Hi,

I´ve followed with interest the discussion about the "standarness" of the
Talairach and think that there are two important points about the work by
Talairach (back in the ´60, don´t forget that) that have been forgotten.

One is the choice of the AC and PC as the key reference points for
localization. These points were chosen after tedious and painstaking work
of dissecting long series of brains and realizing that these two points are
among the most unvarying in location within the brain and more importantly,
the distance between the two is invariant with regards to brain depth and
length (the only measurements that they were able to get from
pneumoencephalography).

The other important (but left behind) issue about the Talairach Atlas is
the grid system. I mean the tessellation of the brain into the 1,056 cells.
The first major division yields 6 different regions on each hemisphere,
three below and three above the AC-PC plane: anterior to AC, between AC and
PC, and behind PC. A second division of those six hemispheric regions into
grid cells originates the 1,056 cells. It´s precisely on those cells where
the homology is grounded. You are most likely to find the same gyrus or the
same brain nuclei in the same grid cell, despite the dimensions of that
cell logically vary across subjects. Talairach stated that very clearly in
his introduction: don´t pay attention to the mm coordinates but to the
cells. If you follow the Talairach subdivision of the brain, your grid
cells are homologous subsections across subjects. The beauty of it is that
the brain size and shape (proportions) remain untouched, yet the grid cells
locate the same structures labelled in the Atlas. Your resolution is then
limited by the size of the cells (about 1.5 to 3 cc) which is fair enough
for some structures and very accurate for major lobes.

Part of the reputation and popularity of the Talairach Atlas comes from its
use for neurosurgery (the original use of the Atlas in the '60). With the
help of the Atlas neurosurgeons are able to locate very tiny nucleus in the
brain, and believe it, it works!

Just my 2 cents...

Regards,

Santiago

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  `·.¸¸.·´¯`·.¸.·´¯`·...¸><((((º>`·.¸¸.·´¯`·.¸.·´¯`·...¸><((((º>`·.¸¸.·´
Santiago Reig, PhD.
    Gregorio Maranon Hospital, Universidad Complutense de Madrid
    Experimental Surgery and Medicine Lab
    Dr. Esquerdo 46, 28007 Madrid, SPAIN
                Fax# 34 91 426 5108, Ph# 34 91 426 5067
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