SENSORY NEURAL PATTERNS AND GUSTATION 



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Since it is difficult to give meaningful labels to individual fibers or to 

 define fiber types, how may this afferent neural message best be viewed? 

 Pfaffmann (1) has suggested that, in taste, the afferent neural message 

 for quality is probably expressed in terms of the relative amounts of 



RAT 



SINGLE CHORDA TYMPANI FIBERS 



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20- 

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S 0- 



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Fig. 3. As Fig. 2 except recordings obtained from single chorda tympani tibers. 



neural activity across many neurons. The present thesis is that it would be 

 more productive to consider the problem in terms of such across-fiber 

 patterns than in terms of many receptor types. Jt should be pointed out 

 that in vision and audition, for example, the color or pitch of the stimulus 

 is probably signaled by a pattern of activity in a number of fiber groups 

 rather than by the activity in any single fiber group alone. Bar graphs 

 which show the across-fiber patterns of activity resulting in fiber groups 1, 

 2 and 3 from stimulation with a single stimulus (P, or Q, or R, or S) are 

 presented in Fig. Ic. For example, let Q represent a green stimulus. 

 Whenever this stimulus is presented (Fig 1a), all fibers in group 1 respond 

 to the extent shown by the intersection of curve 1 with the ordinate at Q, 

 all fibers in group 2 respond to the extent shown by the intersection of 

 curve 2 and this ordinate, and similarly for all fibers in group 3. The 

 resulting across-fiber patterning is given in Fig. Ic, stimulus Q. These 

 three levels of activity in these fiber groups would form a pattern to signal 

 the stimulus Q, or green. Presumably this kind of pattern signals the 

 quality of the stimulus in vision and audition. 



Can evidence be obtained that in gustation too, the significant aspect 

 of the neural message is actually the pattern of activity across many 

 taste neurons ? There are two steps to the resolution of this question, 

 one physiological and the other behavioral. First, the across-fiber 



