Re: Coherent brain oscillations

[Gary Goldberg MD <goldberg@VM.TEMPLE.EDU>]

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 rhythms? 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
>
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