Kalman Rubinson wrote:
>> On Wed, 16 May 2001 05:06:32 GMT, George Hammond
> <ghammond at mediaone.net> wrote:
>> >Kalman Rubinson wrote:
>> >> I am curious what you mean by this.
> >
> >[Hammond]
> >Well, they're both big "X's" sitting nearly congruently one
> >on top of another.. they must be biologically/structurally
> >related. I think there's even a 3rd "X-like" congruent
> >structure connecting the Amagdalyii ventrally to the
> >Thalamii dorsally, no? The fornix connects the Mammilary
> >bodies ventrally to the hippocampii dorsally, of course,
> >in a big X-like structure.
>> Sorry but the proportion of crossing fibers in the fornix is very
> small and characterising it as an "X" (or chiasm) is improper.
> The fornix is basically a direct fiber pathway stretched and bent by
> external forces, a phenomenon easily visualize by comparing fornices
> across verterate species.
[Hammond]
Sorry to have to point out your error. The decussation in the Fornix is
documented and described in my peer reviewed published paper
(online copy) at:
http://people.ne.mediaone.net/ghammond/cart.html
See particularly Section V, paragraph 7, from which the following
quote is taken:
quote from Hammond's peer reviewed paper:
---------------------
A direct examination of the neurocircuitry of this system confirms that
this is the case: The SHS contains a significant decussation. This
decussation takes place in the Papez loop, between the hippocampus and the
mammillary bodies, most of it probably in the supramammillary decussation
but
some of it probably in the body of the fornix or even the septal area.
Swanson and Cowen state: "the dorsal subiculum projects through the
descending column of the fornix to the mammillary complex where its
efferents
end bilaterally" and "The pre- and/or parasubicular input to the mammillary
complex terminates bilaterally in both the medial and lateral mammillary
nuclei," and finally "it is presumably through these...mammillary
projections
that the 'return loop, of the so-called Papez circuit is completed" (Swanson
& Cowen, 1977, pp. 64, 71, and 82). This is irrefutable evidence of a
decussation in the Papez loop. Simply put, the right hippocampus projects
significantly to the left mammillary body, and vice versa for the left
hippocampus.
---------------------
end quote
Note the reference to the "supermammillary decussation" of the
fornix. Full references naturally included at the end of the paper.
Of course, the fornix is basically ipsilaterally double barreled,
however there is a significant (particularly neuropsychologically
significant) decussated component.
>> Kal
--
BE SURE TO VISIT MY WEBSITE, BELOW:
-----------------------------------------------------------
George Hammond, M.S. Physics
Email: ghammond at mediaone.net
Website: http://people.ne.mediaone.net/ghammond/index.html
-----------------------------------------------------------