[Neuroscience] Re: Rat (Long Evans) Cerebellar Cortex Size

Kerry via neur-sci%40net.bio.net (by kbrownk from gmail.com)
Sun Nov 2 20:33:05 EST 2008


On Nov 1, 5:42 pm, Matthew Kirkcaldie
<Matthew.Kirkcal... from removeutas.removeedu.au> wrote:
> In article
> <cef08021-a794-4dbf-871e-9367f62e0... from w1g2000prk.googlegroups.com>,
>
>  Kerry <kbro... from gmail.com> wrote:
> > Sorry, I should have been more explicit w/ the given purpose. I am not
> > trying to use this information for any quantitative analysis. For now
> > I am just trying to get an estimation of width (e.g. Euclidean
> > distance from the most extreme sagittal points end to end). However,
> > if I new the volume of the cerebellar cortex I could calculate the
> > convex hull volume of the section I have to get a more exact
> > proportion.
>
> I don't know if a convex hull is really the right way to approach this
> in terms of proportion - the cerebellum is highly involuted, and its
> function is quite clearly arranged in terms of the sheet (parallel
> fibres running in one direction and the dendrite trees of Purkinje cells
> orthogonal to those fibres, contacting tens of thousands of them).
> Really the only meaningful proportion of the cerebellum is the
> proportion of the cortical sheet area, or the proportion of total
> Purkinje cell numbers.
>
> Your parasagittal sections are good, however, because of course the
> folding and involution is mostly at right angles to the sagittal plane.
> A good first-draft approximation of sheet proportion would be to look at
> an unfolded surface and draw lines parallel to the midline. I don't
> think the convex hull is going to help because the depth of infolding
> varies considerably.
>
> > I would guess the total volume is more readily available,
> > but if I could find a picture w/ a scale bar of the cerebellum viewed
> > from the rostral or caudal direction I could get an idea of how much
> > section I have. The latter may be quantitatively meaningless but
> > qualitatively, for those who have knowledge of the cerebellar cortical
> > size and shape, one could infer what proportion of the cortex I am
> > studying. A crude approximation is good enough as I am just trying to
> > provide a cartoon that gives a rough idea (e.g. it is meaningful to
> > say whether I have closer to 1% or 90% of the entire cerebellar
> > cortex).
>
> If you want a dimensionally accurate view of the cerebellum in three
> planes, I'd recommend you to the atlas by Paxinos and Watson, The Rat
> Brain in Stereotaxic Co-ordinates, 6th edition 2007. It's the standard
> reference work on the subject.
>
> If you're not sure how far from the midline your sections were taken,
> the atlas has a parasagittal series at known distances from the midline
> which may allow you to match up your sections. It also had a series
> sectioned in the horizontal plane which should show you the full lateral
> extent of the cerebellum at most levels.
>
> Another major variable to consider is tissue processing and the
> resultant shrinkage. A fixed brain can shrink by up to 15%, and the
> degree of shrinkage varies in white matter and grey matter, making
> things even more complicated!
>
> Sorry for such a fastidious answer, but with a complex three-dimensional
> structure like the cerebellum, back-of-the-envelope approximations are
> often startlingly wrong.
>
> Cheers,
>
> Matthew.
> ** Posted fromhttp://www.teranews.com**

Thanks for the advice. I'll have to take a look around for an
appropriate atlas or pick up the one you mentioned.

Thanks again,
K


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