Cocaine administration decreases functional connectivity in human primary visual and motor cortex as detected by functional MRI

Functional magnetic resonance imaging (fMRI) was conducted to observe the e ffects of cocaine administration on the physiological fluctuations of fMRI signal in two brain regions. Seven long-term cocaine users with an average age of 32 years and 8 years of cocaine use history were recruited for the s tudy. A T-2*-weighted fast echo-planar imaging (EPI) pulse sequence was emp loyed at 1.5 T to acquire three sets of brain images for each subject under three conditions (at rest, after saline injection, and after cocaine injec tion [0.57 mg/kg]), Cross-correlation maps were constructed using the synch ronous, low frequency signal from voxel time courses after filtering respir atory, cardiac, and other physiological noise. A quantitative evaluation of the changes in functional connectivity was made using spatial correlation coefficient (SCC) analysis. A marked 50% reduction in SCC values in the reg ion of primary visual cortex and 43% reduction in SCC values in the region of primary motor cortex were observed after cocaine administration. This si gnificant reduction in SCC values in these cortical regions is a reflection of changes in neuronal activity. It is suggested that the observed changes in low frequency components after acute cocaine administration during a re sting, no-task situation may be used as a baseline reference source when as sessing the effects of cocaine on task-driven activation or on mesolimbic d opamine pathways. Magn Reson Med 43:45-51, 2000. (C) 2000 Wiley-Liss, Inc.