Summary: Researchers have identified the specific brain circuits of fruit flies responsible for color perception. These optic lobe neurons respond selectively to various hues, including those perceived as violet and ultraviolet by humans.
This groundbreaking discovery provides insight into how the brain transforms raw sensory signals into meaningful perceptions and could help us better understand the neural mechanisms underlying color vision in other animals, including humans.
Highlights:
- Specific neurons in the fruit fly’s optic lobe respond selectively to different colors.
- The discovery of these circuits was made possible by the availability of a detailed brain connectome of a fruit fly.
- This research sheds light on how the brain transforms sensory signals into perceptions of the world.
Source: Columbia University
To perceive something – anything – in your environment is to become aware of what your senses are detecting. Now, Columbia University neuroscientists 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 Natural neuroscience.
“Many of us take for granted the rich colors we see every day – the red of a ripe strawberry or the dark brown of a child’s eyes. But these colors don’t exist outside of our brains,” said Rudy Behnia, PhD, a senior research fellow at Columbia’s Zuckerman Institute and corresponding author of the paper.
Rather, she says, colors are perceptions that the brain constructs when 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,” Dr. Behnia said.
“Asking how we perceive the world seems like a simple question, but answering it is a challenge,” added Dr. Behnia.
“I hope that our efforts to uncover the neural principles underlying color perception will help us better understand how the brain extracts features from the environment that are important for surviving each day.”
In their new paper, the research team reports discovering specific networks of neurons, a type of brain cell, in fruit flies that respond selectively to various hues. Hue refers to the perceived colors associated with specific wavelengths or combinations of wavelengths of light, which themselves are not inherently colored. These hue-selective neurons are found in the optic lobe, the area of the brain responsible for vision.
Among the hues these neurons respond to are those that people would perceive as purple and others that correspond to ultraviolet wavelengths (not detectable by humans). Detecting UV tints is important for the survival of certain creatures, such as bees and perhaps fruit flies; many plants, for example, have ultraviolet patterns that can help guide insects to pollen.
Scientists had previously reported discovering neurons in the brains of animals that reacted selectively to different colors or hues, for example red or green. But no one had been able to trace the neural mechanisms making this hue selectivity possible.
This is where the recent availability of a fly-brain connectome has come in handy. This complex map details how some 130,000 neurons and 50 million synapses in the brain of a fruit fly, the size of a poppy seed, are interconnected, said Dr. Behnia, who is also an assistant professor of neuroscience. at Columbia’s Vagelos College of Physicians and Surgeons.
With the connectome serving as a reference – similar to a picture on a puzzle box serving as a guide for how a thousand pieces fit together – the researchers used their observations of brain cells to develop a diagram they suspected represented the neural circuitry behind hue selectivity.
The scientists then presented these circuits as mathematical models for simulating and probing circuit activities and capabilities.
“Mathematical models serve as tools that allow us to better understand something as complicated and complex as all those brain cells and their interconnections,” said Matthias Christenson, PhD, co-first author of the paper and former member from Dr. Behnia’s laboratory.
“Using models, we can work to make sense of all this complexity. » Dr. Larry Abbott, William Bloor Professor of Theoretical Neuroscience, Professor of Physiology and Cellular Biophysics, and Principal Investigator at the Zuckerman Institute, also made crucial contributions to the modeling work.
“Not only did the modeling reveal that these circuits can host the activity necessary for hue selectivity, but it also highlighted a type of cell-to-cell interconnectivity, known as recurrence, without which color selectivity tints cannot occur.
“In a recurrent neural circuit, the outputs of the circuit return to become inputs. And that suggested yet another experiment,” said Álvaro Sanz-Diez, PhD, a postdoctoral researcher in Dr. Behnia’s lab and another co-first author of the study. Natural neuroscience paper.
“When we used a genetic technique to disrupt some of this recurrent connectivity in fruit fly brains, neurons that previously showed hue-selective activity lost this property,” Dr. Sanz-Diez said. “This increased our confidence that we had actually discovered the brain circuits involved in color perception.”
“We now know a little more about how the brain’s wiring builds a perceptual representation of color,” Dr. Behnia said. “I hope our new findings can help explain how the brain produces all kinds of perceptions, including color, sound and taste.”
About this research news on color perception and visual neuroscience
Author: Ivan Amato
Source: Columbia University
Contact: Ivan Amato – Columbia University
Picture: Image is credited to Neuroscience News
Original research: Free access.
“Hue selectivity from recurrent circuits in Drosophila” by Rudy Behnia et al. Natural neuroscience
Abstract
Hue selectivity from recurrent circuits in Drosophila
In color perception, the wavelengths of light reflected from objects are transformed into derived quantities of brightness, saturation, and hue.
Hue-selectively responding neurons have been reported in primate cortex, but it is unclear how their tight tuning in color space is produced by upstream circuit mechanisms.
We report the discovery of neurons in the Drosophila optical lobe with hue selection properties, which enables circuit-level analysis of color processing.
From our analysis of a volume in electron microscopy of a set Drosophila brain, we build a circuit model constrained by connectomics which takes into account this hue selectivity.
Our model predicts that recurrent connections in the circuit are essential for generating hue selectivity.
Experiments using genetic manipulations to disrupt recurrence in adult flies confirm this prediction.
Our results reveal a circuit basis for hue selectivity in color vision.