Focal interictal activity in the mouse visual cortex interferes with slow-wave oscillations and visual processing in the contralateral hemisphere

Epileptiform activity is associated with impairment of brain function even in absence of seizures, as demonstrated by failures in various testing paradigm in presence of hypersynchronous interictal spikes (ISs). Clinical evidence suggests that cognitive deficits might be directly caused by the anomalous activity rather than by its underlying etiology. Here, I seek to understand whether focal ISs interfere with neuronal processing in connected areas not directly participating in the hypersynchronous activity. I caused focal ISs in the visual cortex of anesthetized mice and we determined that, even if IS did not invade the opposite hemisphere, the EEG was subtly disrupted with a modulation of firing probability imposed by the contralateral IS activity. Finally, we found that visual perception was altered depending on the temporal relationship between ISs and stimulus presentation. We conclude that focal ISs interact with normal cortical dynamics far from the epileptic focus, disrupting endogenous oscillatory rhythms and affecting information processing