Abstract
Probabilistic reward learning reflects the ability to adapt choices based on probabilistic feedback. The dopaminergically innervated corticostriatal circuit in the brain plays an important role in supporting successful probabilistic reward learning. Several components of the corticostriatal circuit deteriorate with age, as it does probabilistic reward learning. We showed previously that D1 receptor availability in NAcc predicts the strength of anticipatory value signaling in vmPFC, a neural correlate of probabilistic learning that is attenuated in older participants and predicts probabilistic reward learning performance. We investigated how white matter integrity in the pathway between nucleus accumbens (NAcc) and ventromedial prefrontal cortex (vmPFC) relates to the strength of anticipatory value signaling in vmPFC in younger and older participants. We found that in a sample of 22 old and 23 young participants, fractional anisotropy in the pathway between NAcc and vmPFC predicted the strength of value signaling in vmPFC independently from D1 receptor availability in NAcc. These findings provide tentative evidence that integrity in the dopaminergic and white matter pathways of corticostriatal circuitry supports the expression of value signaling in vmPFC which supports reward learning, however, the limited sample size calls for independent replication. These and future findings could add to the improved understanding of how corticostriatal integrity contributes to reward learning ability.
Highlights
The ability to flexibly update one’s actions based on valuerelated changes in the environment deteriorates with age, as shown in decision-making studies comparing older and younger adults (Samanez-Larkin et al 2012; Chowdhury et al 2013b; Samanez-Larkin and Knutson 2015; de Boer et al 2017)
We showed previously that D1 receptor availability in nucleus accumbens (NAcc) predicts the strength of anticipatory value signaling in ventromedial prefrontal cortex (vmPFC), a neural correlate of probabilistic learning that is attenuated in older participants and predicts probabilistic reward learning performance
We investigated how white matter integrity in the pathway between nucleus accumbens (NAcc) and ventromedial prefrontal cortex relates to the strength of anticipatory value signaling in vmPFC in younger and older participants
Summary
The ability to flexibly update one’s actions based on valuerelated changes in the environment deteriorates with age, as shown in decision-making studies comparing older and younger adults (Samanez-Larkin et al 2012; Chowdhury et al 2013b; Samanez-Larkin and Knutson 2015; de Boer et al 2017). Animal studies and neuroanatomical evidence suggest that reward learning necessary for optimal value-based decision-making in changeable environments recruits corticostriatal loops (Haber and Knutson 2010; Seger et al 2010; Haber 2016; Smittenaar et al 2017). These loops are modulated by dopaminergic projections from the midbrain. We have previously shown that value anticipation in vmPFC is related to performance on a two-armed bandit task (TAB) (de Boer et al 2017) In that study, this signal proved weaker in a sample of older participants, compared with younger participants. This suggested that as people age, the brain’s ability to produce a strong value signal needed to perform adaptive choices may change
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