Cerebral processing of sharp mechanical pain measured with arterial spin labeling.

INTRODUCTION: Arterial spin labeling (ASL) is a functional neuroimaging technique that has been frequently used to investigate acute pain states. A major advantage of ASL as opposed to blood-oxygen-level-dependent functional neuroimaging is its applicability for low-frequency designs. As such, ASL represents an interesting option for studies in which repeating an experimental event would reduce its ecological validity. Whereas most ASL pain studies so far have used thermal stimuli, to our knowledge, no ASL study so far has investigated pain responses to sharp mechanical pain. METHODS: As a proof of concept, we investigated whether ASL has the sensitivity to detect brain activation within core areas of the nociceptive network in healthy controls following a single stimulation block based on 96 s of mechanical painful stimulation using a blunt blade. RESULTS: We found significant increases in perfusion across many regions of the nociceptive network such as primary and secondary somatosensory cortices, premotor cortex, posterior insula, inferior parietal cortex, parietal operculum, temporal gyrus, temporo-occipital lobe, putamen, and the cerebellum. Contrary to our hypothesis, we did not find any significant increase within ACC, thalamus, or PFC. Moreover, we were able to detect a significant positive correlation between pain intensity ratings and pain-induced perfusion increase in the posterior insula. CONCLUSION: We demonstrate that ASL is suited to investigate acute pain in a single event paradigm, although to detect activation within some regions of the nociceptive network, the sensitivity of our paradigm seemed to be limited. Regarding the posterior insula, our paradigm was sensitive enough to detect a correlation between pain intensity ratings and pain-induced perfusion increase. Previous experimental pain studies have proposed that intensity coding in this region may be restricted to thermal stimulation. Our result demonstrates that the posterior insula encodes intensity information for mechanical stimuli as well.

The glutamate to γ-aminobutyric acid ratio in the posterior insula is associated with pain perception in healthy women but not in women with borderline personality disorder.

This study aimed to investigate whether the differences in pain perception between patients with borderline personality disorder (BPD) and healthy subjects (HCs) can be explained by differences in the glutamate/GABA ratio in the posterior insula. In total, 29 BPD patients and 31 HCs were included in the statistical analysis. Mechanical pain sensitivity was experimentally assessed with pinprick stimuli between 32 and 512 mN on a numeric rating scale. The metabolites were measured in the right posterior insula using the MEshcher-GArwood Point-RESolved Spectroscopy sequence for single-voxel magnetic resonance spectroscopy (1H-MRS). The 256- and the 512-mN pinprick stimuli were perceived as significantly less painful by the BPD patient group compared with HCs. No differences were found between groups for the glutamate/GABA ratios. A positive correlation between the glutamate/GABA ratio and the pain intensity ratings to 256- and 512-mN pinpricks could be found in the combined and in the HC group. In the BPD patient group, the correlations between the glutamate/GABA ratio and the pain intensity ratings to 256- and 512-mN pinpricks did not reach significance. In conclusion, the study showed that individual differences in pain perception may in part be explained by the individual glutamate/GABA ratio in the posterior insula. However, this possible mechanism does not explain the differences in pain perception between BPD patients and HCs.

The Exercising Brain: Changes in Functional Connectivity Induced by an Integrated Multimodal Cognitive and Whole-Body Coordination Training.

This study investigated the impact of "life kinetik" training on brain plasticity in terms of an increased functional connectivity during resting-state functional magnetic resonance imaging (rs-fMRI). The training is an integrated multimodal training that combines motor and cognitive aspects and challenges the brain by introducing new and unfamiliar coordinative tasks. Twenty-one subjects completed at least 11 one-hour-per-week "life kinetik" training sessions in 13 weeks as well as before and after rs-fMRI scans. Additionally, 11 control subjects with 2 rs-fMRI scans were included. The CONN toolbox was used to conduct several seed-to-voxel analyses. We searched for functional connectivity increases between brain regions expected to be involved in the exercises. Connections to brain regions representing parts of the default mode network, such as medial frontal cortex and posterior cingulate cortex, did not change. Significant connectivity alterations occurred between the visual cortex and parts of the superior parietal area (BA7). Premotor area and cingulate gyrus were also affected. We can conclude that the constant challenge of unfamiliar combinations of coordination tasks, combined with visual perception and working memory demands, seems to induce brain plasticity expressed in enhanced connectivity strength of brain regions due to coactivation.