Summary: Researchers have identified the specific brain circuits in fruit flies responsible for color perception. These neurons in the optic lobe respond selectively to different hues, including those perceived as violet and ultraviolet by humans.
This groundbreaking discovery provides insight into how brains transform raw sensory signals into meaningful perceptions and may help us better understand the neural mechanisms that underlie color vision in other animals, including humans.
Key facts:
- Specific neurons in the visual lobe of the fruit fly respond selectively to different colors.
- The discovery of these circuits was made possible by the availability of a detailed brain connector of a fruit fly.
- This research sheds light on how brains transform sensory signals into perceptions of the world.
source: Columbia University
Perceiving something—anything—in your surroundings means becoming aware of what your senses are detecting. Today, Columbia University neuroscientists identify for the first time circuits of brain cells in fruit flies that convert raw sensory signals into color perceptions that can guide behavior.
Their findings were published in the journal Nature Neurology.
“Many of us take for granted the rich colors we see every day – the red of a ripe strawberry or the rich brown of a child’s eyes. But these colors don’t exist outside of our brains,” said Dr. Rudy Begna, principal investigator at the Zuckerman Institute in Columbia and the paper’s corresponding author.
Rather, she explained, colors are perceptions that the brain constructs as it makes sense of the longer and shorter wavelengths of light detected by the eyes.
“Transforming sensory signals into perceptions of the world is how the brain helps organisms survive and thrive,” said Dr. Benhnia.
“Asking how we perceive the world seems like a simple question, but the answer is challenging,” added Dr. Benhnia
“I hope that our efforts to uncover the neural principles underlying color perception will help us better understand how brains extract features in the environment that are important for getting through each day.”
In their new paper, the research team reports the discovery of specific networks of neurons, a type of brain cell, in fruit flies that respond selectively to different hues. Hue refers to the perceived colors associated with specific wavelengths or combinations of wavelengths of light that are not themselves colored. These color-selective neurons are located in the optic lobe, the brain region responsible for vision.
Among the hues to which these neurons respond are those that humans would perceive as violet and others that correspond to ultraviolet wavelengths (undetectable by humans). Detection of UV shades is important for the survival of some creatures, such as bees and perhaps fruit flies; many plants, for example, possess ultraviolet patterns that can help insects target pollen.
Scientists have previously reported finding neurons in animal brains that respond selectively to different colors or hues, say red or green. But no one has been able to trace the neural mechanisms that make this color selectivity possible.
This is where the recent availability of the Flying Brain Connectome came in handy. This complex map details how the roughly 130,000 neurons and 50 million synapses in the poppy-seed-sized fruit fly brain are interconnected, said Dr. Behnia, who is also an assistant professor of neurology at Columbia’s Vagelos College of Physicians and Surgeons.
With the connectome as a reference—like a picture on a puzzle box serving 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 neural circuitry behind selectivity of the color.
Scientists then described these circuits as mathematical models to simulate and study the circuits’ activities and capabilities.
“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 Dr. Mathias Christensen, co-author of the paper and former member of the Dr. Behnia’s laboratory.
“With models, we can work to understand all of this complexity.” Also contributing greatly to Dr. Larry Abbott’s modeling work is the William Bloor Professor of Theoretical Neuroscience, Professor of Physiology and Cell Biophysics and Principal Investigator at the Institute Zuckerman.
“Not only did the modeling reveal that these circuits can host the activity required for hue selectivity, but it also pointed to a type of cell-to-cell interconnection, known as a repeat, without which color selectivity cannot occur.”
” In a recurrent neural circuit, the outputs of the circuit feed back to become inputs. And that suggests another experiment,” said Dr. Alvaro Sanz-Diez, a postdoctoral fellow in Dr. Beña’s lab and the other co-author of Nature Neurology paper.
“When we used a genetic technique to disrupt some of this recurrent connectivity in fruit fly brains, neurons that had previously shown color-selective activity lost this property,” said Dr. Sanz-Diez. “This strengthened our confidence that we had indeed discovered brain circuits involved in color perception.”
“We now know a little more about how the brain’s wiring makes it possible to construct a perceptual representation of color,” said Dr Benhnia. “I hope our new findings can help explain how brains produce all kinds of perceptions, including color, sound and taste.”
About this news about color perception research and visual neuroscience
Author: Ivan Amato
source: Columbia University
Contact: Ivan Amato – Columbia University
Image: Image credit: Neuroscience News
Original research: Free access.
“Shade Selectivity by Repeated Chains in Drosophila” by Rudy Behnia et al. Nature Neurology
Summary
Shade selectivity by repeat chains in Drosophila
In color perception, the wavelengths of light reflected by objects are transformed into the resulting amounts of brightness, saturation, and hue.
Hue-selective neurons have been reported in primate cortex, but it is not known how their narrow tuning in color space is produced by upstream circuit mechanisms.
We report the discovery of neurons in Drosophila an optical lobe with hue selection properties, allowing for circuit-level color processing analysis.
From our analysis of electron microscopic vol Drosophila brain, we construct a link-constrained circuit model that accounts for this hue selectivity.
Our model predicts that recurrent connections in the circuit are critical for generating hue selectivity.
Experiments using genetic manipulations to inhibit relapse in adult flies confirmed this prediction.
Our findings reveal a schematic basis for hue selectivity in color vision.
