulatory responses, possibly involving the appraisal and control of attention necessary for pain modulation. Together, the results suggest a possible role of brainstem areas in anticipatory mechanisms involved in the maintenance of chronic pain.
"This finding corroborates previous studies that have reported decreased nociceptive processing when fasting (Davidson et al. 1992; de los Santos-Arteaga et al. 2003; McGivern et al. 1979; McGivern and Berntson 1980). A contribution by parahippocampal cortex (or very closely related areas) to evoked pain responses has been postulated previously in EEG source analysis studies (Stancak et al. 2013; Stancak and Fallon 2013; Valeriani et al. 1996, 2000, 2002), and experiments with fMRI have cited PHG as being involved in processes such as reactivating memories of pain (Kattoor et al. 2013), pain anticipation (Fairhurst et al. 2007), and pain sensitivity (Piche et al. 2010). Interestingly, in the present study the effects of session on PHG activation were not correlated with pain ratings but rather with ratings of food photograph hedonicity. "
"Their coordinates were based on previous studies. We specified the sgACC (x = 0, y = 22, z = −6) (Fairhurst et al., 2007) and PAG (left: x = − 2, y = -28, z = − 8; right: x = 3, y = -28, z = − 6) (Yoshida et al., 2013). In each ROI, the peak value per subject and per contrast was obtained with a homemade Matlab program. "
"Coordinates for small volume correction were based on peak coordinates obtained from previous studies on pain processing and pain modulation. The PAG65, the ventral striatum62 were corrected using spheres of 4 mm radius. The anterior MPFC66 and the pregenual rostral anterior cingular cortex (rACC)67 were corrected using spheres of 9 mm radius. "
[Show abstract][Hide abstract] ABSTRACT: In this study, we investigated cortical thickness and functional connectivity across longitudinal acupuncture treatments in patients with knee osteoarthritis (OA). Over a period of four weeks (six treatments), we collected resting state functional magnetic resonance imaging (fMRI) scans from 30 patients before their first, third and sixth treatments. Clinical outcome showed a significantly greater Knee Injury and Osteoarthritis Outcome Score (KOOS) pain score (improvement) with verum acupuncture compared to the sham acupuncture. Longitudinal cortical thickness analysis showed that the cortical thickness at left posterior medial prefrontal cortex (pMPFC) decreased significantly in the sham group across treatment sessions as compared with verum group. Resting state functional connectivity (rsFC) analysis using the left pMPFC as a seed showed that after longitudinal treatments, the rsFC between the left pMPFC and the rostral anterior cingulate cortex (rACC), medial frontal pole (mFP) and periaquiduct grey (PAG) are significantly greater in the verum acupuncture group as compared with the sham group. Our results suggest that acupuncture may achieve its therapeutic effect on knee OA pain by preventing cortical thinning and decreases in functional connectivity in major pain related areas, therefore modulating pain in the descending pain modulatory pathway.
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