You are probably interested in the power (ie, "can I detect an effect with this many trials scheduled in this way?"). It is not possible to answer this question without an effect size. Having said that, I generally feel comfortable when the VRF is 20-40. Note that this assumes an FIR (not assuming a shape to the hemodynamic response) and dPSD=TR. If you assume a shape, you will get much more power out of it (assuming your assumed shape is close to correct:).

On 7/16/19 9:51 AM, Tugce Duran wrote:

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Thank you, Dr. Greve! This was helpful.

When we look at the .sum file, what are the reference ranges for Eff and VRF avg?

I saw 20-40 for VRF on the help page but wasn’t fully sure.

Thanks!

Tugce

*Tugce Duran* *Graduate Student, Biomedical Sciences MS Program/ /Neuroscience Concentration | **Section on Gerontology & Geriatric Medicine, WFSM* 2color *Graduate Programs in Biomedical Sciences* 525 Vine Street, Suite 150, Winston-Salem, NC 27101**

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*From:*Greve, Douglas N.,Ph.D. DGREVE@mgh.harvard.edu *Sent:* Monday, July 15, 2019 11:03 PM *To:* Tugce Duran tduran@wakehealth.edu; Freesurfer support list freesurfer@nmr.mgh.harvard.edu *Subject:* Re: optseq2 parameters setup

On 7/15/2019 12:50 PM, Tugce Duran wrote:

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Hi Dr. Greve,

I am interested in designing the Face Name Associative Memory Exam
(FNAME) fMRI task for our study.

There are *80* face-name pairs that we will use and the duration
can be between 3.5 and 4.75 secs.  I have used the following command:

*optseq2 --ntp 200 --tr 2 --psdwin 0 32 2  --ev facename 4 80 
--nkeep 3 --o trial2 --tnullmin 0 --tnullmax 6 --nsearch 10000*

Total scan time appx 6-7 mins.

Q1: For NULL, why do we have only 2 sec and 4 sec jitters? Can we
change the variety amount of the jitters? Are more jitters good or
bad (instead of just having 2 secs and 4 secs, let’s say we get
0.25, 1, 2, 3 and 4 secs) ?

It always makes the NULL durations a integer multiple of the dPSD. You set this to 2 (--psdwin 0 32 2). If you are assuming the shape to the hemodyamic response (eg, the canonical SPM HRF), then it won't matter much if you decrease it to 1 or less). The benefit of jitter in that case depends more on the psychology than the signal processing.

Q2: For the event design I am interested in above, what would be
the “best” parameters used?

Usually, you set the total time for the NULL to be equal to that of a stimulus type. In this case, you have one stimulus type presented for a total of 320 sec (4*80), so you could set the scan duration to be 320*2=640sec=10min 40sec. That would be optimum for testing your stimulus against baseline, but that is probably not what you are planning to do.

*Trial2-001.par:*

*0.0000    1 4.000   1.0000      facename*

*  4.0000 1    4.000   1.0000      facename*

*  8.0000 1    4.000   1.0000      facename*

*12.0000 0    2.000   1.0000          NULL*

*14.0000 1    4.000   1.0000      facename*

*18.0000 1    4.000   1.0000      facename*

*22.0000 1    4.000   1.0000      facename*

*26.0000 1    4.000   1.0000      facename*

*30.0000 1    4.000   1.0000      facename*

*34.0000 1    4.000   1.0000      facename*

*38.0000 1    4.000   1.0000      facename*

*42.0000 0    4.000   1.0000          NULL*

*46.0000 1    4.000   1.0000      facename*

*50.0000 1    4.000   1.0000      facename*

*54.0000 1    4.000   1.0000      facename*

*58.0000 1    4.000   1.0000      facename*

*62.0000 1    4.000   1.0000      facename*

*66.0000 1    4.000   1.0000      facename*

*70.0000 1    4.000   1.0000      facename*

*74.0000 0    2.000   1.0000          NULL*

*76.0000 1    4.000   1.0000      facename*

*80.0000 0    2.000   1.0000          NULL*

*82.0000 1    4.000   1.0000      facename*

*.*

*.*

*.*

*.*

**

*372.0000 0    4.000   1.0000          NULL*

*376.0000 1    4.000   1.0000      facename*

*380.0000 1    4.000   1.0000      facename*

*384.0000 1    4.000   1.0000      facename*

*388.0000 1    4.000   1.0000      facename*

*392.0000 1    4.000   1.0000      facename*

*396.0000 1    4.000   1.0000      facename*

Thank you in advance!

Tugce

*Tugce Duran*
*Graduate Student, Biomedical Sciences MS Program/
/Neuroscience Concentration | Section on Gerontology & Geriatric
Medicine, WFSM*
2color
*Graduate Programs in Biomedical Sciences*
525 Vine Street, Suite 150, Winston-Salem, NC 27101

*(*317-893-9100 *| ****_tduran@wakehealth.edu
<mailto:tduran@wakehealth.edu>_| |Image result for linked
inlinkedin.com/in/tugceduran/ [linkedin.com]
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