A technique has been developed for “editing” sensations felt by the brain, paving the way for equipment that could delete pain, copy and paste patterns of activity and add non-existent aspects into our memories.

Developed by scientists at UC Berkeley, and described in the journal Nature Neuroscience, the “holographic brain modulator” uses projections to activate or suppress specific neurons. The aim is to be able to do this reactively to modify the brain’s activity and insert false sensations.

One potential application, flagged by the researchers, is using the tech to help a patient control a prosthetic limb: “This has great potential for neural prostheses, since it has the precision needed for the brain to interpret the pattern of activation. If you can read and write the language of the brain, you can speak to it in its own language and it can interpret the message much better,” said Alan Mardinly, assistant professor of molecular and cell biology at UC Berkeley.

“This is one of the first steps in a long road to develop a technology that could be a virtual brain implant with additional senses or enhanced senses.”

While the potential for the technology reaches into science-fiction territory, particularly the scope for it to edit our impressions of surroundings – or layer non-existent aspects into our memories – the modulator is still at a nascent stage. In their study, the scientists honed in on a tiny section of a mouse brain, consisting of around 2,000 to 3,000 neurons. Using a technique called optogenetics, these neurons were outfitted with a protein, using a genetically altered virus, which meant the cell could be turned on or off with a flash of light.

To focus this light so that it only hit certain neurons, the team used computer-generated holography. This allowed them to create a 3D hologram of light points, which was projected through a layer of tissue at the surface of the mice’s somatosensory cortex, into the brain.

(Video showing neuron activity in a chunk of the somatosensory cortex of a mouse’s brain. Activated neurons are green. Neurons activated by holographic laser light are indicated by a purple arrow. Credit: UC Berkeley)

“The major advance is the ability to control neurons precisely in space and time,” said co-author Nicolas Pégard. “In other words, to shoot the very specific sets of neurons you want to activate and do it at the characteristic scale and the speed at which they normally work.”

The prototype was tested in the touch, vision and motor areas of mice on treadmills, each with their heads immobilised. The researchers didn’t notice any behavioural changes, but the brain activity was similar to what would be expected if the mice were responding to actual sensory stimuli.

The next step will be to improve the technology, scaling it so that it can work with more than the brain’s outer layer. The size of the equipment also needs to be shrunk, eventually with the aim of fitting into a backpack. The scientists additionally want to capture real patterns of activity in the brain’s cortex, all the better to reproduce those sensations using the holographic projections.