The source of any color light for the “LED-on-Skull” (LS200) electrode is a powerful (500 mW max) LED. Light is delivered to the brain by a 200 um optical fiber. The fiber should be cut before implantation to the desired length. A twisted pair of wires on the top serves to implant the fiber and deliver current to the LED over an electrical commutator.
The source of the blue light for the “LED-on-Tip” electrode (LT250i, 450 um diameter with insulation) is an extremely small LED, 320*240 um, affixed on the very tip of a twisted pair of wires. The power of this LED at 20 mA current is 30 mW. The electrode can be chronically implanted into the brain. These electrodes are reusable. Chronically implanted electrodes demonstrate stable response*. The electrodes are powered by any type of conventional stimulator, pulse generator and simple driver or Invilog In Vivo Voltammetry Setup via its electrical commutator or by the Invilog wireless opto-stimulation device.
The light source (LED) of the LT250i electrode is located in close proximity to brain tissue. Traditional stimulation by an optical fiber (LS200) delivers light to the brain via a 35-450 light beam below the tip. In contrast, the LED on our electrode’s tip transmits light more circularly; this means that the tip can be located not only above but also within the targeted area (see photograph above of the two electrodes in fluorescein).
Opto-electrodes are inserted in the brain during stereotaxic surgery in exactly the same way as conventional stimulating electrodes. After implantation, the opto-stimulating electrode is cemented onto the skull. Invilog proprietary method makes these electrodes reusable. The flexible shaft permits implantation of several electrodes with their electrical connectors which can be compactly fixed to the animal’s skull.
*Montgomery et al., Nature Methods 12 (2015) 969