In the primary visual cortex of the brain, neurons are organized into alternating columns that receive inputs from either the left or right eye. This organization is strongly dependent on early visual experience.
When one eye is deprived of visual inputs during a critical developmental period, the corresponding columns fail to develop properly, whereas those receiving inputs from the unaffected eye grow larger than normal.
The cortex consists primarily of two different types of neuron: excitatory neurons that synthesize and release the neurotransmitter glutamate, and inhibitory interneurons which use the transmitter ã-aminobutyric acid (GABA). How each of these cell types contributes to experience-dependent changes in the visual cortex is, however, unknown.
To investigate this, Tadaharu Tsumoto of the RIKEN Brain Science Institute, Wako, and his colleagues injected a calcium-sensitive dye, Fura-2, into the visual cortex of genetically engineered mice whose inhibitory interneurons express a fluorescent protein called Venus1. The intensity of Fura-2 fluorescence changes in response to the increase in calcium ion concentration that is characteristic of neuronal activity.
This approach enabled the researchers to both identify the interneurons in the visual cortex and monitor their activity. In animals reared normally, they first identified the ‘binocular’ regions of the primary visual cortex by visually stimulating each eye in turn, and using two-photon laser-scanning microscopy to locate the cells that responded to both. This revealed that inhibitory interneurons are more responsive to inputs from both eyes than excitatory neurons.
The responses in mice deprived of visual inputs to one eye for two days during the critical period were then examined. The change in the responses of both cell types was found to be similar—both had become more responsive to inputs from the open eye.
When mice were deprived of visual inputs to one eye after the critical period, however, the effect observed was far stronger on the inhibitory interneurons. They tended to receive inputs from the open eye, and their responses to inputs from the closed eye were also depressed, whereas those of the excitatory neurons remained almost stable. The interneurons normally act to inhibit the excitatory neurons, so their depressed responses may contribute to the stability of excitatory neuron responses to the deprived eye.
“Inhibitory interneurons are divided into several subtypes,” says Tsumoto. So, the next step is to determine which particular subtypes are involved in maintaining plasticity after the critical period.
The corresponding author for this highlight is based at the Laboratory for Cortical Circuit Plasticity, RIKEN Brain Science Institute
1. Kameyama, K., Sohya, K., Ebina, T., Fukuda, A., Yanagawa, Y. & Tsumoto, T. Difference in binocularity and ocular dominance plasticity between GABAergic and excitatory cortical neurons. Journal of Neuroscience 30, 1551–1559 (2010)
Saeko Okada | Research asia research news
Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory
How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy