While electrophysiology studies show fast neural activity propagation in the time scales of 30 ms – 40 ms across different layers within the same brain area (Godlove et al. 2014; Ninomiya et al. 2015), the magnitude of the neural activity decays rapidly. The initial neural activity in the feed-forward input layers IV of the primary visual cortex is by far the strongest activity. The magnitude of the further propagated activity in superficial and deeper layers is significantly lower as about 25%−40% (Ninomiya et al. 2015). Even though inter-layer connectivity can contribute to the overall signal, it is often negligible in magnitude to the original initial layer-specific input.
