Hi Rick: Good to see some action on TIPs.
I have been thinking about related issues for some time. If you look at the back of the eye then there are lots of locations where visual stimulation will not affect the retina. Obviously there is the blind spot. Notice that people don’t experience a blind spot even when one eye is closed (such that the other eye can’t compensate). Similarly, there are blood vessels that block activating photoreceptors all the time but we don’t experience lines in our vision . (And even more interesting is that when we do experience “floaters” then it is detritus that is changing location in out eyes—thus changing the receptors that are affected.) Here is my solution. The important fact is that our eyes are changing gaze locations (through saccades) several times per second. Whenever we change gaze location then that portion of the world is activating a new set of receptors. Sometimes I am looking at one location and a portion of the world is falling on my blind spot and then I change my gaze location and that portion of the world is falling on a set of active receptors. The old stabilized retinal image studies show that the visual system is expecting visual changes when you make a saccade. So here is my answer. The fovea may be functionally shut down in low light but the effect is similar to the blind spot. Eye movements cause the area subtended by the fovea to hit a different world location with subsequent eye movements and such locations will be affecting other parts of the dark-adapted retina. Ken --------------------------------------------------------------------------------------------- Kenneth M. Steele, Ph.D. steel...@appstate.edu <mailto:steel...@appstate.edu> Professor Department of Psychology http://www.psych.appstate.edu <http://www.psych.appstate.edu/> Appalachian State University Boone, NC 28608 USA --------------------------------------------------------------------------------------------- > On Sep 7, 2018, at 2:46 PM, Rick Stevens <stevens.r...@gmail.com> wrote: > > > > > > > TIPS had been quiet lately. A question occurred to me when talking about rod > vs cone functioning. > > When light levels get low, the cones lose function. Since the fovea is 100% > cones, why don't we have a blind spot in the center of our vision in low > light, low enough to lose color, but still enough light to move around in a > dark room. While the blind spots of right and left eyes can be 'filled in' > by information from the other eye, I would think that the foveas would be > aimed at exactly the same spot. > > My first thought would be the memory of looking close to some spot, getting > the information with the rods and remembering it when shifting my gaze to > that spot. I know memory stuff better than physiology stuff, so I thought > that there might be a better or at least a more physio-oriented answer. > > Rick Stevens > School of Behavioral and Social Sciences > University of Louisiana at Monroe > > --- > > You are currently subscribed to tips as: steel...@appstate.edu > <mailto:steel...@appstate.edu>. > > To unsubscribe click here: > http://fsulist.frostburg.edu/u?id=13524.94845a3ed9806f1cef14973830dd8c39&n=T&l=tips&o=52744 > > <http://fsulist.frostburg.edu/u?id=13524.94845a3ed9806f1cef14973830dd8c39&n=T&l=tips&o=52744> > (It may be necessary to cut and paste the above URL if the line is broken) > > or send a blank email to > leave-52744-13524.94845a3ed9806f1cef14973830dd8...@fsulist.frostburg.edu > <mailto:leave-52744-13524.94845a3ed9806f1cef14973830dd8...@fsulist.frostburg.edu> > > > > --- You are currently subscribed to tips as: arch...@mail-archive.com. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=52747 or send a blank email to leave-52747-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
