Age Differences in Striatal Delay Sensitivity during Intertemporal Choice in Healthy Adults

Gregory R Samanez-Larkin,Rui Mata,Laura L Carstensen,Samuel M Mcclure,Ian C Ballard,Peter T Radu

doi:10.3389/fnins.2011.00126

Gregory R Samanez-Larkin, Rui Mata + Show 4 more

Open Access

https://doi.org/10.3389/fnins.2011.00126

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Abstract

Intertemporal choices are a ubiquitous class of decisions that involve selecting between outcomes available at different times in the future. We investigated the neural systems supporting intertemporal decisions in healthy younger and older adults. Using functional neuroimaging, we find that aging is associated with a shift in the brain areas that respond to delayed rewards. Although we replicate findings that brain regions associated with the mesolimbic dopamine system respond preferentially to immediate rewards, we find a separate region in the ventral striatum with very modest time dependence in older adults. Activation in this striatal region was relatively insensitive to delay in older but not younger adults. Since the dopamine system is believed to support associative learning about future rewards over time, our observed transfer of function may be due to greater experience with delayed rewards as people age. Identifying differences in the neural systems underlying these decisions may contribute to a more comprehensive model of age-related change in intertemporal choice.

Highlights

Intertemporal choice describes any decision making scenario that involves selecting between outcomes available at different times in the future
NEUROIMAGING RESULTS Across age groups, functional neuroimaging analyses identified brain regions that correlated with the β and δ components of the subjective value function described by Eq 1
Δ-related neural activity was observed in the right dorsolateral prefrontal cortex, bilateral anterior insula, and a large cluster in the occipital cortex with peaks extending into bilateral posterior parietal cortex (PPC) (Figure 2A; Table 1)

Summary

Introduction

Intertemporal choice describes any decision making scenario that involves selecting between outcomes available at different times in the future. Assertions are made about reproductive fitness or the physical wherewithal available to enjoy rewards and conclusions are drawn on this basis about how decision making ought to depend on age (Rogers, 1994; Trostel and Taylor, 2001; Read and Read, 2004). This approach has produced theories asserting that delay discounting (i.e., the preference for sooner, smaller rewards relative to larger, later rewards) should decline with age (Rogers, 1994), increase with age (Trostel and Taylor, 2001), or be minimized in middle age (Read and Read, 2004). One important potential contribution to models of intertemporal choice over the life span, which has been overlooked to date, may be that older and younger adults rely differently on the brain systems that underlie valuation of future outcomes

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