Distinct competitive impacts of palatability of taste stimuli on sampling dynamics during a preference test

Abstract

The decision of whether to continue with a current action or to stop and consider alternatives is ever present in the life of an animal. Such continuous-time decision making lies at the heart of food preference tests whose outcomes are typically quantified by a single variable, the total amount consumed. However, the dynamics that give rise to such a quantity in terms of durations of bouts of sampling at a stimulus before pauses, and the impact of alternative stimuli on those bout durations and subsequent actions following a pause, can contain a richness of behavior that is not captured in a single palatability measure. Here we carry out multiple analyses of these dynamics, with a particular focus on assessing how the hedonic value of one taste stimulus impacts the behavior of a rat sampling a second taste stimulus during a preference test. We find evidence for an explicit competitive interaction between bout durations, such that the more palatable a stimulus the longer the bout durations when the rat samples the stimulus and the shorter the bout durations at the alternative. Such competition is reproduced in a model of a neural circuit that could underlie the continuous decision of when to end a sampling bout. We find that the competitive impact on bout durations is relatively short-lived whereas a competitive impact on the choice of which stimulus to approach following a pause persists. Such a discrepancy in the timescales for the decay of the impact of the alternative stimulus suggests different neural processes are involved in the choice of which stimulus to approach versus the choice of how long to sample from it. Since these two choices together combine to determine net consumption and therefore the inferred palatability or preference of a gustatory stimulus, our results suggest that palatability is not a unitary quantity but the result of at least two distinct, context-dependent neural processes.

Changes in taste palatability across the estrous cycle are modulated by hypothalamic estradiol signaling

“…It is also possible that our delivery of tastes ranging from highly pleasant to unpleasant in single sessions may have influenced the rats' behavior, thereby causing a difference between ours and this earlier work. As noted earlier, taste palatability is intrinsically a comparative measure-an animal's preference evaluation is dependent on the nature of the other tastes available (Ballintyn et al, 2023;Flaherty et al, 1995;Flaherty & Rowan, 1986; see also Figure 3A herein). It is, therefore, not entirely surprising to find differences in the consumption of a taste when it is delivered alone and when it is delivered among tastants of different palatabilities; the few studies (Clarke & Ossenkopp, 1998;Parker et al, 2002) that have examined cycle-dependent responses to multiple tastes have rendered results that are in broad accord with our own.…”