Cortical oscillations

[Ernst Niebur]

   Concerning Jim Bower's remark on the NIPS workshop on cortical
   oscillations:

   Jim says that "the important conclusion of the visual cortex work is
   that the zero phase oscillations occur only on average over a number
   of stimulus trials and therefore are unlikely to serve as the basis
   for 'binding', attention, or awareness".

   This statement might be misunderstood. This was NOT the conclusion of
   the workshop but the result of Matt's and Jim's modeling work. In
   fact, this was one of the most discussed points during the workshop.
   At present, clear experimental evidence in favor or against this
   hypothesis is absent.

   Actually, two points all participants agreed upon were that the
   oscillations are present and that they are important for some task.
   Differences persisted concerning what this task might be:

   Some people tend to believe that the 40 Hz oscillations somehow serve
   as a fundamental mechanism during information processing, like a
   synchronizing signal. An experiment that clearly shows that phase
   coherence over long distances ONLY occurs on average would support
   this view, but this experiment has yet to be done.

   Other people believe that 40 Hz cortical oscillations do have
   something to do with attention or awareness or "higher order tasks".
   There is some experimental support which shows that oscillations might
    be NECESSARY for this kind of task; in fact, it is known for many
   years that 40 Hz oscillations in the EEG are related to different
   "higher order tasks". One example presented at the workshop is
   clinical work by Dierk Schwender who showed that 40 Hz oscillations in
   the EEG under anesthesia are strongly correlated with the development
   of hallucinations, dreams and with later conscious recall of events
   during surgery.  Obviously, this does not prove that the presence of
   oscillations is also SUFFICIENT for "higher order tasks", but it makes
   this an attractive hypothesis which seems worthwhile to be looked at
   in more detail.

   Eventually, the question will have to be decided experimentally. The
   danger I see is a segregation of "believers" and "non-believers" who
   become somehow blind to the arguments of the "opponents". I think we
   should avoid this.

   Ernst Niebur
   ernst at descartes.cns.caltech.edu