MECHANISMS OF HYPNOTIC ANALGESIA EXPLAINED BY FUNCTIONAL MAGNETIC RESONANCE (fMRI).

Hypnotic-focused analgesia (HFA) was produced in 20 highly hypnotizable subjects receiving nociceptive stimulations while undergoing functional magnetic resonance imaging (fMRI). The fMRI pattern in brain cortex activation while receiving a painful stimulus was recorded both during nonhypnosis and during HFA. The scanning protocol included the acquisition of a T1-weighted structural scan, 4 functional scans, a T2-weighted axial scan, and a fluid attenuated inversion recovery (FLAIR) scan. Total imaging time, including localization and structural image acquisitions, was approximately 60 minutes. Without HFA, the subjects reported subjective presence of pain, and the cortex primary sensory areas S1, S2, and S3 were activated. During HFA, the subjects reported complete absence of subjective pain and S1, S2, and S3 were deactivated. The findings suggest that HFA may prevent painful stimuli from reaching the sensory brain cortex, possibly through a gate-control mechanism.

Cognitive speed and white matter integrity in secondary progressive multiple sclerosis.

BACKGROUND: Processing speed (PS) deficits have been consistently observed in secondary progressive multiple sclerosis (SPMS). However, the underlying neural correlates have not been clarified yet. The present study aimed to investigate the relationship between macrostructural and microstructural white matter (WM) integrity and performance on different cognitive measures with prominent PS load. METHODS: Thirty-one patients with SPMS were recruited and underwent neurological, neuropsychological, and MRI assessments. The associations between a composite index of PS abilities and scores on various tests with prominent PS load and T1-weighted and diffusion tensor image parameters were tested. Analyses were carried out using voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS). RESULTS: VBM results showed that only the semantic fluency task correlated with grey matter (GM) volume in a range of cortical and subcortical areas bilaterally as well as the corpus callosum and the superior longitudinal fasciculus. TBSS analysis revealed consistent results across all the cognitive measures investigated, showing a prominent role of commissural and frontal associative WM tracts in supporting PS-demanding cognitive operations. CONCLUSIONS: In patients with SPMS, PS abilities are mainly dependent on the degree of both macrostructural and microstructural WM integrity. Preservation of associative WM tracts that support information integration seems crucial to sustain performance in tasks requiring fast cognitive processes.