PowerPoint Presentation - Time Series Analysis in AFNI

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Some Features of FMRI Voxel Time Series

• FMRI only measures changes due to neural “activity”

H Baseline level of signal in a voxel means little or nothing about neural activity

H Also, baseline level tends to drift around slowly (100 s time scale or so)

• Therefore, an FMRI experiment must have at least 2 different neural conditions (“tasks” and/or “stimuli”)

H Then statistically test for differences in the MRI signal level between conditions

H Many experiments: one condition is “rest”

• Baseline is modeled separately from activation signals, and baseline model includes “rest” periods