Fig. 1.

Electrode implantation in the brain elicits an immune response that leads to glial encapsulation of the electrode. Illustration of the immune response (A) prior to electrode implantation, (B) 12 h post-implantation—activated microglia migrate toward the electrode, (C) 1 week post-implantation—activated microglia have attached to the electrode and reactive astrocytes migrate toward the electrode, (D) 4 weeks post-implantation—the electrode is encapsulated by a sheath of activated microglia and reactive astrocytes, (E) 12 weeks post-implantation—the encapsulating glial sheath continues to tighten around the electrode. Cross-sectional views of (C), (D), and (E) are shown in (F), (G), and (H), respectively. Reproduced with permission from [19]