Hi Prerona,

That would be the case if every stimulus onset (and duration) were a multiple of the TR. It is usually not the case.

This would be true if TR=2s, for example, and all of the onsets in the stimulus timing file that is provided to afni_proc.py/3dDeconvolve are multiples of 2.
It can be verified on the command line using timing_tool.py using -show_tr_stats, e.g.

cd AFNI_data6/FT_analysis/FT
timing_tool.py -multi_timing AV*.txt -tr 2.0 -show_tr_stats

or

cd AFNI_demos/AFNI_pamenc/AFNI_02_pamenc/sub-10506/timing
timing_tool.py -multi_timing times*.txt -tr 2.0 -show_tr_stats

Each of those examples just happens to have TR=2s, but that does not need to be the case.

Also, this just verifies the onsets. But for PPI, one would want each stimulus duration to be a multiple of the TR as well.
If either of those is not the case, it is probably better to oversample the timing.

- rick