Memory characteristics in mesial temporal lobe epilepsy: Insights from an eye tracking memory game and neuropsychological assessments.

Abstract

To compare different patterns of memory impairment in patients with two subtypes of mesial temporal lobe epilepsy (MTLE) and healthy controls. Thirty-five healthy controls and 41 patients with MTLE were recruited, of which 25 patients were diagnosed as hippocampal sclerosis (HS-MTLE), and the rest 16 patients were lesion-negative (MRI-neg MTLE). Participants completed the Wechsler memory assessment and a short-term memory game on an automated computer-based memory assessment platform with an eye tracker. Both the MRI-neg MTLE and HS-MTLE groups took longer time to complete the short-term memory game than healthy controls (p < 0.001, Cohen's d = 1.087; p = 0.047, Cohen's d = 0.787). During the memory encoding phase, the MRI-neg MTLE group spent significantly shorter time than healthy controls on the difficult levels with three (p = 0.004, Cohen's d = 0.993) and four targets (p = 0.016, Cohen's d = 0.858). During the memory decoding phase, the HS-MTLE group spent less time looking on the targets compared to controls when recalling and finding four targets (p = 0.004, Cohen's d = -0.793), while the MRI-neg MTLE group spent significantly longer time on the distractors and shorter time on the region of interests (ROIs) for all difficulty levels (all p < 0.05) than controls. Furthermore, the eye tracking data were correlated with the scores of the Wechsler Memory Scale after Bonferroni correction (p < 0.05). Patients with MRI-neg MTLE demonstrate impaired memory mostly due to attention deficits, while those with HS-MTLE show memory impairment with relative sparing of attention. Eye tracking technology has the potential of facilitating the investigation of the mechanism of memory defect in MTLE and can serve as a supplementary neuropsychological tool for clinical diagnosis and long-term monitoring.