Relations between early prespike magnetic field changes, interictal discharges, and return to basal activity in the neocortex of rabbits

To evaluate possible prespike field synchronizations, its relation tc, both interictal discharges and postspike return to baseline, penicillin-induced cortical interictal discharges were recorded in anaesthetized rabbits by m agnetoencephalography (MEG) and electrocorticography (EcoG). Statistical pa rameters of spatial (global field power (GFP)) and temporal properties (Z-p arameter) of field synchronization were calculated. In our previous report, three types of prespike field synchronization were found before the onset of interictal spike. We report here that the continuous and fluctuating, bu t not the abrupt prespike increases, were more often associated with a spik e and wave pattern of interictal discharge than with a spike alone. Further more, the postspike return of these statistical parameters shows the same t h ree patterns as the prespike field synchronizations, but in the inverse t ime sequence. More often than not pre- and postspike pattern were of the sa me type. The results suggest an influence of prespike field synchronization upon interictal discharge and subsequent field return dynamics. (C) 2000 P ublished by Elsevier Science Ireland Ltd.