Abstracts

Rationale: Last year, we presented evidence that interictal epileptiform discharges (IEDs) are associated with effects on temporally distant memory function. We have also previously shown that interictal epileptiform activity can acutely impact memory (Horak et al., Epilepsia 2017). However, there exists controversy over whether IEDs are pathological themselves, whether they are a symptom of some other pathology, or whether they are an attempt to restore normal brain activity. Methods: For this study, we analyzed data from 201 patients undergoing intracranial monitoring who had participated in a free recall task. Recording were analyzed using a previously developed and validated interictal epileptiform discharge (IED) detector to automatically locate IEDs. Brief segments of ECoG from before and after IEDs were then compared in the frequency domain to determine whether there were changes before and after the IEDs. Results: We found that many IEDs are associated with temporary increases in high frequency power (p < 0.05). We found that these IEDs are also accompanied by changes in the ratio of high frequency to low frequency power (p < 0.05). Conclusions: Previous work has shown that 'spectral tilt,' an increase in high frequency power and a decrease in low frequency power, is associated with acutely improved memory. Our results indicate that IEDs are associated with short term changes in brain activity which mirror changes that are brought about during pro-memory brain activity states. This could indicate that the brain state is improved after certain IEDs, and that these IEDs may have a beneficial effect on memory, hinting at a complex relationship between cognition and interictal phenomena. Further study is necessary to fully characterize the causation between IEDs and cognitive performance. Funding: This study was supported by NSF EPSCOR 1632738