A 70-year-old patient with Alzheimer's disease has difficulty forming new memories but can still ride a bicycle and play the piano (skills learned decades ago). Which memory systems are selectively affected and preserved, respectively?

• A Procedural memory impaired; semantic memory preserved
• B Working memory preserved; episodic memory impaired
• C Emotional memory impaired; spatial memory preserved
• D Declarative (explicit) memory impaired; procedural (implicit) memory preserved ✓

Explanation

Declarative (explicit) memory encompasses episodic (personal events) and semantic (facts) memory, both dependent on the hippocampus and entorhinal cortex — structures damaged early in Alzheimer's disease. Procedural (implicit) memory for motor skills relies on the basal ganglia, cerebellum, and motor cortex, which are relatively spared early in Alzheimer's. This explains why patients may lose ability to form new explicit memories while retaining well-rehearsed motor skills.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.