AFNI Message Board

Dear AFNI users-

We are very pleased to announce that the new AFNI Message Board framework is up! Please join us at:

https://discuss.afni.nimh.nih.gov

Existing user accounts have been migrated, so returning users can login by requesting a password reset. New users can create accounts, as well, through a standard account creation process. Please note that these setup emails might initially go to spam folders (esp. for NIH users!), so please check those locations in the beginning.

The current Message Board discussion threads have been migrated to the new framework. The current Message Board will remain visible, but read-only, for a little while.

Sincerely, AFNI HQ

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Gang Chen
December 18, 2003 10:20AM
Theoretically speaking the hemodynamic response from a point stimulus would be the convolution between the time point and the impulse response function, but it seems to me in numerical world what really happens in 'waver' is that a point stimulus is spread out over 0.1 seconds of duration.

Therefore a more revealing comparison than the following one

waver -dt 1.0 -tstim 5:6 -GAM -numout 20 | 1dplot -stdin &
waver -dt 1.0 -tstim 5 -GAM -numout 20 | 1dplot -stdin &

would be this:

waver -dt 1.0 -peak 1 -tstim 5 -GAM -numout 20 > res1
waver -dt 1.0 -peak 1 -tstim 5:5.1 -GAM -numout 20 > res2
1deval -a res2 -expr "10*a" > res3
1dplot -one res1 res3 &

which shows an identical response except numerical errors.

Another comparison would tell the same story:

waver -dt 1.0 -peak 1 -tstim 5:6 -GAM -numout 20 > Oh1
waver -dt 1.0 -peak 1 -tstim 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9 -GAM -numout 20 > Oh2
1deval -a Oh1 -expr "10*a" > Oh3
1dplot -one Oh2 Oh3 &

The '1deval' command is just used to scale up one of the two responses for comparison.

So any point stimulus in 'waver' seems to be numerically implemented with a duration of 0.1 seconds.

Gang
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Subject Author Posted

waver event duration

Luiz Pessoa December 17, 2003 11:39AM

Re: waver event duration

Gang Chen December 17, 2003 02:31PM

Re: waver event duration

bob cox December 17, 2003 02:52PM

Re: waver event duration

Gang Chen December 18, 2003 10:20AM