New Artificial Neurons Send and Receive Chemical Signals

Scientists in China and Singapore have developed a novel artificial neuron. It can both release and receive dopamine. And it opens the door to using chemical signals in brain-machine interfaces (BMIs).

“The brain’s native language is chemical, but current brain-machine interfaces all use an electrical language,” says Benhui Hu (Nanjing Medical University), as reported by New Scientist. “So we devised an artificial neuron to duplicate the way a real neuron communicates.”

Organic neurons in the brain communicate by exchanging chemicals called "neurotransmitters" along communication channels called "synapses."

A paper is published in Nature Electronics. The scientists describe an artificial neuron that can receive and release the neurotransmitter dopamine.

The artificial neuron detects dopamine using an electrochemical sensor with a graphene and carbon nanotube electrode. If enough dopamine is detected by the sensor, a memristor triggers the release of more dopamine at the other end through a heat-activated hydrogel.

The memristor can change the threshold strength of the input dopamine signal that is required to trigger the release of output dopamine. This is similar to how neurons in the brain change how much neurotransmitter is sent between connections in response to external stimuli. Such plasticity is essential for learning.

“To chemically communicate with biological neurons, bioelectronics should at least possess three basic functionalities: neurotransmitter recognition, synaptic plasticity, and firing of action potentials and releasing of neurotransmitters,” note the scientists in the paper.

The system responds to dopamine and releases dopamine in a chemical communication loop similar to the chemical communications between organic neurons. Experimenting with rat brain cells in the lab, the scientists have shown that the artificial neuron can trigger the controllable movement of a rat leg and robotic hand.

“The scientists connected the chip to a nerve in a mouse’s leg,” explains SingularityHub. “Depending on the level of dopamine, the leg flexed ... in another proof of concept, the team hooked up the chip to a robotic hand.”

“This actually has quite a lot of potential for expanding into more sophisticated learning systems,” comments Yoeri van de Burgt (Eindhoven University of Technology), as reported by New Scientist. “You can do a lot of new cool things here.”

The scientist explains that the current device is too big for applications to BMIs. But it could be used in prosthetic devices.

Looking farther ahead, this research program could enable future BMIs to use chemical communications besides electric communications. “Such chemical BMIs could complement electrical BMIs, potentially allowing neuronal information to be correctly and comprehensively interpreted for use in neuroprosthetics, human-machine interactions, and cyborg construction,” say the scientists as reported by SingularityHub.

There’s also the possibility that electrical BMIs could be unable to “comprehensively interpret human consciousness.” In this case, BMIs able to use the brain’s native chemical information could boost consciousness studies.