As humans age, the attenuation of dopamine and norepinephrine neuromodulation in the fronto-striatal network could lead to deficits in decision-making and reward learning. However, the questions about the nature of how age-related decline in the dopamine and norepinephrine systems may alter decision-making and reward learning are not well understood. This doctoral dissertation used a multimodal approach to investigate the contributions of dopamine and norepinephrine in decision-making and reward learning in old age.
The first study of this dissertation focused on how age-related decline in the norepinephrine system may affect anticipatory values and reward prediction errors during reward learning. Specifically, a probabilistic decision-making task was conducted, and a reinforcement Q-learning model was applied to investigate anticipatory values of choice options for each trial and individual’s value sensitivity. Potential psychophysiological proxies of norepinephrine functioning, such as task-related pupillary responses and locus coeruleus structural integrity, were assessed in younger and older adults. Results showed that after the choice options and feedback were shown, younger adults’ pupil dilations negatively correlated with anticipatory values, suggesting uncertainty about outcome probabilities. However, this effect was smaller in the choice phase and absent in the feedback phase in older adults, indicating impairments in value estimation and updating in old age. Although older adults showed a lower locus coeruleus integrity than younger adults, which might indicate reduced norepinephrine functioning, individual’s value sensitivity was only associated with task-related pupil dilations but not with locus coeruleus integrity.
The second study investigated whether increasing the saliency of specific information of choice options may improve older adults’ decision performance during value-based decision-making and what the mechanisms of increasing information saliency could be. In particular, the saliency of outcome probabilities was highlighted using a color-coding scheme as a decision-aid in a mixed lottery choice task. Spontaneous eye-blink rate and pupillary responses were measured in younger and older adults as potential proxies of dopamine and norepinephrine functioning, respectively. In addition, the task-related pupil dilations also served as the function of cognitive demands during value computation. Results showed that older adults exhibited lower value sensitivity than younger adults; however, increasing information saliency benefitted choice behaviors in both age groups. Furthermore, the decision-aid reduced pupil size during decision-making in both age groups, suggesting decreased cognitive demands of value computation. The beneficial effects from the decision-aid were related to individual’s value sensitivity and the psychophysiological indicators of dopamine and norepinephrine functioning in old age.
Lastly, in the third study, a time-vary drift diffusion model that includes starting time parameters was applied to fit the behavioral datasets acquired from the second study. It was aimed to better understand how increasing the saliency of outcome probabilities may affect the dynamics of value-based decision-making. Results showed that older adults started to consider probability, relative to magnitude information, sooner than younger adults, but that their evidence accumulation processes were less sensitive to reward probabilities than that of younger adults. These findings may indicate a noisier and more stochastic information accumulation process during value-based decisions in old age. The decision-aid increased the influence of probability information on the evidence accumulation rate in both age groups but did not alter the relative timing of accumulation for probability versus magnitude in either group.
Taken together, the findings in this dissertation not only showed age-related deficits in decision-making and reward learning but also demonstrated that the psychophysiological measures such as spontaneous eye-blink rate, pupillary responses, and locus coeruleus structural integrity may serve as indicators of age and/or individual differences in dopamine and norepinephrine functioning during decision-making and reward-based learning. Moreover, the model-based approach further unraveled age-related alterations in the psychometrics and dynamics of the decision process. The present dissertation may help to identify mechanisms to promote successful aging and the discovery of understanding the role of dopamine and norepinephrine neuromodulation in many fundamental cognitive functions.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:78186 |
| Date | 24 February 2022 |
| Creators | Chen, Hsiang-Yu |
| Contributors | Scherbaum, Stefan, Deserno, Lorenz, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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