brain antedation (Libet) implications

harkyl kharvey06 at hotmail.com
Sun Mar 16 14:21:37 EST 2003


I have posted this thread at a forum I more frequently visit.  It
brought no reply.  I regret if Libet's brain antedation has been
pounded into oblivion here, but would be obliged for any additional
interpretation or conclusion.  What follows is a brief review of
Libet's findings followed by a conclusion/questions.

There is a separation (in time) of conscious awareness from
electrochemical events in the brain as shown by by Libet et al.

It has been shown that conscious sensation does not occur immediately
as neuronal electrochemical signals reach the cerebral cortex.  When
the signal reaches the cortex, there is an incubation period during
which there is propagation and attenuation of the neuronal
transmission until it reaches the appropriate level before awareness.

This period may be as long as .5s, but the self -conscious mind is
shown to be able to antedate the perception so that it is perceived to
happen up to .5s before the triggering neuronal event.  This process
is called antedation.  The apparent paradox:  "My hand on the oven
coil coincides with the pain I am aware of even though the time it
takes to be aware of my hand burning takes .5s from the time the
signal had reached the cortex".  Keeping in mind that actual neuronal
transmission (long tract nerve fibers) is around .015s from skin to
cerebral cortex as shown by evoked potential (EP):  added to the .5s
of cortical activity before it can be experienced, it should take
.515s before being aware of the pain.  However the event is antedated
by being referred in time to the initial evoked response of the
cortex.  Thus only seeming to take the .015s from long tract fibers to
cortex.

It is agreed that a conscious experience does not 'light up' as soon
as impulses in some sensory pathway reaches the primary somatosensory
areas in the cerebral hemisphere.  But our conscious awareness some
how tricks us into thinking our hand burned coincidently in time with
our awareness of it.  This anomaly seems to strengthen the dual nature
of mind brain.  Perhaps this anomaly is the result of a conceptual
error.  Does it also question Kantian time as a priori valid?

Kyle



More information about the Neur-sci mailing list