Fos expression16 in response to optogenetic activation of the sweet and bitter cortical fields was used to label activated neurons. a, Schematic of optogenetic stimulation strategy in the bitter cortex for Fos induction. b, Fos expression in the amygdala in response to photostimulation of the bitter cortex. The majority of Fos+ neurons are localized in the CEA. c, Fos expression in a control mouse without light stimulation. d–f, Photostimulation of the sweet cortex induces Fos expression in the amygdala. Note that the CEA, as a major local output of the BLA11,36, also shows strong Fos labelling in response to photostimulation. Scale bars, 200 μm. Similar results were obtained in three animals for each experiment.