  A bidirectional brain interface with both "write" and "read" functions can be
an important tool for fundamental studies and potential clinical treatments for
neurological diseases. Here we report a miniaturized multifunctional fiber
based optoacoustic emitter (mFOE) that first integrates simultaneous
non-genetic optoacoustic stimulation for "write" and electrophysiology
recording of neural circuits for "read". The non-genetic feature addresses the
challenges of the viral transfection required by optogenetics in primates and
human. The orthogonality between optoacoustic waves and electrical field
provides a solution to avoid the interference between electrical stimulation
and recording. We first validated the non-genetic stimulation function of the
mFOE in rat cultured neurons using calcium imaging. In vivo application of mFOE
for successful simultaneous optoacoustic stimulation and electrical recording
of brain activities was confirmed in mouse hippocampus in both acute and
chronical applications up to 1 month. Minimal brain tissue damage has been
confirmed after these applications. The capability of non-genetic neural
stimulation and recording enabled by mFOE opens up new possibilities for the
investigation of neural circuits and brings new insights into the study of
ultrasound neurostimulation.
