Epilepsy and Cognitive Neurophysiology Laboratory
Auras (focal aware seizure; FAS) are subjective ictal events with retained consciousness. Epileptiform activities can disrupt cognitive tasks, but studies are limited to seizures with impaired awareness. As a proof of concept, we examined the cognitive effects of direct electrical stimulation to the left hippocampus which induced a habitual FAS in a patient with left mesial temporal lobe epilepsy. During the induced habitual FAS, verbal memory performance declined significantly as compared to pre-stimulation testing. Tasks measuring auditory working memory and psychomotor processing speed were not affected by the stimulation. The study confirms that FAS can impair episodic verbal memory and learning.
Keywords: Verbal memory, Aura, Focal aware seizure, Learning, Hippocampus, Epilepsy
Figure 1 A: Intracranial EEG with recordings from left amygdala–hippocampus, orbitofrontal, insula and lateral temporal regions. Electrical stimulation artifact (highlighted) in hippocampal channels followed by an induced seizure. Co-registered MRI to demonstrate the orthogonal trajectory of left hippocampal depth electrode. B: Serial cognitive test performances in percentile. C: Spectrogram (1–100 Hz) showing seizure in the hippocampal channel and spread to orbitofrontal regions.