On Fri, 2 Aug 2002, Thalamus wrote:
> There are TWO pathways from the retina (motion/direction vs shape/colour),
> so it would take excessive place to have a feedback-mechanism from the
> Occipital lobe.
Space could be found, if required. But you're right - it would have to
'justify' its presence somehow - perhaps as an evolutionary relic, or by
doing something important.
> And why should there BE any feedback anyway from the Occipital lobe ?
Why not - the majority (I recall 80%) of inputs to the LGN are from V1,
and I believe the majority of inputs to V1 are from higher visual areas.
There are plenty of reciprocal connections in the retina. So if there is
no back projection to the retina, then this might come as something of a
surprise. However, I'm sure I 'remember' that retinal processing cannot be
influenced directly by cortical processing.
Burt - textbook of Neuroanatomy, pg. 239
> There are already a feedback-mechanism, when referring to the pupillary
> constriction/dilation (via the cilliary ganglion) and it is mediated in the
> Pretectum, not the Occipital lobe.
But these nerves innervate skeletal muscle and mediate accommodation and
light-sensitivity - they do not project to the retina, as far as I'm
aware.
Thanks,
Kit
>> Brian
>> "C.J.L. Wolf" <C.J.L.Wolf at ncl.ac.uk> skrev i melding
> news:Pine.SOL.4.21.0208021630440.15544-100000 at aidan.ncl.ac.uk...> > I'm looking for a reference to the effect that there are no
> > back-projections to the retina - which I think I recall from UG
> > courses.
> >
> > Many thanks,
> >
> > Kit Wolf
>>>
