Deciphering the neural patterns underlying brain functions is essential to understanding how neurons are organized into networks. This deciphering has been greatly facilitated by optogenetics and its combination with optoelectronic devices to control neural activity with millisecond temporal resolution and cell type specificity. However, targeting small brain volumes causes photoelectric artefacts, in particular when light emission and recording sites are close to each other. We take advantage of the photonic properties of tapered fibres to develop integrated ‘fibertrodes’ able to optically activate small brain volumes with abated photoelectric noise. Electrodes are positioned very close to light emitting points by non-planar microfabrication, with angled light emission allowing the simultaneous optogenetic manipulation and electrical read-out of one to three neurons, with no photoelectric artefacts, in vivo. The unconventional implementation of two-photon polymerization on the curved taper edge enables the fabrication of recoding sites all around the implant, making fibertrodes a promising complement to planar microimplants.

B.S., A.B., M.B., F. Pisano and F. Pisanello acknowledge funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme (no. 677683); M.P. and M.D.V. acknowledge funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme (no. 692943). M.B., M.D.V. and F.Pisanello acknowledge funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme (no. 966674). F. Pisano, M.D.V. and F. Pisanello acknowledge funding from the European Union's Horizon 2020 research and innovation programme (no. 101016787). L.S., M.D.V. and B.L.S. are funded by the US National Institutes of Health (U01NS094190). M.P., L.S., F. Pisanello, M.D.V. and B.L.S. are funded by the US National Institutes of Health (1UF1NS108177-01). A.B., F. Pisanello and M.D.V. also acknowledge funding from the European Union's Horizon 2020 research and innovation programme (no. 828972). We also acknowledge J. Lee for help setting up the optrode fibre launch system.