Hi Amanda, This statement refers to the average spacing of vertices e.g. along the midthickness. Multiple voxels will almost always contribute to a give vertex’s input because of partial volume effects. It is true that in ribbon mapping we intentionally collapse across the cortical thickness. If one is interested in studying laminar fMRI, CIFTI can be expanded to allow this.
Peace, Matt. From: <[email protected]<mailto:[email protected]>> on behalf of Amanda Mejia <[email protected]<mailto:[email protected]>> Date: Tuesday, April 17, 2018 at 9:11 AM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: [HCP-Users] cortical surface vertex spacing in 32K In the HCP FAQ and several HCP-related publications (e.g., A Multi-modal Parcellation of Human Cerebral Cortex by Glasser et al.), there is a statement about the surface vertices in 32K resolution and the 2mm isotropic voxels being on a "similar scale". The aforementioned paper further states that the average cortical vertex spacing is 2mm. If I'm reading this correctly, this would imply that the average distance in two dimensions between each vertex is similar to the distance between two 2mm voxels in a *single* layer. This would seem to imply that since the cortical ribbon in volumetric space is several voxels thick, each vertex would be equivalent to multiple voxels. But this isn't consistent with the fact that there are a similar number of cortical gray matter 2mm voxels and cortical surface vertices (~60,000 across both hemispheres). It would seem to me that the only way to keep the number of locations the same, while transforming the data from multiple layers (of voxels) to a single layer (of vertices) would be to make the vertices closer together than 2mm. Can someone please clarify? Amanda -- AMANDA F MEJIA, PhD Assistant Professor Department of Statistics Indiana University Bloomington https://mandymejia.wordpress.com/ _______________________________________________ HCP-Users mailing list [email protected]<mailto:[email protected]> http://lists.humanconnectome.org/mailman/listinfo/hcp-users _______________________________________________ HCP-Users mailing list [email protected] http://lists.humanconnectome.org/mailman/listinfo/hcp-users
