Correlational vs. Differential Tractography

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Cristina A. F. Román

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Dec 16, 2021, 12:44:48 PM12/16/21
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Hi DSI Studio Community,

I was hoping you could expound on the difference between correlational vs. differential tractography, outside of the fact that one runs regression and the other runs a group/time difference. Basically, I am wondering if differential tractography is the same as connectometry except that you are comparing groups (rather than running a regression). In the past, I dummy coded two group to look at differences using the regular connectometry pipeline, but now should I just use differential tractography? 

Thanks!
Cristina

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Frank Yeh

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Dec 16, 2021, 1:21:03 PM12/16/21
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Hi Cristina,

    Thanks for bringing this up. The terms are indeed confusing for most people.

    Correlational tractography (cT) is "tracking the correlation", where the correlation is calculated from a regression model. Thus it assumes a group of the population, and there is a regression analysis correlating dMRI metrics (Y) with a study variable (scalar or categorical, the X).

    Connectometry is the statistical method (or framework) that calculates the significance value for cT. The framework uses bootstrap resampling and permutation test to derive FDR as the significance measure.

    Differential tractography (dT) is "tracking the differences," where the differences are derived by comparing either subject-to-subject or subject-to-template data. It assumes one-on-one comparison. The "one" can be a subject's data or a group average.

    The statical method (framework) for dT is the "sham setting" approach mentioned in the dT paper (Yeh 2019). It relies on experiment design to get FDR from a group of subjects/scans.

    Both cT and dT can be applicable to most studies, but they aim at answering questions from two different aspects. cT is from group-wise perspectives, whereas dT is from subject perspectives. For diseases that often lead to pathology at the same location, cT may be more useful. In comparison, for diseases that often have different lesion locations, dT may be more useful.

    There are youtube videos at https://www.youtube.com/c/FrankYeh/videos showing each of the approaches.

Best,
Frank

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Cristina A. F. Roman

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Jan 10, 2022, 11:37:43 PM1/10/22
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Thank you for your response, Frank. 

From your response, it seems that if I have two groups I want to compare and covariates to account for, then I should be using group connectometry rather than differential tractography, correct? 

If this is the case, and I dummy code my groups as 1 and -1, how do you interpret the positive and negative correlation results? 

Frank Yeh

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Jan 11, 2022, 12:30:50 AM1/11/22
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positive correlation: integrity increases in group 1
negative correlation integrity decrease in group 1
Frank

Cristina A. F. Román

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Jan 11, 2022, 12:38:25 AM1/11/22
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Got it, and when you say “group 1,” that’s compared to group -1,correct? 

Thanks so much, Frank! 
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Cristina A. F. Román, Ph.D. 

National MS Society Fellow

Neuropsychology and Neuroscience Lab

Kessler Foundation 


Affiliation: Assistant Professor (Research), Department of Physical Medicine & Rehabilitation and of Neurology, Rutgers New Jersey Medical School

1199 Pleasant Valley Way

West Orange, NJ 07052

P. 973.965.6637
Twitter: @CristinaAFRoman
pronouns: she/her(s)/ella

“We cannot seek achievement for ourselves and forget about progress and prosperity for our

community…Our ambitions must be broad enough to include the aspirations and needs of others,

for their sakes and for our own.”

-César Chávez


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Frank Yeh

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Jan 11, 2022, 12:47:26 AM1/11/22
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Yes.
Frank

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Cristina A. F. Román, Ph.D. 

National MS Society Fellow

Neuropsychology and Neuroscience Lab

Kessler Foundation 


Affiliation: Assistant Professor (Research), Department of Physical Medicine & Rehabilitation and of Neurology, Rutgers New Jersey Medical School

1199 Pleasant Valley Way

West Orange, NJ 07052

P. 973.965.6637
Twitter: @CristinaAFRoman
pronouns: she/her(s)/ella

“We cannot seek achievement for ourselves and forget about progress and prosperity for our

community…Our ambitions must be broad enough to include the aspirations and needs of others,

for their sakes and for our own.”

-César Chávez


________________________________

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