Figure 3

Spontaneous calcium activity reveals significant functional remodeling over three weeks of development in vitro. (A) Average correlation coefficients of microtissues significantly decrease (p = 0.0026) from week 2 to week 3, followed by a significant increase (p = 0.0151) from week 3 to week 4. (B) Clustering coefficients follow the same trend as the correlation, with a significant decrease (p = 0.0032) of average clustering coefficient in week 3 and a subsequent significant increase (p = 0.016) in week 4. (C) Path length between nodes followed the inverse trend, with a significant increase (p = 0.0054) in average path length in week 3 and a significant decrease (p = 0.0263) in week 4. (D) Whole-tissue firing rate showed no significant differences (week2-week3, p = 0.5851; week 3-week 4, p = 0.4209) over 3 weeks of development. (E) Whole-tissue calcium traces recorded in a single example microtissue from week 2, week 3, and week 4 show changes in firing patterns over time. (F) Correlograms from pairwise Pearson cross-correlations coefficients between nodes from recordings shown in (E), exhibit progression of node connectivity across weeks. (G) Correlational connectomes overlay the cross-correlation values above 0.5 onto the physical node positions. Line color connecting nodes correlates to the correlation coefficient value. (H) Plots of the correlation coefficients versus the physical distance between nodes, shows no preference for strong local connections over cross-tissue connections. Significance to compare multiple weeks was determined with a one-way ANOVA and post-hoc Tukey test with p < 0.05 (*p < 0.05, **p < 0.01).