Nav: Home

Seeing color in 'blindsight'

October 27, 2008

By manipulating the brain noninvasively in a new way with magnetic stimulation, researchers have shown that they can restore some experience of color where before there was no visual awareness whatsoever. They report their findings in the October 28th issue of Current Biology, a Cell Press publication.

The researchers made their discovery while studying a patient known as GY, who lacks vision in half of his visual field as a result of damage in one hemisphere of the primary visual cortex (a brain region also known as V1). That part of the brain had been considered absolutely essential for visual awareness, a notion that is challenged by the current findings, according to Juha Silvanto of the University of Essex.

"The implication is that even though [lesions in this part of the brain] abolish visual awareness, it can be restored," Silvanto said. "The neural processes that make V1 critical may be taken over by other brain regions--not automatically, but you can make it happen."

In the portion of his visual field controlled by the damaged part of the brain, GY has a condition called blindsight. This phenomenon can occur when people do not consciously see as a consequence of a V1 lesion. However, when forced to guess which way a moving object they "observed" was traveling, for instance, they get it right most of the time. In other words, despite the fact that they do not experience vision, they nonetheless continue to detect things around them.

In the new study, the researchers applied a method called transcranial magnetic stimulation (TMS) to GY's primary visual cortex. By stimulating both the normal and the damaged hemispheres of the brain, the method can induce visions of flashes of light (or phosphenes) in the blind fields of people like GY.

This method has previously been used in a general way to stimulate entire brain regions. In the new study, Silvanto's team developed a more targeted method to activate particular neurons with TMS by taking advantage of a trend that had been seen before: TMS preferentially activates those neurons that were less active to begin with.

They asked GY to look at a screen in the color red for a time; this adapts the brain to the color red, leaving the neurons responsible for the experience of red to become less active. They then applied TMS to GY's damaged and intact visual processing centers. The result: he saw the color red.

"This was the first time this patient [consciously] experienced a colored visual percept in his blind field," Silvanto said.

"In summary," the researchers wrote, "our results show that in the absence of V1, color perception may be possible via the intact hemisphere."

The more targeted TMS method the team developed is also an important technical advance for cognitive neuroscience, Silvanto added. "Now we can target the stimulation at specific populations of neurons," he said. "It makes the resolution of the technique much higher."
-end-
The researchers include Juha Silvanto of Beth Israel Deaconess Medical Center and Harvard Medical School, and University of Essex; Alan Cowey of University of Oxford; and Vincent Walsh of Institute of Cognitive Neuroscience, University College London.

Cell Press

Related Neurons Articles:

The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.
Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.
How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.
A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.
Shaping the social networks of neurons
Identification of a protein complex that attracts or repels nerve cells during development.
With these neurons, extinguishing fear is its own reward
The same neurons responsible for encoding reward also form new memories to suppress fearful ones, according to new research by scientists at The Picower Institute for Learning and Memory at MIT.
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.
Connecting neurons in the brain
Leuven researchers uncover new mechanisms of brain development that determine when, where and how strongly distinct brain cells interconnect.
More Neurons News and Neurons Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Meditations on Loneliness
Original broadcast date: April 24, 2020. We're a social species now living in isolation. But loneliness was a problem well before this era of social distancing. This hour, TED speakers explore how we can live and make peace with loneliness. Guests on the show include author and illustrator Jonny Sun, psychologist Susan Pinker, architect Grace Kim, and writer Suleika Jaouad.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.