Why Musk start-up Neuralink seeks people for brain-implant trial

At the start of the six-year study, a robot would be used to surgically place 64 flexible threads, thinner than a human hair, on to a part of the brain that controlled "movement intention", the company said.

These allow Neuralink's experimental N1 implant - powered by a battery that can be charged wirelessly - to record and transmit brain signals wirelessly to an app that decodes how the person intends to move.

The company says people may qualify for the trial if they have quadriplegia due to injury or amyotrophic lateral sclerosis (ALS) - a disease in which the nerve cells in the spinal cord and brain degenerate.

While Mr Musk's involvement raises the profile of Neuralink, he faces rivals, some with a track record dating back nearly two decades. Utah-based Blackrock Neurotech implanted its first of many BCIs in 2004.

Precision Neuroscience, formed by a Neuralink co-founder, also aims to help people with paralysis. And its implant resembles a very thin piece of tape that sits on the surface of the brain and can be implanted via a "cranial micro-slit", which it says is a much simpler procedure.

Meanwhile, existing devices are generating results. In two separate recent US scientific studies, implants were used to monitor brain activity when a person tried to speak, which could then be decoded to help them communicate.

Dr Adrien Rapeaux, a research associate in the Neural Interfaces Lab at Imperial College London told the BBC that "Neuralink no doubt has an advantage in terms of implantation" as their procedure was robotically assisted.

But Dr Rape aux who is also a co-founder of a neural implant start-up Mintneuro, said it wasn't clear how their method for converting brain signals into useful actions would do better than that used by Black Rock Neurotech for example, and whether it is able to stay accurate and reliable over time, "a known issue in the field".

Is it safe?

There are three elements to this: short term physical risks; long term medical concerns; and ethical safety.

Any surgery involving the brain carries inherent danger, both of physical harm and rejection by the host. There has been extensive (and controversial) testing of the chips on animals.

A complaint filed in February to the US Department of Agriculture alleged cruel treatment of macaque monkeys who are being used to test the technology.

The fact that the FDA has approved the start of human testing, however, implies the company has overcome some of the challenges.

Maybe the more serious concerns come around the long-term consequences of having a device like this operating within the human brain, a vastly complex organ we are only beginning to understand.

Understandably there is no data as to what the potential harms may be. That will change with testing on humans and will be key to the development of similar products.

The final element, ethical safety, is more subjective. Technology like this is riven with concerns about data protection, potential uses and the possibility of human enhancement.

This means augmenting or enhancing the capabilities of the human brain beyond what we are currently capable of doing. For example, improving human cognition, sensory perception, or physical abilities. This always stirs strong emotions and raises ethical questions so there will be calls for close regulation of the sector.