Dolphins etc.

Joe Joseph_Pullara at Maillink.berkeley.edu
Thu Jul 28 14:31:52 EST 1994


In article <316ru6$bca at news.cc.oberlin.edu>
ssl7091 at ocvaxa.cc.oberlin.edu (We have met the enemy, and they are
illiterate.) writes:

>  From what I understand about split-
> brained humans, no one suggest that one OR the other hemisphere was
> active at once; indeed, at least in Sperry's and Sperry-type tests, it's
> obvious that the two hemispheres are active simultaneously.  In dolphins,
> the suggestion is that they use one OR the other side at any given time
> (I don't know if it's known/hypothesized if the other side of the brain
> is asleep or in some other state),

It is true that humans, spit brained or not, have one hemisphere which
is dominant at any one time.  I assume this is true in dolphins as
well, though perhaps to a greater degree.  I would be extremely
suprised if they completely shut down one hemisphere; ever. I think the
original post refered to an article stating that each hemiphere
alternately showed delta wave activity (indicitave of slow wave sleep).
 I assume that this was only occurring during part of a 24 hour period.
 The suggestion was that perhaps this is how they sleep, one half of
the brain at a time, since breathing in cetaceans requires
consciousness. This would make sense. I know that for some time it's
been thought that cetaceans only sleep in brief "catnaps" of 10 minutes
or so between breaths.

All of this raises lots of interesting questions. Would each hemisphere
alternate some equivalent of REM sleep? In humans and other terrestrial
mammals it seems to be REM sleep that's necessary. Is this true in
cetaceans as well?

Of course we still don't really know why any animal must sleep at all.
Lots of interesting theories but no answers.

> so that a great degree of circuitry
> would have to be duplicated , present in both hemispheres, and thus in
> essence they would/do have two brains, of which they alternate use.

Oh NO the dolphin with two brains!

Hmmm. Duplicate circuity.  IMO not likely based on current
understanding of neuroscience or even basic evolution.  Why would this
evolve? What advantage would it give? A lot of energy would be put into
something not needed. Kind of reminds me of the myth that we only use
10% of our brains. (no flame intended, really, just think about it)

Split brain researchers have often said that humans do in fact have 2
brains. In this context it makes sense - a division of labor so to
speak - but both are needed and both are used. I supsect it the same in
dolpnins.

>I just heard, read, and noted these ideas... 

I'm glad you did. It's an interesting topic.:-)

- Joe Pullara
  




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