Measuring sub-millisecond delays in spiking activity with millisecond time-bins

Recent evidence indicates that sub-millisecond delays in neuronal spiking activity may be relevant for neural coding. Estimates of these delays are usually made from cross-correlation histograms (CCH) binned to 1 ms. We investigated the degree to which it is possible to measure delays with sub-millisecond precision when one computes CCHs with bin sizes ≥1 ms. To this end, we introduced sub-millisecond shifts into spike trains recorded from cat visual cortex. The bin sizes of 1/2 to 2 ms were the most optimal for measuring the artificial shifts, even when detecting shifts smaller than 0.5 ms. The results suggest that preferably, one should use CCHs with ∼1 ms binning even when investigating differences in delays considerably smaller than 1 ms.