Introducing the eye: a study of retina cells (Introduction)

by David Turell , Sunday, April 09, 2023, 16:20 (592 days ago) @ David Turell

Not exactly like a camera:

https://medicalxpress.com/news/2023-04-functional-cells-retina-natural-panoramic.html

"Existing neuroscientific models of the visual system suggest that it represents the visual world just as a camera would, encoding the positions of different objects similarly. An animal's surrounding environment, however, constantly changes, and these changes could also influence the processing of visual information.

"Researchers at the Institute of Science and Technology in Austria and LMU in Germany recently gathered evidence supporting this hypothesis and showing that the organization of neurons in the mouse retina is affected by panoramic (i.e., wide view) visual statistics, such as non-uniformities in light levels.

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"To examine the organization of sensory space that activate each neuron in the mouse retina (receptive fields) in relation to the scenes that mice are observing, Jösch and his colleagues developed a new optical imaging technique. This technique allows them to measure and track the activity of thousands of neurons in a single retina simultaneously.

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"The researchers conducted their experiments on extracted mice retinas. Like that of most mammals, the mouse retina does not include the small area known as the fovea, a small slump in the retina that allows humans and other primates to see at high definition. The fovea, which makes up less than 1% of the entire human retina, is known to play a key role in the visual perceptions of which humans are more conscious. The remaining 99% of the human retina also contributes to visual perceptions, from which many appear to be unconscious processes. Thus, from a human centric perspective, this study focuses on the processing happening the latter 99%.

"Jösch and his colleagues found that the computations performed by neurons in the mice retina changed depending on the panoramic visual statistics of what that part of the retina usually sees during daylight. This supports their initial hypothesis that the visual system is not inherently homogenous and is in fact adapted to the external environment.

"'To our surprise, we found that retinal neurons are more likely to inform the rest of the brain when a stimuli change is unexpected," Jösch said. "Importantly, the unexpected depends on where the neuron looks, either the sky or the ground. Thus, retina circuits systematically adapted their properties from the lower to the higher visual field to represent the world more efficiently."

"Overall, the findings gathered by this team of researchers suggest that the panoramic structure of natural scenes affects the organization of different processing strategies in different regions of the retina. This expands previous models of the visual system, highlighting its adaptive and dynamic nature.

"'We usually assume that the visual system is homogenous, or in other words, that the visual world is represented like a camera, measuring each position similarly," Jösch added. "However, our natural surroundings are not similar; they systematically change from ground to sky. Thus, a system that evolved to live in nature should consider this. Our results indicate that living organisms' visual system has adapted to cope with natural constraints to improve the efficiency of their neuronal code.'"

Comment: such complex organization requires design in my view. Our eyes don't mimic cameras, they mimic our eyes.