Graduate Student Geisel School of Medicine at Dartmouth Lebanon, New Hampshire
Rationale: Epilepsy has long been known to impact both short- and long-term memory. In more recent years, a specific long-term memory deficit known as Accelerated Long-Term Forgetting (ALF) has been commonly described in temporal lobe epilepsy patients (TLE). ALF is characterized by what appears to be a normal initial retention of learned information, followed by an accelerated rate of memory decay (Kapur et al., Brain Cogn 1997) that impacts both recall and recognition of previously learned information (Narayanan et al., Epilepsy Behav 2012). However, the precise point at which ALF becomes pathologic is still unclear, as delay intervals and memory types vary across research designs in the literature. Thus, we aimed to quantify and characterize long-term memory in epilepsy using a video task. Methods: Subjects undergoing EEG monitoring watched a nature documentary. Then, they were tested on their retrieval of the film’s content immediately after viewing and after a 24-hour delay. In order to test both recall and recognition, subjects were able to choose their question style for each question presented; if subjects felt certain of their ability to accurately retrieve their answer, they could choose to freely type their response (a test of recall memory) or if they were more uncertain of their memory capability, they could opt for a multiple choice selection (a test of recognition memory). We also collected the reaction time of each subject in deciding between recall and recognition question styles. Additionally, participants answered a seven-point Likert scale about their answer confidence after completing each question. Results: Our preliminary results show a significant effect of delay on question choice. Epilepsy subjects were significantly less likely to choose the recall option after the 24-hour delay (p=2.746e-05). We also found a significant reduction in baseline recall accuracy for the epilepsy group (p=0.016696). When this was examined across the delay, we found that this impairment is driven primarily by same-day recall deficits (p=0.0003757). Epilepsy subjects also had significantly longer reaction times compared to the other groups (p=2.33e-07). Finally, Likert score was significantly correlated to memory accuracy (p=0.003593), and the epilepsy group had the lowest confidence ratings. Conclusions: Overall, subjects with epilepsy display subjective and objective memory deficits over the course of a 24-hour delay. Epilepsy subjects initially display high certainty of their answers as shown by their decision to recall at the same rates as controls. However, their recall accuracy is significantly worse, and thus this high rate of “false positives” in recall memory reflects false familiarity (Martin et al., Memory 2019). Thus, epilepsy subjects are showing misplaced certainty of their answers due to a false belief that they are familiar with the question at hand. The epilepsy group was also significantly less likely to choose the recall option after the 24-hour period, indicating diminished certainty of their answers in response to our time delay. This is further supported by the low confidence scores epilepsy subjects reported and their slower reaction times. In the future, we aim to enroll more participants, extend our testing period, and correlate our EEG findings with the deficits observed. These results further support the need for more effective therapies aimed at improving memory in epilepsy. Funding: Please list any funding that was received in support of this abstract.: This work was supported by the Geisel School of Medicine at Dartmouth, through a medical student research grant.
