Neocortical and medial temporal seizures have distinct impacts on brain responsiveness.

Focal epileptic seizures are characterized by abnormal neuronal discharges that can spread to other cortical areas and interfere with brain activity, altering the patient's experience and behavior. The origin of these pathological neuronal discharges encompasses various mechanisms that converge towards similar clinical manifestations. Recent studies suggested that medial temporal lobe (MTL) and neocortical (NC) seizures are often underpinned by two characteristic onset patterns, which respectively affect and spare synaptic transmission in cortical slices. However, these synaptic alterations and their effects have never been confirmed nor studied in intact human brains. To fill this gap, we here evaluate whether responsiveness of MTL and NC are differentially affected by focal seizures, using a unique dataset of cortico-cortical evoked potentials (CCEPs) collected during seizures triggered by single pulse electrical stimulation (SPES). We find that responsiveness is abruptly reduced by the onset of MTL seizures, despite increased spontaneous activity, while it is preserved in the case of NC seizures. The present results provide an extreme example of dissociation between responsiveness and activity and show that brain networks are diversely affected by the onset of MTL and NC seizures thus extending at whole brain level the evidence of synaptic alteration found in vitro.