Electronic synapses
Physicists have created the first artificial analogue of the synapse of nerve cells
American researchers have created the first semiconductor analogue of the synapse – the connection between nerve cells, which will allow scientists to create computing systems that mimic the work of the brain and study its secrets in "hardware," according to an article published in the journal ACS Nano (Emulating Bilingual Synaptic Response Using a Junction-Based Artificial Synaptic Device).
"The main distinguishing feature of synapses is that they can simultaneously transmit both excitatory and inhibitory signals to other nerve cells. All attempts to copy their device require the use of 10-20 transistors, the combination of which allows you to simulate only one nerve ending. The human brain, in turn, contains 100 trillion synapses," says Han Wang from the University of Southern California in San Francisco (in the press release Hacking the human brain—lab-made synapses for artificial intelligence – VM).
Synapses, or nerve endings, are special structures on the surface of nerve cells that allow them to transmit information in the form of electrical and chemical signals to neighboring neurons, exchanging with them special molecules-neurotransmitters. The brain cells of humans and other animals contain dozens of similar substances, some of which excite neurons, forcing them to produce signals more often, while others suppress their work.
Synapses contain many "sacs" with similar substances, which they transmit to the neuron connected to it when the corresponding "command" enters the nerve cell from other cells connected to it by their own nerve endings. As scientists have recently found out, real neurons, unlike transistors and man-made analogues of nerve cells, can simultaneously transmit both inhibitory and excitatory signals and "switch" between different modes of operation, which gives them incredible flexibility in operation.
Wang and his colleagues created the first full–fledged analogue of the synapse by assembling a kind of "sandwich" of several pieces of different semiconductors - the so-called "black" phosphorus and tin selenide, as well as two gold contact pads and a silicon dioxide substrate.
The key part of this artificial synapse is a thin layer of phosphorus oxide separating the phosphoric semiconductor and the substrate, as scientists say, it may seem to many scientists to be a mistake or a manufacturing defect, since such layers are usually formed with poor insulation of microcircuits and when they come into contact with air during manufacture.
In fact, this part of the "sandwich" of Wang and his colleagues allows him to switch between different modes of operation, passing or not passing current when an electric field is applied to one or two gold electrodes. How much current this layer passes can be flexibly changed using these electrodes, which allows it to completely simulate how synapses and nerve cells work in general.
Accordingly, combinations of a large number of such artificial nerve endings can be used not only to create artificial neural networks without spending a huge number of transistors or computing resources, but also to create analogs of the brain and chains of neurons of living beings and study how they work. This, scientists hope, will bring us closer to uncovering the secrets of human consciousness and mind.
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28.06.2017