Episodic recognition memory based on incidental learning of visual associations is largely preserved compared to recall in amnestic mild cognitive impairment and mild Alzheimer's disease

We investigated preserved episodic recognition memory based on incidental learning of visual associations in Alzheimer's disease (AD). In a cross-sectional design, we analyzed episodic memory score profiles of patients with amnestic mild cognitive impairment (a-MCI) (n = 42) or mild AD (n = 19) who had hippocampal atrophy, and healthy elderly controls (n = 43). The Visual Association Test-Extended served as a measure of episodic memory. Multiple-choice cued recognition was compared with paired associate recall and free recall within groups. Results showed that patients recognized learned material much better compared to when they had to recall material, resulting in large effect sizes (Cohen's d) ranging from 1.3 to 3.5. We conclude that episodic recognition memory based on incidental learning of visual associations is largely preserved when compared to recall in a-MCI and mild AD. This suggests that the episodic memory impairment in AD may be characterized as a retrieval impairment rather than a consolidation impairment, indicating that preserved recognition compared to recall may be compatible with AD being the correct diagnosis. Measuring the episodic memory impairment in AD may benefit from using tests that capture different aspects of memory processes such as incidental learning of visual associations.