Accelerated Long-Term Forgetting: Prolonged Delayed Recognition as Sensitive Measurement for Different Profiles of Long-Term Memory and Metacognitive Confidence in Stroke Patients.

OBJECTIVE Deficits in episodic memory are frequently reported after ischemic stroke. In standard clinical care, episodic memory is assessed after a 20-30 min delay, with abnormal memory decay over this period being characterized as rapid forgetting (RF). Previous studies have shown abnormal forgetting over a prolonged interval (days to weeks) despite normal acquisition, referred to as accelerated long-term forgetting (ALF). METHOD We examined whether ALF is present in stroke patients (N = 91) using immediate testing (T1), testing after a short delay (20-30 min, T2), and testing after a prolonged delay (one week, T3). Based on performance compared to matched controls (N = 85), patients were divided into (1) patients without forgetting, (2) patients with RF between T1 and T2, and (3) patients with ALF at T3. Furthermore, confidence ratings were assessed. RESULTS ALF was present in a moderate amount of stroke patients (17%), but ALF was even more prevalent in our stroke sample than RF after a 20-30 min delay (which was found in only 13% of our patients). Patients reported a lower confidence for their responses, independent of their actual performance. CONCLUSIONS Adding a one-week delayed measurement may potentially assist in identifying patients with memory decrements that may otherwise go undetected.