Features of intracranial interictal epileptiform discharges associated with memory encoding

Abstract

Objective Interictal epileptiform discharges (IEDs) were shown to be associated with cognitive impairment in persons with epilepsy. Previous studies indicated that IED rate, location, timing, and spatial relation to the seizure onset zone could predict an IED's impact on memory encoding and retrieval if they occurred in lateral temporal, mesial temporal, or parietal regions. In this study, we explore the influence that other IED properties (e.g., amplitude, duration, white matter classification) have on memory performance. We were specifically interested in investigating the influence that lateral temporal IEDs have on memory encoding. Methods Two hundred sixty‐one subjects with medication‐refractory epilepsy undergoing intracranial electroencephalographic monitoring performed multiple sessions of a delayed free‐recall task (n = 671). Generalized linear mixed models were utilized to examine the relationship between IED properties and memory performance. Results We found that increased IED rate, IEDs propagating in white matter, and IEDs localized to the left middle temporal region were associated with poorer memory performance. For lateral temporal IEDs, we observed a significant interaction between IED white matter categorization and amplitude, where IEDs with an increased amplitude and white matter propagation were associated with reduced memory performance. Additionally, changes in alpha power after an IED showed a significant positive correlation with memory performance. Significance Our results suggest that IED properties may be useful for predicting the impact an IED has on memory encoding. We provide an essential step toward understanding pathological versus potentially beneficial interictal epileptiform activity.

Hippocampal theta and episodic memory

“…While these and other clinical factors are outside the scope of this paper, as they do not bear directly on our hypotheses, they may bear on the study of memory in patients with epilepsy more generally. (Camarillo-Rodriguez et al, 2022; Quon et al, 2021).…”

Functional Reorganization of the Mesial Frontal Premotor Cortex in Patients With Supplementary Motor Area Seizures

“…We coregistered postimplant head computed tomographies with preoperative brain MRIs to obtain accurate 3D location data for each electrode 11 (Figure 1), using a rigid-body registration method from Statistical Parametric Mapping 12 toolbox (SPM12, https://www.fil.ion.ucl.ac.uk/spm/). 12-16 After manual segmentation, electrodes were projected to the nearest cortical surface using the iterative closest point algorithm to account for brain shift 17 and translated into Montreal Neurologic Institute (MNI) brain space on a normalized brain model 18 to facilitate comparison of mapping across subjects.…”

“…ucl.ac.uk/spm/). [12][13][14][15][16] After manual segmentation, electrodes were projected to the nearest cortical surface using the iterative closest point algorithm to account for brain shift 17 and translated into Montreal Neurologic Institute (MNI) brain space on a normalized brain model 18 to facilitate comparison of mapping across subjects.…”

Multisensory Flicker Modulates Widespread Brain Networks and Reduces Interictal Epileptiform Discharges in Humans

“…The effects of sensory flicker on pathological neural activity are unclear. Of particular interest are interictal epileptiform discharges (IEDs) which are suspected to play a causal role in cognitive deficits 46,47 and have increased prevalence in multiple brain diseases including epilepsy, AD 48,49 , autism, attention deficit hyperactivity disorder (ADHD), and multiple sclerosis 50 . Prior work provides conflicting insights into how flicker may affect IEDs.…”