Multimode fiber optic patch cable

We implanted a multi-mode fiber optic patch cable (Ø150μm, Thorlabs) via a 1.25mm OD multimode ceramic zirconia ferrule (Precision Fiber Products, Inc, Milpitas, CA 95035), which was glued together with the S1R electrode to form an optrode configuration and implanted in the distal site (~1–1.5mm) of the microgyrus location (Figure 6a, d). The multi-mode fiber optic patch cable was coupled to a blue laser (473nm, 100 mW, DPSS blue laser, www.lasercentury.com) via a SMA mating end. Laser pulses were delivered via a custom-made pulse generator at three frequencies (1, 5 and 10Hz). It was estimated that an area approximately 0.3mm deep and 0.3mm wide was illuminated upon activation of the fiber, based on tests using a similar fiber in brain slices in vitro [73 (link)]. During the online recording period, bandwidth filtered (8–15Hz) of the EEG trace is displayed for the detection of spike-wave discharges, which is defined based on our initial characterization [25 (link)]. Upon detection of spike-wave discharges, laser stimulation is delivered for a period of 5–10 seconds.

The home built microscope is shown in Figure 1. The excitation source, a 405 nm, 150 mW, diode laser (Thorlabs, Inc.), 3.8 mm beam diameter, is driven by a 250 mA blue laser diode drive board (Thorlabs, Inc.). Transmitted light is focused into a multimode fiber optic patch cable (Thorlabs, Inc.) and the beam is reflected with a 409 nm 25 × 36 mm Bright line single edge dichroic (Semrock, Inc.) and focused with a 1.4 numerical aperture 100x objective lens (Carl Zeiss, A.G., 440780-9904). Glass slides are mounted to the stage on a hollow aluminum cylinder that is secured with a through bolt to minimize motion. The samples may be viewed from above or from the side by shifting the position of the stage. Stage movement is facilitated with 3 axis adjustment micrometers (Mitutoyo Corp and Newport Corp.). The focal length is adjusted with a differential actuator (1/2” manual drive with .5 μM graduated lockable thumbscrews (Thorlabs, Inc.). Emitted light passes through a 500 nm cutoff long pass filter FEH 0500 (Thorlabs, Inc.) enabling red and green to be visualized simultaneously. Emitted light is captured with 1.4 MP Nikon DS-Ri1 camera, Peltier cooled to −10 degrees. Exposure time at 80 msec provides optimal image quality while preserving sample integrity. The diode laser is controlled and synchronized to the corresponding exposure period. The pixel size is 55 nm.