Extended Data Fig. 3: Ultraminiaturized, battery powered, head-mounted, wireless recording and stimulation platform.
From: Wireless closed-loop optogenetics across the entire dorsoventral spinal cord in mice
Step 1: System overview: the implants (9 stainless steel wires for ground and 4 differential EMG recording channels, micro-LEDs connected by 3 copper wires) are connected by a 16 pin Omnetics connector to the PCB assembly of the wireless headstage platform. Step 2: Illustration of the antenna design as integrated on the PCB of the head-stage. Step 3: Head-stage wireless link reliability assessment in a typical laboratory/office environment based on received signal strength indication (RSSI) measurements versus line-of-sight distance. A sufficient link is maintained for over 10 m of distance. Step 4: Verification of the LED pulsed current driver performance: LED current can be controlled in 1 mA steps and is monitored on-chip for each issued pulse to verify micro-LED-implant condition and ensure experiment validity. Step 5: Tablet user interface for pulse(-train) stimulation and configuration ranges for all parameters. Step 6: Measurement of closed-loop performance: a EMG signal, simulated as a short sine-wave burst, the triggering of the software algorithm (SW trig), and the issued LED current pulse (I LED) have been acquired by an oscilloscope to measure the delay between the beginning of EMG activity and the closed-loop response. A delay of 11.3 ms is caused by the signal processing, which includes characteristics preventing spiking caused by noise (low-pass). A delay of 0.9 ms is caused by the construction of signal to drive the LED activation. Step 7: Tablet user interface for closed-loop experiments, consisting of an experiment parameter configuration interface and a live preview of all four acquired EMG traces.
