Fig. 19

The average nerve impulses to taste stimuli in 5 N fibers, 5 S fibers, 5 Q fibers and 5 H fibers in which the responses of 4 different concentrations of 7 taste stimuli representing the 4 taste qualities are plotted. The concentrations for the different stimuli were: 0.05–0.2 M NaCl; 20–100 mM citric acid; 0–200 mM ascorbic acid; 1–30 mM QHCl; 0.2–2 mM denatonium benzoate; 0.1–0.8 M sucrose; and 0.01–1 mM SC45647. Thus, the concentration ranged at least 4 times and for some stimuli, 100 times between the lowest and highest used. It is evident that each fiber type maintained its response to the same taste quality throughout concentration changes. This would not be the case in across-fiber pattern coding but supports the labelled-line theory. GH unpublished