Using a tool that looks suspiciously identical to the Injection Carbon Reader, the stem line provides electrical current to nerve endings. It is inserted directly into the alien head and then controlled wirelessly via unseen controls on a nearby touch-sensitive slate pad.
The output on the stem line device animates with changes, but it seems the numbers appear near the middle and then slide to fixed positions on the top and bottom. If the point of the display was output, and it is meant to be seen from a distance, wouldn’t a simpler large-number display make more sense? If motion is meant to convey the meaning, like a digital gauge on a multimeter, then the text should be fixed on the graduated background and slide with it.
By stimulating the locus coeruleus of the alien, the Prometheus scientists seek to “trick it into thinking it’s still alive,” even though they have not confirmed the physiology of this 2000 year old alien specimen, or even that (in a quick Googling, the author learned that) this is the panic area of the nervous system. Were the results really that surprising?