The Role of Vision in Inhibitor Network Development - Neuroscience News

Summary: The inhibitory and excitatory networks in the visual system of the brain develop by different processes, even if the organization of the networks is similar.

Source: Max Planck Florida

Brain function, like many other areas of life, is about balance.

Excitatory neurons that increase the activity of connected neurons are offset by inhibitory neurons that suppress this activity. In this way, excitation and inhibition work together throughout the brain to process information and guide behavior. Imbalances in this system, which sometimes appear during development, contribute to neurodevelopmental disorders such as autism.

To date researchers have mostly focused on excitatory neurons, while the function and development of inhibitory neural circuits has been studied.

New research from the Max Planck Florida Institute for Neuroscience shows that the inhibitory and excitatory neural circuits of the visual system develop by different processes, even if the organization of the mature circuits is similar.

These findings, published in Nature Communication highlights the importance of continued study of the development of these two systems, the understanding of which is fundamental to understanding neurodevelopmental disorders.

The area of ​​the brain that processes visual information, the primary visual cortex, is highly organized, forming patches of neighboring neurons that tend to activate together and respond to similar visual features.

In mammals, this modular functional map is made up of excitatory and inhibitory neurons that work together to create an accurate representation of the world.

Scientists Jeremy Chang and David Fitzpatrick have now characterized the development of this functional map for inhibitory neurons in the primary visual cortex.

Although excitatory and inhibitory functional maps are matched at maturity, their development occurs via different parallel processes.

Excitatory neurons exhibit modular organization early on, before eyes are opened and visual input is received. Neighboring neurons respond to visual images in a correlated manner and show similar preferences for stimuli presented in a particular orientation.

While visual experiences enhance certain properties of these maps, such as the alignment of visual information from each eye, the basic features of modular organization come before visual experiences.

Dr. Chang found that inhibitory neurons, on the other hand, lack much of this modular activity prior to visual experience.

“It’s surprising,” he admits. “We did not expect the functional map seen before eye opening in excitatory neurons to be almost absent in inhibitory neurons.”

This suggests that developing a mature functional organization of inhibitory neurons requires visual experience. In fact, if visual input is delayed, the development of many features of the functional inhibitory neuron map is also delayed.

The area of ​​the brain that processes visual information, the primary visual cortex, is highly organized, forming patches of neighboring neurons that tend to activate together and respond to similar visual features. Image is in public domain

This work contributes to a fundamental understanding of the larger question of the role of inhibition in the cortex, which the lab will continue to pursue.

“New techniques developed over the last decade have allowed us to describe the activity of inhibitory neurons in response to visual images. We are beginning to understand the importance of the inhibitory function in visual processing and how the role of inhibition changes throughout development.

“During development, inhibitory and excitatory neurons must solve different puzzles to end up in the right place, connect to the right partners, and repair their connections in response to experience,” Chang said. Future work will focus on understanding how these puzzles are solved.

Funding: The research was supported by the National Eye Institute of the National Institutes of Health with award numbers EY011488 and EY026273 and the Florida Max Planck Institute for Neuroscience.

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About this visual neuroscience research news

Author: Katie Edwards
Source: Max Planck Florida
Contact: Katie Edwards – Max Planck Florida
Picture: Image is in public domain

Original Research: Open access.
“Development of visual response selectivity in cortical GABAergic interneurons” by Chang, JT, & Fitzpatrick, D. Nature Communication

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Abstract

Development of visual response selectivity in cortical GABAergic interneurons

The visual cortex of carnivores and primates displays a high degree of modular network organization characterized by local clustering and structured long-term correlation of activity and functional traits.

The excitatory network displays modular organization prior to the onset of sensory experience, but the developmental timeline for the GABAergic interneuron modular network remains unexplored.

Using in vivo calcium imaging of the ferret visual cortex, we found evidence that prior to visual experience, interneurons display weak orientation tuning and extensive and correlated activity in response to visual stimuli. Robust modular organization and onboarding setup are proven with just one week of visual experience.

Furthermore, we found that the maturation of orientation tuning required visual experience, whereas the reduction of correlated broad network activity did not.

Thus, maturation of the inhibitory cortical network occurs in a parallel process that is delayed relative to excitatory neurons.

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