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Correlation of Functional MR Imaging Activation Data with Simple Reaction Times¹

¹ From the Russell H. Morgan Department of Radiology and Radiological Sciences, Divisions of Neuroradiology (K.K.O., N.M.B., M.A.K., D.M.Y.) and Psychiatric Neuro-Imaging (V.D.C.), Johns Hopkins Hospital, 600 N Wolfe St, Phipps B-112, Baltimore, MD 21287; and Office of Biostatistics Research, National Heart, Lung, and Blood Institute (C.W.). Received February 22, 2002; revision requested May 15; revision received June 24; accepted July 31. Supported by RPN 99-01-21-03. K.K.O. supported in part by TUBITAK (Scientific and Technical Research Council of Turkey). Address correspondence to D.M.Y. (e-mail: yousem@rad.jhu.edu).

PURPOSE: To determine the relationship between subject reaction times (RTs) and activation volume in the brain during visuomotor functional magnetic resonance (MR) imaging.

MATERIALS AND METHODS: Twenty-four subjects performed a simple RT task during single-event functional MR imaging, and RTs were recorded. The six subjects with the fastest RTs were designated the fast RT group, and the six subjects with the slowest RTs were designated the slow RT group. The data were processed with noncorrected height threshold (P < .001) for individual comparisons and corrected height threshold (P < .05) for group comparisons (t tests). The activation volumes in both occipital lobes, the left sensorimotor cortex, and the supplemental motor cortices were compared for the two groups.

RESULTS: The mean RT ± SD was 342 msec ± 20.15 for the fast RT group and 475 msec ± 36.17 for the slow RT group (P < .0001). More voxels of activation were seen in the fast RT group than in the slow RT group in the occipital lobes, left sensorimotor cortices, and supplemental motor cortices on individual and group maps. This difference was statistically significant in the left sensorimotor (P = .03) and left visual (P = .05) cortices. In the right visual cortex, a trend toward more activation in the fast RT group was noted (P = .15). There was a negative correlation between RTs and activation volume in the left sensorimotor cortex (P = .048).

CONCLUSION: There was a greater activation volume in motor and visual cortices in the fast RT group than in the slow RT group.

© RSNA, 2002

Index terms: Brain, cortex • Brain, function, 133.12144 • Brain, MR, 10.121412, 10.12144 • Magnetic resonance (MR), functional imaging, 10.121412, 10.12144

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