Film recall reveals intact event memory but impaired sequence memory in temporal lobe epilepsy patients

Patients with epilepsy (PWE), especially temporal lobe epilepsy (TLE), experience impaired memory for personally experienced events. However, current assessments of episodic memory are limited in their ecological validity with a potential to miss detection of subtle cognitive decline. We conducted an exploratory study to determine whether a naturalistic film-viewing task with open-ended spoken recall could detect memory differences between TLE patients and healthy controls (HCs).

TLE patients (ages 18-60, fluent in English, not legally blind) were recruited from a Level 4 Epilepsy Center (2018-2024). TLE diagnosis was based on seizure semiology, MRI Brain, and EEG. TLE patients scored ≥ 22/30 on the Montreal Cognitive Assessment (MOCA); HCs scored ≥ 26/30. Subjects watched five short films and then freely recalled film details. Spoken responses were recorded, transcribed, segmented, and scored for film- and event-level recall. Recall order was assessed using the Damerau-Levenshtein distance. Semantic and causal centrality were quantified using sentence embeddings and rater-identified causal links, respectively. Beta regression with cluster-robust standard errors assessed group and centrality effects on recall probability. Beta regression evaluated the influence of age, MOCA, and testing platform on sequence recall error.

We recruited 51 subjects (27 TLEs; 24 HCs, 70.1% F, mean 29.9 ± 8.3 years). TLE patients and HCs showed similar recall of films (HC 89% ± 11% vs TLE 88% ± 18%, p = 0.54), coarse-grained events (HC 50% ± 16% vs TLE 44% ± 18%, p = 0.24) and fine-grained events (HC 25% ± 10% vs. TLE 22% ± 12%, p = 0.17). Both groups recalled high causal centrality events better. However, TLE patients showed significantly greater fine-grained event sequence deviations at recall than HCs (HC 15% ± 13% vs TLE 23% ± 18%, p = 0.027, Hedges' g = 0.53, Cliff's δ = 0.36), with RTLE demonstrating more sequence deviations than HCs (15% ± 13% vs. 29% ± 21%, p = 0.021, Hedges' g = 0.85, Cliff's δ = 0.51). Age, education, MOCA, and performance on standard verbal and visual memory tasks were unrelated to film, event, and sequence recall performance.

We demonstrate that a short film task with spontaneous spoken recall can identify group level differences in episodic memory. TLE patients demonstrate impaired sequence memory despite intact film- and event-level recall compared to healthy controls. Sequence memory may represent a subtle manifestation of memory impairment that is not detected by standard cognitive testing.