ABSTRACT
By providing sensory information important for decisions about ingestion and rejection, the sense of taste serves as the gateway to the body’s internal milieu. Gustatory neurobiologists generally agree on the existence of at least four basic taste qualitiessweet, salty, sour, and bitter-although they disagree about the possible existence of others (e.g., the taste of amino acids). These qualities and the behaviors they elicit help to ensure the animal’s energy supply (carbohydrates, amino acids), maintain the proper electrolyte and pH balance (salts, acids), and avoid the ingestion of toxins (acids, alkaloids). Of considerable debate is the way in which taste quality is represented in the activity of gustatory neurons. Many investigators accept the idea that peripheral gustatory nerve fibers and central neurons can be classified into groups on the basis of similarities and differences in their response profiles and other biological properties. Taste neurons have typically been characterized by analyses that employ a neuron classification scheme in an attempt to impose some order on these data. However, the breadth of tuning and multimodal sensitivity of central gustatory neurons make it difficult to accept a strict labeled-line code for taste quality, in which each neuron type signals a particular quality. Rather, it is likely that the various neuron types play a critical role in defining unique across-neuron patterns, which can unambiguously represent gustatory quality.
