Re: Coherent brain oscillations

[Andrew Neher <anneher@CABRILLO.CC.CA.US>]

I would add to what Gary Goldgerg said only that another theorist who makes much of this 40 Hz frequency, and its potential role in the binding process, is Francis Crick (in The Astonishing Hypothesis).

Now I have a (distantly related) question of my own.  Someone mentioned the sensitivity of the alpha rhythm to stimuli in its range (8-13 Hz); this is called photic driving.  I did the first work on auditory driving years ago.  It has been replicated, and






 now Mickey Hart, the Grateful Dead drummer (!) wants to fund research to pinpoint the specific brain areas involved.  For example, the tonotopic cortex lies predominantly within the Sylvian fissure, and the theta rhythm that is recruited may involve the 






limbic system, parts of which have a similar rhythm as well as being geographically near the tonotopic cortex.  This might account for the altered states of consciousness reported.  Auditory driving may even constitute a laboratory model of temporal lobe 






epilepsy.  At any rate, such subcortical responses are likely to be difficult to pick up with cortical imaging alone.  In which case, what imaging techniques might tease out a subcortical rhythmic response?  Mickey Hart's chie!
f
interest, of course, is how auditory driving might explain responses observed in drum ceremonies around the world; ethnographic reports indicate that the most effective rhythm lies in the 4-8 Hz range, which is encouraging.  (This, of course, lies outside






 the focus of this group.)

Gary Goldberg MD wrote:

> Without getting into a lot of detail, there is accumulating evidence to suggest that cortical electric field oscillations in the 40-Hz range arise out of thalamocortical interactions (see work by Steriade, Singer, Llinas and others) and may be important






 as a means of synchronizing activity in neurons within distributed networks. It has also been proposed as a mechanism for the operation of attentional modulation of cortical activity and for dealing with the 'binding problem'--i.e. how a unified percept 






emerges from neurons that are activated by the separately-analyzed features of a particular real-world object (e.g. for visual percepts, the fact that an object will activate different groups of neurons is spatially separate color, shape and motion maps (






to name a few only) in the cortex). The question remains as to what extent these intrinsic rhythms based on thalamocortical interaction may be: 1. responsive to stimuli whose properties may oscillate at or near the intrinsic r!
hythms?
> and 2. neuroactive chemicals which may alter wakefulness and arousal? The former question relates to the issue of steady state cortical evoked potentials, while the second relates to the issue of physiologic response to anesthetic agents.
> --GG
>
> > As other people hav not respected Dr. Goldberg's request
> > for personal replies, I am posting a part of my reply to
> > him as it may provoke some discussion:
> >
> > The intriguing aspect of the brain macro oscillations is
> > that they are continually being related to brain
> > function and cognitive activity. But on the other hand
> > brain function is increasingly associated with a
> > dispersed parallel distribution of functional elements.
> > It is likely that huge numbers of neurons are involved
> > in such dispersed functional activity. If the macro
> > oscillations can be so easily influenced by external
> > intervention, how can they be related to the subtleties
> > of content and of temporal variability and timing of
> > cognition? Macro oscillations must be a manifestation of
> > lower order events. John Shaw
> >
> >-------------------------------------
> >Name: John C Shaw
> >E-mail: crosley@tcp.co.uk
> >Date: 03/13/98
> >Time: 05:57:47
> >
> >This message was sent by Chameleon
> >-------------------------------------