Fractional anisotropy correlates with auditory simple reaction time performance

During the last two decades, modern imaging studies focused intensively on the broad field of reaction time paradigms and significantly enhanced the understanding of behavioral performance. However, interindividual variations of simple reaction time (SRT) have been barely investigated. in this study, we intended to identify neural correlates of interindividual variation in auditory SRT (aSRT) employing the Poffenberger paradigm with auditory stimuli, in order to investigate neural processing speed performance. We conducted a whole-head voxel based morphometry analysis of fractional anisotropy (FA) in 19 healthy, right handed subjects. Simple regression analysis between FA and interindividual aSRT measures was performed for each voxel. Significant positive correlation (R-2: 0.44/0.78 min/max) for FA vs. individual mean aSRT was found in the right central cerebellum dorsocranial of the dentate nucleus. A significant correlation (R-2: 0.453/0.633 min/max) was also detected between FA and the hand performance index, which characterizes the intraindividual RT difference between left and right hand, within the precentral portion of the pyramidal tract in the left hemisphere. Fast right handed response correlated with high local FA values located within neural structures participating in right hand control. Against the background of only right handed participants in our study, the hypothesis of local myelination as one basic condition influencing reaction time performance is strongly supported. The presented results identify brain areas involved in the processing speed of the aSRT tasks. We propose that the presented findings are due to an influence of participants' right hand preference on both FA and aSRT measures. (c) 2007 Elsevier B.V. All rights reserved.