Figure 1.
Order and duration of behavioral tasks.
The number of days (d) of each behavioral testing phase (below arrow) and inter-test periods (grey zones) are indicated. RGT: Rat Gambling task, FI-EXT: multiple fixed-interval/extinction schedules, Emerg. Task: Light-dark emergence task, FCN16: Fixed consecutive number 16 cue schedule, DDT: Delay discounting task.
Figure 2.
Principle of the Rat Gambling Task.
Rats can nose-poke among four different holes (A, B, C and D) in an operant cage, to earn food reward (1-hour test). The selection of one option is immediately rewarded, but can also be followed by a penalty (time-out) of variable duration, according to different probabilities. Two options (C, D) are equally more advantageous than the other two (A, B), which are equally disadvantageous in the long term.
Figure 3.
Meta analysis of the RGT data.
This analysis is based on 12 distinct experiments (n = 228) using the same protocol. It reveals a bimodal distribution of RGT scores (% of favourable choices during the last 20 min) with a majority of good decision makers (good DM, with scores above 70%), a minority of poor decision makers (poor DM, with scores below 30%) and the remaining, undecided rats with intermediate scores.
Figure 4.
Animal’s performance on the Rat Gambling Task (RGT), RGT-reversed version and the light-dark emergence test.
Grey lines represent the median used to compute proportions of high and low scores in good and poor decision makers (DM). (A) Time-course of advantageous choices (%) of good and poor DM on the RGT and individual scores during the last 20 min of good (n = 14) and poor (n = 6) DM. (B) Relationship between individual RGT scores and the mean latency to collect food pellets (one missing value) during the RGT. (C) Relationship between individual RGT scores and flexibility (final scores in the RGT-reversed version). (D) Time-course of advantageous choices of flexible (FG), undecided (UG) and inflexible (IG) good DM and inflexible (IP) poor DM groups on the RGT-reversed version. Comparison with the indifference level, dotted line, t-test: * and ° p<.05 at least. (E, F) Relationship between individual RGT scores and (E) the number of risk assessments before the first emergence in the risky compartment, or (F) the individuals’ sum of the score ranks for each behavior.
Figure 5.
Decision-making and impulsivity.
Good and poor decision makers (DM) performances in the (FCN16) Fixed Consecutive Number of 16 lever press schedule (A-C), in the multiple fixed-interval (FI) and extinction (EXT) schedules (D-F) and in the (DDT) delay-discounting task (G-H). Grey lines represent the median used to compute proportions of high and low scores in good and poor DM. (A) Frequency distribution (%) of chain length in the two groups. Optimal chain length (16) is indicated by the vertical dotted line. Inset: Percentage of rewarded chains for good and poor DM (Mean ± SEM). (B,C) Relationship between individual scores in the RGT and (B) response efficiency or (C) the number of reinforcement lever presses. (D,E,F) Relationship between individual scores in the RGT and (D) the mean number of lever presses during the 1-min FI or (E) during the 5-min EXT. (F top panel) Mean number of lever presses of good and poor DM during one 1-min FI component as a function of time. (F lower panel) Mean number of lever presses during the 5-min EXT component as a function time. (G) Percentage of choice for the large, delayed reinforcement as a function of delay in the two groups. (H) Relationship between individual scores in the RGT and the mean number of lever press during DDT training. Dotted line represents chance level.
Table 1.
Correlations within and between different measures of decision making, flexibility, impulsivity and risk-taking behaviours.
Table 2.
Summary of individual behavioral profiles of poor and good DM.
Figure 6.
Model’s performance on the RGT, reversal conditions and estimates of individual behavioral levels when fitted to the experimental performance profile of each rat.
Grey lines represent the median used to compute proportions of high and low scores in good and poor decision makers (DM). (A) Simulated time-course of advantageous choices (%) of good and poor DM on the RGT. (B) Relationship between simulated individual RGT scores and the estimated reward seeking parameters during the RGT + Reversal. (C) Relationship between simulated individual RGT scores and the estimated flexibility parameters affecting the learning rate. (D) Simulated time-course of advantageous choices of flexible (FG), undecided (UG) and inflexible (IG) good DM and inflexible (IP) poor DM groups on the RGT-reversed version. (E) Relationship between simulated individual RGT scores and the estimated risk seeking parameters. (F) The sum of the simulated score ranks for each modelled behavior. (G) 3-D representation of model parameters for the simulated traits of individual rats. (H) 3-D representation of behavioral measures of the behavioral traits of individual rats.
Figure 7.
Model comparison and correlations between estimated parameters and behavioral traits.
(A) Bayesian Information Criterion scores for each model (a low score is better). Models based on two traits fare uniformly better than models based on a single trait. Models with two traits including cognitive inflexibility have better scores than equivalent or simpler models. The model with all three simulated traits provides the best fit to the data even when penalizing for the increased model complexity (number of free parameters). (B) Learned Q-Values for advantageous and disadvantageous choices by both Good and Poor DM. Bars represent the mean Q-values assigned to the disadvantageous choices (A & B; dark-grey) and advantageous choices (C & D; light-grey) averaged over all poor or good decision makers at the end of an RGT session. Error bars represent 95% CI around the mean Q-value for all the rats of the population of interest. Poor decision makers vastly over-value disadvantageous choices in comparison to advantageous choices. (C-F) Scatter plot illustrating the correlation between: (C) The sum of ranks for all the behavioral traits measured experimentally (x-axis) and those estimated by the model (y-axis); (D) The measure of cognitive inflexibility (x-axis) and the estimated inflexibility parameter (area under α; y-axis); (E) The measured reward sensitivity (x-axis) and the estimated reward sensitivity (y-axis). (F) The measured risk seeking (latency to emerge in light compartment; x-axis) and the estimated risk-seeking parameter (y-axis). All estimated parameters correlated significantly with their behavioral counterpart.
Table 3.
Summary of individual modeled behavioral traits of poor and good DM.