Carryover effects alter fMRI statistical analysis in an acupuncture study
Journal
American Journal of Chinese Medicine
Journal Volume
36
Journal Issue
1
Pages
55-70
Date Issued
2008
Author(s)
Abstract
Carryover effects can contaminate ON/OFF BOLD contrasts designated in an fMRI experiment. Yet, the ON/OFF contrasts are essential to facilitate statistical analysis based on the significance of contrast levels. Here, we conducted an fMRI experiment with acupuncture stimulation applied on ST42 acupoint as well as with tactile stimulation on its skin surface. Experiment consisted of three two-block acupuncture and one two-block tactile fMRI runs. Each block started with 26-sec OFF period followed by either 26-sec needle manipulation in the acupuncture runs or by scratching skin surface with sand paper in the tactile. To test if carryover effects could alter the BOLD contrasts, we analyzed different portions of fMRI data using GLM method. Our results showed analyses on different portions of acupuncture fMRI data gave significantly different results. Statistical parametric maps of group random effects resulted from the analysis on the very first fMRI trial formed the broadest coverage of the active brain areas. BOLD model time course also best explained the adjusted raw time course at peak active voxel (coefficient of determination = 0.88). Analyses on other portions of fMRI data only selected subset of the active brain areas delineated by the analysis on the very first data trial and the BOLD model only mildly accounted for the adjusted raw time courses. In tactile runs, results were more consistent across analyses. Therefore, in fMRI experiments with strong carryover effects, a single-block experimental design with multiple repetitions, separated by long enough periods of time, should be more suitable to extract task BOLD effects. ? 2008 World Scientific Publishing Company & Institute for Advanced Research in Asian Science and Medicine.
Subjects
BOLD; Carryover Effects; Contrast-Based Statistics; fMRI, Acupuncture; GLM; Single-Block; Tactile
SDGs
Other Subjects
acupuncture; adult; article; blood oxygenation; brain region; contrast enhancement; controlled study; data analysis; female; functional magnetic resonance imaging; human; human experiment; image analysis; male; normal human; patient positioning; sensory evaluation; signal noise ratio; signal processing; skin surface; statistical analysis; statistical model; tactile stimulation; time; volunteer; Acupuncture; Acupuncture Points; Acupuncture Therapy; Adult; Brain; Brain Mapping; Female; Humans; Magnetic Resonance Imaging; Male; Needles; Oxygen; Reference Values; Sensation
Type
journal article