Fig. 5.

Gel embedding accelerates neuronal maturation and supports robust neurite outgrowth.

a) Representative spontaneous calcium responses of SCOs at day 40. DF/F indicates the fluorescence intensity over baseline fluorescence. Arrows show cells analyzed.

b) Neural activity patterns in SCOs at day 40. Representative heat maps of electrical activity for each group (top) and electrical oscillation traces of a single electrode (middle), where red dots represent events with more than 5 spike bursts within 100 ms, and electrical signal spikes (bottom) are shown.

c) Differences in patterns of neural activity. Bar graphs indicate the mean ± SD of the firing rate[<0.05 (∗), <0.01 (∗∗)].

d) Bar graphs indicate the mean ± SD in mean burst rate.

e) Bar graphs represent mean ± SD in number of spikes each burst.

f) Synchronization between electrodes.

g) Representative images of neurite outgrowth of mature spinal cord organoids (D55) collected at 5 days and 15 days post-embedding and elongation patterns.

h) Transmission electron microscope images of axonal sections 20 days after embedding. The white dotted line indicates the location; NF: Neurofilaments; SV: Synaptic vesicles; Mi: Mitochondria.