Fig. 7: Arc and c-Fos expression patterns diverge in the LH across all memory states.

A Left: representative section (LH in dotted outline) showing Arc (green) and c-Fos (magenta) expression with a Hoechst nuclear counterstain (blue). Right: inset, with Arc and c-Fos channels presented separately. White arrow: example Arc⁺c-Fos⁺ cell. B LH c-Fos⁺ cell density was greater than that of Arc at every timepoint. c-Fos⁺ cell density was also greater at 5-day than 1-day retrieval. Among complements of cells, C Arc⁺c-Fos⁻ cell density increased only from no shock to encoding timepoints, while D Arc⁺c-Fos⁺ cell density increased only from no shock to 5-day retrieval timepoints. E There was no difference in the density of Arc⁻c-Fos⁺ cells in the LH across timepoints. F Total LH Arc⁺ or c-Fos⁺ cell density decreased from CFC encoding to 1-day retrieval but did not differ from either timepoint to no shock or 5-day retrieval. G The level of Arc⁺c-Fos⁺ co-labeling normalized to expected chance levels (dotted line) decreased from no shock to both encoding and 5-day retrieval. At each timepoint, mean co-labeling was above chance (one-sample t-tests, *p = 0.0209, * p = 0.0135, ****p < 0.0001, and ***p = 0.0006 respectively). H–K Among complements of all labeled LH cells, a greater proportion were Arc⁻c-Fos⁺ than Arc⁺c-Fos⁻ and than Arc⁺c-Fos⁺ at every memory state. K All labeled LH cells for each group, summed across all sections quantified for all mice, represented as a Venn diagram of Arc expression (green), c-Fos expression (magenta), and their overlap (blue) (n = 1444, n = 1974, n = 1627, and n = 1857 cells, respectively). Percentages of total cells in each complement are overlaid for each timepoint. N = 4 (no shock) or 8 (encoding, 1-day retrieval, 5-day retrieval) mice. Error bars indicate ±SEM. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. LH lateral habenula, ∪ union.