Impact of monetary incentives on cognitive performance and error monitoring following sleep deprivation

SLEEP LOSS DUE TO SLEEP DEPRIVATION OR FRAGMENTATION AND ITS CONSEQUENCE, I.E., SLEEPINESS, ARE COMMON IN MODERN SOCIETY. SLEEP loss and sleepiness contribute significantly to performance decrements and accidents, such as motor vehicle crashes and work error-related damages.1 Performance decrements after sleep loss are generally attributed to attention deficit, and this proposition is supported by several behavior,2,3 electrophysiologic,4,5 and functional brain imaging studies.6 Attention is a multidimensional cognitive process, and the results of several studies have suggested that sleep loss induces selective impairment of attention processes, particularly the top-down attention control processes that rely on the frontal lobe.2,3,6 This corresponds with the view of Horne7 that frontal lobe functions are sensitive to total sleep loss. The frontal lobe is critically involved in executive function, including the ability to plan or set goals, supervisory attention processes, response inhibition, and action monitoring, such as error detection and conflict processing. A series of recent studies conducted by us8–10 and others11,12 have shown that all components of error monitoring, including error detection, error correction, and posterror speed and accuracy adjustments, are impaired following sleep deprivation. Thus, sleep deprivation-related performance decrements and accidents appear to result from deficits in both attention processes and performance monitoring, particularly error monitoring in the latter. The results of previous studies have suggested that the decline in vigilance task performance during sleep deprivation is in part related to reduced motivation.13–15 The feedback of the knowledge of results14,15 and monetary rewards13 reduce some negative effects of sleep loss on vigilance task performance. Vigilance is commonly defined as sustained attention or tonic alertness.1 Given that the reduction of vigilance related to a low arousal level gives rise to performance decrements following sleep deprivation, monetary incentives are thought to have general effects on the performance of vigilance tasks, such as effects related to arousal, alertness, or mental effort.14–16 Additionally, monetary incentives have recently been proposed to selectively influence the top-down attention mechanisms in the performance of tasks that require a high degree of top-down attention control processes.17–20 A previous study used a cued attention task in which subjects responded to targets preceded by spatially valid, invalid, or neutral (noninformative) cues and illustrated that monetary incentives enhanced the response speed in the case of the trials with the valid and invalid cues but not those with the neutral cues.19 Furthermore, a recent study has shown that a continuous 2-hour performance of a task that requires a high degree of cognitive control results in performance reduction in terms of the response speed, accuracy, and stability.21 Performance decrements due to prolonged task performance are accompanied by a decrease in the brain activity, including the amplitude of the contingent negative variation component of the event-related potential (ERP) that indexes the preparatory attention22,23 and the amplitude of the P300 component that is related to the deployment of attention resources.24 Increasing the motivation level by financial rewards attenuates the changes in behavior performance and brain activity during prolonged task performance.21 However, whether motivation incentives attenuate the negative effects of sleep deprivation on the performance of tasks that require a high degree of cognitive control needs to be studied, despite the many studies that have used vigilance tasks to investigate this.13–15 Thus, the first objective of this study was to examine whether motivation incentives reduce the effects of sleep deprivation while subjects perform tasks that require higher cognitive control processes. We used a flanker task,25 which requires a high degree of top-down attention control processing and action monitoring, with concurrent electroencephalographic (EEG) recordings for behavior and electrophysiologic examination of the effects of monetary incentives on attention processes and action monitoring after 1 night of total sleep deprivation, which was similarly applied in our previous studies.8–10 A previous study26 has shown that financial penalties for errors not only increase the performance accuracy, but also enhance error detection, as reflected by the increase in the amplitude of event-related negativity (ERN), which is a negative component of the response-locked ERPs and is frontocentrally maximized.27 As mentioned above, continuous 2-hour task performance also results in a reduction in error monitoring, such as in error detection (as reflected by the reduced ERN amplitude), error correction, and posterror slowing.21 In addition, monetary rewards lead to attenuation of the changes in error monitoring during prolonged task performance. It is proposed that the anterior cingulate cortex, located in the medial frontal cortex, is the generator of ERN (reviewed in28,29). Considering that monetary incentives can facilitate the activation of the medial frontal cortex in putatively well-rested subjects17,19 and can improve the reductions in error monitoring (ERN amplitude, error correction, and posterror slowing) during prolonged task performance,21 it is likely that monetary incentives can also reduce, if not completely block, the effect of sleep deprivation on error monitoring. Since the flanker task has been frequently used to study error monitoring and was used in this study, we also examined whether motivation incentives interacted with sleep deprivation to influence error monitoring.