Energetic effects of stimulus intensity on prolonged simple reaction-time performance

Visual perceptual processing is unaffected by cognitive fatigue

Cognitive fatigue (CF) can lead to an increase in the latency of simple reaction time, although the processes involved in this delay are unknown. One potential explanation is that a longer time may be required for sensory processing of relevant stimuli. To investigate this possibility, the current study used a visual inspection time task to measure perceptual processing speed before and after a CF (math and memory) or non-fatiguing (documentary film) intervention. Subjective fatigue and simple reaction time significantly increased following the CF, but not the non-fatiguing intervention, confirming that CF was induced. Conversely, there was no effect of CF on inspection time task performance. It was therefore concluded that the speed of perceptual processing is not significantly impacted by CF, and thus is unlikely to underlie CF-related reaction time increases. Instead, increases in simple reaction time latency in CF may be due to delays in response preparation or initiation.

Effect of transcranial static magnetic stimulation over unilateral or bilateral motor association cortex on performance of simple and choice reaction time tasks

Background

Transcranial static magnetic stimulation (tSMS) is a non-invasive brain stimulation technique that place a strong neodymium magnet on scalp to reduce cortical excitability. We have recently developed a new tSMS device with three magnets placed close to each other (triple tSMS) and confirmed that this new device can produce a stronger and broader static magnetic field than the conventional single tSMS. The aim of the present study was to investigate the effect of the conventional single tSMS as well as triple tSMS over the unilateral or bilateral motor association cortex (MAC) on simple and choice reaction time (SRT and CRT) task performance.

Methods

There were two experiments: one involved the conventional tSMS, and the other involved the triple tSMS. In both experiments, right-handed healthy participants received each of the following stimulations for 20 min on different days: tSMS over the unilateral (left) MAC, tSMS over the bilateral MAC, and sham stimulation. The center of the stimulation device was set at the premotor cortex. The participants performed SRT and CRT tasks before, immediately after, and 15 min after the stimulation (Pre, Post 0, and Post 15). We evaluated RT, standard deviation (SD) of RT, and accuracy (error rate). Simulation was also performed to determine the spatial distribution of magnetic field induced by tSMS over the bilateral MAC.

Results

The spatial distribution of induced magnetic field was centered around the PMd for both tSMS systems, and the magnetic field reached multiple regions of the MAC as well as the sensorimotor cortices for triple tSMS. SD of CRT was significantly larger at Post 0 as compared to Pre when triple tSMS was applied to the bilateral MAC. No significant findings were noted for the other conditions or variables.

Discussion

We found that single tSMS over the unilateral or bilateral MAC did not affect performance of RT tasks, whereas triple tSMS over the bilateral MAC but not over the unilateral MAC increased variability of CRT. Our finding suggests that RT task performance can be modulated using triple tSMS.

Vigilance described by the time-on-task effect in EEG activity during a cued Go/NoGo task

Vigilance refers to the ability to maintain attention and to remain alert to stimuli in prolonged and monotonous tasks. Vigilance decrement describes the decline in performance in the course of such sustained attention tasks. Time-related alterations in attention have been found to be associated with changes in EEG. We investigated these time-on-task effects on the basis of changes in the conventional EEG spectral bands with the aim of finding a compound measure of vigilance. 148 healthy adults performed a cued Go/NoGo task that lasted approximately 21 min. Behavioural performance was examined by comparing the number of errors in the first and last quarters of the task using paired t-test. EEG data were epoched per trial, and time-on-task effects were modelled by using multiple linear regression, with frequency spectra band power values as independent variables and trial number as the dependent variable. Behavioural performance decreased in terms of omission errors only. Performance of the models, expressed by predicted R-squared, was between 0.10 and 0.27, depending on the particular task condition. The time-on-task EEG spectral changes were characterized by broad changes in the alpha and frontal changes in the beta and gamma bands. We were able to identify a set of EEG spectral features that predict time-on-task. Our output is considered to be a measure of vigilance, reflecting the allocation of mental resources for the maintenance of attention.

Slowed reaction times in cognitive fatigue are not attributable to declines in motor preparation

Cognitive fatigue (CF) can result from sustained mental effort, is characterized by subjective feelings of exhaustion and cognitive performance deficits, and is associated with slowed simple reaction time (RT). This study determined whether declines in motor preparation underlie this RT effect. Motor preparation level was indexed using simple RT and the StartReact effect, wherein a prepared movement is involuntarily triggered at short latency by a startling acoustic stimulus (SAS). It was predicted that if decreased motor preparation underlies CF-associated RT increases, then an attenuated StartReact effect would be observed following cognitive task completion. Subjective fatigue assessment and a simple RT task were performed before and after a cognitively fatiguing task or non-fatiguing control intervention. On 25% of RT trials, a SAS replaced the go-signal to assess the StartReact effect. CF inducement was verified by significant declines in cognitive performance (p = 0.003), along with increases in subjective CF (p < 0.001) and control RT (p = 0.018) following the cognitive fatigue intervention, but not the control intervention. No significant pre-to-post-test changes in SAS RT were observed, indicating that RT increases resulting from CF are not substantially associated with declines in motor preparation, and instead may be attributable to other stages of processing during a simple RT task.

Attentional interference by pain in a dishabituation procedure: an experimental investigation

ABSTRACT

The ability to habituate to pain may be adaptive, and it may enable us to pursue valuable goals despite the pain. In this study, we experimentally investigated this idea using the primary task paradigm in which participants had to identify the color of a circle (blue or yellow) as quickly as possible while ignoring painful or tactile distractors that are presented on some of the trials. In the first experiment, we were interested whether the attentional interference effect because of the presentation of the distractors and its habituation would differ between painful and tactile distractor stimuli. In the second experiment, we investigated dishabituation (ie, the phenomenon that the introduction of a different stimulus results in an increase of the decremented response to the original stimulus). We expected habituation of the attentional interference to occur both in the tactile and the painful distractor condition, but to be less complete in the painful condition. Moreover, we hypothesized that the dishabituation would be stronger for the painful than for the tactile distractors. We did find evidence for an interference effect because of the presence of distractors. We also found habituation of attentional interference. However, the interference and its habituation were no different for tactile and painful distractors. Moreover, we did not find evidence for dishabituation. These are the first studies of their kind. Implications and guidelines for future research are formulated.

Alcohol Hangover and Multitasking: Effects on Mood, Cognitive Performance, Stress Reactivity, and Perceived Effort

The aim of this study was to examine the effects of hangover on mood, multitasking ability, and psychological stress reactivity to cognitive demand. Using a crossover design and semi-naturalistic methodology, 25 participants attended the laboratory in the morning following a night of (i) alcohol abstinence and (ii) alcohol self-administration during a typical night out (with order counterbalanced across participants). They completed a four-module multitasking framework (MTF, a widely used laboratory stressor) and a battery of questionnaires assessing mood, hangover symptom severity, and previous night’s sleep. The effects of the MTF on mood and perceived workload were also assessed. Participants in the hangover condition reported significantly lower alertness and contentment coupled with a higher mental fatigue and anxiety. Multitasking ability was also significantly impaired in the hangover condition. Completion of the cognitive stressor increased reported levels of mental demand, effort, and frustration, and decreased perceived level of performance. MTF completion did not differentially affect mood. Lastly, participants rated their sleep as significantly worse during the night prior to the hangover compared with the control condition. These findings confirm the negative cognitive and mood effects of hangover on mood. They also demonstrate that hangover is associated with greater perceived effort during task performance.

Cognition in Stroke Rehabilitation and Recovery Research: Consensus-Based Core Recommendations From the Second Stroke Recovery and Rehabilitation Roundtable

Cognitive impairment is an important target for rehabilitation as it is common following stroke, is associated with reduced quality of life and interferes with motor and other types of recovery interventions. Cognitive function following stroke was identified as an important, but relatively neglected area during the first Stroke Recovery and Rehabilitation Roundtable (SRRR I), leading to a Cognition Working Group being convened as part of SRRR II. There is currently insufficient evidence to build consensus on specific approaches to cognitive rehabilitation. However, we present recommendations on the integration of cognitive assessments into stroke recovery studies generally and define priorities for ongoing and future research for stroke recovery and rehabilitation. A number of promising interventions are ready to be taken forward to trials to tackle the gap in evidence for cognitive rehabilitation. However, to accelerate progress requires that we coordinate efforts to tackle multiple gaps along the whole translational pathway.

Cognition in stroke rehabilitation and recovery research: Consensus-based core recommendations from the second Stroke Recovery and Rehabilitation Roundtable

Cognitive impairment is an important target for rehabilitation as it is common following stroke, is associated with reduced quality of life and interferes with motor and other types of recovery interventions. Cognitive function following stroke was identified as an important, but relatively neglected area during the first Stroke Recovery and Rehabilitation Roundtable (SRRR I), leading to a Cognition Working Group being convened as part of SRRR II. There is currently insufficient evidence to build consensus on specific approaches to cognitive rehabilitation. However, we present recommendations on the integration of cognitive assessments into stroke recovery studies generally and define priorities for ongoing and future research for stroke recovery and rehabilitation. A number of promising interventions are ready to be taken forward to trials to tackle the gap in evidence for cognitive rehabilitation. However, to accelerate progress requires that we coordinate efforts to tackle multiple gaps along the whole translational pathway.

Error monitoring and daily life executive functioning

Error monitoring during task execution is reflected in post-error slowing (PES), which refers to the tendency to slow down performance after making an error in order to prevent future mistakes. The key question of the present study is whether poor error monitoring (reduced magnitude of PES) has negative consequences for daily life executive function skills, as well as functioning in different life settings such as work, family, social, and academic settings. Eighty-five university students performed a lexical decision task and completed The Executive Function Index Scale (EFI), and the Weiss Functional Impairments Rating Scale (WFIRS). Individual academic achievement was measured using the Grade Point Average. Statistical analysis revealed that a decreased magnitude of PES was weakly associated with less efficient planning (one of the executive functions). Results suggest that error monitoring, as measured by PES, was not associated with functioning in a naturalistic environment, but could be interpreted to some extent as an experimental marker of planning in daily life executive functioning.

A systematic review of the next-day effects of heavy alcohol consumption on cognitive performance

BACKGROUND AND AIMS

Studies examining the next-day cognitive effects of heavy alcohol consumption have produced mixed findings, which may reflect inconsistencies in definitions of 'hangover'. Recent consensus has defined hangover as 'mental and physical symptoms, experienced the day after a single episode of heavy drinking, starting when blood alcohol concentration (BAC) approaches zero'. In light of this, we aimed to review the literature systematically to evaluate and estimate mean effect sizes of the next-day effects of heavy alcohol consumption on cognition.

METHODS

Embase, PubMed and PsycNET databases were searched between December 2016 and May 2018 using terms based on 'alcohol' and 'hangover'. Studies of experimental designs which reported the next-day cognitive effects of heavy alcohol consumption in a 'hangover' group with BAC < 0.02% were reviewed. A total of 805 articles were identified. Thirty-nine full-text articles were screened by two independent reviewers and 19 included in the systematic review; 11 articles provided sufficient data to be included in the meta-analysis; 1163 participants across 19 studies conducted since 1970 were included in the analysis. Data for study design, hangover severity, BAC at testing and cognitive performance were extracted and effect estimates calculated.

RESULTS

The systematic review suggested that sustained attention and driving abilities were impaired during hangover. Mixed results were observed for: psychomotor skills, short- (STM) and long-term memory (LTM) and divided attention. The meta-analysis revealed evidence of impairments in STM [g = 0.64, 95% confidence interval (CI) = 0.15-1.13], LTM (Hedges' g = 0.59, 95% CI = 0.01-1.17) sustained attention (g = 0.47, 95% CI = 0.07-0.87) and psychomotor speed (Hedges' g = 0.66, 95% CI = 0.31-1.00) during alcohol hangover.

CONCLUSION

The research literature suggests that alcohol hangovers may involve impaired cognitive functions and performance of everyday tasks such as driving.

Pupillary Correlates of Fluctuations in Sustained Attention

The current study examined pupillary correlates of fluctuations and lapses of sustained attention. Participants performed a sustained attention task with either a varied ISI or a fixed ISI (fixed at 2 or 8 sec) while pupil responses were continuously recorded. The results indicated that performance was worse when the ISI was varied or fixed at 8 sec compared with when the ISI was fixed at 2 sec, suggesting that varied or long ISI conditions require greater intrinsic alertness compared with constant short ISIs. In terms of pupillary responses, the results demonstrated that slow responses (indicative of lapses) were associated with greater variability in tonic pupil diameter, smaller dilation responses during the ISI, and subsequently smaller dilation responses to stimulus onset. These results suggest that lapses of attention are associated with lower intrinsic alertness, resulting in a lowered intensity of attention to task-relevant stimuli. Following a lapse of attention, performance, tonic pupil diameter, and phasic pupillary responses, all increased, suggesting that attention was reoriented to the task. These results are consistent with the notion that pupillary responses track fluctuations in sustained attention.

Both Reaction Time and Accuracy Measures of Intraindividual Variability Predict Cognitive Performance in Alzheimer's Disease

Dementia researchers around the world prioritize the urgent need for sensitive measurement tools that can detect cognitive and functional change at the earliest stages of Alzheimer's disease (AD). Sensitive indicators of underlying neural pathology assist in the early detection of cognitive change and are thus important for the evaluation of early-intervention clinical trials. One method that may be particularly well-suited to help achieve this goal involves the quantification of intraindividual variability (IIV) in cognitive performance. The current study aimed to directly compare two methods of estimating IIV (fluctuations in accuracy-based scores vs. those in latency-based scores) to predict cognitive performance in AD. Specifically, we directly compared the relative sensitivity of reaction time (RT)-and accuracy-based estimates of IIV to cognitive compromise. The novelty of the present study, however, centered on the patients we tested [a group of patients with Alzheimer's disease (AD)] and the outcome measures we used (a measure of general cognitive function and a measure of episodic memory function). Hence, we compared intraindividual standard deviations (iSDs) from two RT tasks and three accuracy-based memory tasks in patients with possible or probable Alzheimer's dementia (n = 23) and matched healthy controls (n = 25). The main analyses modeled the relative contributions of RT vs. accuracy-based measures of IIV toward the prediction of performance on measures of (a) overall cognitive functioning, and (b) episodic memory functioning. Results indicated that RT-based IIV measures are superior predictors of neurocognitive impairment (as indexed by overall cognitive and memory performance) than accuracy-based IIV measures, even after adjusting for the timescale of measurement. However, one accuracy-based IIV measure (derived from a recognition memory test) also differentiated patients with AD from controls, and significantly predicted episodic memory performance. The findings suggest that both RT- and accuracy-based IIV measures may be useful indicators of underlying neuropathology. The present study therefore contributes toward an understanding of the relative utility of RT- and accuracy-based IIV measures in detecting neurocognitive impairment in older adults, and also advances the empirical evaluation of sensitive markers of cognitive change in patients with AD.

Detecting and Quantifying Mind Wandering during Simulated Driving

Mind wandering is a pervasive threat to transportation safety, potentially accounting for a substantial number of crashes and fatalities. In the current study, mind wandering was induced through completion of the same task for 5 days, consisting of a 20-min monotonous freeway-driving scenario, a cognitive depletion task, and a repetition of the 20-min driving scenario driven in the reverse direction. Participants were periodically probed with auditory tones to self-report whether they were mind wandering or focused on the driving task. Self-reported mind wandering frequency was high, and did not statistically change over days of participation. For measures of driving performance, participant labeled periods of mind wandering were associated with reduced speed and reduced lane variability, in comparison to periods of on task performance. For measures of electrophysiology, periods of mind wandering were associated with increased power in the alpha band of the electroencephalogram (EEG), as well as a reduction in the magnitude of the P3a component of the event related potential (ERP) in response to the auditory probe. Results support that mind wandering has an impact on driving performance and the associated change in driver’s attentional state is detectable in underlying brain physiology. Further, results suggest that detecting the internal cognitive state of humans is possible in a continuous task such as automobile driving. Identifying periods of likely mind wandering could serve as a useful research tool for assessment of driver attention, and could potentially lead to future in-vehicle safety countermeasures.

A functional near-infrared spectroscopy study of the effects of configural properties on sustained attention

Forty-five participants performed a vigilance task during which they were required to respond to a critical signal at a local feature level, while the global display was altered between groups (either a circle, a circle broken apart and reversed, or a reconnected figure). The shape in two of the groups formed a configurative whole (the circle and reconnected conditions), while the remaining shape had no complete global element (broken circle). Performance matched the results found in the previous experiments using this stimulus set, where a configural superiority effect was found to influence accuracy over time. Physiological data, measured using functional near-infrared spectroscopy, revealed elevated activation in the right pre-frontal cortex compared to the left pre-frontal cortex during the task. Additionally, bilateral activation was found in the conditions that formed configurative wholes, while hemispheric differences over time were found in the condition that did not. These findings suggest that configural aspects of stimuli may explain why non-typical laterality effects have been found in similar research.

Robust modulation of arousal regulation, performance, and frontostriatal activity through central thalamic deep brain stimulation in healthy nonhuman primates

The central thalamus (CT) is a key component of the brain-wide network underlying arousal regulation and sensory-motor integration during wakefulness in the mammalian brain. Dysfunction of the CT, typically a result of severe brain injury (SBI), leads to long-lasting impairments in arousal regulation and subsequent deficits in cognition. Central thalamic deep brain stimulation (CT-DBS) is proposed as a therapy to reestablish and maintain arousal regulation to improve cognition in select SBI patients. However, a mechanistic understanding of CT-DBS and an optimal method of implementing this promising therapy are unknown. Here we demonstrate in two healthy nonhuman primates (NHPs), Macaca mulatta, that location-specific CT-DBS improves performance in visuomotor tasks and is associated with physiological effects consistent with enhancement of endogenous arousal. Specifically, CT-DBS within the lateral wing of the central lateral nucleus and the surrounding medial dorsal thalamic tegmental tract (DTTm) produces a rapid and robust modulation of performance and arousal, as measured by neuronal activity in the frontal cortex and striatum. Notably, the most robust and reliable behavioral and physiological responses resulted when we implemented a novel method of CT-DBS that orients and shapes the electric field within the DTTm using spatially separated DBS leads. Collectively, our results demonstrate that selective activation within the DTTm of the CT robustly regulates endogenous arousal and enhances cognitive performance in the intact NHP; these findings provide insights into the mechanism of CT-DBS and further support the development of CT-DBS as a therapy for reestablishing arousal regulation to support cognition in SBI patients.

Mid-Task Break Improves Global Integration of Functional Connectivity in Lower Alpha Band

Numerous efforts have been devoted to revealing neurophysiological mechanisms of mental fatigue, aiming to find an effective way to reduce the undesirable fatigue-related outcomes. Until recently, mental fatigue is thought to be related to functional dysconnectivity among brain regions. However, the topological representation of brain functional connectivity altered by mental fatigue is only beginning to be revealed. In the current study, we applied a graph theoretical approach to analyse such topological alterations in the lower alpha band (8~10 Hz) of EEG data from 20 subjects undergoing a two-session experiment, in which one session includes four successive blocks with visual oddball tasks (session 1) whereas a mid-task break was introduced in the middle of four task blocks in the other session (session 2). Phase lag index (PLI) was then employed to measure functional connectivity strengths for all pairs of EEG channels. Behavior and connectivity maps were compared between the first and last task blocks in both sessions. Inverse efficiency scores (IES = reaction time/response accuracy) were significantly increased in the last task block, showing a clear effect of time-on-task in participants. Furthermore, a significant block-by-session interaction was revealed in the IES, suggesting the effectiveness of the mid-task break on maintaining task performance. More importantly, a significant session-independent deficit of global integration and an increase of local segregation were found in the last task block across both sessions, providing further support for the presence of a reshaped topology in functional brain connectivity networks under fatigue state. Moreover, a significant block-by-session interaction was revealed in the characteristic path length, small-worldness, and global efficiency, attributing to the significantly disrupted network topology in session 1 in comparison of the maintained network structure in session 2. Specifically, we found increased nodal betweenness centrality in several channels resided in frontal regions in session 1, resembling the observations of more segregated global architecture under fatigue state. Taken together, our findings provide insights into the substrates of brain functional dysconnectivity patterns for mental fatigue and reiterate the effectiveness of the mid-task break on maintaining brain network efficiency.

The sustained attention to response task (SART) does not promote mindlessness during vigilance performance

OBJECTIVE

In this study, we evaluated the validity of the Sustained Attention to Response Task (SART) as a means for promoting mindlessness in vigilance performance.

BACKGROUND

Vigilance tasks typically require observers to respond to critical signals and to withhold responding to neutral events. The SART features the opposite response requirements, which supposedly leads it to promote a mindless, non-thoughtful approach to the vigilance task To test that notion, we compared the SART to the traditional vigilance format (TVF) in terms of diagnostic accuracy assessed through decision theory measures of positive and negative predictive power (PPP and NPP), perceived mental workload indexed by the Multiple Resource Questionnaire, and oculomotor activity reflected in the Nearest Neighbor Index and fixation dwell times.

METHOD

Observers in TVF and SART conditions monitored a video display for collision flight paths in a simulated air traffic control task.

RESULTS

Diagnostic accuracy in terms of NPP was high in both format conditions. While PPP was poorer in the SART than in the TVF, that result could be accounted for by a loss of motor control rather than a lack of mindfulness. Identical high levels of workload were generated by the TVF and SART tasks, and observers in both conditions showed similar dynamic scanning of the visual scene.

CONCLUSION

The data indicate that the SART is not an engine of mindlessness.

APPLICATION

The results challenge the widespread use of the SART to support a model in which mindlessness is considered to be the principal root of detection failures in vigilance.

Translating working memory into action: behavioral and neural evidence for using motor representations in encoding visuo-spatial sequences

The neurobiological organization of action-oriented working memory is not well understood. To elucidate the neural correlates of translating visuo-spatial stimulus sequences into delayed (memory-guided) sequential actions, we measured brain activity using functional magnetic resonance imaging while participants encoded sequences of four to seven dots appearing on fingers of a left or right schematic hand. After variable delays, sequences were to be reproduced with the corresponding fingers. Recall became less accurate with longer sequences and was initiated faster after long delays. Across both hands, encoding and recall activated bilateral prefrontal, premotor, superior and inferior parietal regions as well as the basal ganglia, whereas hand-specific activity was found (albeit to a lesser degree during encoding) in contralateral premotor, sensorimotor, and superior parietal cortex. Activation differences after long versus short delays were restricted to motor-related regions, indicating that rehearsal during long delays might have facilitated the conversion of the memorandum into concrete motor programs at recall. Furthermore, basal ganglia activity during encoding selectively predicted correct recall. Taken together, the results suggest that to-be-reproduced visuo-spatial sequences are encoded as prospective action representations (motor intentions), possibly in addition to retrospective sensory codes. Overall, our study supports and extends multi-component models of working memory, highlighting the notion that sensory input can be coded in multiple ways depending on what the memorandum is to be used for.

Event-related cerebral hemodynamics reveal target-specific resource allocation for both "go" and "no-go" response-based vigilance tasks

Transcranial Doppler sonography was used to measure cerebral blood flow velocity (CBFV) in the right and left cerebral hemispheres during the performance of a 50-min visual vigilance session. Observers monitored a simulated flight of unmanned aerial vehicles for cases in which one of the vehicles was flying in an inappropriate direction relative to its cohorts. Two types of vigilance tasks were employed: a traditional task in which observers made button press ("go") responses to critical signals, and a modification of the traditional task called the Sustained Attention to Response Task (SART) in which "go" responses acknowledged nonsignal events and response withholding ("no-go") signified signal detection. Signal detections and global CBFV scores declined over time. In addition, fine-grained event-related analyses revealed that the detection of signals was accompanied by an elevation of CBFV that was not present with missed signals. As was the case with the global scores, the magnitude of the transient CBFV increments associated with signal detection also declined over time, and these findings were independent of task type. The results support the view of CBFV as an index of the cognitive evaluation of stimulus significance, and a resource model of vigilance in which the need for continuous attention produces a depletion of information-processing assets that are not replenished as the task progresses. Further, temporal declines in the magnitude of event-related CBFV in response to critical signals only is evidence that the decrement function in vigilance is due to attentional processing and not specific task elements such as the required response format.

Are reaction times obtained during fMRI scanning reliable and valid measures of behavior?

Assuming that behavior observed during functional magnetic resonance imaging (fMRI) is comparable with behavior outside the scanner appears to be a basic tenet in cognitive neuroscience. Nevertheless, this assumption has rarely been tested directly. Here, we examined the reliability and validity of speeded performance during fMRI scanning by having the same 30 participants perform a battery of five reaction time (RT) tasks in two separate fMRI sessions and a standard laboratory (i.e., outside-scanner) session. Medium-to-high intra-class correlations between the three sessions showed that individual RT differences were conserved across sessions. Thus, for the range of tasks used, test-retest reliability and criterion validity of performance during scanning were satisfactory. Further, the pattern of between-task relations did not change within the scanner, attesting to the construct validity of performance measurements during scanning. In some tasks, however, RTs obtained from fMRI conditions were significantly shorter than those observed under normal laboratory conditions. In summary, RTs obtained during fMRI scanning appear to be largely reliable and valid measures of behavior. The observed RT speed-up during scanning might reflect task-specific interactions with a slightly different neuro-cognitive state, indicating some limits to generalizing brain-behavior relations observed with fMRI. These findings encourage further efforts in fMRI research to establish the external validity of within-scanner task performance.

Gating of attentional effort through the central thalamus

The central thalamus plays an important role in the regulation of arousal and allocation of attentional resources in the performance of even simple tasks. To assess the contribution of central thalamic neurons to short-term adjustments of attentional effort, we analyzed 166 microelectrode recordings obtained from two rhesus monkeys performing a visuomotor simple reaction time task with a variable foreperiod. Multiunit responses showed maintained firing rate elevations during the variable delay period of the task in ∼24% of recording sites. Simultaneously recorded local field potentials demonstrated significant decreases in power at ∼10-20 Hz and increases in power at 30-100 Hz during the delay period when compared against precue baselines. Comparison of the spectral power of local field potentials during the delay period of correct and incorrect trials showed that, during incorrect trials, similar, but reduced, shifts of spectral power occurred within the same frequency bands. Sustained performance of even simple tasks requires regulation of arousal and attention that combine in the concept of "attentional effort". Our findings suggest that central thalamic neurons regulate task performance through brief changes in firing rates and spectral power changes during task-relevant short-term shifts of attentional effort. Increases in attentional effort may be reflected in changes within the central thalamic local populations, where correct task performance associates with more robust maintenance of firing rates during the delay period. Such ongoing fluctuations of central thalamic activity likely reflect a mix of influences, including variations in moment-to-moment levels of motivation, arousal, and availability of cognitive resources.

Sustaining attention to simple tasks: a meta-analytic review of the neural mechanisms of vigilant attention

Maintaining attention for more than a few seconds is essential for mastering everyday life. Yet, our ability to stay focused on a particular task is limited, resulting in well-known performance decrements with increasing time on task. Intriguingly, such decrements are even more likely if the task is cognitively simple and repetitive. The attentional function that enables our prolonged engagement in intellectually unchallenging, uninteresting activities has been termed vigilant attention. Here we synthesized what we have learned from functional neuroimaging about the mechanisms of this essential mental faculty. To this end, a quantitative meta-analysis of pertinent neuroimaging studies was performed, including supplementary analyses of moderating factors. Furthermore, we reviewed the available evidence on neural time-on-task effects, additionally considering information obtained from patients with focal brain damage. Integrating the results of both meta-analysis and review, we identified a set of mainly right-lateralized brain regions that may form the core network subserving vigilant attention in humans, including dorsomedial, mid- and ventrolateral prefrontal cortex, anterior insula, parietal areas (intraparietal sulcus, temporoparietal junction), and subcortical structures (cerebellar vermis, thalamus, putamen, midbrain). We discuss the potential functional roles of different nodes of this network as well as implications of our findings for a theoretical account of vigilant attention. It is conjectured that sustaining attention is a multicomponent, nonunitary mental faculty, involving a mixture of (a) sustained/recurrent processes subserving task-set/arousal maintenance and (b) transient processes subserving the target-driven reorienting of attention. Finally, limitations of previous studies are considered and suggestions for future research are provided.

Cerebral Hemovelocity and the Sustained Attention to Response Task (SART)

Vigilance tasks in the traditional format (TVF) require observers to respond to critical signals on their monitored displays and withhold responding to neutral events. The Sustained Attention to Response Task (SART) features the opposite response requirements which supposedly lead it to promote a mindless, non-thoughtful approach to the vigilance task. To test that possibility, this study compared the SART to the TVF in terms of cerebral blood flow velocity (CBFV) secured in the performance of a simulated UAV monitoring assignment. Previous studies have consistently shown that CBFV declines significantly over time for observers who monitor in the TVF while it remains temporally stable in control observers who view the display without a work imperative – perhaps a maximum case of mindlessness. In the present study, CBFV declined over time in a similar manner for observers performing under SART and TVF conditions while it remained stable over time for non-engaged controls. The results are consistent with studies using psychophysical, workload, and stress measures that challenge the view that the SART is an engine of mindlessness.

Default mode network connectivity predicts sustained attention deficits after traumatic brain injury

Traumatic brain injury (TBI) frequently produces impairments of attention in humans. These can result in a failure to maintain consistent goal-directed behavior. A predominantly right-lateralized frontoparietal network is often engaged during attentionally demanding tasks. However, lapses of attention have also been associated with increases in activation within the default mode network (DMN). Here, we study TBI patients with sustained attention impairment, defined on the basis of the consistency of their behavioral performance over time. We show that sustained attention impairments in patients are associated with an increase in DMN activation, particularly within the precuneus and posterior cingulate cortex. Furthermore, the interaction of the precuneus with the rest of the DMN at the start of the task, i.e., its functional connectivity, predicts which patients go on to show impairments of attention. Importantly, this predictive information is present before any behavioral evidence of sustained attention impairment, and the relationship is also found in a subgroup of patients without focal brain damage. TBI often results in diffuse axonal injury, which produces cognitive impairment by disconnecting nodes in distributed brain networks. Using diffusion tensor imaging, we demonstrate that structural disconnection within the DMN also correlates with the level of sustained attention. These results show that abnormalities in DMN function are a sensitive marker of impairments of attention and suggest that changes in connectivity within the DMN are central to the development of attentional impairment after TBI.

Mental fatigue modulates dynamic adaptation to perceptual demand in speeded detection

When stimulus intensity in simple reaction-time tasks randomly varies across trials, detection speed usually improves after a low-intensity trial. With auditory stimuli, this improvement was often found to be asymmetric, being greater on current low-intensity trials. Our study investigated (1) whether asymmetric sequential intensity adaptation also occurs with visual stimuli; (2) whether these adjustments reflect decision-criterion shifts or, rather, a modulation of perceptual sensitivity; and (3) how sequential intensity adaptation and its underlying mechanisms are affected by mental fatigue induced through prolonged performance. In a continuous speeded detection task with randomly alternating high- and low-intensity visual stimuli, the reaction-time benefit after low-intensity trials was greater on subsequent low- than high-intensity trials. This asymmetry, however, only developed with time on task (TOT). Signal-detection analyses showed that the decision criterion transiently became more liberal after a low-intensity trial, whereas observer sensitivity increased when the preceding and current stimulus were of equal intensity. TOT-induced mental fatigue only affected sensitivity, which dropped more on low- than on high-intensity trials. This differential fatigue-related sensitivity decrease selectively enhanced the impact of criterion down-shifts on low-intensity trials, revealing how the interplay of two perceptual mechanisms and their modulation by fatigue combine to produce the observed overall pattern of asymmetric performance adjustments to varying visual intensity in continuous speeded detection. Our results have implications for similar patterns of sequential demand adaptation in other cognitive domains as well as for real-world prolonged detection performance.

The effects of arousing negative and neutral picture stimuli on target detection in a vigilance task

OBJECTIVES

The present study was designed to explore whether target detection in a vigilance task is influenced by task-irrelevant negative emotional and neutral picture stimuli and to test predictions derived from the boredom-mindlessness versus resource depletion accounts of vigilance performance.

BACKGROUND

Previous research indicates that emotional stimuli can capture spatial attention. Research on the effect of negative emotional and neutral visual stimuli on temporal aspects of attention has not, however, been researched in detail.

METHOD

For this study, 51 participants (15 men and 36 women) were assigned at random to one of three vigilance conditions: a visual vigil with task-irrelevant negative-arousing pictures, a visual vigil with task-irrelevant neutral pictures, or a no-picture visual vigil control. Vigilance performance was assessed in all conditions.

RESULTS

Overall performance efficiency was negatively influenced by the negative-arousing pictures and was interpreted to favor resource depletion to boredom-mindlessness accounts of vigilance performance.

CONCLUSION

Task-unrelated negative emotional stimuli appear to impair absolute levels of target detections in a vigilance task.

APPLICATION

In monitoring settings where negative emotional stimuli are present, the intrusion of negative emotional stimuli should be mitigated via alterations in the system design, or if this is implausible, the monitors may need additional stress coping and emotional resilience training.

Staying responsive to the world: modality-specific and -nonspecific contributions to speeded auditory, tactile, and visual stimulus detection

Sustained responsiveness to external stimulation is fundamental to many time-critical interactions with the outside world. We used functional magnetic resonance imaging during speeded stimulus detection to identify convergent and divergent neural correlates of maintaining the readiness to respond to auditory, tactile, and visual stimuli. In addition, using a multimodal condition, we investigated the effect of making stimulus modality unpredictable. Relative to sensorimotor control tasks, all three unimodal detection tasks elicited stronger activity in the right temporo-parietal junction, inferior frontal cortex, anterior insula, dorsal premotor cortex, and anterior cingulate cortex as well as bilateral mid-cingulum, midbrain, brainstem, and medial cerebellum. The multimodal detection condition additionally activated left dorsal premotor cortex and bilateral precuneus. Modality-specific modulations were confined to respective sensory areas: we found activity increases in relevant, and decreases in irrelevant sensory cortices. Our findings corroborate the modality independence of a predominantly right-lateralized core network for maintaining an alert (i.e., highly responsive) state and extend previous results to the somatosensory modality. Monitoring multiple sensory channels appears to induce additional processing, possibly related to stimulus-driven shifts of intermodal attention. The results further suggest that directing attention to a given sensory modality selectively enhances and suppresses sensory processing-even in simple detection tasks, which do not require inter- or intra-modal selection.

Distraction by irrelevant sound during foreperiods selectively impairs temporal preparation

When the interval between a warning signal (WS) and an imperative signal (IS), termed the foreperiod (FP), is variable across trials, reaction time (RT) to the IS typically decreases with increasing FP length. Here we examined the auditory filled-FP effect, which refers to a performance decrement after FPs filled with irrelevant auditory stimulation compared to FPs without additional stimulation. According to one account, irrelevant stimulation distracts individuals from processing time and probability information during the FP (distraction-during-FP hypothesis). This should predominantly affect long-FP trials. Alternatively, the filled-FP effect may arise from a failure to shift attention from FP modality to IS modality (attention-to-modality hypothesis). The first hypothesis focuses on preparatory processing, predicting a selective RT increase on long-FP trials, whereas the second hypothesis focuses on target processing, only predicting a global RT increase irrespective of FP length. Across four experiments, a filled-FP (compared to a blank-FP) condition consistently yielded a selective RT increase on long-FP trials, irrespective of FP-IS modality pairing. This pattern of results contradicts the attention-to-modality hypothesis but corroborates the distraction-during-FP hypothesis. More generally, these data have theoretical implications by supporting a multi-process view of temporal preparation under time uncertainty.