Quantifying Individual Variation in the Propensity to Attribute Incentive Salience to Reward Cues

Abstract

If reward-associated cues acquire the properties of incentive stimuli they can come to powerfully control behavior, and potentially promote maladaptive behavior. Pavlovian incentive stimuli are defined as stimuli that have three fundamental properties: they are attractive, they are themselves desired, and they can spur instrumental actions. We have found, however, that there is considerable individual variation in the extent to which animals attribute Pavlovian incentive motivational properties (“incentive salience”) to reward cues. The purpose of this paper was to develop criteria for identifying and classifying individuals based on their propensity to attribute incentive salience to reward cues. To do this, we conducted a meta-analysis of a large sample of rats (N = 1,878) subjected to a classic Pavlovian conditioning procedure. We then used the propensity of animals to approach a cue predictive of reward (one index of the extent to which the cue was attributed with incentive salience), to characterize two behavioral phenotypes in this population: animals that approached the cue (“sign-trackers”) vs. others that approached the location of reward delivery (“goal-trackers”). This variation in Pavlovian approach behavior predicted other behavioral indices of the propensity to attribute incentive salience to reward cues. Thus, the procedures reported here should be useful for making comparisons across studies and for assessing individual variation in incentive salience attribution in small samples of the population, or even for classifying single animals.

The role of learning-related dopamine signals in addiction vulnerability

“…This forms the core of the actor-critic model (Barto et al, 1983;O'Doherty et al, 2004). Experimentally, it is perhaps most directly demonstrated by conditioned reinforcement experiments (Everitt and Robbins, 2005;Meyer et al, 2012), where instrumental behaviours can be reinforced by Pavlovian CSs.…”

“…Second, sign-trackers exert more instrumental effort than goal-trackers for presentation of the CS in the absence of food reward. Thus, the cue acts as a more powerful conditioned reinforcer for sign-trackers than for goal-trackers Lomanowska et al, 2011;Meyer et al, 2012). Evidence demonstrating individual variation in the third fundamental property of an incentive stimulus, i.e.…”

“…As discussed above, there is growing evidence that the natural tendency to sign-track is both highly variable (Meyer et al, 2012) and a risk factor predisposing to addiction (Saunders and Robinson, 2010;Saunders et al, 2013a,b). That is, individual variation in cue reactivity is associated with individual differences in vulnerability to addiction.…”

Influence of reward motivation on human declarative memory

“…In rodent research, incentive salience of a Pavlovian cue is a threefold property: the cue is attractive (induces approach behavior), desired (animals work to obtain the cue), and stimulates instrumental actions (animals can learn to perform a new action to get the cued reward; Berridge and Robinson, 2003;Meyer et al, 2012;Pecina et al, 2003). Yet, the attribution of incentive value is not always expressed by the same behavior in all rats.…”

“…Yet, the attribution of incentive value is not always expressed by the same behavior in all rats. During appetitive conditioning, when the cues signaling the arrival of the food and the location of the food pellet are at different locations, some rats would learn to approach the location of food delivery ('goal-trackers') while others would rather approach the illuminated lever or the conditioned cue (CS+), as if such a sign had higher incentive value than the food itself ('sign-trackers ', Flagel et al, 2011;Meyer et al, 2012). The latter behavior is a conditioned orienting response and indicates that incentive salience has been transferred to the cue and induces behavioral 'wanting'.…”