In future, "people could become telepathic to some degree" and being able to read someone else's thoughts raises ethical issues, experts said.

This could become especially worrying if those thoughts were shared with corporations.

Commercial products should not come from "a handful of companies", they added

In the study - iHuman: Blurring Lines between Mind and Machine - leading scientists at the UK's Royal Society lay out the opportunities and risks of brain-to-computer devices.

Such interfaces refer to gadgets, either implanted in the body or worn externally, that stimulate activity in either the brain or nervous system.

It looked at some of the future possibilities of neural technology, such as:

• the ability to beam a "neural postcard" to someone so they could see what you see even if they are not there
• people being able to converse without speaking through access to each other's thoughts
• people being able to simply download new skills

As part of the report, scientists asked the public what they thought of such interfaces and found strong support for their use in allowing patients to recover from injury or a medical condition.

But there was far less support for using such devices to enhance functions such as memory or physical strength in healthy people.

'Benefit of humanity'

Among the risks highlighted by the report was the idea of thoughts or moods being accessed by big corporations as well as the bigger question about whether such devices fundamentally change what it means to be human.

Dr Tim Constandinou, director of the next generation neural Interfaces (NGNI) Lab, at Imperial College London and co-chair of the report, said: "By 2040 neural interfaces are likely to be an established option to enable people to walk after paralysis and tackle treatment-resistant depression, they may even have made treating Alzheimer's disease a reality.

"While advances like seamless brain-to-computer communication seem a much more distant possibility, we should act now to ensure our ethical and regulatory safeguards are flexible enough for any future development.

"In this way we can guarantee these emerging technologies are implemented safely and for the benefit of humanity."

The report recommends:

• a national investigation of the ethical issues presented by neural interfaces to address what data should be collected, how it is kept safe and the acceptability of merging machines and humans
• creation of a neural interface ecosystem to encourage industry and universities to innovate and collaborate in the field
• the UK's Medicines and Healthcare Products Regulatory Agency to trial new ways to bring such products to market, and to prevent a monopoly by big tech firms

In July, Elon Musk announced that his firm Neuralink was applying to start human trials in the US, with electrodes inserted into the brains of patients with paralysis.

And Facebook is supporting research that aims to create a headset with the ability to transcribe words at a rate of 100 per minute, just by thinking.

In the US it is estimated that 60,000 spinal-cord stimulators are implanted annually and around the world some 400,000 people have benefited from cochlear implants.

Thousands of people with Parkinson's disease and similar conditions have been treated with deep brain stimulation, and artificial pancreases and wireless heart monitors are also common.