afni.nimh.nih.gov

Maegan,

One possibility is that a lot of data variability was not accounted for in the model; thus, the high spatial correlation could lead to a small cluster size threshold. Are you trying to assess the contrast between two conditions? If possible, try 3dttest++ with either '-Clustsim' or '-ETAC', and see if the results are more reasonable.

Another option is to adopt a different reporting approach: [afni.nimh.nih.gov]

Gang