COMPUTER-SIMULATION OF ELECTROCORTICAL ACTIVITY AT MILLIMETRIC SCALE

We report a simulation of electrocortical wave activity at millimetric scale, during the ''desynchronised'' state. Asymmetric sigmoid pulse/ wave relations, short-range excitatory/inhibitory interactions and lon g-range excitatory couplings of pools of cortical cells were modelled. Frequency/wave number analysis of cat electrocorticogram was compared with the results of simulation. Local standing waves, with wave numbe rs from about 0.25/mm to 3.3/mm independent of temporal frequency, app eared in real and simulated ECoG. These arise from interactions of exc itatory and inhibitory cells and reciprocal excitation of pyramidal ce lls. The simulation also exhibits long wave length activity consistent with that of the real ECoG. Serial relay of excitation gives rise to travelling waves with a velocity of about 0.6 m/sec, which approximate s earlier experimental estimates based on coherence. Interaction of th e local and travelling waves results in group waves with high phase ve locities (32 m/sec at 5 Hz, to 0.6 m/sec at 50 Hz). Such group waves h ave not yet been experimentally identified and would be readily confus ed with effects of volume conduction. However, the frequency response characteristics of the simulation, along with the group waves, may acc ount for experimental findings of action potential correlation with lo cal field potentials at 40-50 Hz and long-range synchronisation of act ion potentials.