Differential cognitive substrates of verbal episodic memory performance in semantic variant primary progressive aphasia and Alzheimer's disease.

Performance on neuropsychological measures of verbal memory requires cognitive abilities beyond memory. We examined the contribution of semantic knowledge in verbal episodic memory for semantic variant primary progressive aphasia (svPPA) or Alzheimer's disease (AD). 415 AD and 68 svPPA participants completed measures of episodic memory (visual and verbal) and semantic knowledge. A double dissociation existed visual recall predicted verbal recognition in AD, whereas semantic knowledge contributed to verbal recognition in svPPA.