Abstract
Objective: To explore quantitative measurements of the visual attention and neuroelectrophysiological relevance of memory deficits in temporal lobe epilepsy (TLE) by eye tracking and electroencephalography (EEG).Methods: Thirty-four TLE patients and twenty-eight healthy controls were invited to complete neurobehavioral assessments, cognitive oculomotor tasks, and 24-h video EEG (VEEG) recordings using an automated computer-based memory assessment platform with an eye tracker. Visit counts, visit time, and time of first fixation on areas of interest (AOIs) were recorded and analyzed in combination with interictal epileptic discharge (IED) characteristics from the bilateral temporal lobes.Results: The TLE patients had significantly worse Wechsler Digit Span scores [F(1, 58) = 7.49, p = 0.008]. In the Short-Term Memory Game with eye tracking, TLE patients took a longer time to find the memorized items [F(1, 57) = 17.30, p < 0.001]. They had longer first fixation [F(1, 57) = 4.06, p = 0.049] and more visit counts [F(1, 57) = 7.58, p = 0.008] on the target during the recall. Furthermore, the performance of the patients in the Digit Span task was negatively correlated with the total number of IEDs [r(28) = −0.463, p = 0.013] and the number of spikes per sleep cycle [r(28) = −0.420, p = 0.026].Conclusion: Eye tracking appears to be a quantitative, objective measure of memory evaluation, demonstrating memory retrieval deficits but preserved visual attention in TLE patients. Nocturnal temporal lobe IEDs are closely associated with memory performance, which might be the electrophysiological mechanism for memory impairment in TLE.
Highlights
Temporal lobe epilepsy (TLE) is the most common focal epilepsy in adults and is associated with a generalized pattern of cognitive impairment (Elger et al, 2004; Sen et al, 2018)
We found that in the memory encoding process, there was no significant difference between TLE patients and healthy controls in total visit time and total visit counts, which means that both groups performed actively in visual attention and were target focusing
We did not find any correlation between the Wechsler visual recognition scores and the time to find the target items or any eye tracking measures in the memory game, suggesting that visual attention might be unaffected in memory encoding in TLE patients, and this finding was in line with the finding that the TLE group did not perform significantly worse than the control group on the Wechsler visual recognition test
Summary
Temporal lobe epilepsy (TLE) is the most common focal epilepsy in adults and is associated with a generalized pattern of cognitive impairment (Elger et al, 2004; Sen et al, 2018). Seventy percent of TLE patients have memory dysfunction, which has been documented to be related to hippocampal sclerosis (Ozkara et al, 2004; Helmstaedter and Kockelmann, 2006; Postma et al, 2020), seizure frequency and duration (Aldenkamp and Arends, 2004; Elger et al, 2004; Black et al, 2010), interictal epileptic activity (Dinkelacker et al, 2016; Ung et al, 2017) and antiepileptic medication (Aldenkamp et al, 2003; Bernardi and Barros, 2004) This traditional epilepsy-centric view of cognitive deficits has recently been challenged by observations that cognitive deficits, including memory impairment, may well precede the onset of epilepsy and be viewed as a biomarker for disease development and prognosis assessment (Hermann et al, 2012; Witt and Helmstaedter, 2012, 2015). Observation behavior and associative processing are often confused, rendering the interpretation of cognitive deficits ambiguous (Voss et al, 2017)
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