Applying this method to single-trial voltage-sensitive dye imaging data, we show that the stimulus-evoked population response in primary visual cortex of the awake monkey propagates as a travelling wave, with consistent dynamics across trials. 
voltage-sensitive dye imaging
One possibility is that these waves are systematically missed in trial-averaged data, due to variability. 
trial-averaged data
A network model suggests that this reliability is the hallmark of the horizontal fibre network of superficial cortical layers. 
network model