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. Author manuscript; available in PMC: 2018 Feb 1.
Published in final edited form as: Curr Opin Behav Sci. 2017 Jan 5;13:178–185. doi: 10.1016/j.cobeha.2016.12.004

Figure 1. Characterization of a “sign-tracker” and “goal-tracker”.

Figure 1

A) Sign-trackers (STs) approach and manipulate the lever (conditional stimulus, CS), reflective of incentive salience attribution. B) Goaltrackers (GTs) approach the location of food reward (unconditional stimulus, US) delivery upon presentation of the lever-CS. Images adapted from [58]. C) Mean +/− SEM Pavlovian conditioned Approach Index, a composite score used to assess the propensity of an individual rat to approach the lever-CS vs. the food cup (see [59]), is shown across 5 conditioning sessions for GTs (n=1867), those in the intermediate group (IG, n=2296) that vacillate between the two responses, and STs (n=1934). An Approach Index of −1 indicates behavior directly solely towards the food cup, whereas that of +1 indicates that behavior is directly solely towards the lever-CS. D) A histogram illustrating the population distribution of the propensity to attribute incentive salience to a reward cue in 6097 rats (the same rats used for panel C). Phenotype classification is based on an Approach Index of −1 to −0.5 for GTs, −0.5 to 0.5 for IG and 0.5 to 1 for STs. The large population of rats used for C and D has come from a database generated using Sprague-Dawley rats that have been screened for Pavlovian conditioned approach behavior in the labs of Drs. Shelly Flagel, Jonathan Morrow and Terry Robinson at the University of Michigan.