Message Number: SG17265 | New FHL Archives SearchFrom: sukiec@optonline.net
Date: Tue, 2 May 2006 18:59:34 +0100 (BST)
To: ferrethealth@smartgroups.com
Subject: [ferrethealth] RE: new study abstracts (my questions asked on influenza,vision definitions, early wild polecat kit care
Author wrote:
> Pam opened my eyes (LOL!) to this new interesting abstract:
> <http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?
> cmd=3DRetrieve&db=3Dpubmed&dopt=3DAbstract&list_uids=3D16647737&query_hl=3D=
3&itool
> =3Dpubmed_docsum>
> > Vision Res. 2006 Apr 27; [Epub ahead of print]
> > Motion perception deficits in albino ferrets (Mustela putorius furo).
> > Hupfeld D, Distler C, Hoffmann KP.
> > Allgemeine Zoologie & Neurobiologie, Ruhr-Universitaet Bochum,
> > Universitaetsstr. 150, ND 7/31, 44780 Bochum, Germany.
> >
> > Albino ferrets contrary to their pigmented conspecifics show no
> > optokinetic nystagmus. Therefore, in this study motion perception
> > was compared between pigmented and albino ferrets (Mustela putorius
> > furo) trained to discriminate between coherently moving random dot
> > patterns and dynamic noise stimuli in a two-alternative forced
> > choice task. Fully coherently versus incoherently moving patterns
> > could be distinguished by ferrets of both phenotypes. Motion
> > coherence thresholds, however, were significantly higher in
> > albinos. These results indicate that albino ferrets are not motion
> > blind as could be expected from their total lack of optokinetic
> > reactions. However, they are severely impaired in global motion
> > perception.
> >
Ah! I found a definition that could be taken up large enough in size when =
seen as an HTML version of the pdf:
http://www.deejayvision.org/PDFs/Z&Zchapter.pdf
START QUOTE
=93Global motion=94, as opposed to =93local motion=94, is the perceived dir=
ection of a =
dynamic input when that direction is the result of a combination of many in=
di- =
vidual motion signals within the stimulus. Although individual local motion=
=
vectors remain visible, if not easily independently discriminable, a single=
overall =
direction of the pattern motion =96 the global motion =96 is also perceived=
. It is a =
matter of definition whether there is really a global percept when all loca=
l signals =
are identical to each other and to the overall percept of motion. As a gene=
ral rule =
one assumes that not all contributing local signals imply movement in that =
same =
global direction when discussing motion in these terms. Furthermore, the di=
stinc- =
tion of global motion as opposed to local motion strongly suggests that dis=
parate =
motion signals are integrated from several locations in order to extract th=
e overall =
direction. =
END QUOTE
So, if I read this right is like seeing the over-all direction of a herd ev=
en when there is also some independent motion going on like when young anim=
als are playing back and forth while the herd is also moving.
So (again, if I read it right) these albino ferrets would be able to pick o=
ut that individual motion exists but would not be able to discern the gener=
al direction of the herd, and they have some trouble discerning overall dir=
ection with individuals, too.
=
=
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