Documentation on the Quality check values for the FreeSurfer data

Each left and right hemisphere brain surface was individually examined, with a
tool (developed by Roberto Toro) that allowed easy investigation of the surface.

Codes and their meanings

0: Missing data
1: OK
2: Minor brain surface issues
We detected some small irregularities or defects
in the surface. These irregularities should not affect analyses that  use
data about subcortical structures, or total brain volume and ICV. Most often
the irregularities were located in the prefrontal cortex, and analyses
concerning the thickness, volume or folding of the rest of the cerebral
cortex should not be affected. However, these may affect analyses that 
address the prefrontal cortex, its thickness, volume and folding. In general,
global analyses of the properties of the cerebral cortex may be affected.
3: Major brain surface issues
We detected a major issue in the brain surface.
Part of the meninges were attached to the brain surface, or part of the brain
was missing. Data should probably not used unless you know what you are
doing.