Perirhinal Cortex

Author: Jean Augustinack

Perirhinal cortex (area 35) is located in the parahippocampal gyrus. Perirhinal area 35 usually sits on the medial bank of the collateral sulcus but also on the lateral bank of the rhinal sulcus anteriorly, if the rhinal sulcus is present. Using high-resolution ex vivo imaging, we mapped perirhinal cortex (area 35) onto a surface template. Two different resolutions were collected 1) a "standard" 1 mm isotropic scan and 2) a high resolution 100 um isotropic scan. The high resolution scan showed architectural features (lamina and boundaries) while the standard 1mm scan provided the surface template that works with FreeSurfer. This perirhinal label was validated with histological staining and thus cytoarchitecturally-defined for perirhinal cortex (Brodmann's area 35).

Reference for Perirhinal cortex, Cytoarchitecturally-defined labels:

Augustinack JC et al, Predicting the location of human perirhinal cortex, Brodmann's area 35, from MRI, Neuroimage 2013 Jan 1;64:32-42.

Where to find the perirhinal (cytoarchitectural-defined) labels in FreeSurfer

Right and left labels for perirhinal are available in freesurfer 5.3 and 6.0+.

The labels are in freesurfer surface space and located in subjects dir:

subj/label/?h.perirhinal_exvivo.label

They are generated by default by:

recon-all -all

but can be regenerated with:

recon-all -ba-labels

In freeview, after loading a surface, the label can be viewed either by loading the Annotation file:

subj/label/?h.BA_exvivo.annot

or by loading the Label file:

subj/label/?h.perirhinal_exvivo.label

(which allows selection of 'Heat Scale' viewing mode to display the probability mapping), or by loading the Label file:

subj/label/?h.perirhinal_exvivo.thresh.label

which is a thresholded version, more suitable as an ROI.

Stats on this label are found in:

subj/stats/?h.BA_exvivo.stats