P16-T Early signs of transformation of neocortical activity to epileptiform patterns in experimental model of epilepsy

Abstract

This study was aimed at receiving information concerning organization of the cortical cellular activity in relation to the epileptiform EEG patterns, using ionic model of experimental formation of epileptic focus. This investigation was supported by the KBN grant, Nr4-T11E-006-22. Evaluation of the relationship between EEG patterns and cellular activity was attempted in the region of parietal association cortex (middle suprasylvian gyrus) in the group of five adult cats. Multiunit cellular activity was recorded with sampling frequency 4 kHz, using permanently implanted multicontact concentric electrode: 16 contacts, each about 40 micrometers of diameter and the distance between contacts of 200 micrometers. The electrode was implanted in the vicinity of cannula enabling subdural transfer of artificial cerebrospinal fluid with increased concentration of potassium ions. The recording and perfusion was performed in quiet, awake animal without necessity of using any pharmacological treatment. Early signs of transformation of neocortical activity to epileptiform patterns show considerable degree of independence of the patterns of cellular activity with respect to EEG. The incident of increased intensity and generalization of cellular activity creates the development of variable, irregular superficial electric fields within wide frequency range. This early stage of transformation of cortical activity to epileptiform patterns ends with the appearance of definite patterns of cellular activity, predominantly in internal cortical cell layers with corresponding EEG slow waves and/or spikes. The results suggest the possibility of existence of transient “paroxysmal” cellular activities without coexistence of standard epileptiform patterns in EEG records.