Using LFP Generators to Detect Abnormal Activity in Multiple Networks: A Tool to Explore Diaschisis

Following focal brain insults, besides primary lesions others in remote sites undergo secondary damage, a phenomenon known as diaschisis. The mechanisms underlying secondary damage are not known. Presumably, the damage is transmitted through vascular or neural pathways, but current techniques are poorly sensitive to detect changes in activity of specific pathways. We proposed here the use of local field potential (LFP) generators obtained through spatial discrimination techniques applied to high-density intracerebral recordings. These allow the characterization of normal and abnormal ranges of activity in isolated synaptic pathways. As a test in anesthetized animals we used the generation of spreading depolarization (SD) waves, characteristic of the ischemic penumbra. We found that unilateral SDs in the hippocampus led to changes of activity in nearby populations, but also in specific remote locations in both hemispheres. These remote LFP generators displayed distinct temporal patterns, and their relative variance is modified in a complex manner. The initial findings indicate that irradiation of abnormal synaptic activity to several interlaced networks may promote secondary malfunctioning in distant brain regions through both hypo and hyperactivity.