retrograde amnesia

Meaning: Retrograde amnesia is loss of memories that were formed before the onset of brain damage, such as head trauma. The person cannot recall past events or facts (explicit memory, especially episodic), yet may learn new information normally. It often shows a temporal gradient: memories from shortly before the injury are lost more than remote ones. This fits the consolidation idea that the hippocampus helps stabilize new memories, which over time come to be stored in the cortex and depend less on it.

On the MCAT: A passage describes a patient who, after head trauma or damage to the medial temporal lobe, cannot recall events from the months before the damage but forms new memories normally. You label the deficit as retrograde. Related questions ask which structure is involved (hippocampus and nearby regions) or which memory is often spared (implicit and procedural memory, such as riding a bike).

Common confusion: Students swap retrograde and anterograde. Anchor on the injury date: retrograde reaches backward and erases memories from before it, while anterograde fails to form memories after it. Patient H.M. is the classic mainly anterograde case, and many patients show both types together.