Anterograde amnesia
From Memory Alpha, the free Star Trek reference
Anterograde amnesia is a medical condition which prevents the sufferer storing new memories. Those afflicted with the condition can remember events up to the onset of the amnesia, but nothing after it. Any new events are not laid down in long-term memory, and information given to the sufferer will not be remembered after a short time.
In an alternate timeline, Jonathan Archer was affected by anterograde amnesia after being infested with interspatial parasites in 2154. Consequently, he was unable to discharge his duties as captain of Enterprise, and was forced to resign his commission. The condition was eliminated when the parasites were retroactively removed from his brain in 2165. (ENT: "Twilight")
