Please may I ask a few questions about the spm_graph.m routine posted a few
1. When averaging over sessions, the s.e. appears to be really large in
comparison to the magnitude of the fitted response even for highly
significantly activated voxels (see attachment). Needless to say it becomes
smaller when we divide s.e. by the sqrt of the total number of sessions but
there may be a better explanation?
2. When plotting event-related responses averaged over sessions, s.e. is
plotted as several curves, do these correspond to confidence intervals?
3. At fixed time points, e.g. for event-related at t=0 and t=12 s, s.e.
becomes zero. Why?
4. In an event-related study, what does it mean if at t=0 (event onset) the
fitted response happens not to be 0?
Thank you very much for your help!
Rik Vandenberghe, M.D., Ph.D.
Visiting research associate
Cognitive Neurology and Alzheimer's Disease Center
Northwestern University Medical School
320 East Superior Street
Chicago, Illinois 60611
phone: (312) 908-8571
fax: (312) 908-8789