"George studied for a test while taking an amphetamine. After the drug wore off, he was not able to remember what he had learned while studying. This is an example of the phenomenon called state ."

state-dependent memory

Explanation:

State-dependent memory is, as the name implies, a memory that depends on something and disappears when that "something" is not present. This phenomenon occurs when people remember things when their brain state is at the same level as it was when these memories were created.

In the case shown in the question above, George used amphetamines while he was studying, to improve his performance, amphetamines created a state in George's brain, that state, left the memories about what he studied dependent on. In that case, when George's brain leaves that state and returns to its normal state, George will forget everything he has learned.

there is an explationation of this on a site called crash   course world history 1