Re: [Freesurfer] Hemodynamic Lag Shift

not sure what you are trying to do. can you send a picture? the default lag is TR/2

On 3/29/18 2:30 PM, Sarah Cole wrote:

Thanks, Doug.

I added (-4s) delay and plotted the data but I got the same delay as no shift. Also I did (+4) delay and lost most of the activation.

Do you have any recommendations?

Thanks, Sarah

On Wed, Mar 28, 2018 at 4:39 PM, Douglas N. Greve <dgreve@mgh.harvard.edu mailto:dgreve@mgh.harvard.edu> wrote:

You can use the -delay flag in mkanalysis-sess

doug


On 03/28/2018 05:35 PM, Sarah Cole wrote:
> Hi Doug,
>
> I have a block design experiment. After analyzing the data and
> plotting the response magnitude across the TRs, we see that
there is a
> systematic lag in the response. For example, in a 16s block (TR=2s),
> at TR-1 and TR-2 the response goes down and then starts rising from
> TR-3. This is consistent across the subjects and blocks.
>
> We used to shift our raw data by 2 TRs when we were using SPM.
>
> How can we do this in FreeSurfer?
>
> Thank you,
>
> Sarah
>
>
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