Connectionists: Physics and Psychology (and the C-word)

[james bower]

Hi Barak,

Yes, was trying to be funny I suppose.  Didn’t mean to imply at all that the mammalian arrangement didn’t make sense or vice versa.  Aquatic animals also live in a space with lower photon flux.

The fact that the neuronal structure of the retina itself is remarkably similar, but the entire structure is flipped, I think makes the point even more strongly that evolution found the same neuronal solution in two sets of animals independently.

But thanks - isn’t biology remarkable.

Jim



On Jan 30, 2014, at 3:52 AM, Barak A. Pearlmutter <barak at cs.nuim.ie> wrote:

> Jim,
> 
> As a pure aside...
> 
>> ... accept (sic) that the Cepholapod retina is pointed in the “right”
>> direction - i.e. towards the light source ...
> 
> I think this is a bit of a "myth of science".  It is true that the
> mammalian retina has the circuitry and blood vessels between the lens
> and the photoreceptors, while the cepholapod retina has them the other
> way around.  But the conclusion that this is a design flaw in the
> mammalian eye is not quite so clear.  There are four advantages that I
> know of to putting the photoreceptors behind the circuitry.
> 
> (1) If the back of the eyeball is reflective (as in a cat) light gets
> two chances to be caught by a photoreceptor.  Resolution when doing this
> is degraded if the photoreceptors are moved away from the reflective
> surface.
> 
> (2) It is easier to keep the sheet of photoreceptors smooth.
> 
> (3) If blood vessels are between the eyeball and the photoreceptors, the
> heartbeat can make the photoreceptors wiggle.
> 
> (4) The photoreceptors are very metabolically demanding, and can be
> easier to maintain (nourish, clear toxic wastes) from the eyeball.
> 
> 					--Barak.
> --
> Barak A. Pearlmutter
> Hamilton Institute & Dept Comp Sci, NUI Maynooth, Co. Kildare, Ireland
> http://www.bcl.hamilton.ie/~barak/

 

 

Dr. James M. Bower Ph.D.

Professor of Computational Neurobiology

Barshop Institute for Longevity and Aging Studies.

15355 Lambda Drive

University of Texas Health Science Center 

San Antonio, Texas  78245

 

Phone:  210 382 0553

Email: bower at uthscsa.edu

Web: http://www.bower-lab.org

twitter: superid101

linkedin: Jim Bower

 

CONFIDENTIAL NOTICE:

The contents of this email and any attachments to it may be privileged or contain privileged and confidential information. This information is only for the viewing or use of the intended recipient. If you have received this e-mail in error or are not the intended recipient, you are hereby notified that any disclosure, copying, distribution or use of, or the taking of any action in reliance upon, any of the information contained in this e-mail, or

any of the attachments to this e-mail, is strictly prohibited and that this e-mail and all of the attachments to this e-mail, if any, must be

immediately returned to the sender or destroyed and, in either case, this e-mail and all attachments to this e-mail must be immediately deleted from your computer without making any copies hereof and any and all hard copies made must be destroyed. If you have received this e-mail in error, please notify the sender by e-mail immediately.

 


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.srv.cs.cmu.edu/pipermail/connectionists/attachments/20140130/bac643aa/attachment.html>