[Eeglablist] Re-Referencing Question

[Thomas Ferree]

There is no question that linking the ears is a bad idea.
It forces the potential at the ears to be equal, which it
otherwise would not be.  This distorts the scalp map in a
way that can not be undone, since the act of linking the
ears actually changes the volume conductor properties of
the head, i.e., introduces a zero-impedance path between
the two points.  It is possible that in some studies this
may be a small effect, e.g., if the scalp map was already
nearly symmetric about the midline, but in general this
is going to effect your data in a way which confounds
attempts at source localization, and can not be undone
with post-processing.

Tom Ferree

-- 

Thomas Ferree, Ph.D.
Dynamic Neuroimaging Lab
Department of Radiology
UC San Francisco

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