The present article provides a unified systematic account of the role of cognitive control, motivation and dopamine pathways in relation to the development of fatigue. Since cognitive fatigue is considered to be one aspect of the general control system that manages goal activity in the service of motivational requirements (Hockey, 2011), our focus is also broader than fatigue itself. The paper shall therefore first focus on the motivation-control interactions at the level of networks of the brain. A motivational control network is argued to play a critical role in shaping goal-directed behavior, in conjunction with dopamine systems that energize the network. Furthermore, motivation-control interactions as implemented in networks of the brain provide an important element to elucidate how decision making weighs both the anticipated benefits and costs of control operations, in optimal and suboptimal conditions such as mental fatigue. The paper further sketches how fatigue affects the connectivity of large-scale networks in the brain during effortful exercition, in particular the high-cost long striatal-cortical pathways, leading to a global reduction of integration in the brain's network architecture. The resulting neural state within these networks then enters as interoceptive information to systems in the brain that perform cost-benefit calculations. Based on these notions we propose a unifying cost-benefit model, inspired by influential insights from the current neuroscience literature of how fatigue changes the motivation to perform. The model specifies how the reward value, effort costs and fatigue aspects of task performance converge in the medial prefrontal cortex to calculate the net motivation value of stimuli and select the appropriate actions.

The present study focuses on the question of whether there is a decline in the capacity of the information-processing system with advancing age. Attention is first paid to general theoretical issues like the distinction between fluid and crystallized abilities, the reduction of processing capacity, and the effect of task complexity and stressful conditions on task performance in elderly subjects. Then, results of a series of experiments are reported that were carried out to determine to what extent the agerelated decline in performance in more demanding cognitive tasks is also affected by stressors such as noise, sleep loss and caffeine. The results clearly demonstrated that, with respect to speed measures, the complexity effect, that is the greater slowing of old subjects in more complex than in simple RT tasks, is a robust phenomenon. It was further concluded that the combined effects of task complexity and stress conditions yielded a complex pattern of performance measures, which could not be explained simply on the basis of a simple resource-depletion model of aging.

Considering how computational properties of the brain inform cognitive functions, this book presents a unique conceptual introduction to cognitive neuroscience. This essential guide explores the complex relationship between the mind and the brain, building upon the authors' extensive research in neural information processing and cognitive neuroscience to provide a comprehensive overview of the field. Rather than providing detailed descriptions of different cognitive processes, Functions of the Brain: A Conceptual Approach to Cognitive Neuroscience focuses on how the brain functions using specific processes. Beginning with a brief history of early cognitive neuroscience research, Kok goes on to discuss how information is represented and processed in the brain before considering the underlying functional organization of larger-scale brain networks involved in human cognition. The second half of the book addresses the architecture of important overlapping areas of cognition, including attention and consciousness, perception and action, and memory and emotion. This book is essential reading for upper-level undergraduates studying Cognitive Neuroscience, particularly those taking a more conceptual approach to the topic.

The effects of a 3mg/kg body weight (BW) dose of caffeine were assessed on behavioral indices of response inhibition. To meet these aims, we selected a modified AX version of the Continuous Performance Test (CPT), the stop task, and the flanker task. In three double-blind, placebo-controlled, within-subjects experiments, these tasks were administered to healthy participants. While the results for the AX-CPT were indicative of improved response inhibition after caffeine, they might also reflect caffeine-induced changes in mechanisms other than response inhibition (e.g., attentional processes). The results for the stop task and flanker task were more straightforward. That is, the effects of caffeine on overall flanker performance and selective response suppression as revealed by distribution-analytical techniques were negligible. In the stop task a global effect of caffeine on processing speed was seen, rather than specific effects on response inhibition. Taken together, these experiments showed that both active and reactive inhibition were not significantly modulated by caffeine. The present results are linked to neural circuits that underlie inhibitory control and the role of caffeine-induced strategic changes.

A central question in the study of selective attention is whether top–down attentional control mechanisms are generalized or specialized for the type of information that is to be attended. The current study examined this question using a voluntary orienting task that cued observers to attend to either one of two locations or to one of two colors. Location (spatial) and color (nonspatial) conditions were presented either randomly intermixed within the same block of trials or in separate blocks. Functional magnetic resonance imaging revealed that directing attention to a location or to a color activated a network of overlapping dorsal frontal and parietal areas, previously implicated in attentional control. The pattern of observed overlap was not affected by the intermixed versus blocked presentation of location and color conditions. Although portions of the frontal–parietal network were more active in response to location cues than to color cues, a secondary analysis also revealed that medial dorsal frontal and parietal cortex were specifically engaged in shifting visual attention regardless of the cued dimension (location or color). Together, the present results support the conclusion that attentional control is the combination of a generalized network that works in concert with subregions of the frontoparietal network that are highly specialized for directing attention based on the content of the to-be-attended information.

This event-related potential study investigated (i) to what extent incongruence between attention-directing cue and cued target modality affects attentional control processes that bias the system in advance to favor a particular stimulus modality and (ii) to what extent top-down attentional control mechanisms are generalized for the type of information that is to be attended. To this end, both visual and auditory word cues were used to instruct participants to direct attention to a specific visual (color) or auditory (pitch) stimulus feature of a forthcoming multisensory target stimulus. Effects of cue congruency were observed within 200 ms post-cue over frontal scalp regions and related to processes involved in shifting attention from the cue modality to the modality of the task-relevant target feature. Both directing visual attention and directing auditory attention were associated with dorsal posterior positivity, followed by sustained fronto-central negativity. However, this fronto-central negativity appeared to have an earlier onset and was more pronounced when the visual modality was cued. Together the present results suggest that the mechanisms involved in deploying attention are to some extent determined by the modality (visual, auditory) in which attention operates, and in addition, that some of these mechanisms can also be affected by cue congruency.

Effects of caffeine on task switching were studied using ERPs in a cued task-switch paradigm. The need for advance preparation was manipulated by varying the number of task-set aspects that required switching. In a double-blind, within-subjects experiment, caffeine reduced shift costs compared to placebo. ERPs revealed a negative deflection developing within the preparatory interval, which was larger for shift than for repeat trials. Caffeine increased this shift-induced difference. Furthermore, shift costs increased as a function of the number of task-set features to be switched, but this pattern was not modulated by caffeine. The results suggest that caffeine improves task-switching performance by increasing general effects on task switching, related to task-nonspecific (rather than task-specific) anticipatory processes. Caffeine's actions may be mediated by dopaminergic changes in the striatum or anterior cingulate cortex.

An ongoing controversy concerns whether executive control mechanisms can actively reconfigure the cognitive system in preparation for switching to a new task set. To address this question, we recorded brain activity from 14 healthy participants, using event-related functional magnetic resonance imaging, while they performed a cued attention task. Critically, in any particular trial, the cued task set was either the same as that in the previous trial or switched. As was hypothesized, cue-related, switch-specific preparatory activity was observed in a network of dorsal frontal and parietal brain areas that are typically associated with cognitive control processes. Moreover, the magnitude of switch-specific preparatory activity varied with the number of possible task sets that could be presented in a given trial block. These findings provide compelling support for the existence of top-down, preparatory control processes that enable set switching. Furthermore, they demonstrate that global task structure is a critical determinant of whether switch-specific preparatory activity is observed.

To assess selective attention processes in young and old adults, behavioral and event-related potential (ERP) measures were recorded. Streams of visual stimuli were presented from left or right locations (Experiment 1) or from a central location and comprising two different spatial frequencies (Experiment 2). In both experiments, results were compared in visual-only and visual + auditory stimulus context conditions. Participants were forced to respond fast in both experiments, while maintaining high accuracy. In Experiment 1, no behavioral effects of aging were found; however, an enlargement of the N1 component in the older age group suggested that older adults initial selection process was larger than that of young adults. A late frontal effect following the P300 elicited by attended non-targets was larger in the visual + auditory condition than in the visual-only condition in the old age group. This effect was interpreted as reflecting a memory update of the relevant target location. In Experiment 2, older adults made relatively more errors in the visual + auditory condition than in visual-only condition, more so than the young adults. Older adults' ERP data were also characterized by an enlargement of the occipital selection negativity, compared to the young age group. In contrast to experiment 1, no late frontal post-P3 effect could be found, suggesting that the memory trace of the relevant stimulus feature was updated less frequently, explaining the reduction in response accuracy in the visual + auditory stimulus context conditions.

In this introductory article of the special issue of Brain Research, we first present an overview of some general questions relating to cognitive control. For instance, one of the questions that remain to be answered is what control mechanisms and their neural underpinnings really ‘do’, beyond what is done by more basic ‘computational’ or data processing systems in the brain. We then briefly describe the four major issues addressed in the separate articles of this issue, namely attentional orienting, task set switching, performance and error monitoring, and response inhibition. In conclusion, we focus on some new methodological directions and illustrate how the study of cognitive control may be augmented by relatively newly emerging theoretical and empirical perspectives.

The principal aim of the present study was to clarify how stop-signal modality affected the speed and efficacy of stopping, using ERP components as converging measures of stop processes. Both performance and ERP latency findings suggested faster processing of stop signals in the auditory than visual version of the stop task. The effects of successful versus unsuccessful stopping on the amplitude and topography of N2/P3 components elicited by the stop signals appeared to be largely independent of the modality of the stop signals. Stop signals elicited a fronto-central N2 that was much larger on unsuccessful than successful stop trials in stimulus-locked waveforms. N2 was followed by a P3 component that showed a fronto-central distribution on successful stop trials. P3 elicited on unsuccessful stop trials showed a posterior-parietal focus, but this topography was manifested more clearly in response-locked than stimulus-locked waveforms. A dipole source analyses confirmed these topographical differences of P3, and further showed that the location of the corresponding dipoles remained largely identical across the visual and auditory versions of the stop-signal task. Taken together, the present findings support the suggestion that ERP components in the stop task reflect endogenous aspects of stop-signal processing, such as effective inhibition of responses on successful stop trials and detection of errors on failed inhibition trials.

We studied the effects of moderate amounts of caffeine on task switching and task maintenance using mixed-task (AABB) blocks, in which participants alternated predictably between two tasks, and single-task (AAAA, BBBB) blocks. Switch costs refer to longer reaction times (RT) on task switch trials (e.g. AB) compared to task-repeat trials (e.g. BB); mixing costs refer to longer RTs in task-repeat trials compared to single-task trials. In a double-blind, within-subjects experiment, two caffeine doses (3 and 5mg/kg body weight) and a placebo were administered to 18 coffee drinkers. Both caffeine doses reduced switch costs compared to placebo. Event-related brain potentials revealed a negative deflection developing within the preparatory interval, which was larger for switch than for repeat trials. Caffeine increased this switch-related difference. These results suggest that coffee consumption improves task-switching performance by enhancing anticipatory processing such as task set updating, presumably through the neurochemical effects of caffeine on the dopamine system.

In the present randomized, mixed-trial event-related fMRI study, we examined the neural mechanisms underlying inhibitory control using a stop-signal paradigm in which stop-signal frequency was manipulated parametrically across blocks. As hypothesized, presenting stop signals less frequently was accompanied by a stronger set to respond to the go stimuli as subjects were faster in responding to go stimuli on no stop-signal trials and made more commission errors (i.e., were less successful in inhibiting the go response) on stop-signal trials. When response inhibition was successful, having to inhibit responses more frequently compared to less frequently was associated with greater activation in occipital areas. This presumably reflects enhanced visual attention to the stop signal. When response inhibition failed, greater activity was observed in bilateral insula when stop signals were presented less compared to more frequently. The insula may thus play a role in processing the significance of inhibitory failure.

The effects of caffeine on different information processing stages were examined by using choice reaction time tasks. Independent variables were stimulus degradation, stimulus-response compatibility, time-uncertainty, state of the subject, and caffeine treatment. The task variables were assumed to affect the following processing stages; encoding, response selection and motor preparation, respectively. A 200 mg dose at the beginning of the experiment and a maintenance dose of 50 mg caffeine or lactose half-way through the session were administered to well rested and fatigued subjects, double-blind and deceptively. Behavioural measurements, event-related potentials (ERPs) and mood questionnaires were used to assess caffeine effects. The data showed that caffeine shortened reaction time. This effect showed an interaction with stimulus degradation and time uncertainty. In addition, ERP results supported the view that caffeine increases cortical arousal and perceptual sensitivity. Stimulating effects of caffeine were mainly located at input and output stages of the information processing system. Central processes were unaffected by caffeine. Fatigued subjects showed larger improvements in performance after caffeine than well-rested subjects. The results also indicated that caffeine effects were not stimulating in all subjects: 6 out of 30 subjects did not show arousing effects of caffeine.

This study investigated the nature and dynamics of the top-down control mechanisms that afford attentional selection using event-related potentials (ERPs) and dipole-source modeling. Subjects performed a task in which they were cued to direct attention to color, location, a conjunction of color and location or no specific feature on a trial-by-trial basis. Overall, similar ERP patterns were observed for directing attention to color and location, suggesting that spatial and non-spatial attention rely to a great extent on similar control mechanisms. The earliest attention-directing effect, at 340 ms, was localized to ventral posterior cortex and may reflect processes by which the cue is linked to its associated feature. Only late in the cue-target interval, differences in ERP were observed between directing attention to color and location. These originated from anterior and ventral posterior areas and may represent differences in, respectively, maintenance and perceptual biasing processes. The ventral posterior sources estimated for these late effects of directing attention to location and color were located posterior to those estimated for the modulatory effects of, respectively, spatial and non-spatial attention. This suggests that the precise neural populations involved in perceptual biasing and attentional modulation may differ. Conjunction cues initially elicited less posterior positivity than color and location cues, but evoked greater central positivity from 540 ms on. This central effect may reflect feature integration or ongoing processes related to cue-symbol translation. These results extend our understanding of the spatio-temporal dynamics of top-down attentional control.

This study investigated the electrophysiological correlates of shifting, maintaining, and relaxing the focus of attention, using a symbolic cuing task. Cues and imperative stimuli were presented in rapid succession, and the ADJAR procedure was used to remove the contribution of event-related potential (ERP) activity associated with the imperative stimulus from the cue-related ERP waveforms. Initial analyses, comparing left and right attention-directing cues, replicated previous findings of early directing attention negativity (EDAN) and anterior directing attention negativity (ADAN) effects. To isolate ERP activity that is common to leftward and rightward attention shifts, the combined ERP activity elicited by attention-directing cues was compared to the ERP activity elicited by non-informative cues. This analysis revealed a strong and broadly distributed early positivity followed by a sustained central negativity, possibly reflecting the controlled orienting and subsequent maintenance of attentional focus. Finally, imperative stimuli preceded by non-informative cues were characterized by an enhanced posterior P2 effect, with a scalp distribution indicative of generators in visual areas. This result suggests a relatively late (re)activation in visual areas associated with the processing of stimuli that had not been cued in advance.