SENSORY NEURAL PATTERNS AND GUSTATION* 



Robert P. Erickson 



Department of Psychology, Duke University, Durham, North Carolina 



At present there is no thorough understanding of the nature of the afferent 

 neural message for taste quality.f This is due in large part to our lack of 

 knowledge about the significant aspects of the taste stimulus. However, 

 it is possible to come to a partial analysis of the neural message without 

 this knowledge about the stimulus. The nature of this analysis will be 

 made clear by reference to those sensory systems where the neural message 

 has been worked out in some detail. 



METHOD TO DETERMINE NUMBER OF 

 SENSORY FIBER TYPES 



Tn color vision there are probably very few receptor types, these being 

 represented in the optic nerve by a corresponding number of fiber types. J 

 Assume that there are only three such receptor-fiber types, and let the 

 three curves in Fig. 1a represent the responsiveness of these three types 

 to the various wavelengths of light. Since in taste the significant parameters 

 of the stimulus are not understood fully (as pH, etc.), let us suppose that 

 in vision also the nature of the stimulus for color is not understood. 

 Assume that four colors are available as stimuli and recordings are obtained 

 from a series of single optic nerve fibers using first the stimulus indicated 

 as Q in the figure. What kind of recordings will result ? It is seen from 

 the ordinate erected at Q that the amount of neural activity that would 

 be recorded may take only three values depending on which type of optic 

 nerve fiber was being sampled. If the recording was from fiber type 1, 

 the value that would be obtained is indicated by the intersection of this 

 ordinate and the 1 curve ; similarly, for fiber types 2 and 3, the amount 

 of activity that would be obtained is represented by the values of curves 

 2 and 3 at the Q ordinate. Since there are only three fiber types in this 



* Supported by NSF grant G-18124. 



t " Taste quality " refers to the " salt-sour-sweet-etc." aspect of taste as distinct from 

 intensity. 



I Although perhaps inexact, the assumption is made in this paper that the stimulus 

 sensitivity functions of receptors are reflected without change in their lower-order afi'erent 

 neurons, and that arguments referring to one apply also to the other. 



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