We therefore investigated the expression pattern of cFos and Zif-268, the immediate early genes frequently used as markers for neuronal activity47, in brain nuclei belonging to the anxiety circuitry, including the hippocampus, the medial prefrontal cortex (mPFC), the basolateral (BLA), and central (CeA) amygdala and the hypothalamic paraventricular nuclei (PVN). Here, FOS is linked to Anxiety.