"Neurons that fire together wire together" (aka Hebb's theory) is a very important rule that describe the basis of how our brain functions. The theory says that when two neurons are firing together, the synapses that connect that connect the two neurons will be strengthen, and such mechanism is very important for our cerebrum to form new memories.
Therefore, one of the important strategies to create a brain-like machine (i.e., neuromorphic computing) that can potentially be connected to a real cerebrum (i.e., brain computer interface technology) is to find a physical entity that can mimic the behavior of a synapse, and "memristors" is one of the possible options that can get the job done.
A memristor was first proposed theoretically by Leon Chua (a professor in the electrical engineering and computer sciences department at the University of California, Berkeley) in 1971, which is a resistor whose electrical resistance is correlated to the current passing through it and is capable of forming a memory about the previous resistance (just like a synapse).
In order to connect a memristive device to a real human wetware, however, one must first overcome a critical problem: a traditional computing device has the typical switching voltages between 0.2 to 2 V, while nervous system works on a much lower voltages that are typically around only 80 mV.
In a paper published on Nature Communications in 20 April 2020 by (read the original paper), Tianda Fu et al. from the University of Massachusetts Amherst proposed a new kind of diffusive memristor based on the protein nanowires sourced from the bacterium named Geobacter sulfurreducens that can potentially resolve the problem. The artificial neurons built on such memristors can function on the level of biological voltages, and they express “temporary integration feature that is similar to real neurons in our brain” according to the authors.
Protein-based nanowires also have the following advantages over silicon-based nanowires:
It can be cheaper in price.
The manufacturing process requires no toxic chemicals and lower energy.
It's more stable in body fluid.
Recently, brain computer interface has become more and more common in medical applications with the help from artificial intelligence. For instance, scientists have created prostheses that can be controlled directly by one's mind and send signals to the user's brain allowing him or her to "feel" the touch. Thus, it's safe to say that devices that can communicate with human nervous system and be planted within human body stably are very important to future medicine (to see how technology is changing the medical field, please refer to the following article), and the new memristors proposed by Tianda and his colleagues may hold the answer to the next breakthrough.
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