From my understanding qdec fits a glm to each vertex. It also smooths the data.

 

From the documentation I do not have a clear understanding of whether qdec uses smoothed data for input (It appears that is does) or smooths the coefficients or t-tests after analysis, or both.

 

Additionally, the resulting contrast results appear to have patches of significance. What is the processes that makes patches out of individual vertex results? Do a certain number of contiguous vertexes need to be significant for their values to be connected into a patch? 

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Best Wishes,

Richard E. Frye, M.D., Ph.D., F.A.A.P.
Assistant Professor of Pediatrics and Neurology
University of Texas Medical School at Houston
7000 Fannin -- UCT 2478
Houston, TX 77030
Office: 713-500-3245
e-mail: richard.frye@gmail.com