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Questions about response times to auditory/visual stimuli

Michael Edelman mje at mich.com
Tue Feb 16 14:13:16 EST 1999



F. Frank LeFever wrote:

> Michael is no doubt correct in saying that most of the delay is farther
> upstream, but the details of his exposition are misleading.
>
> Not sure what he means by saying visual input takes a path "through the
> limbic system"--maybe "as the crow flies" ?? i.e., the main route may
> pass by some limbic landmarks, but it is a non-limbic route on its way
> to the thalamus.
>
> - - - - - - - - - - - - - - - - - - - - - - - - - - -
>
> WAIT--NEVER MIND--JUST RE-READ HIS COMMENT!  Sorry  about that.  Just
> back from several days at INS mtg in Boston and dead tired, not reading
> so carefully.  Obviously, he is talking about route from thalamus to
> amygdala vs. from thalamus to visual cortex.  Well, my "correction"
> which follows (i.e. I'm inserting this after writing that) is not a
> correction but simply an elaboration of his point.
>

Yeah, but my post was unclear. Point taken.

> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>
> BOTH visual and auditory "main streams" are relayed from the thalamus,
> to primary visual and auditory cortex; as are all sensory modalities
> except olfaction.  For complexly-determined, context-relevant
> responses, further intracortical relays in parallel streams through
> associative cortex contribute further to the latency of the response.
>
> There are detours and short-cuts, however.  Joseph LeDoux, for example,
> has described a sort of "short-circuit" from the thalamus to the
> amygdala, and from there to motor/behavioral output AND (a separate
> route) to autonomic/physiological output--providing a basis for very
> rapid "reflexive" but learned responses.
>
> (And of course both visual and auditory inputs also have side-road
> routes bypassing the thalamus to superior and inferior colliculi, etc.)
>

I'm still curious regaridng the initial post- that responses to auditory
stimuli take longer than responses to visual. What's the specific data?

-- mike




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