A major challenge in research on executive control is to reveal its functional decomposition into underlying neural mechanisms. A typical assumption is that this decomposition occurs solely through anatomically based dissociations. Here we tested an alternative hypothesis that different cognitive control processes may be implemented within the same brain regions, with fractionation and dissociation occurring on the basis of temporal dynamics. Regions within lateral prefrontal cortex (PFC) were examined that, in a prior study, exhibited contrasting temporal dynamics between older and younger adults during performance of the AX-CPT cognitive control task. The temporal dynamics in younger adults fit a proactive control pattern (primarily cue-based activation), whereas in older adults a reactive control pattern was found (primarily probebased activation). In the current study, we found that following a period of task-strategy training, these older adults exhibited a proactive shift within a subset of the PFC regions, normalizing their activity dynamics toward young adult patterns. Conversely, under conditions of penalty-based monetary incentives, the younger adults exhibited a reactive shift some of the same regions, altering their temporal dynamics toward the older adult baseline pattern. These experimentally induced crossover patterns of temporal dynamics provide strong support for dual modes of cognitive control that can be flexibly shifted within PFC regions, via modulation of neural responses to changing task conditions or behavioral goals.dorsolateral PFC ͉ event-related fMRI ͉ inhibition ͉ interference control ͉ working memory

It is a truism of cognitive research that participants perform experimental tasks with varying levels of motivation. Some participants appear to show little interest and exert minimal effort in their task performance, whereas others seem to approach the task as a critical test, exhibiting a b burning desire to perform to their utmost ability. Yet, even though this variation in motivation is a well-known phenomenon, it seems to be underappreciated and underexplored. One source of variation might be a participant's motivational state while performing the task. A natural way to explore such a hypothesis is to experimentally manipulate motivational states-for example, by providing performance-based incentives-to assess their impact on cognitive performance. That is, by placing motivational states under experimental control, one can examine how such state-related effects af-f f fect how cognitive tasks are performed.It is also important to appreciate that providing a reward does not automatically and consistently instill motivation in participants, since individuals may differ in their reactions to rewards. Thus, a second source of variation might b be individual differences in motivation-related traits, such as sensitivity to different types of incentives. By measuring such types of trait variation, one can also estimate the impact on cognitive performance of stable individual differences in motivationally relevant variables. Currently, such motivationally oriented individual difference studies are almost nonexistent in the cognitive literature.Yet, even if motivational states are so experimentally controlled that all participants perform a task with equally strong motivation, whether or not increased motivation per se is sufficient to enact a change in task-relevant components of cognitive processing, so as to improve performance, is a separate question. Mere wanting, without appropriate directed action, does not imply obtainment. f Thus, a third source of variation might be the efficacy of the pathway that translates increased motivation into optimized cognitive processing.Neuroimaging techniques provide a particularly promising approach to understanding motivation by showing how variation in motivation-related states and traits affect the neural circuitry engaged during cognitive task performance. With this insight, it is possible to gain a greater understanding into the causal pathway where motivation affects cognition and thereby translates into changes in observable behavior. The goal of the present study was to explore this question by using functional magnetic resonance imaging (fMRI) to examine the following points: (1) r whether d reward-focused motivational states produce sustained d changes in brain activity and behavioral performance, and (2) whether such motivational manipulations show important influences related to individual differences.There has been a recent upsurge in attention in the cognitive neuroscience literature on the impact of reward incentives on brain activity and behavior. A wealth of ...

Increasing the reward value of behavioral goals can facilitate cognitive processes required for goal achievement. This facilitation may be accomplished by the dynamic and flexible engagement of cognitive control mechanisms operating in distributed brain regions. It is still not clear, however, what are the characteristics of individuals, situations, and neural activation dynamics that optimize motivation-linked cognitive enhancement. Here we show that highly reward-sensitive individuals exhibited greater improvement of working memory performance in rewarding contexts, but exclusively on trials that were not rewarded. This effect was mediated by a shift in the temporal dynamics of activation within right lateral prefrontal cortex, from a transient to predominantly tonic mode, with an additional anticipatory transient boost. In contexts with intermittent rewards, a strategy of proactive cognitive control may enable globally optimal performance to facilitate reward attainment. Reward-sensitive individuals appear preferentially motivated to adopt this resource-demanding strategy, resulting in paradoxical benefits selectively for nonrewarded events.executive function | personality | working memory | dopamine | mixed blocked/event-related fMRI I n some task situations, successful behavioral performance leads to the potential for a highly rewarding outcome (e.g., gambling games, college entrance exams, sales contests) . When motivational salience is high, the increased value of the behavioral goal to be achieved needs to be translated into an optimal cognitive strategy (1-3). Previous experimental evidence suggests that such a translation does occur, because both cognitive performance and brain activity are enhanced in behavioral situations paired with motivational incentives (e.g., monetary rewards) (4-11). Importantly, these behavioral and neural enhancements have been found to be associated with the potential reward value available on specific trials. However, there is still very little knowledge regarding the specific behavioral situations, neural mechanisms, and individual trait factors that are critical for such enhancement effects.We have postulated a theoretical framework, known as the Dual Mechanisms of Control (DMC; ref. 12), that distinguishes two cognitive control modes, proactive and reactive (Fig. S1A). The former is characterized by sustained active maintenance and/or anticipatory implementation of behavioral goals in the lateral prefrontal cortex (lPFC) (13,14), whereas the latter is characterized by transient, bottom-up updating of goal-relevant information within a wider brain network (15). In previous work, we have demonstrated that the DMC model predicts age-related and incentive-dependent shifts in activation dynamics in the lPFC (16-18). However, a limitation of the prior work has been the lack of a conclusive demonstration that experimental and individual differences effects in cognitive control modes are both functionally mediated by a shift in the activation dynamics within lPFC. In the current...

BackgroundCognitive control and working memory processes have been found to be influenced by changes in motivational state. Nevertheless, the impact of different motivational variables on behavior and brain activity remains unclear.Methodology/Principal FindingsThe current study examined the impact of incentive category by varying on a within-subjects basis whether performance during a working memory task was reinforced with either secondary (monetary) or primary (liquid) rewards. The temporal dynamics of motivation-cognition interactions were investigated by employing an experimental design that enabled isolation of sustained and transient effects. Performance was dramatically and equivalently enhanced in each incentive condition, whereas neural activity dynamics differed between incentive categories. The monetary reward condition was associated with a tonic activation increase in primarily right-lateralized cognitive control regions including anterior prefrontal cortex (PFC), dorsolateral PFC, and parietal cortex. In the liquid condition, the identical regions instead showed a shift in transient activation from a reactive control pattern (primary probe-based activation) during no-incentive trials to proactive control (primary cue-based activation) during rewarded trials. Additionally, liquid-specific tonic activation increases were found in subcortical regions (amygdala, dorsal striatum, nucleus accumbens), indicating an anatomical double dissociation in the locus of sustained activation.Conclusions/SignificanceThese different activation patterns suggest that primary and secondary rewards may produce similar behavioral changes through distinct neural mechanisms of reinforcement. Further, our results provide new evidence for the flexibility of cognitive control, in terms of the temporal dynamics of activation.

Motivation is an important component of self-regulation that helps set the effort level an organism is willing to expend to achieve a desired goal. However, motivation is an elusive concept in psychological research, with investigations typically targeting either very macro-level (e.g., effects of personality individual differences and experimental manipulations on global behavior) or very micro-level (e.g., physiological interventions targeting specific brain structures) processes. Thus, the current state of knowledge is very poor regarding the particular mechanisms by which motivation influences cognitive and neural systems to drive changes in specific components of behavior. This chapter reviews major perspectives on motivation arising from both the social-personality and neuroscience literatures, and then discuss how a cognitive neuroscience perspective might be fruitfully applied to fill the gaps between them. Specifically, the chapter reviews literature, including our own recent work, that suggests motivational manipulations impact brain regions associated with the exertion of specific cognitive control functions. The chapter concludes by outlining unresolved questions in motivation, and by suggesting directions for future progress in this domain.