Dear experts,
We are struggling in interpreting what is the nature of the 'fitted
responses' generated by SPM2 in the following experiments. Any input
would be greatly appreciated.
We have obtained serial fMRI scans with 1 condition (A) [and rest] over
a period of 20 months. We then performed a Multiple regression analysis
to investigate the effects of several clinical parameters on A response
using 4 covariates including 1) each participant’s clinical rating at
time of scan; 2) time in weeks since first scan (TIME). Individual
participant’s f-maps were entered into this analysis.
We identified significant increases and decreases with each
co-variate. We later explored the Relationship between the response to
condition A in the right insula and time since first scan in weeks.
Figure (attached) represent the linear relationship of the parameter
estimates of condition A-induced activations over time. This responses
was extracted from the right insula.
Question: What does this 'response' (y axis) truly represent? is it a
parameter estimate (and thus what unit) ? Is it a relative signal
change in BOLD from baseline?
Thank you
z
Ziad Nahas, MD, MSCR
Associate Professor
Director, Mood Disorder Program
Medical Director, Brain Stimulation Laboratory
Medical University of South Carolina
Institute of Psychiatry
67 President Street, room 502 North
Charleston, SC 29403 USA
phone: 1 (843) 792 5710; fax: 1 (843) 792 5702
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