Durham University scientists found using a specially equipped helmet to beam invisible waves of light into healthy brains improved people's memories and thought processing.
They said it could pave the way for a dementia therapy – the condition is incurable and affects around 850,000 people in the UK.
The £7,250 helmet works by forcing brain cells to boost their energy levels – which fall in people with dementia – and encouraging blood flow so the brain gets more oxygen.
Durham's Dr Paul Chazot said: "We've shown what appear to be real improvements in memory and other neurological processes for healthy people.
"While more research is needed, there are promising signs that therapy involving infrared light might also be beneficial for people living with dementia and this is worth exploring."