Fig. 2: Correlated stiffness and electrophysiology measurements of neuronal networks.
a, Schematic and protocol for correlating the mechanical stiffness of neuronal somas and the firing rate within neuronal networks over several hours. Neurons are shown in green, squares represent HD-MEA electrodes, and grey filled squares represent user-defined electrodes routed to recording channels. Recorded extracellular waveforms of the neurons are given as coloured traces (blue, red, brown and magenta). b, Time series of mean firing rates of a single neuron (blue lines) and Young’s modulus of the neuronal soma (black dots). Each black dot represents the average of at least three stiffness measurements. c, Zoom-in of the red box in b. Error bars show s.d. d, Scatter plot of mean firing rates from n = 14 individual neurons versus Young’s modulus of their neuronal somas. A linear Pearson correlation test between firing rates and stiffness revealed no strong correlation (r = 0.03, P = 0.56). e, Scatter plot of the mean firing rates of neurons and Young’s modulus of n = 22 neurites measured from n = 11 individual neurons. f,g, Mean firing rate (f) and Young’s modulus (g) of n = 11 individual neurons before and after addition of glutamate receptor antagonists 10 μM DNQX and 40 μM D-AP5. h, Raster plot showing the synchronized spiking activity (action potentials) of neurons, with bursts (red box) and IBIs marked. i, Zoom-in of the red box in h, showing a burst of spikes of the neuronal network. Blue lines indicate the time points at which the force–displacement curves were collected to approximate the Young’s modulus of the soma of a neuron during IBIs; green lines indicate the time points to approximate the Young’s modulus of a neuron during a burst. j, Young’s modulus of n = 15 individual neuronal somas during bursting and IBIs. In all violin plots red dots represent mean values, black dots data from single neurons, and black lines the median of the population. Wilcoxon signed-rank test was used to determine statistical significance. P values are given in figures, with values >0.05 being considered non-significant (NS).
