Fig. 4.

Regional dopamine function and goal-directed decision-making. a The two-stage Markov decision-making task (Daw et al., 2011) involves a first decision phase which leads probabilistically to one of two second-stage decisions. The use of model-based versus model-free learning strategies varies across individuals. b Regional comparisons of dopamine receptors within individuals suggests greater losses in PFC D2/3 receptors relative to ventral striatum receptors in aging. It is currently not known whether reduction in prefrontal cortex (PFC) dopamine function is associated with shifts away from model-based strategies. Aging is also associated with reductions in inter-regional correlations of D1 receptor binding (Rieckmann et al., 2011). These findings suggest that aging is accompanied by a divergence in receptor regulation within nigrostriatal pathways connecting substantia nigra (SN) and dorsal striatum and mesocortical/mesolimbic pathways originating in the ventral tegmental area (VTA). (Color figure online)