Figure 1.

Surgical implantation and explantation of UEAs after 848 days in the left hemisphere (A-C) and 590 days in the right hemisphere (D-E) of the NHP. A) Left hemisphere implantation of two UEAs in the motor and sensory cortices on either side of the central sulcus. B) Explantation of the UEAs in (A) involved removing the section of bone (bone flap) above the arrays. After the bone flap and dura were removed, the UEAs could be extracted. Removing the left sensory UEA revealed clear holes in the tissue. C) However, the UEA in the left motor cortex was fully encapsulated by tissue and no longer implanted in the brain surface, as seen from the image taken of the side of the tissue. Once removed, a depression in the brain surface was observed below the array’s location. D) Right hemisphere implantation of two UEAs in the motor and sensory cortices on either side of the central sulcus. E) Explantation of the UEAs in (D) involved removing the bone flap above the arrays to reveal the two UEAs. After the bone flap was removed, the UEAs could be extracted. Both UEAs were partially or fully implanted in the tissue at the time of explant. Given the similarity between the landmarks surrounding the arrays during implantation (A & D) and explantation (B & E), we determined that the arrays largely retained their positions along the brain surface. All scale bars are 4mm.