Minimum detectable change in motor and prefrontal cortex activity over repeated sessions using 3T functional MRI and a block design.
OBJECTIVE
To determine the minimum detectable change (MDC) in functional magnetic resonance imaging (fMRI) measurements of brain activity over repeated sessions with 95% confidence using a block design of tasks.


METHODS
Fourteen individuals participated in three sessions on different days during which four scans each of a motor task and working memory task were performed. Using a region-of-interest analysis of variance, we calculated the MDC in the volume of activated primary sensorimotor cortex (for motor) and dorsolateral prefrontal cortex (for working memory), as well as the percent increase in MR signal and the center and location of maxima of the activated voxels.


RESULTS
The MDC of activated volume was 5.0-8.8 cm3, and the MDC of percent increase in signal from baseline during tasks was 0.3%-0.6%. The MDC of the center of mass of activity was 3-4 mm, compared to 6-10 mm for the location of maxima.


CONCLUSIONS
fMRI measurements that quantify the strength of activity in response to tasks and centers of mass offer sensitive measurements of change over repeated imaging sessions. fMRI can be used for serial investigations of individual participants using simple motor and cognitive tasks using a simple block design.
Goodyear
Bradley G
BG
Department of Radiology, University of Calgary, Calgary, AB Canada. goodyear@ucalgary.ca
Douglas
Erin A
EA
D000328:Adult; D000465:Algorithms; D001931:Brain Mapping / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D017397:Prefrontal Cortex / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013003:Somatosensory Cortex / Q000502:physiology*