581, p < .0001]. Again, the effect was found for both hands, and the interaction between stimulation condition and hand was again not

significant [F(1,10) = .464, p = .511] ( Fig. 2A). The average increase in contact heat-pain threshold I BET 762 was 1.96 °C. If vestibular signals are able to modulate multiple somatosensory submodalities, then CVS-induced changes in tactile and pain thresholds should be positively correlated with each other, despite being opposite in sign. This correlation would arise because of the common vestibular input both to tactile and nociceptive areas. We therefore investigated correlations across individuals between our established measures of vestibular stimulation effectiveness and modulations of touch and pain thresholds. Specifically, we correlated the CVS-induced changes in tactile and pain thresholds with the corresponding changes in the straight-ahead pointing error, slow-phase velocity and number of fast-phase (Table 2). We found a significant association

across individuals between touch and pain modulations (r = −.631, p = .038, two-tailed) ( Fig. 2B). Previous results ( Ferrè et al., Selleckchem LDK378 2011) allowed us to predict the direction of correlations between vestibular effectiveness measures and changes in touch thresholds, but not between vestibular measures and changes in pain thresholds. We found an association between number of fast-phase and modulation of touch (r = −.549, p = .040, one-tailed), and a trend towards an association Cell press between slow-phase velocity and modulation of touch (r = .466, p = .074, one-tailed), for which we had prior hypotheses ( Ferrè et al., 2011). We found no associations between vestibular measures

and pain modulation using two-tailed testing. A small study such as ours has only low statistical power to detect associations, and individual correlation coefficients should be treated with caution. Therefore, to avoid both Type 1 and Type 2 errors we took an aggregation approach. Because anatomical and physiological studies show common vestibular and multisensory cortical projections, we had a strong prior hypothesis of a single common source of variance affecting both vestibular and multisensory measures. We therefore used principal components analysis to summarise the variance structure underlying the correlation matrix. The first component (eigenvalue 2.33, explaining 45% of the variance) loaded somewhat homogeneously on vestibulo-ocular and somatosensory measures, but not on pointing. The second component (eigenvalue 1.19, explaining only 24%) loaded almost exclusively on the pointing measure. We interpret these components as, first, a common vestibular drive to both oculomotor and somatosensory processes, and a secondary independent effect restricted to spatial orientation.