The metal bits at the back of my neck. I have a bunch of wires in my brain that connect to those. Two are chips to help me run neural interface devices, like my power armor, and one is to an empty port for an AI.

I was part of an experiment that partners human soldiers with AI's directly, allowing the AI more processing power thanks to the human brain, and letting the human overcome mental limits. Essentially become a two person army.

Presumably I was one of the experiment's failure.