Similar construction is used for all implants, but small design variations are used to customize the implants to different nervous system targets. In brain and peripheral implants, current is delivered to a 250-μm diameter extension made of a pair of magnet wires with a micro-LED attached at the tip. The extension can be inserted in the brain or routed to peripheral nerves. The micro-LED of the brain implant points parallel to the extension axis, whereas that of the peripheral nerve ending implant points perpendicular to the extension axis. Such an extension was not included in the spinal implant to avoid damage to the cord; instead, the LED was mounted directly onto the PCB. A “spinal cord” device could equivalently be used for superficial brain targets. Peripheral implants change spatial orientation relative to the cavity more than central implants during the course of locomotion. Due to this variability in orientation of the peripheral implant, the individual turns of the coil were set to be non-parallel, thus minimizing orientation-related power fluctuations.