Consciousness

Dag Stenberg dag.stenberg at nospam.helsinki.fi.invalid
Wed Jan 21 11:10:14 EST 2004


In bionet.neuroscience Dag Stenberg <dag.stenberg at nospam.helsinki.fi.invalid> wrote:
> In bionet.neuroscience k p  Collins <kpaulc@[----------]earthlink.net> wrote:
>> How does the brain feed-forward to the
>> retina during dream-sleep?
> 
> I am not sure it does. Efferent connections to the retina are not so well known.
> I'll have to check it up. 

It seems that "A centrifugal visual system (CVS) involving brain
connections to the retina that influence ganglion cell responses has
long been established in birds and there is evidence that such a system
also exists in different mammalian species (Repérant et al. 1989 for
revue, Shütte 1995).
   "These results demonstrate a direct serotonergic retinopetal
projection in the mouse stemming from the dorsal raphe nucleus whereas
in the pigeon a similar projection system relays via retinal projecting
cells in the NIO.
   "...CVS involvement in retinal melatonin synthesis and coordination
of circadian rhythms (rodents) to visual attentional mechanisms related
to enhanced processing of information concerning novel or meaningful
stimuli within the visual field (birds).

The above from Miceli et al., an abstract at
http://www.asso.univ-paris5.fr/ewcbr/Francais/EWCBR2001/Abstracts2001/Abst67.htm

"This indoleamine-accumulating retinopetal pathway may be involved in
retinal melatonin synthesis, coordination of circadian rhythms, and
interocular phenomena." Schutte, in Vis Neurosci. 1995 Nov-Dec; 12(6):
1083-92. 

There is a lot of literature on a CVS in fish. There is an olfactory
projection to the retina in fish. And reptiles have a CVS.

"Centrifugal fibres arising in brain nuclei and passing back to the
retina have been noted sporadically in mammals but with few details and
no ideas about which brain centers they might derive from. Centrifugal
fibers are particularly well developed in the avian retina (Cajal, 1892;
Maturana and Frenck, 1965; Ogden, 1968). A few centrifugal fibres were
described in the monkey retina by Polyak (1941) and later by Honrubia
and Elliot (1970). According to Polyak (1941) the centrifugal fibres in
monkey have varicose, bulbous terminals that end in the inner plexiform
layer close to amacrine cell bodies. In the human retina they have been
followed across the nerve fiber layer into the inner nuclear layer
before disappearing (Honrubia and Elliot, 1968) (see below).
  "Recently, it has been discovered that centrifugal axons arising in
the hypothalamus project to various parts of the brain including the
retina in the macaque monkey. Interestingly these axons contain
histamine (Gastinger et al., 1999).
  Gastinger, M.J., O'Brian, J.J., Larsen, J.N.J. and Marshak, D.W.
(1999) Histamine immunoreactive axons in the macaque retina. Invest.
Ophthal. Vis. Sci. 40, 487-495.

The above citation was from http://webvision.med.utah.edu/fbloops.html

"It is suggested that the projection from the nucleus oculomotorius to
the retina constitutes a link in the multisynaptic efferent pathway from
the visual cortex to the eye, by which the visual cortex can influence
the functioning of the retina." a rat study by Hoogland et al., Neurosci Lett.
1985 May 23; 56(3): 323-8.

On the other hand, a year before, Schnyder and Kunzle had reached a
negative conlcusion: 
"The results yielded no compelling evidence for the existence of a
direct retinopetal pathway in the rat, which is in contrast to a
recently claimed retinal projection originating from the pretectum.
   "This finding is discussed with regard to the possibility that also
in the rat the lateral tegmentum exerts an early influence on visual
input, but at the "higher" collicular level and not at the "original"
retinal one.
   from Schnyder and Kunzle, Exp Brain Res. 1984; 56(3): 502-8.

It seems from my literature search that people after 1987 more or less
gave up finding a relevant and functional retinopetal connection in
mammals, and turned to fish and birds. The Gastinger paper is an exception.

Dag Stenberg








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