Questions Regarding Correlation Tractography Methodology

[taravat rasooli]

Dear Dr. Yeh,

I hope this message finds you well. I would greatly appreciate your valuable advice on the following points related to our analysis.

We aimed to compare the Hoffman pathway between two groups using correlation tractography. We created masks for each tract of the Hoffman pathway. For example, to generate the mask of the arcuate fasciculus, we defined Wernicke’s area and Broca’s area as ROIs. The tractography parameters were as follows: number of tracts = 10,000; minimum length = 20 mm; maximum length = 300 mm; step size = 1 mm; and all other parameters were kept at their default values. After performing tract reconstruction, we identified the arcuate fasciculus in the tract list and converted it into a tract-to-mask file. Each tract mask was then uploaded as a study region for correlation tractography analysis.

We also performed independent t-tests between the two groups for each tract, and the results were consistent with those obtained from correlation tractography.

I would appreciate your advice on the following questions:

1. Does this overall approach sound methodologically valid for correlation tractography?

2. If yes, when performing correlation tractography, should the tract masks be set as seeds or as ROIs (study regions)?

3. We obtained significant results with 4,000 permutations. Would you recommend increasing the number of permutations to 8,000, or is 4,000 sufficient when the results are already significant and stable?

Thank you very much for your time and guidance.

Best regards,

Taravat Rasooli

[Frank Yeh]

>
> Does this overall approach sound methodologically valid for correlation tractography?

Yes

>
> If yes, when performing correlation tractography, should the tract masks be set as seeds or as ROIs (study regions)?

ROI

>
> We obtained significant results with 4,000 permutations. Would you recommend increasing the number of permutations to 8,000, or is 4,000 sufficient when the results are already significant and stable?
>

I would increase the permutation count by 1,000 at a time and see the
results. If the results become stabilized, then use that value.

Best regards,
Frank

> Thank you very much for your time and guidance.
>
> Best regards,
> Taravat Rasooli
>

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