Analysis of MEG signals of spreading cortical depression with propagation constrained to a rectangular cortical strip II. Gyrencephalic swine model

Currents produced during spreading cortical depression (SCD) in a gyrenceph alic species (swine) were studied with magnetoen- cephalography (MEG) and e lectrocorticography (ECoG). SCD, initiated using electrical stimulation of the cortex, was constrained to propagate within a rectangular cortical stri p in order to simplify the interpretation of the underlying currents. The E CoG signals monitored along the strip revealed that SCD propagated from an initiation site on the gyrus at a rate of 7.9 +/- 3.2 mm/min (n = 23), ente red the deep coronal sulcus and in most cases emerged from the other side o f the sulcus, continuing to propagate across the next gyrus at a rate of 5. 9 +/- 2.7 mm/min (n = 22). The apparent propagation velocity within the sul cus was reduced to 1.7 +/- 0.8 mm/min (n = 21). Strong MEG signals were obs erved as SCD entered the sulcus. The direction of magnetic field was opposi te for SCD's on opposite banks of the sulcus. The currents were directed fr om a superficial layer to deeper layers of the cortex. The characteristics of SCD and associated MEG patterns from a gyrencephalic species may be simi lar to those in human patients during migraine aura. (C) 1999 Published by Elsevier Science B.V. All rights reserved.