Chronic Electrode Implants - Interaction Between Electrode and Tissue

Interaction Between Electrode and Tissue

As mentioned above, if there is to be significant progress towards long-term implantable electrodes, an important step is documenting the response of living tissue to electrode implantation in both the acute and chronic timelines. It is ultimately this tissue response that causes electrodes to fail by encapsulating the electrode itself in a protective layer called a “glial scar,” (see 2.2). One serious impediment to understanding the tissue response is the lack of true standardization of implantation technique or of electrode materials. Common materials for electrode or probe construction include silicon, platinum, iridium, polyimide, ceramic, gold, as well as others. In addition to the variety of materials used, electrodes are constructed in many different shapes, including planar shanks, simple uniform microwires, and probes that taper to a thin tip from a wider base. Implantable electrode research also employs many different techniques for surgically implanting the electrodes; the most critical differences are whether or not the implant is anchored across the skull and the speed of insertion. The overall observed tissue response is caused by a combination of the traumatic injury of electrode insertion and the persistent presence of a foreign body in the neural tissue.