Memory Disorder
A memory disorder involving the inability to recall past information (retrograde) or form new memories (anterograde), most often caused by damage to the hippocampus or thalamus.
Amnesia refers to significant memory impairment beyond ordinary forgetfulness. It's typically divided into anterograde amnesia (difficulty forming new memories after the onset of injury or illness) and retrograde amnesia (difficulty recalling memories from before it), and the two often occur together to varying degrees. Importantly, most forms of amnesia leave general intelligence, attention, and the ability to learn new physical skills relatively intact - it's specifically explicit, factual and episodic memory that's affected.
The hippocampus is the structure most classically associated with amnesia, as demonstrated by the landmark case of Henry Molaison ("H.M."), described in detail on our hippocampus page, whose bilateral hippocampal removal caused severe, permanent anterograde amnesia. The thalamus is another well-documented cause of amnesia when damaged, since it relays memory-related signals between the hippocampus and cortex; thalamic strokes or certain nutritional deficiencies (such as thiamine deficiency in Korsakoff syndrome) can produce a similar memory profile.
Research into amnesia has been central to broader memory science, helping establish that memory isn't a single unified system but several distinct ones - explicit memory for facts and events, and implicit memory for skills and habits - that rely on different, dissociable brain circuits. Current research explores how memory consolidation actually transfers information from the hippocampus to durable cortical storage over time, and whether that process can be supported or accelerated therapeutically after brain injury.
This article is for general education and isn't a substitute for professional medical advice or diagnosis.
Explore the regions involved in amnesia in more depth:
