SIMULTANEOUS RECORDING OF EEG, DC-POTENTIAL AND DIFFUSION-WEIGHTED NMR IMAGING DURING POTASSIUM-INDUCED CORTICAL SPREADING DEPRESSION IN RATS

Electrophysiological recording during in vivo NMR imaging for correlat ion of electrophysiological events with changes in NMR parameters has, until now, not been satisfactory, Mere we present a method that uses specially prepared calomel electrodes for the continuous monitoring of both cortical steady potential and EEG during in vivo NMR imaging stu dies of experimental animal models. In order to demonstrate the reliab ility of this approach we elicited single episodes of cortical spreadi ng depression in rats by intracortical potassium acetate injection, us ing an intracerebral micropipette, During the passage of DC potential shifts and associated reduction in EEG amplitude, hyperintense regions , reflecting the progression of cortical spreading depression over the cortex, were visible in diffusion-weighted images of the rat brains, No susceptibility artifacts due to the electrodes and micropipette wer e visible in the NMR data, Thus, we have demonstrated under controlled experimental conditions, that electrophysiological recording with cal omel electrodes can be performed simultaneously with diffusion-weighte d NMR imaging, The described method enables further NMR investigations of phenomena which are detectable by electrophysiology.