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Researchers at the National Eye Institute (NEI) have defined a crucial window of time that mice need to key in on visual events. As the brain processes visual information, an evolutionarily conserved region known as the superior colliculus notifies other regions of the brain that an event has occurred. Inhibiting this brain region during a specific 100-millisecond window inhibited event perception in mice. Understanding these early visual processing steps could have implications for conditions that affect perception and visual attention, like schizophrenia and attention deficit hyperactivity disorder (ADHD). The study was published online in the Journal of Neuroscience. NEI is part of the National Institutes of Health.
"One of the most important aspects of vision is fast detection of important events, like detecting threats or the opportunity for a reward. Our result shows this depends on visual processing in the midbrain, not only the visual cortex," said Richard Krauzlis, Ph.D., chief of the Section on Eye Movements and Visual Selection at NEI and senior author of the study.
Visual perception -- one's ability to know that one has seen something -- depends on the eye and the brain working together. Signals generated in the retina travel via retinal ganglion cell nerve fibers to the brain. In mice, 85% of retinal ganglion cells connect to the superior colliculus. The superior colliculus provides the majority of early visual processing in these animals. In primates, a highly complex visual cortex takes over more of this visual processing load, but 10% of retinal ganglion cells still connect to the superior colliculus, which manages basic but necessary perceptual tasks.
One of these tasks is detecting that a visual event has occurred. The superior colliculus takes in information from the retina and cortex, and when there is sufficient evidence that an event has taken place in the visual field, neurons in the superior colliculus fire. Classical experiments into perceptual decision-making involve having a subject, like a person or a monkey, look at an image of vertical grating (a series of blurry vertical black and white lines) and decide if or when the grating rotates slightly. In 2018, Krauzlis and Wang adapted these classic experiments for mice, opening up new avenues for research.
[...] In this study, Wang and colleagues used a technique called optogenetics to tightly control the activity of the superior colliculus over time. They used genetically modified mice so that they could turn neurons in the superior colliculus on or off using a beam of light. This on-off switch could be timed precisely, enabling the researchers to determine exactly when the neurons of the superior colliculus were required for detecting visual events. The researchers trained their mice to lick a spout when they'd seen a visual event (a rotation in the vertical grating), and to avoid licking the spout otherwise.
Inhibiting the cells of the superior colliculus made the mice less likely to report that they'd seen an event, and when they did, their decision took longer. The inhibition had to occur within a 100 millisecond (one-tenth of a second) interval after the visual event. If the inhibition was outside that 100-millisecond timeframe, the mouse's decisions were mostly unaffected. The inhibition was side-specific: because the retinal cells cross over and connect to the superior colliculus on the opposite side of the head (the left eye is connected to the right superior colliculus and vice versa), inhibiting the right side of the superior colliculus depressed responses to stimuli on the left side, but not on the right.
"The ability to temporarily block the transmission of neural signals with such precise timing is one of the great advantages of using optogenetics in mice and reveals exactly when the crucial signals pass through the circuit," said Wang.
Lupeng Wang, Kerry McAlonan, Sheridan Goldstein, Charles R. Gerfen, Richard J. Krauzlis. A causal role for mouse superior colliculus in visual perceptual decision-making. The Journal of Neuroscience, 2020; JN-RM-2642-19 DOI: 10.1523/JNEUROSCI.2642-19.2020
(Score: 2) by maxwell demon on Thursday April 09 2020, @11:39AM (5 children)
The answer to your question is right in the summary:
And (emphasis by me):
Thus, the mechanism still exists in humans, but we do much more visual processing elsewhere than mice do.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2, Interesting) by Anonymous Coward on Thursday April 09 2020, @11:48AM (4 children)
Indeed. And really, mice are known to have poor eyesight compared to humans. It's not just the brain, it's the *eye* that has significant differences too.
For example, things like the colours mice can see, peripheral vision, how far they can see, these things are all entirely different.
In fact, any Google always shows responses such as "mice have very poor eyesight". And statements like "Mice will often run into things."
So while there is a shared evolutionary history in the brain, I can't help but wonder precisely what they think this study proves, or does not prove, other than "This is how it is with mice."
IMO, there's zero correlation here, because on top of all of the above, I'm willing to bet that the cells referenced, respond to differently to stimulus than in mice. After all, they're genetically non-identical.
"Hi, trucks and cars both drive on the road, and have steering wheels. Let's test a car's breaking distance, and infer how a truck will stop from that!"
(Score: 4, Funny) by maxwell demon on Thursday April 09 2020, @01:21PM (3 children)
Clearly we need experiments on genetically modified humans instead. :-)
Actually thinking about it, genetically modified people whose brain cells can be selectively disabled would be a great concept for a dystopian novel.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 0) by Anonymous Coward on Thursday April 09 2020, @05:55PM (1 child)
another word for "selective deactivation of brain cells" is lobotomy.
just saying.
(Score: 2) by maxwell demon on Thursday April 09 2020, @06:27PM
Lobotomy cannot be undone. Here, the neurons can be switched on and off at will.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by nishi.b on Friday April 10 2020, @09:11PM
That's not far-fetched at all, this is envisioned in research labs around the world for treatments like this: inject a virus in the region affected by the disease. This virus will insert a gene in the neurons (either just ARN for a temporary effect, or into the neuron's DNA for permanent effect) that allows it to be activated or deactivated by light (as used in mice) with light-sensitive ion channels. Then you insert into the region an optical fiber and modulate the activity of the region as is currently done through electrical stimulation.
Obviously it could be used for delivering pleasure or pain, create a depression and so on...