Fig. 1.

Illustration of the described method, using a bundle of optical microfibers as a multichannel, deep brain recording interface. (a) A standard fluorescent imaging configuration is used to interface with the fiber bundle. The polished imaging surface is mounted below an objective. Excitation light from an LED or other light source passes through a filter cube and is coupled into the fiber bundle; fluorescent emissions return through the objective, pass through the emission arm of the filter cube and are recorded by a camera. The fiber bundle consists of dissociated fibers, each with a diameter of $8\mu \mathrm{m}$. The individual fibers are implanted into the target brain region and secured to the skull. (b) The polished imaging surface as seen by the camera. (c) A bundle of 18,000 fibers prior to implant with gray silicone sheathing cut away. (d) Histology at the tip of a bundle implanted to 2.95 mm in a zebra finch, showing 530 optical microfibers (annotated in green). The fibers displace substantially less tissue (orange circle is cross section of displaced tissue) than existing optical techniques for recording from such a large volume of tissue.