Taste primary stimuli

One of the goals in gustatory neurobiology is to understand how information about taste stimuli is encoded in neural activity. The taste is defined by two parameters taste primary and intensity (stimulus concentration). Historically, there have been two major theories of neural coding in the taste system. These are the labeled line (Frank 1973) and across fibre (or neuron) (Erickson et al. 1965) pattern theories. Both of these theories are focused on the spatial representations of neuronal activity. 

Jiftertaste. The experience that, under certain conditions, foUows removal of the taste stimulus it may be continuous with the primary experience or may foUow as a different quaUty after a period during which swallowing, saUva, dilution, and other influences may have affected the stimulus substance. 

It is interesting that the stimulus compounds used in the study differ widely in their molecular structures, and yet they all interact with antibodies to thaumatin. It is, therefore, probable that a single receptor-structure responds to all sweet stimuli,there being a variation in the relative effectiveness of sweet stimuli across individual nerve-fibers, and the characteristics of all receptor sites do not appear to be identical. Earlier elec-trophysiological studies of single primary, afferent taste-neurons uniformly agreed that individual fibers very often have multiple sensitivities, and that individual, gustatory receptors are part of the receptive field of more than one afferent fiber. " We have yet to learn how these interact, and the nature of their excitatory, or possible inhibitory, relations, or both. 

Recent evidence suggests that the oral detection of fatty acids such as stearic acid do occur in the human and rodent oral cavity, and stimulate a fatty acid taste response. Both animal and human studies indicate that stearic acid elicits a small to moderate taste response in the oral cavity. The hedonic appeal of fats may be enhanced especially when consumed with carbohydrates. Future studies will determine whether long-chain fatty acids such as stearic acid or linoleic acid represent a primary taste stimulus in the human oral cavity. Finally, improved dehvery methods for saturated and unsaturated fatty acids for psychophysical studies will stimulate the advancement of this important field of study. 

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