Hi all,
I was hoping to gain insight regarding two questions associated with the use of FreeSurfer's aseg (Fischl, Neuron 2002):
1. I have been using aseg to assess volumetric differences across populations. For one of our individuals a portion of the right hemisphere was not fully collected. The entirety of the subcortical structures we are interested in were collected (I've attached an image to this message, not sure if images propagate to the list...). Will the lack of whole-brain coverage bias the segmentation for the hemisphere that was not fully collected? I'm assuming that the fully covered hemisphere's data will be ok.
2. Regarding the "ventral diencephalon" region that is segmented using aseg, is there a 'gold standard' citation that describes what anatomical structures are included in this region? Previously on the FreeSurfer list serve there was mention from Anderson Winkler that the VD includes "The region defined as ventral diencephalon is very heterogeneous and I would not classify it either as GM or WM, as it includes mamillary bodies, tuber cinereum/infundibulum (but not hypophysis), some hypothalamic nuclei near the lateral and inferior walls of the 3rd ventricle and sometimes fragments of the optic tracts (but not chiasm, which has its own label). It also includes parts of the mesencephalon (e.g. part of the cerebral crux, part of the substantia nigra and rubra)", but no citation was given. In Glahn et al. (Biological Psychiatry 2012 71, 6-14) it is stated that the VD mostly includes the hypothalamus, but again, as far as I can tell, a citation is not offered.
Any help would be appreciated, thank you,
Matthew
