(no subject)

[anhinga_anhinga]

"Blinking suppresses the neural response to unchanging retinal stimulation."

BBC reports finding made by the Rees Lab at University College London.



"The device, made with fibre optic cable, was placed in the mouths of volunteers who were wearing light proof goggles and lying in a functional magnetic resonance imaging (fMRI) brain scanner.

The optical fibre lit up the eyeballs through the roof of the mouth using a strong light - making the head glow red.

This meant that the light falling on the retina in the eye remained constant even when the participants blinked."



"They found that blinking suppressed brain activity in the visual cortex and other areas of the brain - known as parietal and prefrontal - which are usually activated when people become conscious of visual events or objects in the outside world."



The Rees Lab was trying to figure out why the blinks do not distrurb our feeling of continuity of visual perception.

"A blink lasts for between 100 and 150 milliseconds. We automatically blink 10 to 15 times a minute to moisten and oxygenate the cornea.

During a blink, there is no visual input and no light, but we do not consciously recognise everything has momentarily gone dark."

Comments

[spamsink.livejournal.com]

A related question is how much in the persistence of vision is retinal and how much is neural. With the advent of DLP projectors we have a way to know that within average lighting conditions, the retinal persistence of peripheral vision is negligible. Unless the peripheral cones are morphologically different from the macular ones, we have to assume that it is all neural. The wiring to slow down the persistence decay while the eyes are closed must be very simple.

By the way, on a bright sunny day I can walk with my eyes closed more than 95% of the time. It is enough to "reverse blink" the eyes every 6-7 steps to walk fairly comfortably in an uncrowded street. I can perceive even some sort of motion estimation.

[anhinga-anhinga.livejournal.com]

One would assume it is all neural. (How do the DLP projectors show that?)

> The wiring to slow down the persistence decay while the eyes are closed must be very simple.

Yes, it should be fairly simple; what's interesting is that it also seems quite extensive in its impact. I wonder how detailed are their fMRI pictures...

[spamsink.livejournal.com]

DLP projectors use a rotating (>= 60 rpm) RGB wheel, so that a white field is formed by displaying rapidly alternating red, green, and blue.

Under some conditions (when you turn your head quickly and do not concentrate attention on the screen) you can see a rainbow strip flash at the edge of your field of vision, which means that the 1/180 sec periods of alternating colors were correctly sampled by the retina, but the averaging was not done. That is to say the peripheral motion detection, shape tracking, and the persistence of vision are somewhat interlinked (and mutually exclusive?).

[spamsink.livejournal.com]

I'll tell you more. There was a chapter in the Soviet "Children's Encyclopedia" describing unusual persistence of (black-and-white) vision in children. The children were shown a drawing of a truck on a city street for and were asked questions about the details of the drawing (how many windows the buildings have, how many floors, how many axles the truck has, etc.). able to answer these questions for 5-9 seconds after the drawing was removed. I don't remember if they said anything about children closing their eyes to prolong the effect, though.