Characterization of intra-cortical local field potentials - before, during and after an ischemic event in rats

This study presents different concepts of characterizing local field potentials in the motor cortex before, during, and after ischemic stroke. Ischemic stroke produces cell death and disability and may be followed by a spontaneous process of repair and partial recovery. While recovery after weeks to months is anatomically and physiologically well-documented, the underlying neurological recovery processes still remain unclear. The objective of the present study was to establish methods to characterize the underlying neurological processes based on intra cortical local field potential signals. Ten acute experiments were conducted in an animal model of stroke. Evoked motor responses were recorded by a 16 channel electrode array (placed within the motor cortex, M1) before, during and up to 5 hours after stroke. The artificial stroke was induced by light activation of a photosensitive dye solution to the recording area. Frequency analysis of recorded local field potentials in the range < 200 Hz was performed offline. The results showed that the strongest activity occurred in an experiment specific frequency range. The signal response frequencies did not change during the different phases of stroke, but were strongly amplitude modulated. This amplitude modulation showed a similar development for most of the experiments, i.e. the amplitude increased significantly after stroke onset and declined slowly during the further progress. These preliminary studies indicate that LFPs may be suitable to characterize the electrophysiology of a stroke, however the findings should be substantiated by further studies.