Figure 2.

Modulation of olfactory and taste pathways by internal states. (A) Parallel olfactory pathways are modulated by hunger at the level of sensory neuron output. (B) A variety of taste pathways are modulated by states such as hunger, protein or salt deprivation, or mating. This modulation can act at the level of sensory neurons or downstream. Most downstream neuronal targets of modulation have not yet been identified. Abbreviations not defined in text: tachykinin (Tk); octopamine (OA); dopamine (DA). Gray arrows depict sensory input; black arrows depict neural circuits that generate behavior; blue arrows depict excitatory modulation whereas red arrows depict inhibitory modulation.