Taste as a factor in the management of nutrition

The sense of taste lies at the interface between the external and internal milieux, at the point at which the animal must decide which chemicals from the environment to incorporate into itself. Accordingly, taste is organized along a neural dimension of nutrients versus toxins, which corresponds to a behavioral dimension of acceptance versus rejection, and to a hedonic dim ension of appetitive versus aversive qualities. Reflexive responses; cognit ive analyses, and hedonic reactions appear to be managed at different level s of the nervous system. At the first central relay, the nucleus of the sol itary tract, somatic reflexes for acceptance or rejection, and autonomic re flexes anticipating digestion are orchestrated. At the second, the parabrac hial nucleus of the rodent, associative mechanisms important to the develop ment of conditioned aversions and sodium appetite are manifested. In the th alamic taste relay, gustatory memories associated with non-visceral events may be formed. Primary taste cortex appears to be the site for a cognitive evaluation of gustatory quality and intensity. Finally, a hedonic assessmen t of the chemical may be made in secondary taste cortex and in the ventral forebrain sites to which it projects. With this assessment comes integratio n of the gustatory signal with those from other senses, perhaps to create a perception of flavor. Therefore, a sequence that begins with an analysis o f the molecular structure of a chemical in the mouth serves to incorporate that gustatory component into an appreciation of flavor, and to participate in the control of motivational processes that guide dietary selection. Nut rition 2000;16: 874-885. (C) Elsevier Science Inc. 2000.