Table 1.
Model comparison. Lower BIC values indicate better model fit (in bold); number of free parameters and parameter values ± SEM of the best fitting model are provided for each group. Trial-by-trial choices of the intact animals were best captured by the dynamic learning rate model incorporating RPE scaling proportional to expected uncertainty and facilitation of learning in response to surprising outcomes (Full model). BLA lesions selectively eliminated learning rate scaling in response to surprise (RW+expected uncertainty model provided the best fit). Whereas OFC lesioned animals still increased learning rates in response to surprising events (PH model), RPE scaling proportional to expected outcome uncertainty was lost in this group. Furthermore, the overall learning rates were reduced in OFC-lesioned animals (p=0.01). Finally, we observed significantly lower values of β (inverse temperature parameter in softmax choice rule) in both BLA- and OFC-lesioned animals (p<0.0001), suggesting that their behavior is less stable, more exploratory and less dependent on the difference in learned outcome values. Asterisks indicate parameter values that were significantly different from the control group (in bold).
| Model | RW | PH | RW+expected uncertainty | Full | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| # parameters | 3 | 4 | 5 | 6 | ||||||
| BIC | parameter value ± SEM | |||||||||
| k | α, value | β | η | α, risk | ω | |||||
| sham | 26519.39 | 26900.66 | 26384.18 | 25681.7 | 0.29 ± 0.03 | 0.09 ± 0.01 | 14.1 ± 0.99 | 0.33 ± 0.04 | 0.56 ± 0.08 | 3.04 ± 0.11 |
| BLA lesion | 26201.89 | 26864.74 | 25153.82 | 27162.82 | 0.32 ± 0.02 | 0.07 ± 0.01 | 7.4 ± 0.6* | n/a | 0.58 ± 0.06 | 3.40 ± 0.4 |
| OFC lesion | 24292.54 | 23171.46 | 24630.92 | 23994.5 | 0.3 ± 0.05 | 0.05 ± 0.01* | 5.5 ± 0.68* | 0/32 ± 0.05 | n/a | n/a |