Determinants of Taste Preference and Acceptability: Quality versus Hedonics

Abstract

Several methods exist for reliably determining the motivational valence of a taste stimulus in animals, but few to determine its perceptual quality independent of its apparent affective properties. Individual differences in taste preference and acceptability could result from variance in the perceptual qualities of the stimulus leading to different hedonic evaluations. Alternatively, taste perception might be identical across subjects whereas processing of the sensory signals in reward circuits could differ. Utilizing an operant-based taste cue discrimination/generalization task involving a gustometer, we trained male Long-Evans rats to report the degree to which a test stimulus resembled the taste quality of either sucrose or quinine irrespective of its intensity. The rats, grouped by a characteristic bimodal phenotypic difference in their preference for sucralose, treated this artificial sweetener as qualitatively different with the sucralose-preferring rats finding the stimulus much more perceptually similar to sucrose, relative to sucralose-avoiding rats. Although the possibility that stimulus palatability may have served as a discriminative cue cannot entirely be ruled out, the profile of results suggested otherwise. Subsequent brief-access licking tests revealed that affective licking responses of the same sucralose-avoiding and -preferring rats differed across concentration in a manner roughly similar to that found in the stimulus generalization task. Thus, the perceived taste quality of sucralose alone may be sufficient to drive the observed behavioral avoidance of the compound. By virtue of its potential ability to dissociate the sensory and motivational consequences of a given experimental manipulation on taste-related behavior, this approach could be interpretively valuable.

Examination of the perception of sweet- and bitter-like taste qualities in sucralose preferring and avoiding rats

“…1). This confirms previous reports that SA detect a concentration-dependent aversive taste quality in sucralose [12, 19, 20]. Our current study further revealed that SA switched from drinking sucralose to drinking water approximately 60% of the time at concentrations of sucralose that they avoid (Fig.…”

“…These data provide clear evidence that SA detect a bitter-like taste quality in normally avoided sucralose concentrations. SP also licked more to sucralose than SA in a briefaccess paradigm at these same concentrations [19]. Taken together, these findings confirm that differences in sensory (taste-guided) processing are sufficient to explain the differential acceptance of sucralose in SP and SA.…”

“…Our lab and others have demonstrated that rats display considerable variation in their acceptance of sucralose [12, 14, 32, 33], and that these differences are taste-driven [19]. However, the degree to which SP and SA differ in their perception of bitter- and sweet-like taste qualities remains unclear, as do the potential consequences of this differential perception of taste on caloric intake and diet choice.…”

“…Briefly, animals were trained to report (via an operant response in a gustometer) whether the taste of a given concentration of sucralose generalized to a prototypical sweet-like stimulus (sucrose) or a prototypical bitter-like stimulus (quinine). While SP reported a sweet-like taste quality at all concentrations of sucralose that were treated as different than water (i.e., assumed to be above threshold within this paradigm), SA were more likely to generalize the taste of these same concentration of sucralose to quinine [19]. These data provide clear evidence that SA detect a bitter-like taste quality in normally avoided sucralose concentrations.…”

“…Thus, in the case of a mixture, animals would be expected to choose the taste quality that is more salient to them. Indeed, when the same animals were offered test solutions containing varying mixtures of sucrose and quinine, they reported a sweet-like quality in solutions containing low, suprathreshold concentrations of quinine, and did not report the presence of a bitter-like quality until quinine was sufficiently concentrated and presumably the more salient taste quality within the test solution [19]. Thus, while SP reported that the salient taste quality of sucralose was sweet-like, we cannot infer that “sweet” was the sole quality detected by SP or that SP were unable to perceive a bitter-like taste quality in the sucralose solutions.…”