Applied Maths Seminar: Liley/Frascoli -- Bifurcations and State Changes in the Human Alpha Rhythm

David Liley and Federico Frascoli 
Brain Science Institute, Swinburne University of Technology 

Abstract: Despite many decades investigating scalp recordable 8-13 Hz (alpha)
electroencephalographic activity, no consensus has yet emerged regarding its
physiological origins nor its functional role in cognition.  Here we outline a detailed,
physiologically meaningful, theory for the genesis of this rhythm that may provide
important clues to its functional role.  In particular we find that
electroencephalographically plausible model dynamics, obtained with physiological
admissible parameterisations, reveals a cortex perched on the brink of stability, which,
when perturbed, gives rise to a range of unanticipated complex dynamics that include
40-Hz (gamma) activity.  Preliminary experimental evidence, involving the detection of
weak nonlinearity in resting EEG using an extension of the well-known surrogate data
method, suggests that nonlinear (deterministic) dynamics are more likely to be
associated with weakly damped alpha activity.  Thus rather than the "alpha rhythm" being
an idling rhythm it may be more profitable to conceive it as a readiness rhythm.