First is the case of the monkey “Animal 20.” In December 2019, an internal part of the brain implant being inserted into the primate “broke off” during surgery. Later that night, the monkey scratched at the implant site, drawing blood, and yanked on the implant, partially dislodging it. Follow-up surgery discovered that the wound was infected, but that the placement of the implant prevented treatment. The monkey was euthanized the next month.

Before that, a female monkey designated “Animal 15” began to press her head against the ground after receiving the brain implant, pick at the site until it bled, and eventually lost coordination, shivering when personnel entered the room. Scientists discovered she had brain bleeding, and in March 2019, she too was euthanized.

The following year, a primate called “Animal 22” was put down in March 2020 after its brain implant became so loose that the screws attaching it to the skull “could easily be lifted out,” according to a necropsy report.

“The failure of this implant can be considered purely mechanical and not exacerbated by infection,” the necropsy states.