The use of novel measures to detect Accelerated Long-term forgetting in people with epilepsy: The Crimes Test and Four Doors Test

Detecting accelerated long-term forgetting remotely in a community sample of people with epilepsy: Evidence from the Crimes and Four Doors tests

People with epilepsy often report experiencing memory problems though these are not always detectable using standard neuropsychological measures. One form of difficulty that may be relatively prevalent in epilepsy is termed accelerated long-term forgetting (ALF), typically described as relatively greater loss of memory over days or weeks following initial encoding. The current study used remote assessment to examine memory and forgetting over one week in a broad community sample of people with epilepsy and healthy control participants, using two recently developed tests, one verbal (the Crimes test) and one visual (the Four Doors test). These were administered as part of a short battery of cognitive measures, run remotely with participants over Zoom. Across this community-derived sample, people with epilepsy reported more memory complaints and demonstrated significantly faster forgetting on both the verbal and visual tests. This difference was not attributable to level of initial learning performance and was not detectable through delayed recall on a standard existing test. Our results suggests that ALF may be more common than suspected in people with epilepsy, leading to a potentially important source of memory problems that are currently undetected by standard memory tests.

EXPRESS: Accelerated forgetting in healthy older samples: implications for methodology, future ageing studies and early identification of risk of dementia

Accelerated long-term forgetting (ALF) has been reported in healthy older individuals, and is a possible early marker for risk of developing Alzheimer's disease (AD). The Verbal Associative Learning & Memory Test (VALMT; McGibbon & Jansari, 2013) addresses methodological weaknesses in existing clinical tests and has detected ALF in epilepsy within an hour. We used VALMT to investigate learning and forgetting in healthy older participants. Older (60-69yrs) and Younger (19-31yrs) participants were compared. Using VALMT, unrelated word-pairs were learnt to criterion, then cued-recall tested at delays of 5, 30 and 55 minutes. Unique pairs were tested at each delay. Subjective memory complaints data was gathered, and the Wechsler Memory Scale Logical Memory test (WMS-LM; a standard clinical measure) was administered. VALMT identified a significant difference in delayed recall between Younger and Older groups by 55 minutes (d = 1.32). While 'fast-learning' Older participants scored similarly to Younger participants, 'slow-learning' Older participants were impaired at all delays. Forgetting rates suggested degradation of memory starts during early synaptic consolidation rather than later system-level consolidation. Increased subjective memory complaints were associated with reduced VALMT scores. By contrast, WMS-LM failed to identify significant differences between any groups, and did not correlate with memory complaints. We conclude VALMT may be better able than WMS-LM to identify subtle impairments in healthy older adults within a single clinical visit, and VALMT results better reflect subjective experience. Older slow-learners forget faster and report more subjective memory complaints, which may indicate a group at risk of developing AD.

Detecting accelerated long-term forgetting: A problem and some solutions

While many memory disorders occur with normal rates of forgetting, an accelerated rate of long-term forgetting (ALF) may occur, sometimes in the absence of a learning deficit. Detecting ALF presents a problem as it is desirable that the learned material is re-tested after each of several delays. This may result in earlier retrievals confounding later tests, with evidence suggesting that both positive and negative interaction can occur between successive tests. An earlier study (Baddeley et al., 2019) tested cued recall of a series of four crimes or four visual scenes by probing a different sample of features from all four crimes/scenes at each delay. Even though no question was asked twice, the interpolated tests markedly reduced the rate of forgetting. We suggest that this decelerated forgetting effect may result from the retrieval of probed features activating other associated features within that episode, hence facilitating their recall on subsequent tests. If so, the effect should be removed when only single and separate episodes, or individual items, are tested at each delay. We test this by probing a separate episode at each delay (Experiment 1), or by replacing integrated episodes with recognition memory for isolated words (Experiments 2 and 3) or visual scenes (Experiments 4 and 5). As predicted, we find no reduction in the rate of forgetting, in contrast to our earlier studies. The theoretical and clinical implications of our results are discussed. We conclude that the previously developed Crimes and Four Doors Tests (Baddeley et al., 2019) and the present single item recognition tests are complementary and are both likely to be necessary to ensure the reliable detection of ALF.