Nav: Home

Easy on the eyes

May 02, 2019

Why do our eyes tend to be drawn to certain shapes, colors and silhouettes more than others? For more than half a century, researchers have known that neurons in the brain's visual system respond more to some images than others--a feature that is critical for the ability to recognize, understand and interpret the multitude of visual clues surrounding us. For example, specific populations of visual neurons in an area of the brain known as the inferior temporal cortex fire more when people or other primates--animals with highly attuned and visual systems--look at faces, places, objects or text.

But exactly what these neurons are responding to has remained unclear.

Now a small study in macaques led by investigators in the Blavatnik Institute at Harvard Medical School has generated some valuable clues based on an artificial intelligence system that can reliably determine what neurons in the brain's visual cortex prefer to see.

A report of the team's work is published May 2 in Cell.

The vast majority of experiments to date that attempt to measure neuronal preferences have used real images. But real images carry an inherent bias: They are limited to stimuli available in the real world and to the images that researchers choose to test. The AI-based program overcomes this hurdle by creating synthetic images tailored to the preference of each neuron.

Will Xiao, a graduate student in the Department of Neurobiology at Harvard Medical School, designed a computer program that uses a form of responsive artificial intelligence to create self-adjusting images based on neural responses obtained from six macaque monkeys. To do so, the researchers measured the firing rates from individual visual neurons in the brains of the animals as they were watching images on a computer screen.

Over the course of a few hours, the animals were shown images in 100 millisecond blips, each generated by Xiao's program. The images started out with a random textural pattern in grayscale. Based on how much the monitored neurons fired, the program gradually introduced shapes and colors, morphing over time into a final image that fully embodied a neuron's preference. Because each of these images is synthetic, Xiao said, it avoids the bias that researchers have traditionally introduced by only using natural images.

"At the end of each experiment," he said, "this program generates a super stimulus for these cells."

The results of these experiments were consistent over separate runs, Livingstone explained--specific neurons tended to evolve images through the program that weren't identical but were remarkably similar.

Some of these images were in line with what she and her colleagues expected. For example, a neuron that they suspected might respond to faces evolved round pink images with two big black dots akin to eyes. Others were more surprising. For example, a neuron in one of the animals consistently generated images that looked like the body of a monkey, but with a red splotch near its neck. The researchers eventually realized that this monkey was housed near another that always wore a red collar.

"We think this neuron responded preferentially not just to monkey bodies but to a specific monkey," said study senior investigator Margaret Livingstone, the Takeda Professor of Neurobiology at HMS.

Not every final image looked like something recognizable, Xiao added. One monkey's neuron evolved a small black square. Another evolved an amorphous black shape with orange below.

Livingstone notes that research from her lab and others has shown that the responses of these neurons are not innate--instead, they are learned through consistent exposure over time to visual stimuli. When this ability to recognize and fire preferentially to certain images arises is unknown, Livingstone said. She and her colleagues plan to investigate this question in future studies.

Learning how the visual system responds to images could be key to better understanding the basic mechanisms that drive cognitive issues ranging from learning disabilities to autism spectrum disorders, which are often marked by impairments in a child's ability to process facial cues and to recognize faces.

"This malfunction in the visual processing apparatus of the brain can interfere with a child's ability to connect, communicate and interpret basic cues," she said. "By studying those cells that respond preferentially to faces, for example, we could uncover clues to how social development takes place and what might sometimes go awry."
-end-
The research was funded by National Institutes of Health (grants R01EY16187, R01EY25670, R01EY011379, P30EY012196 and R01EY026025) and National Science Foundation award CCF-1231216.

Harvard Medical School

Related Neurons Articles:

How do we get so many different types of neurons in our brain?
SMU (Southern Methodist University) researchers have discovered another layer of complexity in gene expression, which could help explain how we're able to have so many billions of neurons in our brain.
These neurons affect how much you do, or don't, want to eat
University of Arizona researchers have identified a network of neurons that coordinate with other brain regions to influence eating behaviors.
Mood neurons mature during adolescence
Researchers have discovered a mysterious group of neurons in the amygdala -- a key center for emotional processing in the brain -- that stay in an immature, prenatal developmental state throughout childhood.
Astrocytes protect neurons from toxic buildup
Neurons off-load toxic by-products to astrocytes, which process and recycle them.
Connecting neurons in the brain
Leuven researchers uncover new mechanisms of brain development that determine when, where and how strongly distinct brain cells interconnect.
The salt-craving neurons
Pass the potato chips, please! New research discovers neural circuits that regulate craving and satiation for salty tastes.
When neurons are out of shape, antidepressants may not work
Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed medication for major depressive disorder (MDD), yet scientists still do not understand why the treatment does not work in nearly thirty percent of patients with MDD.
Losing neurons can sometimes not be that bad
Current thinking about Alzheimer's disease is that neuronal cell death in the brain is to blame for the cognitive havoc caused by the disease.
Neurons that fire together, don't always wire together
As the adage goes 'neurons that fire together, wire together,' but a new paper published today in Neuron demonstrates that, in addition to response similarity, projection target also constrains local connectivity.
Scientists accidentally reprogram mature mouse GABA neurons into dopaminergic-like neurons
Attempting to make dopamine-producing neurons out of glial cells in mouse brains, a group of researchers instead converted mature inhibitory neurons into dopaminergic cells.
More Neurons News and Neurons Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

In & Out Of Love
We think of love as a mysterious, unknowable force. Something that happens to us. But what if we could control it? This hour, TED speakers on whether we can decide to fall in — and out of — love. Guests include writer Mandy Len Catron, biological anthropologist Helen Fisher, musician Dessa, One Love CEO Katie Hood, and psychologist Guy Winch.
Now Playing: Science for the People

#543 Give a Nerd a Gift
Yup, you guessed it... it's Science for the People's annual holiday episode that helps you figure out what sciency books and gifts to get that special nerd on your list. Or maybe you're looking to build up your reading list for the holiday break and a geeky Christmas sweater to wear to an upcoming party. Returning are pop-science power-readers John Dupuis and Joanne Manaster to dish on the best science books they read this past year. And Rachelle Saunders and Bethany Brookshire squee in delight over some truly delightful science-themed non-book objects for those whose bookshelves are already full. Since...
Now Playing: Radiolab

An Announcement from Radiolab