Previous research has generally relied on separate devices: needles to inject viral vectors for optogenetics, optical fibres for light delivery, and arrays of electrodes for recording, adding a great deal of complication and the need for tricky alignments among the different devices.
The fibres are designed to mimic the softness and flexibility of brain tissue. The scientists say this could make it possible to leave implants in place and have them retain their functions over much longer periods than is currently possible with typical stiff, metallic fibres, enabling more extensive data collection.
In tests with lab mice, the researchers were able to inject viral vectors that carried genes called opsins, which sensitise neurons to light, through one of two fluid channels in the fibre. They waited for the opsins to take effect, then sent a pulse of light through the optical waveguide in the centre, and recorded the resulting neuronal activity, using six electrodes to pinpoint specific reactions. All of this was done through a single flexible fibre 200µm across.
“Potentially, we could use many of them to observe different regions of activity,” said Polina Anikeeva, Professor in the Department of Materials Science and Engineering. In their initial tests, the researchers placed probes in two different brain regions at once, varying which regions they used from one experiment to the next, and measuring how long it took for responses to travel between them.
The next engineering challenge the team aims to tackle is reducing the width of the fibres further, to make their properties even closer to those of the neural tissue.