Neural evidence for age-related deficits in the representation of state spaces

When under high cognitive demand older adults tend to resort to simpler, model-free decision strategies. This age-related shift in decision behaviour has been attributed to deficits in the representation of the cognitive maps, or state spaces, necessary for more complex model-based decision-making. Yet, the neural mechanism behind this shift remains unclear. We analysed performance on a modified two-stage Markov task using a novel neurocomputational approach including computational modeling and single-trial EEG analyses to establish neural markers of age-related changes in goal-directed decision-making under different representational demands. Our results reveal that the shift to simpler decision strategies in older adults is due a) impairments in the representation of the transition structure of the task and b) a diminished signaling of the reward value associated with decision options. Consistent with the diminished state space hypothesis of human aging, our findings reveal that deficits in goal-directed, model-based behavior in older adults results from impairments in the representation of state spaces of cognitive tasks.