Madoka Matsumoto

Neural basis of the undermining effect of monetary reward on intrinsic motivation

Contrary to the widespread belief that people are positively motivated by reward incentives, some studies have shown that performance-based extrinsic reward can actually undermine a persons intrinsic motivation to engage in a task. This “undermining effect” has timely practical implications, given the burgeoning of performance-based incentive systems in contemporary society. It also presents a theoretical challenge for economic and reinforcement learning theories, which tend to assume that monetary incentives monotonically increase motivation. Despite the practical and theoretical importance of this provocative phenomenon, however, little is known about its neural basis. Herein we induced the behavioral undermining effect using a newly developed task, and we tracked its neural correlates using functional MRI. Our results show that performance-based monetary reward indeed undermines intrinsic motivation, as assessed by the number of voluntary engagements in the task. We found that activity in the anterior striatum and the prefrontal areas decreased along with this behavioral undermining effect. These findings suggest that the corticobasal ganglia valuation system underlies the undermining effect through the integration of extrinsic reward value and intrinsic task value.

Neural correlates of cognitive dissonance and choice-induced preference change

According to many modern economic theories, actions simply reflect an individuals preferences, whereas a psychological phenomenon called “cognitive dissonance” claims that actions can also create preference. Cognitive dissonance theory states that after making a difficult choice between two equally preferred items, the act of rejecting a favorite item induces an uncomfortable feeling (cognitive dissonance), which in turn motivates individuals to change their preferences to match their prior decision (i.e., reducing preference for rejected items). Recently, however, Chen and Risen [Chen K, Risen J (2010) J Pers Soc Psychol 99:573–594] pointed out a serious methodological problem, which casts a doubt on the very existence of this choice-induced preference change as studied over the past 50 y. Here, using a proper control condition and two measures of preferences (self-report and brain activity), we found that the mere act of making a choice can change self-report preference as well as its neural representation (i.e., striatum activity), thus providing strong evidence for choice-induced preference change. Furthermore, our data indicate that the anterior cingulate cortex and dorsolateral prefrontal cortex tracked the degree of cognitive dissonance on a trial-by-trial basis. Our findings provide important insights into the neural basis of how actions can alter an individuals preferences.

How Self-Determined Choice Facilitates Performance: A Key Role of the Ventromedial Prefrontal Cortex

Recent studies have documented that self-determined choice does indeed enhance performance. However, the precise neural mechanisms underlying this effect are not well understood. We examined the neural correlates of the facilitative effects of self-determined choice using functional magnetic resonance imaging (fMRI). Participants played a game-like task involving a stopwatch with either a stopwatch they selected (self-determined-choice condition) or one they were assigned without choice (forced-choice condition). Our results showed that self-determined choice enhanced performance on the stopwatch task, despite the fact that the choices were clearly irrelevant to task difficulty. Neuroimaging results showed that failure feedback, compared with success feedback, elicited a drop in the vmPFC activation in the forced-choice condition, but not in the self-determined-choice condition, indicating that negative reward value associated with the failure feedback vanished in the self-determined-choice condition. Moreover, the vmPFC resilience to failure in the self-determined-choice condition was significantly correlated with the increased performance. Striatal responses to failure and success feedback were not modulated by the choice condition, indicating the dissociation between the vmPFC and striatal activation pattern. These findings suggest that the vmPFC plays a unique and critical role in the facilitative effects of self-determined choice on performance.

Social Equality in the Number of Choice Options Is Represented in the Ventromedial Prefrontal Cortex

A distinct aspect of the sense of fairness in humans is that we care not only about equality in material rewards but also about equality in nonmaterial values. One such value is the opportunity to choose freely among many options, often regarded as a fundamental right to economic freedom. In modern developed societies, equal opportunities in work, living, and lifestyle are enforced by antidiscrimination laws. Despite the widespread endorsement of equal opportunity, no studies have explored how people assign value to it. We used functional magnetic resonance imaging to identify the neural substrates for subjective valuation of equality in choice opportunity. Participants performed a two-person choice task in which the number of choices available was varied across trials independently of choice outcomes. By using this procedure, we manipulated the degree of equality in choice opportunity between players and dissociated it from the value of reward outcomes and their equality. We found that activation in the ventromedial prefrontal cortex (vmPFC) tracked the degree to which the number of options between the two players was equal. In contrast, activation in the ventral striatum tracked the number of options available to participants themselves but not the equality between players. Our results demonstrate that the vmPFC, a key brain region previously implicated in the processing of social values, is also involved in valuation of equality in choice opportunity between individuals. These findings may provide valuable insight into the human ability to value equal opportunity, a characteristic long emphasized in politics, economics, and philosophy.

Neural Correlates of Cognitive Dissonance and Decision Conflict

Research in social psychology has shown that after making a difficult choice between two equally preferred items, individuals come to reduce their preferences for the item they rejected. This phenomenon was explained as “cognitive dissonance,” an uncomfortable feeling induced by simultaneously holding two or more contradictory cognitions (e.g., “I like it” and “I rejected it”). While previous neuroimaging studies indicated that the anterior cingulate cortex (ACC) was involved in cognitive dissonance, it is not known whether the ACC area involved in a type of complex conflict of cognitive dissonance overlaps with areas involved in other types of conflict (i.e., decision-conflict). Our results suggest that the ACC area involved in cognitive dissonance reliably overlapped with areas which were positively correlated with subjects’ trial-by-trial reaction times during a binary choice task, suggesting that the same ACC area is involved in cognitive dissonance and decision conflict.

The Neural Basis of Changing Social Norms through Persuasion

Social norms regulate behavior, and changes in norms have a great impact on society. In most modern societies, norms change through interpersonal communication and persuasive messages found in media. Here, we examined the neural basis of persuasion-induced changes in attitude toward and away from norms using fMRI. We measured brain activity while human participants were exposed to persuasive messages directed toward specific norms. Persuasion directed toward social norms specifically activated a set of brain regions including temporal poles, temporo-parietal junction, and medial prefrontal cortex. Beyond these regions, when successful, persuasion away from an accepted norm specifically recruited the left middle temporal and supramarginal gyri. Furthermore, in combination with data from a separate attitude-rating task, we found that left supramarginal gyrus activity represented participant attitude toward norms and tracked the persuasion-induced attitude changes that were away from agreement.

Neural correlates of cognitive dissonance and preference change in the free-choice paradigm

Reward-induced burst firing of dopaminergic neurons has mainly been studied in the primate midbrain. Voltammetry enables high-speed detection of actual dopamine release in the projection area, but to date, it has been recorded only in rodents. In this study, novel diamond microelectrodes were applied for high-speed dopamine detection in behaving primate brains. Dopamine was detected with constant-voltage amperometry, holding microelectrodes with the surface of boron-doped diamond (BDD) at +600 mV against Ag/AgCl reference electrodes. During Pavlovian cue-reward trials, a sharp response to a reward cue was detected in the caudate of Japanese monkeys. This method allows the measurement of actual dopamine release in specific target areas of the brain, which will expand the knowledge of dopamine neurotransmission obtained by unit recordings.

Neural basis of undermining intrinsic motivation by monetary rewards

In everyday life, we often experience that attentional effort for an on-going task fades away insidiously and our mind starts to wander. Such an absentminded state sometimes causes serious consequences. This functional MRI study aimed to identify the neural bases of absent-mindedness using a blockdesigned Go/NoGo task. In each task block, a NoGo stimulus was always presented at the end, while the remaining was Go stimulus. As a result, we found that shorter reaction time in Go trials was capable of predicting a following NoGo error response. This suggests that the fast and sloppy responses to Go stimuli represent the loss or attenuation of attentional effort for preparing an up-coming NoGo stimulus. We thus explored brain regions whose activity correlated with the mean reaction time in Go trials. Consequently, we found a positive correlation in the extensive frontoparietal regions, including the bilateral intraparietal sulcus, the bilateral frontal eye filed, and the right dorsolateral prefrontal cortex, as well as a negative correlation in the ventromedial prefrontal cortex. The results clearly demonstrated that as attentional effort for avoiding commission errors decreases, the ventromedial prefrontal cortex becomes reciprocally active instead of the attenuation of the dorsal attention network. We conclude that the reciprocal activation pattern represents the neural signature of absent-mindedness.