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Dear FreeSurfer Developers,

I was examining the perirhinal regions from BA_exvivo_thresh.stats when I noted a significant discrepancy between the left and right hemispheres, particularly obvious on the perirhinal volumes. On a set of 166 older adults, I found the following discrepancy:

Left Mean (SD) Left Range Right Mean (SD) Right Range Volume 1694.01 (473.09) 872–3087 943.80 (244.34) 514–1638 Thickness 2.83 (0.27) 2.18 - 3.72 2.98 (0.31) 2.25 - 3.76 Surface Area 492.47 (83.31) 329 - 703 259.76 (38.55) 170 - 357

As you can see the mean and range are almost double that of the right for volume and surface area, though thickness seems relatively unaffected. I have included my colleague who looked at one participant with the most extreme asymmetry and found the following, where it looks like the entorhinal cortex is overlapping the perirhinal. Attached is a screen shot.

I am using this for my dissertation due in a month and would love to know if this is a bug that could be resolved.

Thank you for your time!

Best. Rachel

[UF] Rachel Schade Doctoral Candidate Public Health & Health Professions | Clinical & Health Psychology University of Florida rschade1@ufl.edumailto:rschade1@ufl.edu