Schematic representation of the gustation-salivation neuronal circuitry and how acupuncture may interact with it. Green lines represent input neural signals, red lines output signals. Solid lines represent physiological response of salivation to gustatory stimuli. Dashed lines represent physiological signals from other cortices. Dotted lines represent the hypothetical pathway through which acupuncture activates the opercular and insular cortices. Areas A: thalamus; B: the insular and opercular cortices; C: salivatory nuclei in the pons.