Brain circuitry for color perception identified – Neuroscience News

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Resume: Researchers have identified the specific brain circuits in fruit flies responsible for color vision. These neurons in the optic lobe respond selectively to different hues, including those perceived by humans as violet and ultraviolet.

This groundbreaking discovery provides insight into how brains transform raw sensory signals into meaningful perceptions and could help us better understand the neural mechanisms underlying color vision in other animals, including humans.

Key Facts:

  • Specific neurons in the optic lobe of the fruit fly respond selectively to different colors.
  • The discovery of these circuits was made possible by the availability of a detailed fruit fly brain connectome.
  • This research sheds light on how brains transform sensory signals into perceptions of the world.

Source: Columbia University

Observing something – anything – in your environment means becoming aware of what your senses perceive. Today, neuroscientists at Columbia University are identifying for the first time brain cell circuits in fruit flies that convert raw sensory signals into color perceptions that can guide behavior.

Their findings were published in the journal Nature Neuroscience.

This shows an iridescent eye.
Scientists had previously reported finding neurons in the brains of animals that respond selectively to different colors or shades, for example red or green. Credit: Neuroscience News

“Many of us take for granted the rich colors we see every day: the red of a ripe strawberry or the deep brown of a child’s eyes. But those colors don’t exist outside our brains,” says Rudy Behnia, PhD, principal investigator at Columbia’s Zuckerman Institute and the paper’s corresponding author.

Rather, she explained, colors are perceptions that the brain constructs as they give meaning to the longer and shorter wavelengths of light detected by the eyes.

“Transforming sensory signals into perceptions about the world is how the brain helps organisms survive and thrive,” said Dr. Behnia.

“Asking how we perceive the world seems like a simple question, but answering it is a challenge,” added Dr. Behnia to it.

“My hope is that our efforts to uncover neural principles underlying color perception will help us better understand how the brain extracts the features from the environment that are important for getting through the day.”

In their new paper, the research team reports that they have discovered specific networks of neurons, a type of brain cell, in fruit flies that respond selectively to different hues. Hue denotes the perceived colors associated with specific wavelengths, or combinations of wavelengths, of light, which are not themselves inherently colorful. These color-selective neurons are located in the optic lobe, the area of ​​the brain responsible for vision.

Among the hues to which these neurons respond are those that humans perceive as violet and others that correspond to ultraviolet wavelengths (not perceptible by humans). Detecting UV hues is important for the survival of some creatures, such as bees and perhaps fruit flies; for example, many plants possess ultraviolet patterns that can help insects find pollen.

Scientists had previously reported finding neurons in the brains of animals that respond selectively to different colors or shades, for example red or green. But no one had been able to trace the neural mechanisms that made this hue selectivity possible.

This is where the recent availability of a fly-brain connectome has proven useful. This complicated map details how about 130,000 neurons and 50 million synapses in the poppy-seed-sized brain of a fruit fly are connected, said Dr. Behnia, who is also an assistant professor of neuroscience at the Vagelos College of Physicians and Surgeons in Columbia.

Using the connectome as a reference – similar to a picture on a puzzle box that serves as a guide to how a thousand pieces fit together – the researchers used their observations of brain cells to develop a diagram that they suspect represents the neuronal circuitry behind hue selectivity .

The scientists then portrayed these circuits as mathematical models to simulate and investigate the circuits’ activities and capabilities.

“The mathematical models serve as tools that allow us to better understand something as messy and complex as all these brain cells and their interconnections,” said Matthias Christenson, PhD, co-first author of the paper and former member of Dr. Behnia’s laboratory.

“With the models we can try to understand this complexity.” Also Dr. Larry Abbott, William Bloor Professor of Theoretical Neuroscience, professor of physiology and cellular biophysics and principal investigator at the Zuckerman Institute, made crucial contributions to the modeling work.

“The modeling not only showed that these circuits can house the activity necessary for hue selectivity, it also pointed to a type of cell-to-cell interconnectivity, known as recurrence, without which hue selectivity cannot occur.

In a neural circuit with repetition, the outputs of the circuit cycle back in and become inputs. And that suggested another experiment,” says Álvaro Sanz-Diez, PhD, a postdoctoral researcher in Dr. Behnia and the other co-first author of it Nature Neuroscience paper.

“When we used a genetic technique to disrupt some of this recurrent connectivity in the brains of fruit flies, the neurons that previously showed color-selective activity lost that property,” said Dr. Sanz-Diez. “This increased our confidence that we had really discovered brain circuits involved in color perception.”

“Now we know a little more about how the brain’s wiring allows it to build a perceptual representation of color,” said Dr. Behnia. “My hope is that our new findings can help explain how brains produce all kinds of perceptions, including color, sound and taste.”

About this color perception and visual neuroscience research news

Author: Ivan Amato
Source: Columbia University
Contact: Ivan Amato – Columbia University
Image: The image is credited to Neuroscience News

Original research: Open access.
“Hue selectivity from recurrent circuits in Drosophila” by Rudy Behnia et al. Nature Neuroscience


Abstract

Hue selectivity of recurrent circuits in Drosophila

In the perception of color, wavelengths of light reflected from objects are transformed into the derived quantities of brightness, saturation, and hue.

Neurons selectively responsive to hue have been reported in primate cortex, but it is unknown how their close tuning in color space is produced by upstream circuit mechanisms.

We report the discovery of neurons in the Drosophila optical lobe with hue-selective properties, which allows analysis of color processing at the circuit level.

From our analysis of an electron microscopy volume of a whole Drosophila brain, we construct a connectomics-constrained circuit model that takes this hue selectivity into account.

Our model predicts that recurrent connections in the circuit are critical for generating hue selectivity.

Experiments using genetic manipulations to disrupt repetition in adult flies confirm this prediction.

Our findings reveal a circuit basis for hue selectivity in color vision.

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