Brain Atlases and Brain Templates
The success of a brain atlas depends upon how well the
brains of different anatomies can be matched to the representation
of anatomy in the atlas. Although the atlas of Talairach
and Tournoux has become a universal standard framework for
reporting neuroscientific studies, it does not provide a complete
representation of the human brain anatomy. The ICBM population-
based atlases are constructed by averaging a relatively
large number of brain MRI scans that are transformed into the
Talairach coordinates. Since the low-dimensional Talairach
transformation cannot capture the high-dimensional variability
of the brain anatomy, the standard MNI and ICBM atlases are
representatives of the average brain size and shape, and the cortical
structures are quite vague and blurred in these atlases due
to the effect of low-pass filtering in the averaging process. In
practice, the MNI and ICBM templates and the Talairach brain
atlas are being used as standard frameworks in many functional
neuroimage analysis studies. However, when researchers try
to achieve an accurate functional localization, even through a
tedious manual anatomical labeling and interpretation, by overlaying
functional data onto the Talairach atlas, the inaccuracy
of the registration steps and even the slight differences between
standard templates and the Talairach atlas pose serious limiting
factors.