Document Detail

Stability, repeatability, and the expression of signal magnitude in functional magnetic resonance imaging.
MedLine Citation:
PMID:  10398975     Owner:  NLM     Status:  MEDLINE    
In 23 fMRI studies on six subjects, we examined activation in visual and motor tasks. We modeled the expected activation time course by convolving a temporal description of the behavioral task with an empirically determined impulse response function. We evaluated the signal activation intensity as both the number of activated voxels over arbitrary correlation thresholds and as the slope of the regression line between our modeled time course and the actual data. Whereas the voxel counting was strikingly unstable (standard deviation 74% in visual trials at a correlation of 0.5), the slope was relatively constant across trials and subjects (standard deviation <14%). Using Monte Carlo methods, we determined that the measured slope was largely independent of the contrast-to-noise ratio. Voxel counting is a poor proxy for activation intensity, with greatly increased scatter, much reduced statistical power, and increased type II error. The data support an alternative approach to functional magnetic resonance imaging (fMRI) that allows for quantitative comparisons of fMRI response magnitudes across trials and laboratories.
M S Cohen; R M DuBois
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of magnetic resonance imaging : JMRI     Volume:  10     ISSN:  1053-1807     ISO Abbreviation:  J Magn Reson Imaging     Publication Date:  1999 Jul 
Date Detail:
Created Date:  1999-10-04     Completed Date:  1999-10-04     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9105850     Medline TA:  J Magn Reson Imaging     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  33-40     Citation Subset:  IM    
UCLA Brain Mapping Division, Ahmanson-Lovelace Brain Mapping Center, Los Angeles, California 90095-7085, USA.
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MeSH Terms
Brain / physiology*
Brain Mapping*
Computer Simulation
Image Processing, Computer-Assisted
Linear Models
Magnetic Resonance Imaging / methods*
Middle Aged
Monte Carlo Method
Motor Activity
Motor Cortex / physiology
Photic Stimulation
Sensitivity and Specificity
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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