[Neuroscience] Re: confusion about cerecellar circuity

Peter H. via neur-sci%40net.bio.net (by pjwholm from yahoo.es)
Sun Feb 28 10:46:34 EST 2010


On 26 feb, 21:57, Kalman Rubinson <k... from earthlink.net> wrote:

> Well, I was talking to Rodolfo Llinas...

Great. Perhaps Prof. Llinas is our man. I wonder whether he might
perhaps be willing to give you a written answer by email and allow you
to post it here. If not, please take good notes.

And above all, please don´t forget that the issue of the presumed deep
nucleus cells is only an interesting side point,  but not at the core
of what really is vexing me. The core of what is vexing me I have
emphasized  in the last paragraph of my second response to you (of
02-25-10, starting with "And this is really the crucial point
here..."). And condensing the issue even more, the most central of my
questions is precisely: How do the Purkinje cell axons get to the deep
nuclei of the cerebellum? Do they go around or through the molecular
layer? (since according to what one can see at Brainmaps, the
molecular layer is *in between* the Purkinje cells and the deep
nuclei)

Now, since the granular cells are supposedly located on the same side
of the molecular layer as are the Purkinje cells, I would of course
also like to know how the Mossy Fibers reach them. But -without the
intention to offend you here- it appears to me that you are not very
familiar with cerebellar circuity. Thus, in order to avoid any further
confusions, when talking to Prof. Llinas I would like you to limit
yourself exclusively to the questions at the end of the last
paragraph. So when you see Prof. Llinas the next time, please keep the
term "PURKINJE CELL AXONS" in your mind constantly (where do they
run?), and please do not talk to him about *anything* else but just
that.

And thanks again

Peter


P.S.: This is a postscript, in order to not distract you from the main
issue as defined above in this post. But as far as those presumed deep
nucleus cells are concerned, I have become aware of various issues
surrounding them.

A) In the bottom hemisphere on 205 we are dealing with a dispersed but
uniformly spherical population of cells, which is visible only on this
slide in this series (e.g. on the right side of the right arm of the
"U", as I wrote in my post of 02-24). And it disperses itself
throughout the entire posterior white matter of this hemisphere.
Surprisingly, this population cannot be detected in the top hemisphere
on this slice.

B) The neuronal population of the deep nuclei is by no means as
homogenous as is this spherical cell population in question: The deep
nuclei contain a rich mixture of elongated, triangular and even y-
shaped neurons.

C) I have looked for this spherical cell population on the slices 0398
to 0276 of the very detailed sagittal Nissl series (280 slides) of
Macaca Mulatta, but couldn´t find it. And setting the scale bar at 184
microns you can´t miss it.

So now I am wondering about whether I might not have been wrong in my
initial assumption, that these cells might be deep nucleus neurons -
even though in my opinion they quite obviously are neurons and not
glia. Could they perhaps be an individual unilateral ideosyncrasy of
the specimen used for these horizontal cuts?

At any rate, this population intrigues me, but it does not vex me. So
please *do not* talk to Prof. Llinas about this spherical cell
population, since it obviously *does not* consist of Purkinje cells.
This is only an interesting side issue related to the connectivity
between the molecular layer and the deep nuclei. And what worries me,
is that in your last conversation with him you already seem to have
gotten on the wrong track. Because when I wrote on 02-26 that "you
should also show them these cells", I only said that because I had an
incling that you confused these spherical cells with Purkinje cells
("many large cells deep to the granular layer" you wrote on 02-25).
So please don´t talk to him about this spherical cell population - but
about what I have said above this postscript.

Peter


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