Separating local from global effects in neural pair correlograms.

Cross-correlograms between spike trains of simultaneously recorded units in cortex show peaks that range in width from a few milliseconds to tens of milliseconds regardless of the distance between the units. The peak width reflects the degree of synchronization between the firings resulting from local connectivity and global synchronization. The local connectivity part may be hidden in the much stronger and broader correlations due to diffuse global synchronizing forces. This study proposes an estimator for such global synchronizing effects upon unit-pair correlations based on local field potentials (LFPs). It appears that the relative importance of the global component in the unit-pair correlograms as predicted by LFPs is largest in spontaneous activity and for units recorded on distant electrodes.