Microstructural analysis of conditioned and unconditioned responses to maltodextrin

Abstract

The microstructure of licking responses was analyzed to investigate the interaction between unconditioned responses to maltodextrin and the responses to flavor cues previously associated with maltodextrin. Experiment 1 demonstrated that although the consumption of maltodextrin peaked at intermediate concentrations, the mean lick cluster size showed a positive, monotonic increase with concentration. In Experiment 2, a (conditioned stimulus) CS flavor was paired with 16% maltodextrin, whereas a CS flavor was paired with 2% maltodextrin. During test, consumption of the CS was higher than that of the CS when the flavors were combined with 2% maltodextrin, but not when combined with 16% maltodextrin. In contrast, cluster size was larger with the CS than with the CS , regardless of the concentration of maltodextrin present on test. Previous analyses of licking microstructure indicate that cluster size reflects the palatability of the ingested solution. Thus, the present results indicate that flavor conditioning can change the palatability of the cue flavors. Adding the CS flavor to maltodextrin produced results analogous to increasing the concentration of maltodextrin (in terms of both consumption and licking microstructure measures), which is consistent with the idea that after conditioning, responses to the CS flavor and to the unconditioned stimulus are mediated via the same representation.

Partial reinforcement and latent inhibition effects on stimulus–outcome associations in flavor preference conditioning

“…However, one might question the degree to which such associations play a role in the expression of learned preferences more generally. Others have emphasized the fact that flavor cues can also associate with the post-ingestive consequences of nutrient consumption-for example, their calories or the reinforcement signal generated by processing those calories (see, e.g., Sclafani & Nissenbaum, 1988), as well as, possibly, the positive hedonic responses to highly palatable nutrients (see, e.g., Dwyer, 2008). The present experiments were not designed to address questions concerning the relative contributions of these different types of associations to the expression of preferences more generally.…”

“…It is widely recognized that flavor preference learning can result in a variety of associations that can influence intake. For instance, when a flavor cue is paired with a nutrient, such as sucrose, the cue can enter in to an association with the specific taste of sucrose (e.g., Delamater, Campese, LoLordo & Sclafani, 2006;Dwyer, 2005;Harris et al, 2004), with the reinforcing post ingestive consequences of sucrose (e.g., Sclafani & Nissenbaum, 1988), or with the positive hedonic response to sucrose (e.g., Dwyer, 2008;Harris et al, 2004). When one pairs an initially neutral flavor cue with the oral consumption of sucrose and then demonstrates that rats prefer this flavor cue to another that has not been so paired, this preference can be explained by the operation of any one of these flavor-nutrient associations.…”

Analysis of licking microstructure provides no evidence for a reduction in reward value following acute or sub-chronic phencyclidine administration

“…In addition, studies of conditioned taste aversion have also shown that palatability and consumption can dissociate (e.g. Dwyer et al 2008;Dwyer 2008). …”

Latent inhibition in flavor-preference conditioning: Effects of motivational state and the nature of the reinforcer

“…Specifically, fructose has a sweet taste (there is good generalization between sucrose and fructose in rodents; Nissenbaum & Sclafani, 1987), but it is not readily metabolized; consumed orally, it will support flavor-preference learning, but intragastric infusions are much less effective (Ackroff, Touzani, Peets, & Sclafani, 2001;Sclafani et al, 1993). Maltodextrin, on the other hand, will support the conditioning of a flavor preference when it is presented by intragastric infusion , but although its taste appears to be palatable (e.g., Dwyer, 2008), there is little evidence to indicate that its taste alone would engender a conditioned preference. Elizalde and Sclafani (1988) reported that ingested maltodextrin did not support preference learning when carbohydrate digestion was blocked by a drug treatment.…”