Nav: Home

Seeing begins before we actually see anything

November 22, 2018

How does vision work, and what happens in the brain during the process? As simple as this question may sound, it has yet to be scientifically clarified in full. Dr. Valentin Riedl of the Technical University of Munich (TUM) and his team have now been able to show that the distribution of the two most important neurotransmitters in the brain changes as soon as we open our eyes, regardless of whether we actually see anything.

To communicate with each other, neurons use chemical messengers known as neurotransmitters. The two most important neurotransmitters in the human brain, glutamate and GABA, have opposing effects: glutamate activates neurons, while GABA suppresses them. Glutamate, incidentally, is also used as spicy substance and can be found in tomatoes and Parmesan cheese. By altering the concentrations of the two neurotransmitters, the brain is able to process impressions from the eyes, called visual stimuli.

Privatdozent Dr. Valentin Riedl, research group leader in the Neuroradiology Department of University Hospital rechts der Isar of the TUM, and his team have studied how the concentrations of the two neurotransmitters change in the visual cortex, the region in the brain responsible for vision. The study is unique in that the team used magnetic resonance spectroscopy (MRS) to measure the concentrations of the neurotransmitters in detail and, above all, in parallel.

Visual process triggered by opening the eyes

The experiment consisted of three phases. The subjects first lay in the dark for five minutes with their eyes closed. They then opened their eyes and stared into the darkness. Finally, they were shown a checkerboard pattern that blinked on and off rapidly. Throughout the experiment, the concentrations of both neurotransmitters in the visual cortex were measured simultaneously.

In the resting state with the eyes closed, GABA levels were high. Surprisingly, however, concentrations of this inhibitory neurotransmitter decreased as soon as the subjects opened their eyes, despite the fact that there was still nothing to see. "The brain prepares for forthcoming stimuli as soon as the eyes are opened. This phenomenon had never previously been observed, because other studies had not measured this state," Riedl says. Only when an actual visual stimulus was perceived, i.e. the blinking checkerboard pattern, did the concentration of glutamate, the activating neurotransmitter, increase.

Data consistent with fMRT measurements

For the first time, the researchers also compared their MRS data with data obtained by functional MRI (fMRI), a common method for visualizing human brain activity. In this technique, the consumption of oxygen is measured in specific brain regions. A high consumption is an indirect indicator of neuronal activity in a given area.

They found that changes in neurotransmitter levels in the visual cortex coincided with evidence of brain activity in the fMRI scans. "The results of the two methods agreed perfectly. By combining the two techniques, we're not only able to say that there is increased activity in a region; for the first time we're also able to specifically attribute that activity to the two neurotransmitters," Riedl explains.

Psychiatric disorders as a research field

The findings by Riedl and his team also have clinical relevance. For example, it is suspected that the distribution of the two neurotransmitters is permanently disturbed in psychiatric disorders such as schizophrenia. "To date, however, there is no proof of this. An examination using both spectroscopy and fMRT would provide much more precise and far-reaching information on the concentrations of the neurotransmitters in patients," Riedl says.
-end-
Download high-resolution image: https://mediatum.ub.tum.de/1463716

Publication

Katarzyna Kurcyus, Efsun Annac, Nina M. Hanning, Ashley D. Harris, Georg Oeltzschner, Richard Edden and Valentin Riedl, Opposite dynamics of GABA and glutamate levels in the occipital cortex during visual processing, Journal of Neuroscience, November 14, 2018, DOI: 10.1523/JNEUROSCI.1214-18.2018

http://www.jneurosci.org/content/38/46/9967

Contact

PD Dr. Valentin Riedl
Neuroimaging Center at University Hospital rechts der Isar of the TUM
Tel.: +49 (0)89 4140 - 7972
valentin.riedl@tum.de

More information

Profile of Dr. Valentin Riedl
http://www.neurokopfzentrum.med.tum.de/neuroradiologie/forschung_projekt_intrinsisch.html

Technical University of Munich (TUM)

Related Brain Activity Articles:

What is your attitude towards a humanoid robot? Your brain activity can tell us!
Researchers at IIT-Istituto Italiano di Tecnologia in Italy found that people's bias towards robots, that is, attributing them intentionality or considering them as 'mindless things', can be correlated with distinct brain activity patterns.
Using personal frequency to control brain activity
Individual frequency can be used to specifically influence certain areas of the brain and thus the abilities processed in them - solely by electrical stimulation on the scalp, without any surgical intervention.
Rats' brain activity reveals their alcohol preference
The brain's response to alcohol varies based on individual preferences, according to new research in rats published in eNeuro.
Studies of brain activity aren't as useful as scientists thought
Hundreds of published studies over the last decade have claimed it's possible to predict an individual's patterns of thoughts and feelings by scanning their brain in an MRI machine as they perform some mental tasks.
A child's brain activity reveals their memory ability
A child's unique brain activity reveals how good their memories are, according to research recently published in JNeurosci.
How dopamine drives brain activity
Using a specialized magnetic resonance imaging (MRI) sensor that can track dopamine levels, MIT neuroscientists have discovered how dopamine released deep within the brain influences distant brain regions.
Brain activity intensity drives need for sleep
The intensity of brain activity during the day, notwithstanding how long we've been awake, appears to increase our need for sleep, according to a new UCL study in zebrafish, published in Neuron.
Do babies like yawning? Evidence from brain activity
Contagious yawning is observed in many mammals, but there is no such report in human babies.
Understanding brain activity when you name what you see
Using complex statistical methods and fast measurement techniques, researchers found how the brain network comes up with the right word and enables us to say it.
Your brain activity can be used to measure how well you understand a concept
As students learn a new concept, measuring how well they grasp it has often depended on traditional paper and pencil tests.
More Brain Activity News and Brain Activity 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: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.