As for what Mehta's findings could potentially mean, there are precedents for the brain activity he's observed in rats using virtual reality which, considered in isolation, are alarming. "[The rat's] vision is telling him he's moving forward, his claws are saying he's moving forward, but his sense of acceleration is telling him that he's not going anywhere," says Mehta. "And it's that mismatch between different things that causes these neurons to fire abnormally. And we believe this kind of mismatch may be happening under various diseases as well... Like watching an old television or an old movie that's not working perfectly, in the speech, and the sounds, and the light, the scene is slightly off. You can tell that something is wrong. That's exactly what we think is going on in virtual reality."

It's an established fact that neuroplasticity, the brain's ability to rewire its circuits, remains in place throughout our lives. The fear is that there's a possibility that VR use, which appears to trigger abnormal brain function in rats at least, could 'teach' the brain to rewire itself in an undesirable way. This proves nothing in and of itself, however, and Mehta is keen to stress that much more work is needed to study the issue. His is one single study in a complex subject, and he has no interest in scaremongering.

"The long term consequences are really hard to measure in the human brain," he explains. "Because humans age very slowly. They live for around a hundred years, rats live for roughly two or three years. We can't wait for forty years, for teenagers who are today using virtual reality to see what happens to them when they're sixty. Does it cause Alzheimer's? Does it cause some other [disorder]? Or is it therapeutic? Maybe it's good! I don't know! But we need to measure that in rats, and those experiments can be done in a couple of years. So it's still not too late. And that will be very informative, what happens to rats. For humans in the long term. But that still needs to be done."

...

This follow-up study remains unpublished at time of writing, so Mehta was unable to discuss it, but his hope is that within a few months, it will have been published, and he will have a few more answers to take him and his team a little closer to an understanding of the situation.

(The screens used in the study were 2D and rats don't see in steroscopic vision according to comments at the link)