171 years ago Ivan Petróvich Pavlov was born, one of the great pioneers of basic learning psychology, known among other aspects for developing classical conditioning , when he conditioned dogs to associate a bell with food. Similar to how he did it, now a group of researchers from Northwestern University and the University of Hong Kong have developed new synaptic transistors capable of mimicking the plasticity of the human brain by processing and storing data simultaneously .
After connecting transistors to a device, the scientists conditioned it to associate light with pressure, similar to how Pavlov’s dog associated a bell with food.
The secret of this device would lie in its organic electrochemical “synaptic transistors”, capable of processing and storing information at the same time, as the human brain does. Thus, the researchers demonstrated that the transistor could mimic both the short- and long-term plasticity of synapses in the human brain , relying on memories to learn them over time.
Thus, with a capacity similar to that of the brain, the new transistor and circuit could overcome the limitations of traditional computing, including power-consuming hardware and its limited ability to carry out multiple tasks at the same time. In addition, it would also have greater fault tolerance, continuing to function smoothly even when some of its components fail .
As experts say, although the modern computer is outstanding, the human brain is much better at some complex and unstructured tasks, such as pattern recognition, multisensory integration, and motor control, among other important functions. These functions are due to the plasticity of the synapse , which is the basic building block of the brain’s computational power.
These synapses, for example, allow the brain to function in a highly parallel, energy-efficient, fault-tolerant way. And, as is clear from the work done by scientists, the organic plastic transistor is capable of mimicking the key functions of a biological synapse .
How does the synaptic transistor work?
To develop, the team of scientists optimized the creation of a conductive plastic material within the organic electrochemical transistor capable of trapping ions. In the brain, a synapse consists of a structure through which a neuron can transmit signals to another neuron, using small molecules called neurotransmitters.
In the case of the synaptic transistor developed by the Northwestern team and the University of Hong Kong, ions behave similarly to neurotransmitters , sending different signals between terminals in order to generate an artificial synapse . By retaining the stored data of the trapped ions, the transistor remembers previous activities, thus developing long-term plasticity.
To demonstrate the synaptic behavior of their device, the researchers connected individual synaptic transistors in a neuromorphic circuit to simulate associative learning. To do this, they integrated light and pressure sensors into the circuit, and trained it to associate the two unrelated physical inputs (pressure and light) with each other.
After a training cycle, the circuit made an initial connection between light and pressure. And, after five training cycles, the circuit was able to significantly associate light with pressure . What’s more, the light, by itself, was able to trigger a signal (or “unconditional response”).
What can be the future applications of this device?
Since the synaptic circuit has been manufactured with soft polymers, such as a plastic, it is possible to easily manufacture it in flexible sheets and later integrate it in different portable and soft electronic devices, intelligent robotics or even implantable devices that interact directly with the brain or with the tissues alive.
And, although the application of this first device is a proof of concept, the circuit can be further expanded to include a greater number of sensory inputs, and integrate it with other electronic components, thereby allowing low-power computing in the place. Ultimately, it would be a fundamental advance in the bioelectronics of the future .
