Scientists uncover a new layer in visual brain imaging

October 5, 2015
White matter fiber architecture of the brain. Credit: Human Connectome Project.

Neuroscientists have gained new insight into how the brain perceives the world by using high resolution high field MRI to study activity in different layers of the visual cortex in great detail.

The is the part of the brain that processes sight by receiving feedforward input from the eyes.

But feedback is also required from parts of the brain that conceptualise and contextualise in order for us to fully comprehend what we are seeing.

Scientists eager to study the feedback system in more detail have, thus far, been impeded by the integration of both signals within the six different layers of the cortex. No technique had been able to isolate the contextual feedback signal in human cortical layers, until now.

Researchers at the University of Glasgow have come up with a solution by taking advantage of the fact input from the retina is mapped out in the visual cortex.

Much like light entering the lens of a camera hits a specific portion of a sensor to form a pixel, so too light entering the eye has a corresponding portion in the visual cortex, which when applied to images, is called a voxel.

In order to study the feedback signal, the researchers showed subjects a picture – for example a car – part of which was obscured by a white square. This enabled them to identify and isolate the area of the brain that responded only to the occluded portion of the scene, and thus quieten the feedforward signal.

But even in the absence of sensory input the visual cortex communicates with other brain areas.

By measuring the activity in this part, the researchers were able to see where feedback and feedforward activity took place across the six different layers of the cortex as the brain tried to complete the picture by inferring what the whole scene looked like. The ability to measure layer specific signals in humans was made possible by 7 Tesla MRI techniques pioneered at the University of Minnesota's Center for Magnetic Resonance Research. Professor Essa Yacoub and colleagues have developed techniques that allow visualization of human brain activity at sub-millimeter spatial resolutions and with high degrees of accuracy. Such a capability was previously only possible with invasive studies in animals.

The result, published in the journal Current Biology, reveals the layered cortical organisation of external versus internal processing streams during perception, with activity during normal visual stimulation peaking in mid-layers and contextual information peaking in superficial layers.

Professor Lars Muckli, of the Institute of Neuroscience & Psychology, said: "Understanding the brain's feedback system is important if we are to develop more powerful computers and artificial intelligence systems, but it might also help us to better understand mental illnesses such as schizophrenia and autism.

"The predictive coding hypothesis suggests the brain tries to process efficiently the huge amount of sensory information it receives by creating predictive models of the world based on previous experience.

"For example, the expects to see your favourite armchair in the context of your house, so seeing it suddenly sitting in your office would be regarded as unusual.

"In healthy people, the feedback system plays an important role in understanding concepts and contexts in everyday life. But in people with mental health conditions like autism, we believe that something within the isn't working correctly. For them everyday scenes that should be regarded as familiar can seem strange.

"Our study provides empirical evidence to support theoretical feedback models such as predictive coding and demonstrates the potential of high-resolution MRI in studying sub-millimetre human cortex."

Explore further: Sound and vision: Visual cortex processes auditory information too

More information: "Contextual Feedback to Superficial Layers of V1." Current Biology DOI:

Related Stories

Sound and vision: Visual cortex processes auditory information too

May 25, 2014
Scientists studying brain process involved in sight have found the visual cortex also uses information gleaned from the ears as well as the eyes when viewing the world.

Shapes, lines and movements are in the eye of the beholder

August 4, 2015
New thinking about how we perceive shapes, lines and movement suggests this information is first deciphered in the retina of the eye, rather than within the brain's visual cortex as previously thought.

Results challenge conventional wisdom about where the brain processes visual information

March 2, 2015
Neuroscientists generally think of the front end of the human visual system as a simple light detection system: The patterns produced when light falls on the retina are relayed to the visual cortex at the rear of the brain, ...

Researchers pinpoint where the brain unites our eyes' double vision

July 23, 2015
If you have two working eyes, you are live streaming two images of the world into your brain. Your brain combines the two to produce a view of the world that appears as though you had a single eye—like the Cyclops from ...

Human visual cortex holds neurons that selectively respond to intermediate colors

September 30, 2015
Researchers from Tohoku University's Research Institute of Electrical Communication and RIKEN BSI have found the presence of neurons in the human brain which can each selectively respond to an intermediate color; not just ...

Study finds how feedback from cortex helps mammals make fine distinctions about odors

June 4, 2015
Everyday tasks we may regard as "simple" - for example, knowing the difference between the smell of an orange and a pickle - are actually marvels of evolutionary development, the work of eons. A neuroscience team at Cold ...

Recommended for you

Our memory shifts into high gear when we think about raising our children, new study shows

December 15, 2017
Human memory has evolved so people better recall events encountered while they are thinking about raising their offspring, according to a new study conducted by researchers at Binghamton University, State University of New ...

Offbeat brain rhythms during sleep make older adults forget

December 15, 2017
Like swinging a tennis racket during a ball toss to serve an ace, slow and speedy brainwaves during deep sleep must sync up at exactly the right moment to hit the save button on new memories, according to new UC Berkeley ...

Study finds graspable objects grab attention more than images of objects do

December 15, 2017
Does having the potential to act upon an object have a unique influence on behavior and brain responses to the object? That is the question Jacqueline Snow, assistant professor of psychology at the University of Nevada, Reno, ...

Little understood cell helps mice see color

December 14, 2017
Researchers at the University of Colorado Anschutz Medical Campus have discovered that color vision in mice is far more complex than originally thought, opening the door to experiments that could potentially lead to new treatments ...

Scientists chart how brain signals connect to neurons

December 14, 2017
Scientists at Johns Hopkins have used supercomputers to create an atomic scale map that tracks how the signaling chemical glutamate binds to a neuron in the brain. The findings, say the scientists, shed light on the dynamic ...

Activating MSc glutamatergic neurons found to cause mice to eat less

December 13, 2017
(Medical Xpress)—A trio of researchers working at the State University of New York has found that artificially stimulating neurons that exist in the medial septal complex in mouse brains caused test mice to eat less. In ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Oct 05, 2015
Open access pdf if you click the doi link.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.