Fig. 4: Arc and c-Fos expression differ in the BLA but are not strongly influenced by memory state.

A Left: representative section (BLA 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 c-Fos⁺ cell density was greater than Arc⁺ cell density in the no shock and encoding groups. C Arc⁺c-Fos⁻ cell density increased from no shock to 1-day retrieval. While D Arc⁺c-Fos⁺ cell density did not change with memory state, E Arc⁻c-Fos⁺ cell density decreased from encoding to 5-day retrieval. F The density of the total number of BLA cells expressing Arc or c-Fos did not differ across timepoints. G The level of Arc⁺c-Fos⁺ co-labeling normalized to expected chance levels (dotted line) did not differ between timepoints, but at each timepoint mean co-labeling was above chance (one-sample t-tests, **p = 0.0029, ****p < 0.0001, ****p < 0.0001, and ** p = 0.0021 respectively). Among complements of all cells in H no shock and I encoding groups, the greatest proportion of cells were Arc⁻c-Fos⁺, followed by Arc⁺c-Fos⁺, then Arc⁺c-Fos⁻. J At 1-day retrieval, a greater proportion of cells were Arc⁻c-Fos⁺ than Arc⁺c-Fos⁻. K At 5-day retrieval, a greater proportion of cells were Arc⁻c-Fos⁺ than Arc⁺c-Fos⁻ or Arc⁺c-Fos⁺. L All labeled BLA 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 = 2654, n = 4439, n = 6080, and n = 5248 cells, respectively). Percentages of total cells in each complement are overlaid for each timepoint. N = 4 (no shock), 7 (encoding), or 8 (1-day retrieval, 5-day retrieval) mice. Error bars indicate ±SEM. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. BLA basolateral amygdala complex, ∪ union.