Proefschrift_Holstein

Reward modulation of cognitive function: aging

p = 0.693). Together, these results suggest that more cautious responding during practice (i.e. when determining the response deadlines) can explain the higher earnings in the older group during the test, but that it does not explain the differential task-related effects observed during the test. Discussion The ability to take into account information about potential rewards is crucial for flexible, adaptive behavior. Increasing age is associated with cognitive decline, yet the psychological mechanisms underlying this decline remain uncharted. In the current study, we investigated whether reward motivational deficits underlie age-related changes in flexible cognitive control across the life span. To this end, we investigated age-related changes in the effect of reward motivation on flexible cognitive control in 118 participants with age ranging from 14 to 69. We observed overall age-related slowing and an age-related increase in accuracy across conditions. With increasing age, participants adopted an overall slower but more accurate strategy. However, whereas younger participants adapted their speed-accuracy strategy to the trial type, aging was accompanied by a more rigid strategy across trial types. Specifically, on the more demanding switch trials, younger participants exhibited a reward-related increase in speed over accuracy, while exhibiting a reward-related decrease in speed over accuracy on the less demanding repeat trials. By contrast, such reward- and task-dependent adaptation of speed-accuracy strategy was absent in older participants. The between subject analysis ( figure 5.3b ) confirmed that younger participants modulate their behavior differentially in distinct cognitive conditions. By contrast, in the older group, behavior on the switch trials was indistinguishable from behavior on repeat trials. Thus, with increasing age, participants drifted towards a more uniform strategy, where they preferred accuracy over speed across the task as a whole, but failed to adapt their behavior to changing motivational and cognitive task demands. This is generally in line with a diffusion modeling study by Starns and Ratcliff (2010), showing that older - in contrast to younger - adults do not adapt their speed-accuracy strategy to feedback on simple discrimination tasks. Together these results suggest that alterations in reward-based processing underlie cognitive changes in aging. Previous work has suggested that aging is accompanied by deficits in task switching (Kray et al., 2002). In keeping with this prior work, we observed an age-related increase in the RT switch cost. Also, a number of studies have demonstrated an age-related decrease in reward processing (Schott et al., 2007; Rademacher et al., 2014), although some studies have revealed intact processing of cues predicting an upcoming reward in older individuals (Samanez- Larkin et al., 2007) (Dreher et al., 2008). The present data – showing an age-related decrease in the reward effect as well as in the effects of reward on cognitive control (in terms of SAT) – provide support for the first account. In addition to observing commonly reported age-related changes in task-switching and reward processing, the current results suggest that aging is also

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