Those who have theoretically pure anterograde amnesia are still able to access memories formed before its onset, but they exist in a transient world where anything beyond their immediate attention span disappears from their consciousness permanently. However, theoretically pure anterograde amnesia rarely surfaces: in reality, long-term cases nearly always occur with some degree of retrograde amnesia.
Anterograde amnesia is often informally called “short-term memory loss”, conjuring the idea, as in the movie Memento, that the problem lies with the short-term memory. For this reason, formal (correct technical or scientific) usage demands the term anterograde amnesia, since the condition is a deficit not in short-term memory but in long-term encoding.
Here’s a segment from a BBC Documentary about Clive Wearing, a person who suffers from Anterograde Amnesia.
Clive Wearing has a neurological disorder called Anterograde Amnesia which is a condition that doesn’t allow new memories to transfer into long-term memory. This means that he will never remember anything since his incident, similarly to the movie Memento.
Clive was an accomplished pianist in the 80s’, and fortunately can still play the piano flawlessly. He only remembers his wife, and anything else to him is new information, even if it was presented to him once before.