A 70-year-old man undergoes temporal lobectomy for refractory epilepsy involving the right hippocampus and amygdala. Postoperatively, he develops difficulty forming new declarative memories but retains older memories and procedural skills. This pattern is consistent with damage to which memory system?

• A Working memory mediated by the dorsolateral prefrontal cortex, which was disconnected from the hippocampus
• B Hippocampal-dependent explicit (declarative) memory consolidation; procedural memory depends on the striatum and cerebellum, which are spared ✓
• C Semantic memory exclusively stored in the left temporal neocortex; right temporal lobectomy spares it
• D Implicit priming memory mediated by occipitotemporal cortex, which was disrupted by the surgery

Explanation

The hippocampus is essential for encoding and consolidating new explicit (declarative) memories—both episodic (events) and semantic (facts). Once consolidated into neocortex, older memories become hippocampus-independent (retrograde amnesia is typically temporally graded). Procedural (implicit) memory—motor skills, habits—depends on the striatum, cerebellum, and motor cortex, which are intact. This selective anterograde amnesia with intact remote memories and preserved procedural skills was classically demonstrated in patient H.M. after bilateral medial temporal lobectomy.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.