using carbon nanotubes for neural prostheses

Carbon nanotubes are amazing things – they are electrically conductive, thermally conductive, so dark that materials made from them are blacker than whatever you think black looks like, and they are so strong that we may one day make elevators out of them that reach right out into space.

CSIRO_ScienceImage_1074_Carbon_nanotubes_being_spun_to_form_a_yarn
image: carbon nanofibers being spun into yarn

There have been fears circulating that nanotubes are biologically dangerous.

Every new thing has provoked fear-mongering – GMO, vaccines, the telephone, cars, the loom, but the more high-tech a new technology is, the harder it is to dissuade people of those fears, because it’s hard to explain high-tech in a way that’s easy for those fearful people to understand.

In the case of carbon nanotubes, the main fear is that because they are fibrous in nature (like fibre-glass and asbestos), they’re dangerous to the skin and lungs as an irritant, but because they are also so thin that they can penetrate biological cells (which fibreglass and asbestos can’t do), there is an added fear that they can disrupt the cell functions.

A study by researchers led by Laura Bellerini showed that not only do carbon nanotubes not interfere with the function of cells, but that they may be perfect for creating neural interfaces; something we will need for when we are coming up with ways to either speak directly to the brain, read directly from the brain.

The study also showed that when neurons are embedded in carbon nanotubes, they mature more quickly and grow new synapses (connections with other neurons).

While the potential for this goes well into sci-fi (uploading the brain, for example), the near-term uses are still phenomenal.

An example use in the near-term is to help create a link between an artificial hippocampal prosthesis, and the surrounding brain tissue.

The hippocampus is the simplest part of the brain to understand – data comes in one end, and goes out the other. A team of researchers spent ten years slicing a hippocampus up into tiny slices and measuring the electrical pathways, before recreating it in software, with an array of input probes, and another array of output probes. When the probes were placed in a rat’s brain (after cutting out its hippocampus), it was found that the prosthesis allowed the rat to make new memories. Human trials are currently underway.

Probably the hardest part of replacing the hippocampus is the reconnection, where the existing defunct hippocampus is removed, and the new artificial one is connected. The artifical device doesn’t need to go into the brain itself, but there must be a connection made between the brain and the device. This is currently done with an array of needles, but there is a limit to how fine those needles can get.

With carbon nanotubes, there is no such limit – because they are so much thinner than the thinnest metal needles, it should be possible to simply slide an entire array of them into place and have the carbon nanotubes automatically interface with neurons.

non-invasive deep-brain stimulation

Deep-brain stimulation is used in a number of therapies, for diseases such as Parkinson’s, major depression, OCD, dystonia. It is also used to lessen chronic pain and to help regulate Essential tremors.

This involves drilling a 1.4cm hole in the head, then inserting electrodes into the brain into the affected part.

Obviously, there are risks involved in this.

A team at MIT has come up with a method to provide stimulation at any desired part of the brain using electrodes that are placed on the scalp instead of embedded within the brain. No surgery required.

How it works is that the electrodes, placed on either side of the head, give out waves of electricity. The waves interfere with each other like two waves meeting in a pond, cancelling each other out except for in specific points where the waves are intensified instead.

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An advantage to this method is that the intersection points can be “steered” by adjusting the waves.

My opinion: this method should make a lot of surgeries unnecessary, and will make the therapies for those disease so simple that it might eventually be possible to simple buy an off-the-shelf electrode cap and run some open source software to fix your issues.