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.