SEPARATING LOCAL FROM GLOBAL EFFECTS IN NEURAL PAIR CORRELOGRAMS

CROSS-CORRELOGRAMS between spike trains of simultaneously recorded uni ts in cortex show peaks that range in width from a few milliseconds to tens of milliseconds regardless of the distance between the units. Th e peak width reflects the degree of synchronization between the firing s resulting from local connectivity and global synchronization. The lo cal connectivity part may be hidden in the much stronger and broader c orrelations due to diffuse global synchronizing forces. This study pro poses an estimator for such global synchronizing effects upon unit-pai r correlations based on local field potentials (LFPs). It appears that the relative importance of the global component in the unit-pair corr elograms as predicted by LFPs is largest in spontaneous activity and f or units recorded on distant electrodes.