The third basis function represents the dispersion curve. To confirm this, you can use the following command:
3dDeconvolve -nodata 32 1.0 -num_stimts 1 -polort -1 \
-local_times -x1D stdout: -stim_times 1 '1D: 0' 'SPMG3(2)' \
| 1dplot -thick -one -stdin -xlabel Time -ynames SPMG3
Executing this command generates the following output:
If applicable, you might also consider an alternative and potentially more sensitive approach, which is discussed in detail in this blog post.
Gang