Apropos #fMRI and comparing brain areas across subjects: variations of 3.5x for brain cortical area V1-3 across 118 human subjects.
"Variability of the Surface Area of the V1, V2, and V3 Maps in a Large Sample of Human Observers"
Benson et al. 2022 https://www.jneurosci.org/content/42/46/8629
HT: @Whatishealth