In a recent paper, Pritchard, Krieble, and Duke
(Psychophysiology, 33, 362–368,
1996) studied the validity of spatial embedding of electroencephalographic
(EEG) data and rejected this method in favor of time-delay
embedding. The present paper describes the nonlinear characterization
of brain dynamics using either spatial or time-delay embedding.
We discuss the arguments published in Pritchard et al.
(1996) and demonstrate that the spatial embedding cannot
be rejected on this basis. We also point out the limitations
of both spatial and time-delay embeddings related to the
spatial extension and the high-dimensional dynamics of
brain activity.
