Fig. 2
From: Propagation of temporal and rate signals in cultured multilayer networks
Activity propagation in multilayer networks in culture. a, b Examples of dot rasters showing spikes recorded in cell-attached mode from individual neurons in each layer. Synchronized light stimuli were delivered to ChR2-expressing (non-recorded) neurons in the first layer (30 repetitions of the light stimuli). Data in a, b are, respectively, from sparse and dense networks. c, d Average poststimulus time histogram (PSTH) of action potentials in each layer from sparse (c) and dense (d) networks. A single neuron was recorded in each layer (from black to red for layers 1–4, respectively). e Firing rate measured in a 300 ms time window after the stimulus. Inset, probability of evoking at least one spike vs layer in sparse (orange) and dense (blue) networks. f Firing rate averaged over all layers vs network density. Inset: spike probability in the 4th layer as a function of density. g, h Temporal spread (g) and delay (h) of first spike vs recorded layer in sparse (orange) and dense (blue) networks. In h dashed lines represent a linear fit to the data with slopes of 8.9 ms per layer and 36.2 ms per layer for sparse and dense networks respectively. The statistical significance between the two distributions of slopes for individual networks was assessed using Mann–Whitney U-test (P = 1.7 × 10−6). In e–h all data are shown and the mean ± SEM is represented as thick lines. Data for PSTH in c, d and plots in e–h are compiled from n = 15 sparse (347 ± 81 neurons·mm−2) and n = 16 dense (686 ± 122 neurons·mm−2) networks
