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
Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München
Second research flight into zero gravity
21.10.2016 | Universität Zürich
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences