Figure 5

Lipopolysaccharide significantly increases functional connectivity 5–9 days after exposure. (A) Experimental timeline: LPS or PBS was added to the media at DIV 25, allowed to recover for 2 h, and then imaged (2 h). Subsequent image sessions were done at DIV 26, 27, 28 (1–3 Days) and DIV 30,32,34 (5–9 days). A media change was performed on DIV 27, with a 2-h recovery before imaging. At 2 h after exposure, there was no significant difference in average correlation coefficients (p = 0.9805, B), clustering coefficients (p = 0.9924, C), path length (p = 0.5195, D), or whole tissue firing rate (p = 0.0636, E) between PBS and LPS exposed tissues at 2 h. The 2 h treated samples were then compared to matched, untreated samples. The firing rate of PBS samples did not change (p = 0.4479, F), while the LPS samples significantly decreased (p = 0.0249, G). At 1–3 days after treatment, there was no statistical difference between PBS and LPS samples in average correlation coefficients (p = 0.1539, H), clustering coefficients (p = 0.0769, I), path length (p = 0.0627, J), or whole tissue firing rate (p = 0.0580, K). Example correlational connectomes from representative samples at 2 days after PBS (L) or LPS (M) treatment show similar correlation coefficient distributions above 0.5. At 5–9 days after treatment, LPS samples showed a significant increase in average correlation coefficients (p = 0.0014, N) and clustering coefficients (p = 0.0096, O), and a significant decrease in path length (p = 0.0198, P) compared to PBS samples. LPS exposure produced no statistical difference (p = 0.2126) in firing rate (Q) at 5–9 days. An example correlational connectome from a representative microtissue 9 days after PBS exposure (R) shows similar correlation coefficient distributions above 0.5 to its 2-day counterpart, while the LPS connectome (S) reflects the increase in correlation compared to its 2-day counterpart as well as to the day-matched PBS sample. Significance comparing LPS to PBS samples was determined with unpaired, two tailed t-tests with p < 0.05 (*p < 0.05, **p < 0.01). Significance comparing firing rate before and after treatment (F,G) was determined with a paired, two tailed t-test with p < 0.05 (*p < 0.05).