Visual sustained attention: image degradation produces rapid sensitivity decrement over time

Assessing selective sustained attention in 3- to 5-year-old children: evidence from a new paradigm

Selective sustained attention (SSA) is crucial for higher order cognition. Factors promoting SSA are described as exogenous or endogenous. However, there is little research specifying how these factors interact during development, due largely to the paucity of developmentally appropriate paradigms. We report findings from a novel paradigm designed to investigate SSA in preschoolers. The findings indicate that this task (a) has good psychometric and parametric properties and (b) allows investigation of exogenous and endogenous factors within the same task, making it possible to attribute changes in performance to different mechanisms of attentional control rather than to differences in engagement in different tasks.

Fit and vigilant: the relationship between poorer aerobic fitness and failures in sustained attention during preadolescence

With the growing trend toward engagement in sedentary behaviors during childhood, a greater understanding of the relationship between cardiorespiratory fitness and cognition during development is of increasing importance.

OBJECTIVE

The aim of this investigation was to assess the extent to which failures in sustained attention may underlie deficits in cognition associated with poorer aerobic fitness.

METHOD

A sample of 62 preadolescent children between the ages of 9 and 10 years were separated into higher- and lower-fit groups according to their cardiorespiratory fitness.

RESULTS

Findings indicated that lower-fit children exhibited poorer overall response accuracy during a task requiring aspects of cognitive control relative to their higher-fit counterparts, with a disproportionately greater number of errors of omission, and longer, more frequent sequential errors of omission.

CONCLUSIONS

These findings suggest that poorer vigilance may contribute to deficits in cognitive control associated with poorer aerobic fitness.

Impaired sustained attention in euthymic bipolar disorder patients and non-affected relatives: an fMRI study

OBJECTIVE

Behavioral deficits in sustained attention have been reported during both acute and euthymic phases of type I bipolar disorder (BD-I) and also in non-affected relatives of bipolar disorder (BD) patients. In particular, selective failure in target recognition was proposed as a potential trait marker for BD, but there are few studies exploring the neural correlates. The aim of the present study was to analyze the behavioral and functional magnetic resonance imaging (fMRI) response of euthymic BD-I patients and non-affected relatives during a sustained attention task.

METHODS

Twenty-four euthymic BD-I patients, 22 non-affected first-degree relatives of BD-I subjects, and 24 matched controls underwent a continuous performance test (CPT) with two levels of difficulty during event-related fMRI scanning.

RESULTS

Both patients and relatives showed a lower accuracy in target detection when compared to controls. The fMRI data analysis revealed between-group differences in several brain regions involved in sustained attention. During error in target recognition, both patients and relatives showed a larger activation in the bilateral insula and the posterior part of the middle cingulate cortex. By contrast, during correct target response, only patients failed to activate the right insula, whereas relatives showed an increased activation of the left insula and bilateral inferior parietal lobule - limited to the higher attention load - and an augmented deactivation of the posterior cingulate/retrosplenial cortex.

CONCLUSIONS

A selective impairment in target recognition during a CPT was behaviorally and functionally detectable in both euthymic BD-I patients and non-affected first-degree relatives, suggesting that specific sustained attention deficits may be a potential trait marker for BD-I.

Auditory working memory impairments in individuals at familial high risk for schizophrenia

OBJECTIVES

The search for predictors of schizophrenia has accelerated with a growing focus on early intervention and prevention of psychotic illness. Studying nonpsychotic relatives of individuals with schizophrenia enables identification of markers of vulnerability for the illness independent of confounds associated with psychosis. The goal of these studies was to develop new auditory continuous performance tests (ACPTs) and evaluate their effects in individuals with schizophrenia and their relatives.

METHODS

We carried out two studies of auditory vigilance with tasks involving working memory (WM) and interference control with increasing levels of cognitive load to discern the information-processing vulnerabilities in a sample of schizophrenia patients, and two samples of nonpsychotic relatives of individuals with schizophrenia and controls. Study 1 assessed adults (mean age = 41), and Study 2 assessed teenagers and young adults age 13-25 (M = 19).

RESULTS

Patients with schizophrenia were impaired on all five versions of the ACPTs, whereas relatives were impaired only on WM tasks, particularly the two interference tasks that maximize cognitive load. Across all groups, the interference tasks were more difficult to perform than the other tasks. Schizophrenia patients performed worse than relatives, who performed worse than controls. For patients, the effect sizes were large (Cohen's d = 1.5), whereas for relatives they were moderate (d = ~0.40-0.50). There was no age by group interaction in the relatives-control comparison except for participants <31 years of age.

CONCLUSIONS

Novel WM tasks that manipulate cognitive load and interference control index an important component of the vulnerability to schizophrenia.

Kraepelin and Bleuler had it right: people with schizophrenia have deficits sustaining attention over time

An inability to sustain attention was noted in the original clinical descriptions of schizophrenia, but the vast majority of experimental studies have failed to report a performance decrement over time, calling this observation into question. To test for such deficits when task conditions conform to basic science taxonomy for the validity of sustained attention tasks, a dynamic stimulus array was presented in which targets, differing subtly from standard stimuli, were presented infrequently and unpredictably. Both people with schizophrenia (PSZ, n=40) and healthy control subjects (HCS, n=29) displayed a reduction in hit rate and an increase in reaction time (RT) from the first to the second 5-min period. Thereafter, the hit rate of HCS recovered and remained stable, while that of PSZ continued to decline. When performance at task onset was equated between groups, the decrement over time in PSZ remained of the same robust magnitude. Thus, when the nature of the task challenges sustaining attention over time, PSZ display a clear deficit in this ability.

Age and distraction are determinants of performance on a novel visual search task in aged Beagle dogs

Aging has been shown to disrupt performance on tasks that require intact visual search and discrimination abilities in human studies. The goal of the present study was to determine if canines show age-related decline in their ability to perform a novel simultaneous visual search task. Three groups of canines were included: a young group (N = 10; 3 to 4.5 years), an old group (N = 10; 8 to 9.5 years), and a senior group (N = 8; 11 to 15.3 years). Subjects were first tested for their ability to learn a simple two-choice discrimination task, followed by the visual search task. Attentional demands in the task were manipulated by varying the number of distracter items; dogs received an equal number of trials with either zero, one, two, or three distracters. Performance on the two-choice discrimination task varied with age, with senior canines making significantly more errors than the young. Performance accuracy on the visual search task also varied with age; senior animals were significantly impaired compared to both the young and old, and old canines were intermediate in performance between young and senior. Accuracy decreased significantly with added distracters in all age groups. These results suggest that aging impairs the ability of canines to discriminate between task-relevant and -irrelevant stimuli. This is likely to be derived from impairments in cognitive domains such as visual memory and learning and selective attention.

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.

Remission and recovery during the first outpatient year of the early course of schizophrenia

BACKGROUND

Although in the early course of schizophrenia relapse prevention is of paramount importance, there is an increasing emphasis on establishing and maintaining sustained periods of symptom remission. Recovery in the early course of illness is also possible, although the rates of recovery are lower than for symptom remission. Symptom remission and recovery rates vary considerably across recent-onset schizophrenia studies because of a lack of consistency in treatment interventions and in applying operational outcome criteria.

METHOD

Patients who were within two years of their first psychotic episode (N=77) that were treated with continuous antipsychotic medication in conjunction with psychosocial interventions (without targeted work rehabilitation) were assessed during the first outpatient year after hospital discharge. Published operational criteria were used to classify symptom remission and recovery.

RESULTS

The rate of full symptom remission maintained for 6 months was 36%, while the rate of recovery for 6 months was 10%. When the same criteria were applied for a continuous period of one year, 22% of patients were found to achieve symptom remission but only 1% of patients met recovery criteria. Using multivariate prediction, the WAIS Comprehension score was a significant predictor of 6 months of good functional outcome.

CONCLUSIONS

Although some schizophrenia patients can achieve both symptom remission and recovery in the early course of illness, the overall rate of symptom remission during the first post-hospitalization year is much higher than the rate of recovery. This suggests that interventions targeting work and social functioning are likely necessary to raise the chances of recovery. Cognitive factors can be predictive of good functional outcome even in the early course of schizophrenia.

Search asymmetry, sustained attention, and response inhibition

In the present experiment, we used search asymmetry to test whether the sustained attention to response task is a better measure of response inhibition or sustained attention. Participants performed feature present and feature absent target detection tasks using either a sustained attention to response task (SART; high Go low No-Go) or a traditionally formatted task (TFT; high No-Go low Go) response format. In addition to performance, we employed functional near infrared spectroscopy (fNIRS) to measure lateral cerebral oxygenation levels and self-reports of Tense Arousal, Energetic Arousal, task related and unrelated thoughts occurring during the tasks. Detections were lower and reaction times longer in the feature absent search than the feature present search regardless of response format. Detections were lower, but reaction times shorter in the SART than the TFT regardless of feature search. Greater right than left frontal hemisphere activation occurred in the SART than the TFT. In addition, the SART was more fatiguing based on self-reports than the TFT, but there were no differences in Task-Unrelated Thoughts across task conditions. Overall, the results suggest the SART places high response inhibition, not necessarily sustained attention, demands on participants.

CHRNA7 haplotypes are associated with impaired attention in euthymic bipolar disorder

BACKGROUND

Bipolar disorder (BD) patients show a deficit in sustained attention during euthymic periods. This deficit may be relevant for genetic studies in these patients. The α7 cholinergic receptor plays an important role in attentional deficit in humans and animal models. Moreover, there is evidence suggesting the role of the alpha 7 nicotinic cholinergic receptor subunit gene (CHRNA7) in BD susceptibility. The aim of the present study was to investigate the impact of CHRNA7 in sustained attention performance.

METHODS

We studied the association of a promoter variant (-86C/T) and three intronic polymorphisms, rs883473, rs6494223 and rs904952, in the non-duplicated region of CHRNA7 with sustained attention in 143 euthymic BD patients (based on DSM-IV criteria) and 101 healthy subjects. Sustained attention was assessed by the degraded stimulus (DS-CPT) version of Continuous Performance Test. Age, gender, years of education and IQ (WAIS vocabulary subtest) were controlled in the analyses as potential confounders.

RESULTS

Several candidate polymorphisms showed significant associations with different measures of the neuropsychological task for bipolar group. The CTCT haplotype was associated with an improvement in the attentional task performance in the BD group (p ≤ 0.025). On the other hand, different low frequency haplotypes showed influence in bipolar attentional performance (p ≤ 0.026).

LIMITATIONS

A replication study using larger samples may be required for conclusive results.

CONCLUSIONS

Our results point toward a slight association of CHRNA7 genotypes and haplotypes with sustained attention performance in euthymic patients with BD.

Analysis of 94 candidate genes and 12 endophenotypes for schizophrenia from the Consortium on the Genetics of Schizophrenia

OBJECTIVE

The authors used a custom array of 1,536 single-nucleotide polymorphisms (SNPs) to interrogate 94 functionally relevant candidate genes for schizophrenia and identify associations with 12 heritable neurophysiological and neurocognitive endophenotypes in data collected by the Consortium on the Genetics of Schizophrenia.

METHOD

Variance-component association analyses of 534 genotyped subjects from 130 families were conducted by using Merlin software. A novel bootstrap total significance test was also developed to overcome the limitations of existing genomic multiple testing methods and robustly demonstrate significant associations in the context of complex family data and possible population stratification effects.

RESULTS

Associations with endophenotypes were observed for 46 genes of potential functional significance, with three SNPs at p<10(-4), 27 SNPs at p<10(-3), and 147 SNPs at p<0.01. The bootstrap analyses confirmed that the 47 SNP-endophenotype combinations with the strongest evidence of association significantly exceeded that expected by chance alone, with 93% of these findings expected to be true. Many of the genes interact on a molecular level, and eight genes (e.g., NRG1 and ERBB4) displayed evidence for pleiotropy, revealing associations with four or more endophenotypes. The results collectively support a strong role for genes related to glutamate signaling in mediating schizophrenia susceptibility.

CONCLUSIONS

This study supports use of relevant endophenotypes and the bootstrap total significance test for identifying genetic variation underlying the etiology of schizophrenia. In addition, the observation of extensive pleiotropy for some genes and singular associations for others suggests alternative, independent pathways mediating pathogenesis in the "group of schizophrenias."

Neurocognitive predictors of work outcome in recent-onset schizophrenia

While the role of neurocognitive impairment in predicting functional outcome in chronic schizophrenia is now widely accepted, the results that have examined this relationship in the early phase of psychosis are surprisingly rather mixed. The predictive role of cognitive impairment early in the illness is of particular interest because interventions during this initial period may help to prevent the development of chronic disability. In a University of California, Los Angeles (UCLA) longitudinal study, we assessed schizophrenia patients with a recent first episode of psychosis using a neurocognitive battery at an initial clinically stabilized outpatient point and then followed them during continuous treatment over the next 9 months. Three orthogonal cognitive factors were derived through principal components analysis: working memory, attention and early perceptual processing, and verbal memory and processing speed. All patients were provided a combination of maintenance antipsychotic medication, case management, group skills training, and family education in a UCLA research clinic. A modified version of the Social Adjustment Scale was used to assess work outcome. Multiple regression analyses indicate that the combination of the 3 neurocognitive factors predicts 52% of the variance in return to work or school by 9 months after outpatient clinical stabilization. These data strongly support the critical role of neurocognitive factors in recovery of work functioning after an onset of schizophrenia. Cognitive remediation and other interventions targeting these early cognitive deficits are of major importance to attempts to prevent chronic disability.

The cognitive impact of the ANK3 risk variant for bipolar disorder: initial evidence of selectivity to signal detection during sustained attention

BACKGROUND

Abnormalities in cognition have been reported in patients with Bipolar Disorder (BD) and their first degree relatives, suggesting that susceptibility genes for BD may impact on cognitive processes. Recent genome-wide genetic studies have reported a strong association with BD in a single nucleotide polymorphism (SNP) (rs10994336) within ANK3, which codes for Ankyrin 3. This protein is involved in facilitating the propagation of action potentials by regulating the assembly of sodium gated ion channels. Since ANK3 influences the efficiency of transmission of neuronal impulses, allelic variation in this gene may have widespread cognitive effects. Preclinical data suggest that this may principally apply to sequential signal detection, a core process of sustained attention.

METHODOLOGY/PRINCIPAL FINDINGS

One hundred and eighty-nine individuals of white British descent were genotyped for the ANK3 rs10994336 polymorphism and received diagnostic interviews and comprehensive neurocognitive assessment of their general intellectual ability, memory, decision making, response inhibition and sustained attention. Participants comprised euthymic BD patients (n = 47), their unaffected first-degree relatives (n = 75) and healthy controls (n = 67). The risk allele T was associated with reduced sensitivity in target detection (p = 0.0004) and increased errors of commission (p = 0.0018) during sustained attention regardless of diagnosis. We found no effect of the ANK3 genotype on general intellectual ability, memory, decision making and response inhibition.

CONCLUSIONS/SIGNIFICANCE

Our results suggest that allelic variation in ANK3 impacts cognitive processes associated with signal detection and this mechanism may relate to risk for BD. However, our results require independent replication and confirmation that ANK3 (rs10994336) is a direct functional variant.

Histamine H1 receptor antagonist cetirizine impairs working memory processing speed, but not episodic memory

BACKGROUND AND PURPOSE

The histaminergic neurotransmitter system is currently under investigation as a target for drug treatment of cognitive deficits in clinical disorders. The therapeutic potential of new drugs may initially be screened using a model of histaminergic dysfunction, for example, as associated with the use of centrally active antihistamines. Of the selective second generation antihistamines, cetirizine has been found to have central nervous system effects. The aim of the present study was to determine whether cetirizine can be used as a tool to model cognitive deficits associated with histaminergic hypofunction.

EXPERIMENTAL APPROACH

The study was conducted according to a three-way, double-blind, cross-over design. Treatments were single oral doses of cetirizine 10 and 20 mg and placebo. Effects on cognition were assessed using tests of word learning, memory scanning, vigilance, divided attention, tracking and visual information processing speed.

KEY RESULTS

Cetirizine 10 mg impaired tracking performance and both doses impaired memory scanning speed. None of the other measures indicated impaired performance.

CONCLUSION AND IMPLICATIONS

Cetirizine affects information processing speed, but these effects were not sufficient to serve as a model for cognitive deficits in clinical disorders.

Deficits in visual sustained attention differentiate genetic liability and disease expression for schizophrenia from Bipolar Disorder

BACKGROUND

There is mounting evidence for shared genetic liability to psychoses, particularly with respect to Schizophrenia (SZ) and Bipolar Disorder (BD), which may also involve aspects of cognitive dysfunction. Impaired sustained attention is considered a cardinal feature of psychoses but its association with genetic liability and disease expression in BD remains to be clarified.

METHODS

Visual sustained attention was assessed using the Degraded Symbol Continuous Performance Test (DS-CPT) in a sample of 397 individuals consisting of 50 remitted SZ patients, 119 of their first degree relatives, 47 euthymic BD patients, 88 of their first degree relatives and 93 healthy controls. Relatives with a personal history of schizophrenia or bipolar spectrum disorders were excluded. Performance on the DS-CPT was evaluated based on the response criterion (the amount of perceptual evidence required to designate a stimulus as a target) and sensitivity (a signal-detection theory measure of signal/noise discrimination).

RESULTS

We found no effect of genetic risk or diagnosis for either disorder on response criterion. In contrast, impaired sensitivity was seen in SZ patients and to a lesser degree in their relatives but not in BD patients and their relatives. These findings were not attributable to IQ, medication, age of onset or duration of illness.

CONCLUSIONS

Our results argue for the specificity of visual sustained attention impairment in differentiating SZ from BD. They also suggest that compromised visual information processing is a significant contributor to these deficits in SZ.

Sustained attention as a potential endophenotype for bipolar disorder

OBJECTIVE

Nowadays, it is accepted that to identify the biological basis of psychiatric illnesses it would be useful to deconstruct them into the most basic manifestations, such as cognitive deficits. The aim of this study was to set attention deficit as a stable vulnerability marker of bipolar disorder.

METHOD

Sustained attention was evaluated by the Continuous Performance Test (DS-CPT) in 143 euthymic bipolar patients and 105 controls. To estimate the influence of clinical profile in attention, patients completed a semi-structured interview.

RESULTS

Bipolar patients showed a deficit in attention during euthymic periods. This disturbance correlated with years of evolution, age of onset and age of first hospitalisation; and was not influenced by other clinical data.

CONCLUSION

Sustained attention may be considered as an endophenotype of the illness.

Avoidant personality disorder symptoms in first-degree relatives of schizophrenia patients predict performance on neurocognitive measures: the UCLA family study

Whether avoidant personality disorder symptoms are related to neurocognitive impairments that aggregate in relatives of schizophrenics is unknown. We report the relationship between avoidant personality disorder symptoms and neurocognitive performance in the first-degree relatives of probands with schizophrenia. 367 first-degree relatives of probands with schizophrenia and 245 relatives of community controls were interviewed for the presence of avoidant personality symptoms and symptoms of paranoid and schizotypal personality disorders and administered neurocognitive measures. Relationships between neurocognitive measures and avoidant symptoms were analyzed using linear mixed models. Avoidant dimensional scores predicted performance on the span of apprehension (SPAN), 3-7 Continuous Performance Test (3-7 CPT), and Trail Making Test (TMT-B) in schizophrenia relatives. These relationships remained significant on the SPAN even after adjustment for paranoid or schizotypal dimensional scores and on the TMT-B after adjustment for paranoid dimensional scores. Moreover, in a second set of analyses comparing schizophrenia relatives to controls there were significant or trending differences in the degree of the relationship between avoidant symptoms and each of these neurocognitive measures even after adjustments for paranoid and schizotypal dimensional scores. The substantial correlation between avoidant and schizotypal symptoms suggests that these personality disorders are not independent. Avoidant and in some cases schizotypal dimensional scores are significant predictors of variability in these neurocognitive measures. In all analyses, higher levels of avoidant symptoms were associated with worse performance on the neurocognitive measures in relatives of schizophrenia probands. These results support the hypothesis that avoidant personality disorder may be a schizophrenia spectrum phenotype.

Intensive meditation training improves perceptual discrimination and sustained attention

The ability to focus one's attention underlies success in many everyday tasks, but voluntary attention cannot be sustained for extended periods of time. In the laboratory, sustained-attention failure is manifest as a decline in perceptual sensitivity with increasing time on task, known as the vigilance decrement. We investigated improvements in sustained attention with training (approximately 5 hr/day for 3 months), which consisted of meditation practice that involved sustained selective attention on a chosen stimulus (e.g., the participant's breath). Participants were randomly assigned either to receive training first (n = 30) or to serve as waiting-list controls and receive training second (n = 30). Training produced improvements in visual discrimination that were linked to increases in perceptual sensitivity and improved vigilance during sustained visual attention. Consistent with the resource model of vigilance, these results suggest that perceptual improvements can reduce the resource demand imposed by target discrimination and thus make it easier to sustain voluntary attention.

Cerebral lateralization of vigilance: a function of task difficulty

Functional near infrared spectroscopy (fNIRS) measures of cerebral oxygenation levels were collected from participants performing difficult and easy versions of a 12 min vigilance task and for controls who merely watched the displays without a work imperative. For the active participants, the fNIRS measurements in both vigilance tasks showed higher levels of cerebral activity than was present in the case of the no-work controls. In the easier task, greater activation was found in the right than in the left cerebral hemisphere, matching previous results indicating right hemisphere dominance for vigilance. However, for the more difficult task, this laterality difference was not found, instead activation was bilateral. Unilateral hemispheric activation in vigilance may be a result of employing relatively easy/simple tasks, not vigilance per se.

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

The efficiency of cognition is modulated by energetic factors like effort, fatigue or circadian variation, which affect even the most basic cognitive operations. For instance, speeded detection in simple reaction-time (SRT) tasks usually slows down over time. The literature suggests that either mindlessness due to routinization or mental fatigue due to attentional resource depletion might underlie this decrement. We tested these assumptions in three 25-min visual SRT tasks using easy-to-detect high-intensity and hard-to-detect low-intensity stimuli presented in both blocked and mixed fashion. Mindlessness theory predicts that less monotonous stimulation (i.e. the mixed presentation) would mitigate the time-related decrement for high- and low-intensity stimuli alike, whereas resource-depletion theory predicts opposite effects of mixed presentation on high- versus low-intensity stimuli. Indeed, stimulus intensity and presentation mode cross-interacted significantly, indicating that the performance decline was steeper for high-intensity stimuli but less steep for low-intensity stimuli during mixed compared to blocked presentation, respectively. These results strongly suggest that the time-related efficiency decrement during prolonged SRT performance is related to accumulating mental fatigue. A conjecture is put forward that explains both resource depletion and mindlessness from the perspective of self-regulation. Our study underscores the need to incorporate energetic factors into models of cognition to facilitate their translation into real-world applications.

Cognitive impairments, emotion, stress, and language in schizophrenia

Language symptoms in schizophrenia are exacerbated by arousal of negative affect; the extent of this effect varies widely among patients. The present study assessed predictors of affective speech reactivity. Based on earlier research, it was expected that speech reactivity would be predicted by a combination of neurocognitive and emotional variables. We assessed patients (n=50) for baseline depression; neurocognitive functioning in the domains of sustained attention, immediate auditory memory, organizational sequencing, and conceptual sequencing ability; and clarity of speech communication in both stress and non-stress conditions. Twenty-three subject-nominated "significant others" (SOs) also participated in the study, and were assessed for levels of expressed emotion (EE) as an index of relationship stressors. Patients, in turn, rated the subjective stressfulness of being in the presence of their SOs, from which the propensity to perceive interpersonal experiences as stressful was calculated by regressing out EE ratings. As predicted, baseline depression and sensitivity to interpersonal stressors were related to affective reactivity of speech, with stress sensitivity mediating the relationship between depression and speech reactivity. Contrary to expectations, baseline neurocognitive functioning was not related to speech reactivity. These findings are discussed in terms of their implications for understanding both schizophrenic language disturbance and stress vulnerability.

Interactions between endogenous and exogenous attention during vigilance

The ability to remain vigilant over long periods of time is critical for many everyday tasks, but controlled studies of visual sustained attention show that performance declines over time when observers are required to respond to rare stimulus events (targets) occurring in a sequence of standard stimulus events (nontargets). When target discrimination is perceptually difficult, this vigilance decrement manifests as a decline in perceptual sensitivity. We examined whether sudden-onset stimuli could act as exogenous attentional cues to improve sensitivity during a traditional sustained attention task. Sudden-onset cues presented immediately before each stimulus attenuated the sensitivity decrement, but only when stimulus timing (the interstimulus interval [ISI]) was constant. When stimulus timing was variable, exogenous cues increased overall sensitivity but did not prevent performance decline. Finally, independent of the effects of sudden onsets, a constant ISI improved vigilance performance. Our results demonstrate that exogenous attention enhances perceptual sensitivity during vigilance performance, but that this effect is dependent on observers' being able to predict the timing of stimulus events. Such a result indicates a strong interaction between endogenous and exogenous attention during vigilance. We relate our findings to a resource model of vigilance, as well as to theories of endogenous and exogenous attention over short time periods.

Impulsive responding and the sustained attention to response task

Two studies investigated whether the sustained attention to response task (SART) is a better measure of impulsive responding than of sustained attention. Participants performed target detection tasks with global-local letter stimuli using one of two response formats: standard, responding to targets; and SART, withholding to targets. In the first experiment, performance in the SART changed rapidly over time, whereas performance in the standard format was stable over time. In the second experiment, performance in the SART was susceptible to global-local condensation tasks, a result previously found with highly impulsive individuals. Overall the results indicate that the SART is sensitive to impulsive responding.

Vigilance requires hard mental work and is stressful

OBJECTIVE

We describe major discoveries and developments in vigilance research.

BACKGROUND

Vigilance tasks have typically been viewed as undemanding assignments requiring little mental effort. The vigilance decrement function has also been considered to result from a decline in arousal brought about by understimulation.

METHODS

Recent research in vigilance is reviewed in four areas: studies of task type, perceived mental workload during vigilance, neural measures of resource demand in vigilance, and studies of task-induced stress.

RESULTS

Experiments comparing successive and simultaneous vigilance tasks support an attentional resource theory of vigilance. Subjective reports also show that the workload of vigilance is high and sensitive to factors that increase processing demands. Neuroimaging studies using transcranial Doppler sonography provide strong, independent evidence for resource changes linked to performance decrement in vigilance tasks. Finally, physiological and subjective reports confirm that vigilance tasks reduce task engagement and increase distress and that these changes rise with increased task difficulty.

CONCLUSIONS

Converging evidence using behavioral, neural, and subjective measures shows that vigilance requires hard mental work and is stressful.

APPLICATION

This research applies to most human-machine systems that require human monitoring, particularly those involving automated subsystems.

'Noisy patients'--can signal detection theory help?

Signal detection theory tests an observer's ability to discriminate between signal and noise. Deciding whether or not a patient's symptoms warrant further investigation or treatment is an example of this task in the clinical setting. Noise can exist within the observer--for example, in the brain of a tired or inexperienced doctor--or can arise from an external source such as the patient. Patients can produce external noise by giving numerous unrelated presenting complaints, providing overly detailed accounts of their symptoms, or simply talking too quickly. The more noise that is present, the harder the signal (such as a new disease or a notable change in an old condition) is to detect. Patients in the neurology clinic seem to be 'noisier' than average, perhaps owing to the long duration of their condition in many cases and the relatively high proportion of patients with medically unexplained symptoms. The ability to interpret such 'noisy' histories often underpins the neurological diagnosis. This Review aims to promote the relevance of signal detection theory to the overworked neurologist on the ward or in the clinic and explores strategies to reduce the noise generated both within the brain of the doctor and by patients.

Neuropsychological deficits in individuals with an at risk mental state for psychosis - working memory as a potential trait marker

OBJECTIVE

To investigate the neuropsychological profile of individuals with an at risk mental state for psychosis (ARMS, N=60) compared to healthy controls (HC, N=51) and to identify those cognitive domains which discriminate best between groups.

METHOD

Study subjects and controls were compared using a neuropsychological test battery covering the domains of intelligence (LPS3, MWT-A), executive functions (ToH, WCST, TAP - Go/NoGo), working memory (Tests for Attentional Performance (TAP) - Working Memory), and attention (CPT-OX). A multivariate analysis of variance (MANOVA) comparing ARMS subjects with HC was conducted. A stepwise logit regression procedure was performed in order to determine the subset of measures which best distinguish ARMS subjects from HC.

RESULTS

ARMS subjects revealed deficiencies in intelligence, executive functions, working memory and attention. Verbal intelligence, executive functions, and, in particular, working memory discriminated best between the groups.

CONCLUSION

Individuals with an at risk mental state for psychosis already show impairment of neuropsychological functions prior to the onset of the first psychotic episode and can best be distinguished from healthy controls on the basis of working memory.

The abbreviated vigilance task and cerebral hemodynamics

Transcranial Doppler sonography (TCD) and transcranial cerebral oximetry (TCCO) measures of cerebral blood flow velocity and oxygenation levels were collected during an abbreviated 12-min vigilance task. Both the TCD and TCCO measures showed higher levels of cerebral vascular activity in the right than in the left cerebral hemisphere; the cerebral laterality of vigilance occurs in an abbreviated task. Although there was a significant decline in performance over time, there was no significant change in the physiological measures over time during the abbreviated vigil. This latter finding does not match the physiological changes detected in long-duration vigils.

Effects of cigarette smoking on prepulse inhibition, its attentional modulation, and vigilance performance

Startle eyeblink modification was measured during a degraded stimulus continuous performance test following both smoking and overnight abstinence among student smokers to measure the effects of smoking on both early and late attentional processes. A group of nonsmokers was tested twice without nicotine manipulation. A startling noise was presented either 240 or 1200 ms following target and nontarget stimuli presented during the task. Startle inhibition at 240 ms was greater following targets than nontargets following smoking and during both nonsmoker tests, but this attentional modulation was absent following abstinence. At the 1200-ms probe position, target and nontarget stimuli produced nondifferential inhibition during both tests for both groups. Abstinence among smokers produced reliably lower vigilance performance compared to ad lib smoking. The results indicate that smoking abstinence affects the early stages of stimulus processing.

Intraindividual Variability in Vigilance Performance: Does Degrading Visual Stimuli Mimic Age-Related “Neural Noise”?

Intraindividual performance variability, or inconsistency, has been shown to predict neurological status, physiological functioning, and age differences and declines in cognition. However, potential moderating factors of inconsistency are not well understood. The present investigation examined whether inconsistency in vigilance response latencies varied as a function of time-on-task and task demands by degrading visual stimuli in three separate conditions (10%, 20%, and 30%). Participants were 24 younger women aged 21 to 30 years (M = 24.04, SD = 2.51) and 23 older women aged 61 to 83 years (M = 68.70, SD = 6.38). A measure of within-person inconsistency, the intraindividual standard deviation (ISD), was computed for each individual across reaction time (RT) trials (3 blocks of 45 event trials) for each condition of the vigilance task. Greater inconsistency was observed with increasing stimulus degradation and age, even after controlling for group differences in mean RTs and physical condition. Further, older adults were more inconsistent than younger adults for similar degradation conditions, with ISD scores for younger adults in the 30% condition approximating estimates observed for older adults in the 10% condition. Finally, a measure of perceptual sensitivity shared increasing negative associations with ISDs, with this association further modulated as a function of age but to a lesser degree by degradation condition. Results support current hypotheses suggesting that inconsistency serves as a marker of neurological integrity and are discussed in terms of potential underlying mechanisms.

Sustained and Transient Attention in the Continuous Performance Task

One of the most frequently applied methods to study abnormal cognition is the Continuous Performance Task (CPT). It is unclear, however, which cognitive functions are engaged in normal CPT performance. The aims of the present study were to identify the neurocognitive functions engaged in the main variants of the CPT and to determine to what extent these variants differentially engage these functions. We hypothesized that the main CPT versions (CPT-X, CPT-AX, CPT-Identical Pairs) can be distinguished by whether they demand sustained or transient attention and sustained or transient response preparation. Transient attention to objects like letters or digits, that is, the need to switch attention to different objects from trial to trial, impairs target detection accuracy relative to sustained attention to a single object. Transient response preparation, that is, the possibility to switch response preparation on and off from trial to trial, improves response speed relative to having to sustain response preparation across all trials. Comparison of task performance and Event-Related brain Potentials (ERPs) of healthy participants obtained in the main CPT variants confirmed these hypotheses. Behavioral and ERP measures indicated worse target detection in the CPT-AX than in the CPT-X, consistent with a higher demand on transient attention in that task. In contrast, behavioral and ERP measures indicated higher response speed in the CPT-AX than in the CPT-X, associated with more response preparation in advance of the targets. This supports the idea of increased transient response preparation in the CPT-AX. We conclude that CPTs differ along at least two task variables that each influences a different cognitive function.

The Consortium on the Genetics of Endophenotypes in Schizophrenia: model recruitment, assessment, and endophenotyping methods for a multisite collaboration

BACKGROUND

The Consortium on the Genetics of Schizophrenia (COGS) is an ongoing, National Institute of Mental Health-funded, 7-site collaboration investigating the occurrence and genetic architecture of quantitative endophenotypes related to schizophrenia. The purpose of this article is to provide a description of the COGS structure and methods, including participant recruitment and assessment.

METHODS

The hypothesis-driven recruitment strategy ascertains families that include a proband with a Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition diagnosis of schizophrenia, and at least one unaffected full sibling available for genotyping and endophenotyping, along with parents available for genotyping and (optional depending on age) endophenotyping. The family structure is selected to provide contrast in quantitative endophenotypic traits and thus to maximize the power of the planned genetic analyses. Probands are recruited from many sources including clinician referrals, local National Alliance for the Mentally Ill chapters, and advertising via the media. All participants undergo a standardized protocol that includes clinical characterization, a blood draw for genotyping, and endophenotype assessments (P50 suppression, prepulse inhibition, antisaccade performance, continuous performance tasks, letter-number span, verbal memory, and a computerized neurocognitive battery). Investigators participate in weekly teleconferences to coordinate and evaluate recruitment, clinical assessment, endophenotyping, and continuous quality control of data gathering and analyses. Data integrity is maintained through use of a highly quality-assured, centralized web-based database.

RESULTS

As of February 2006, 355 families have been enrolled and 688 participants have been endophenotyped, including schizophrenia probands (n = 154, M:F = 110:44), first-degree biological relatives (n = 343, M:F = 151:192), and community comparison subjects (n = 191, M:F = 81:110).

DISCUSSION

Successful multisite genetics collaborations must institute standardized methodological criteria for assessment and recruitment that are clearly defined, well communicated, and uniformly applied. In parallel, studies utilizing endophenotypes require strict adherence to criteria for cross-site data acquisition, equipment calibration and testing and software equivalence, and continuous quality assurance for many measures obtained across sites. This report describes methods and presents the structure of the COGS as a model of multisite endophenotype genetic studies. It also provides demographic information after the first 2 years of data collection on a sample for whom the behavioral data and genetics of endophenotype performance will be fully characterized in future articles. Some issues discussed in the reviews that follow reflect the challenges of evaluating endophenotypes in studies of the genetic architecture of endophenotypes in schizophrenia.

The Consortium on the Genetics of Schizophrenia: neurocognitive endophenotypes

The Consortium on the Genetics of Schizophrenia (COGS) is a 7-site collaboration that examines the genetic architecture of quantitative endophenotypes in families with schizophrenia. Here we review the background and rationale for selecting neurocognitive tasks as endophenotypic measures in genetic studies. Criteria are outlined for the potential of measures as endophenotypic vulnerability markers. These include association with illness, state independence (ie, adequate test-retest stability, adequate between-site reliability, impairments in patients not due to medications, impairments observed regardless of illness state), heritability, findings of higher rates in relatives of probands than in the general population, and cosegregation within families. The COGS required that, in addition, the measures be "neurocognitive" and thus linked to neurobiology and that they be feasible in multisite studies. The COGS neurocognitive assessment includes measures of attention, verbal memory, working memory, and a computerized neurocognitive battery that also includes facial processing tasks. Here we describe data demonstrating that these neurobehavioral measures meet criteria for endophenotypic candidacy. We conclude that quantitative neurocognitive endophenotypes need further evidence for efficacy in identifying genetic effects but have the potential of providing unprecedented insight into gene-environment interaction related to dimensions of brain and behavior in health and disease.

Neural anomalies during sustained attention in first-degree biological relatives of schizophrenia patients

BACKGROUND

A deficit in sustained attention might serve as an endophenotype for schizophrenia and therefore be a useful tool in understanding the genetic underpinnings of the disorder. We sought to detail functional brain abnormalities associated with sustained attention (i.e., vigilance) in individuals with genetic liability for schizophrenia.

METHODS

We gathered electrophysiological data from 23 schizophrenia patients, 28 first-degree biological relatives of schizophrenia patients, and 23 nonpsychiatric control subjects while they performed a degraded-stimulus continuous performance task. Inclusion of sensory control trials allowed separation of target detection and vigilance effects on brain potentials.

RESULTS

Schizophrenia patients, but not relatives, showed a behavioral deficit in sustained attention. During target detection, relatives exhibited diminished late positive amplitudes (P3b, i.e., P300) over parietal brain regions and augmented early posterior (P1) and right frontal (anterior N1) potentials. Electrophysiological anomalies were still evident after the exclusion of three relatives with histories of psychosis.

CONCLUSIONS

Genetic liability for schizophrenia is associated with augmented early and diminished late brain potentials during sustained attention. Electrophysiological anomalies suggestive of right frontal-posterior parietal dysfunction might represent neural expression of genetic liability for schizophrenia. Electrophysiological indices also seem to be more sensitive than behavioral measures in assessing genetic liability for schizophrenia.

The role of stimulus salience in CPT-AX performance of schizophrenia patients

CPT-AX performance deficit in schizophrenia is well documented but it is unclear what causes this impairment. Past studies have focused on the roles of sustained attention and context processing in CPT-AX but the role of working memory (WM) has not been fully examined even though encoding and maintenance of the cue in WM may be critical to CPT-AX. The major goal of this study was to investigate the effects of stimulus encoding in WM on CPT-AX. Encoding was manipulated by presenting different colored (i.e., salient) cue stimuli on 20% of the trials. WM maintenance was manipulated by varying the cue-target interstimulus interval (ISI). A control task (CPT-Single) that does not require WM but assesses sustained attention was also administered. Schizophrenia patients (SZ) were impaired compared with normal controls (CO) on the CPT-AX overall but not in CPT-Single. For both groups, CPT-AX accuracy improved on salient cue trials in the long ISI condition. In the short ISI condition, where accuracy was already high, the cue saliency effect was observed in the faster RT and SZ benefited significantly more than CO. The effect of target salience was not observed in the CPT-Single, which assesses sustained attention. These results suggest that the facilitation of WM encoding by enhancing cue salience may be a key to improving CPT-AX performance.

Functional dysconnectivity in schizophrenia associated with attentional modulation of motor function

It is not known whether there is a core abnormality that occurs in all cases of schizophrenia. The cognitive dysmetria hypothesis proposes that there is such an abnormality which is characterized cognitively by a disruption in control and coordination processes, and functionally by abnormal inter-regional connectivity within the cortico-cerebellar-thalamo-cortical circuit (CCTCC). In the current study, we used functional MRI (fMRI) to investigate these two key aspects of the hypothesis. Since patients with schizophrenia show deficits in attention which have been characterized extensively using the continuous performance task (CPT) and since functional imaging studies have also demonstrated that this task engages the CCTCC, we used this task to investigate whether two patient groups with distinct symptom profiles would show functional dysconnectivity within this network. Three groups of subjects participated in the study: healthy volunteers (n = 12), schizophrenia patients with both negative and positive symptoms (n = 11) and schizophrenia patients with primarily positive symptoms (n = 11). Patient groups were matched for age of illness onset and medication, and to the control group for age, gender and handedness. Subjects were scanned using fMRI whilst they performed a modified version of the CPT, involving both degraded and non-degraded stimuli. Stimulus degradation has been shown to produce decrements in sensitivity, which is thought to reflect increased demands on the limited capacity of visual attention. Between-group comparisons revealed that patients with schizophrenia, irrespective of symptomatology, showed attenuation of the anterior cingulate and cerebellar response to stimulus degradation in comparison with control subjects. We also observed disruptions of inter-regional brain integration in schizophrenia. A task-specific relationship between the medial superior frontal gyrus and both anterior cingulate and the cerebellum was disrupted in both patient groups in comparison with controls. In addition, patients with negative symptoms showed impaired behavioural performance, and abnormal task-related connectivity between anterior cingulate and supplementary motor area. These findings are consistent with theoretical accounts of schizophrenia as a disorder of functional integration, and with the cognitive dysmetria hypothesis, which posits a disconnection within the CCTCC as a fundamental abnormality in schizophrenia, independent of diagnostic subtype. Furthermore, these data show evidence of additional functional deficits in patients with negative symptoms, deficits which may explain the accompanying attentional impairment.

Sustained attention in mild Alzheimer's disease

The vigilance decrement in perceptual sensitivity was examined in 10 patients with mild Alzheimer's disease (AD) and 20 age-matched controls. A visual high-event rate digit-discrimination task lasting 7.2 min. (six 1.2 min blocks) was presented at different levels of stimulus degradation. Previous studies have shown that sensitivity decrements (d') over time at high-stimulus degradation result from demands on effortful processing. For all degradation levels, the overall level of vigilance (d') was lower in AD patients than in controls. All participants showed sensitivity decrement over blocks, with greater decrement at higher degradation levels. AD patients exhibited greater sensitivity decrement over time at the highest degradation level they all could perform relative to control participants. There were no concomitant changes in either response bias (C) or response times. The results indicate that mild AD patients have overall lower levels of vigilance under conditions that require both automatic and effortful processing. Mild AD patients also exhibit a deficit in the maintenance of vigilance over time under effortful processing conditions. Although the sample of AD patients was small, results further suggest that both possible and probable AD patients had greater sensitivity decrement over time at the highest degradation level than did control participants, but only probable AD patients had lower overall levels of vigilance. In the possible AD patients as a group, the decrement in vigilance occurred in the absence of concurrent deficits on standard attentional tasks, such as the Stroop and Trail Making tests, suggesting that deficits in vigilance over time may appear earlier than deficits in selective attention.

Beyond hypofrontality: a quantitative meta-analysis of functional neuroimaging studies of working memory in schizophrenia

Although there is considerable evidence that patients with schizophrenia fail to activate the dorsolateral prefrontal cortex (DLPFC) to the degree seen in normal comparison subjects when performing working memory or executive tasks, hypofrontality may be coupled with relatively increased activity in other brain regions. However, most imaging studies of working memory in schizophrenia have focused on DLPFC activity. The goal of this work is to review functional neuroimaging studies that contrasted patients with schizophrenia and healthy comparison subjects during a prototypical working memory task, the n-back paradigm, to highlight areas of hyper- and hypoactivation in schizophrenia. We utilize a quantitative meta-analysis method to review 12 imaging studies where patients with schizophrenia were contrasted with healthy comparison subjects while performing the n-back paradigm. Although we find clear support for hypofrontality, we also document consistently increased activation in anterior cingulate and left frontal pole regions in patients with schizophrenia compared to that in controls. These data suggest that whereas reduced DLPFC activation is reported consistently in patients with schizophrenia relative to healthy subjects, abnormal activation patterns are not restricted to this region, raising questions as to whether the pathophysiological dysfunction in schizophrenia is specific to the DLPFC and about the relationship between impaired performance and aberrant activation patterns. The complex pattern of hyper- and hypoactivation consistently found across studies implies that rather than focusing on DLPFC dysregulation, researchers should consider the entire network of regions involved in a given task when making inferences about the biological mechanisms of schizophrenia.

Effects of perceptual processing demands on startle eyeblink modification

Startle eyeblink modification was measured during a continuous performance test (CPT) with either clearly focused stimuli or visually degraded stimuli to measure the effects of early perceptual processing demands on startle modification. A startling noise was presented either 120, 240, or 1200 ms following target and nontarget CPT stimuli. In the degraded stimulus CPT, startle inhibition at 240 ms was greater following targets than nontargets and was as great during targets at 240 ms as at 120 ms, whereas in the clearly focused CPT, inhibition declined significantly from 120 to 240 ms. The results indicate that maximum prepulse inhibition is extended in time when the task involves discrimination of degraded visual stimuli and when early perceptual processing demands are high. At 1200 ms, targets and nontargets produced nondifferential inhibition during both CPTs, suggesting that modality-specific attention occurred equally for the two tasks.

Cognitive impairments and disordered speech in schizophrenia: thought disorder, disorganization, and communication failure perspectives

This article posits that basic cognitive impairments in schizophrenia are more highly related to speech disorder measured as communication failures than speech disorder measured as thought disorder or disorganization. The author tested 47 schizophrenia patients and 36 control participants for sustained attention, sequencing, and conceptual sequencing ability. Their speech was also rated for communication failures, thought disorder, and conceptual disorganization. Attention and sequencing impairments, examined hierarchically, explained a substantial 38% of the variance in the communication measure of speech disorder but little of the variance in formal thought disorder or conceptual disorganization. The author concludes that (a) impairments in attention and sequencing abilities contribute substantially to schizophrenic communication failures, and (b) it is important to consider lower level cognitive "3rd variables" when examining higher level cognitive associates of speech disorder.

The role of memory representation in the vigilance decrement

Working memory load is critically important for the overall level of performance on vigilance tasks. However, its role in a key aspect of vigilance-sensitivity decrement over time-is unclear. We used a dual-task procedure in which either a spatial or a nonspatial working memory task was performed simultaneously with a spatial vigilance task for 20 min. Sensitivity in the vigilance task declined over time when the concurrent task involved spatial working memory. In contrast, there was no sensitivity decrement with a nonspatial working memory task. The results provide the first evidence of a specific role for working memory representation in vigilance decrement. The findings are also consistent with a multiple resource theory in which separate resources for memory representation and cognitive control operations are differentially susceptible to depletion over time, depending on the demands of the task at hand.

Neurocognitive impairments in boys on the life-course persistent antisocial path

This study addresses 5 unresolved issues in the neuropsychology of antisocial behavior using a community sample of 325 school boys in whom neurocognitive measures were assessed at age 16-17 years. Antisocial behavior measures collected from age 7-17 years were cluster analyzed and produced 4 groups: control, childhood-limited, adolescent-limited, and life-course persistent. Those on the lifecourse persistent path and also on the childhood-limited path were particularly impaired on spatial and memory functions. Impairments were independent of abuse, psychosocial adversity, head injury, and hyperactivity. Findings provide some support for the life-course persistent versus adolescent-limited theory of antisocial behavior and suggest that (a) neurocognitive impairments are profound and not artifactual and (b) childhood-limited antisocials may not be free of long-lasting functional impairment.

Equating tasks and sustaining attention in children and adults: The methodological and theoretical utility ofd’ matching

The present study develops a method to create task equivalency for children and adults in vigilance research. Experiment 1 employed the signal detection index of perceptual sensitivity (d') to calibrate vigilance tasks for 32 children (ages 7-8) and 32 adults. The results of Experiment 1 suggest that task equivalency across groups can be attained, and a vigilance decrement was observed for children. In Experiment 2, the task parameter of event rate was manipulated across two vigils. Again, 32 children (ages 7-8) and 32 adults participated. The results suggest that a reverse event rate effect emerged for both children and adults. In addition, developmental differences in response to the event rate manipulation and with respect to the vigilance decrement emerged: Children benefited less from the manipulation and were more likely to demonstrate a vigilance decrement than were adults. No developmental differences emerged for the sensitivity decrement. The results are explained with reference to how task demands interact with participant arousal, and implications for development and for future research are discussed.

Processing efficiency and sustained attention in bipolar disorder

We hypothesized that patterns of sustained attention performance in bipolar disorder were consistent with processing efficiency theory--a theory of the relationship between central processing capacity and performance. We predicted (1) sustained attention deficits during mania because symptoms interfere with limited-capacity executive control processes resulting in decreased performance effectiveness; and (2) decreased processing efficiency during euthymia, as indicated by speed/accuracy tradeoffs, consistent with a stable phenotypic abnormality. Twenty-five manic bipolar, 23 euthymic bipolar, and 28 healthy comparison participants were compared on a continuous performance task and administered symptom-rating scales. The manic group was significantly impaired on overall perceptual sensitivity and demonstrated a significant linear decrease in performance over time, consistent with impaired sustained attention. The euthymic group evidenced significantly slower overall hit reaction time (RT), but when RT was controlled they performed similarly to the healthy group over time. Two discriminant functions combined to separate the groups on manic symptom severity and on-task effort/strategy use. These findings are consistent with processing efficiency theory. They suggest that euthymic patients sustain attention through effortful control at the expense of processing efficiency, while acute mania reduces the capacity for control and impairs sustained attention. Problems with processing efficiency are viewed as trait characteristics of bipolar disorder that may be overlooked by traditional error-based assessments.