Prototype of a live brain-computer interface
Scientists from the Weizmann Institute have created an artificial neural network
Evgeny Birger, Nanonews Network
There are known results on connecting the brain directly to computers by means of metal electrodes in the hope of obtaining information about what is happening inside the brain and using the obtained measurement data in the treatment of blindness and epilepsy. In the future, the interface between the brain and an artificial system may be built on nerve cells specially grown for this purpose.
A group of Israeli scientists from the Weizmann Institute of Science, led by Professor Elisha Moses, took the first step in this direction by artificially creating circuits and logic gates from living nerves grown in the laboratory. The results are published in the journal Nature Physics (Ofer Feinerman, Assaf Rotem, Elisha Moses. Reliable neuronal logic devices from patterned hippocampal cultures, – Nature Physics 4, 967 – 973, 2008, doi: 10.1038/nphys1099, Article).
Neurons (nerve cells of the brain) grown in biological culture do not form a "thinking" neural network. Israeli scientists have set the task of creating such a physical structure of the nervous network that would be close to the natural one that exists in the brain. To simplify the task at the first stage, they grew a one-dimensional model of the network in a specially made groove in a glass substrate. The researchers found that these nerves can be excited by a magnetic field (all previous results in this direction showed that nerves can only be excited by an electrical signal).
Experimenting further with the linear contour, the group found that variations in the thickness of the nerve fiber affect the transmission of the signal. Nerve cells in the brain are connected to a huge number of other cells by means of axons (long and thin processes) and they must receive a certain minimum number of incoming signals in order to recognize the source and develop a response signal. The researchers determined the threshold thickness of the nerve, which ensures the growth of approximately 100 axons. Below this number of axons, the response signal was problematic, and the presence of literally several processes greater than 100 significantly increased the probability of passing the response signal.
Next, the scientists took two tapes of 100 axons each and created a logic gate in the likeness of one used in electronic computers. Both of these "wires" were connected to a small number of nerve cells.
When the cells received a signal through one of the "nerve wires", the response signal was indeterminate. At the same time, the signal sent through both "wires" received an instant and clearly expressed response signal. Such a logic gate is known as an I-gate.
In a subsequent experiment, the group constructed structures with neural tapes assembled in such a sequence that axons could send and transmit signals in only one direction. Several such contours were then combined to form a closed contour in the manner of a loop. At the same time, there was a regular signal transmission over a closed circuit, according to the type of biological clock or pacemaker.
It is difficult to overestimate the results obtained both in importance and in the opportunities they open up.
The details of the work can be found on the web page of the laboratory of E. Moses
Portal "Eternal youth" www.vechnayamolodost.ru02.02.2009