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

Self-efficacy and neurocognition may be related to coping responses in recent-onset schizophrenia

Although stressful life events can trigger psychotic and depressive symptom exacerbation in schizophrenia, many patients who experience stressful events do not subsequently relapse. Models of vulnerability, stress, and protective factors in schizophrenia suggest that effective coping responses may serve as protective factors. Coping behavior, in turn, may be influenced by a schizophrenia patient's level of self-efficacy and neurocognitive functioning. Using the Coping Responses Inventory, we examined how 29 recent-onset schizophrenia outpatients and 24 demographically matched normal comparison subjects responded to a negative interpersonal life event. Approach oriented coping responses, such as "Think of different ways to deal with the problem" and "Make a plan of action and follow it," were used significantly more often by normal subjects (M=2.27) than by schizophrenia patients (M=1.89; p < 0.02). Among schizophrenia patients, greater use of approach, problem-focused coping strategies was associated with high self-efficacy (r=0.55, p < 0.01) and better performance on a measure of sustained attention emphasizing perceptual processing (r=0.42, p < 0.05). Multiple regression indicated that self-efficacy and sustained attention accounted for 56% of the variance in the use of problem-focused coping, strategies by schizophrenia patients.

Psychopharmacological approaches to modulating attention in the five-choice serial reaction time task: implications for schizophrenia

RATIONALE

In schizophrenia, attentional disturbance is a core feature which may not only accompany the disorder, but may precede the onset of psychiatric symptoms.

OBJECTIVES

The five-choice serial reaction time task (5CSRTT) is a test of visuo-spatial attention that has been used extensively in rats for measuring the effects of systemic and central neurochemical manipulations on various aspects of attentional performance, including selective attention, vigilance and executive control. These findings are relevant to our understanding of the neural systems that may be compromised in patients with schizophrenia.

METHODS

The 5CSRTT is conducted in an operant chamber that has multiple response locations, in which brief visual stimuli can be presented randomly. Performance is maintained using food reinforcers to criterion levels of accuracy. Various aspects of performance are measured, including attentional accuracy and premature responding, especially under different attentional challenges.

RESULTS

The effects of systemic and intra-cerebral infusions of selective dopamine, serotonin and cholinergic receptor agents on the 5CSRTT are reviewed with a view to identifying attention-enhancing effects that may be relevant to the treatment of cognitive deficits in schizophrenia. In addition, some novel agents such as modafinil and histamine receptor agents are also considered. Examining the effects of selective neurochemical lesions helped define the neural locus of attentional effects. Similarly, findings from microdialysis studies helped identify the extracellular changes in neurotransmitters and their metabolites in freely moving rats during performance of the 5CSRTT.

CONCLUSIONS

The monoaminergic and cholinergic systems have independent but complementary roles in attentional function, as measured by the 5CSRTT. These functions are predominantly under the control of the prefrontal cortex and striatum. These conclusions are considered in the context of their application towards therapeutic approaches for attentional disturbances that are typically observed in schizophrenic patients.

Preattentional and attentional cognitive deficits as targets for treating schizophrenia

BACKGROUND AND RATIONALE

Pharmacotherapy of schizophrenia has traditionally targeted positive psychotic symptoms. An emerging view is that developing medications that improve cognition in schizophrenia patients is a major step forward in achieving better functional outcome. The cognitive deficits that are often observed in schizophrenia can be assessed using (1) neuropsychological tests; and (2) neurophysiological tests, the topic of this article. These neurophysiological measures cover a spectrum from automatic preattentional to attention-dependent processes.

OBJECTIVES

This article focuses on cognitive deficits that appear to be promising targets for a new "third generation" of medications that may be used to treat schizophrenia and other patients with specific deficits in cognition and functioning. We discuss the possible use of the following six measures of preattentional and attention-dependent cognitive deficits: mismatch negativity, P50 event-related potential suppression, prepulse inhibition of the startle response, P300 event-related potential, continuous performance task performance, and oculomotor antisaccade performance.

CONCLUSIONS

The use of preattentional and attention-dependent measures offer unique opportunities to improve our armamentarium of pharmacologic strategies for the treatment of cognitive deficits in schizophrenia patients. This review illustrates the usefulness of these measures as targets for existing and new antipsychotic medications that will potentially (1) characterize the cognitive deficits that occur in schizophrenia patients and (2) assess medication-related improvement on these measures and the potential associated improvement in functional outcome.

Abnormal brain response of chronic schizophrenia patients despite normal performance during a visual vigilance task

Deficits of attention are common among individuals with schizophrenia (SZ) and are related both to genetic liability to the disorder and to functional outcome among patients. To explore the brain systems underlying these attentional abnormalities, we compared the response of nine patients with chronic SZ or schizoaffective disorder to that of 10 matched healthy individuals performing a simple visual vigilance task during functional magnetic resonance imaging. The two groups performed equivalently on the task. When the blood oxygen level dependent (BOLD) signal during identification of a target letter among similar-looking letters was compared to the response during fixation trials, both groups showed multiple clusters of significant brain response in widespread cortical regions. Compared with healthy participants, SZ patients showed a diminished response in the inferior frontal cortex and an abnormally enhanced response in right postcentral gyrus, right medial temporal lobe and left cerebellum. The results suggest that abnormalities of functional brain response to attentional tasks can be observed among patients with SZ even when behavioral performance is unimpaired, and provide further evidence that brain systems related to attention are likely to be involved in the pathophysiology of the disorder.

Age differences in perceived workload across a short vigil

The main objective of this research was to investigate age differences in the perceived workload associated with the performance of a demanding, high event rate, vigilance task. Younger participants (n=26) aged 16 to 35 years (M=27.8) and older participants (n=24) aged 45 to 65 years (M=52.2) completed perceived workload scales (NASA-TLX) following a brief practice session (pretest) on the vigilance task, and then again following a test session (posttest) lasting nine minutes. In relation to the vigilance task, a statistically significant performance decrement was identified, but there was no evidence that performance differed according to age in respect to that decrement. However, a dissociation was found in relation to the perceived workload ratings: while no age differences were found in vigilance performance, the workload ratings revealed older participants to perceive a significantly greater increase in workload from pretest to posttest. These findings are considered theoretically in relation to the demands placed upon attentional resources, and their implications for both laboratory-based vigilance research, and workplace systems monitoring situations, are discussed.

Covert auditory attention generates activation in the rostral/dorsal anterior cingulate cortex

The anterior cingulate cortex (ACC) is believed to mediate conscious information processing or high-capacity attention. However, previous functional imaging studies have largely relied on tasks that involve motor function as well as attention. The work from our group utilizing an auditory continuous performance task demonstrated increased activity in a caudal division of the ACC that borders the supplementary motor area (SMA). Activity in this region was attributed to motor responding as well as attention. In the present study, we used (15)O H(2)O positron emission tomography (PET) to map brain activation during nonmotor, covert auditory attention. Our hypothesis was that a different region within the ACC, anterior to the SMA, would be active during covert attention (CA). Six men and six women were asked to monitor aurally presented syllables presented at a 1-sec interstimulus interval. During the CA condition, subjects were asked to continuously discriminate target (.19 probability) from nontarget stimuli. Simultaneous recording of event-related potentials (ERPs) confirmed the discrimination of target and nontarget stimuli and the allocation of attention capacity. Comparison of the monitored versus nonmonitored presentation of stimuli demonstrated significant activity in a rostral/dorsal division of the right ACC, anterior to SMA. Other regions of activation included the lateral prefrontal cortex and posterior superior temporal gyrus in the left hemisphere, consistent with neurocognitive models of language and vigilance. We conclude that a rostral/dorsal subdivision of the right ACC is specific for conscious attention during auditory processing, in contrast to premotor response formation.

The structure of schizotypy: relationships between neurocognitive and personality disorder features in relatives of schizophrenic patients in the UCLA Family Study

Schizotypal personality features and certain neurocognitive deficits have been shown to aggregate in the relatives of schizophrenic patients, supporting the view that both are likely to reflect genetic contributions to liability to schizophrenia. Within the relatives of schizophrenic patients, however, the interrelationships between these potential indicators of liability to schizophrenia are not well known. Using data from the UCLA Family Study, we examine the interrelationships between personality disorder symptoms and neurocognitive functioning in nonpsychotic first-degree relatives of schizophrenic patients. Factor analyses indicate that several dimensions of schizotypy can be identified. A neurocognitive dysfunction dimension includes loadings from measures of sequential visual conceptual tracking, rapid perceptual encoding and search, and focused, sustained attention as well as the rating of odd and eccentric behavior from schizotypal personality disorder. Other aspects of schizotypal personality disorder form separate positive schizotypy and negative schizotypy dimensions. These analyses support the view that schizotypy is multidimensional in relatives of schizophrenic patients and indicate that neurocognitive deficits in perception and attention are associated with particular schizotypal personality features.

Reaction time measures of sustained attention differentiate bipolar disorder from schizophrenia

Although continuous performance tasks (CPTs) are becoming more common in psychiatric research, it remains unclear which performance measures best differentiate psychiatric patient groups and along which psychological dimensions. To address this the authors examined sustained attention decrements in patients with bipolar disorder and schizophrenia using CPT measures of perceptual sensitivity, response bias, and psychomotor processing speed. Patients with bipolar disorder with psychotic features (N=20), schizophrenia (N=20), and healthy controls (N=20) were evaluated using structured clinical interviews. These patients were rated with the Scale for the Assessment of Positive Symptoms and the Young Mania Rating Scale before completing a degraded-stimulus version of the CPT. Psychomotor processing speed was the only measure that reliably differentiated the groups across the entire vigilance period and was the strongest predictor of group membership. These findings suggest that reaction time measures may be sensitive to differences in the sustained attention abilities of patients with bipolar disorder and schizophrenia. By incorporating reaction time measures into CPT assessments, discriminant ability may be enhanced.

Time-related changes in task performance after lesions restricted to the frontal cortex

Behavioural studies in patients and functional neuroimaging studies in normal subjects suggest that the right frontal cortex plays an important role in sustaining attention to a task. However, the contribution of different regions of the frontal lobe to performance changes has not been clearly established. First, the assessment of sustained attention has not been carried out in patients with lesions that are restricted to cortical regions of the frontal lobe. Second, although sustained attention is often measured by performance on a task requiring effortful attention, it may be more meaningful to measure changes in performance as a function of time-on-task. Two studies were carried out in five groups of subjects: patients with left or right frontal cortical resections, patients with left or right anterior temporal lobe resections, and normal controls. In the first experiment, a brief (4-min) selective attention task was performed. The right frontal group, unlike the other groups, did not show improved reaction times after the first minute on the task. The second experiment involved a long (30-min) shifting attention task. Both the left and right frontal groups were slower than control groups; however, reaction times in the right frontal group increased with time spent on the task. We conclude that the right frontal cortex plays an essential role in modulating arousal during performance of a task and may also underlie aspects of learning during the early stages of task performance.

Comparison of the continuous performance test with and without working memory demands in healthy controls and patients with schizophrenia

The Penn Continuous Performance Test (PCPT), a measure of sustained visual attention developed for use in functional neuroimaging studies, was compared with a standard CPT developed by Gordon Diagnostic Systems (GDS; Vigilance subtest). The PCPT and the GDS CPT were administered with a standard neuropsychological battery to 68 healthy adults to assess reliability and construct validity. The test had adequate internal consistency, and convergent validity was established through significant correlations between measures of efficiency on the PCPT and the GDS CPT. With the exception of a significant correlation between efficiency measures on the GDS CPT and a measure of auditory sustained attention, neither version of the CPT correlated significantly with other measures in the battery. Factor analysis showed that the PCPT loaded with the GDS CPT. In 39 patients with schizophrenia and 39 matched, healthy controls, equivalent impairment was evident on the two CPT tasks. Neither version correlated significantly with symptom measurements. These results support previous conclusions that sustained visual attention in schizophrenia is a core information processing deficit, not directly related to symptomatology.

Sustained and selective attention as measures of genetic liability to schizophrenia

We tested for a relationship between attention and genetic liability to schizophrenia. Samples of probands with DSM-IV schizophrenia (n=20), their well first-degree relatives (n=40) and healthy controls (n=82) were tested using measures of sustained attention (degraded-stimulus continuous performance test: DS-CPT) and selective attention (spatial negative priming task). Assuming a liability-threshold model, we predicted that probands would display greater attentional decrements than controls and that the relatives would show intermediate levels of decrement. We did not observe the predicted pattern of effect using either measure, although the probands showed a trend towards less negative priming. However, our results may have been affected by self-selection bias in probands and relatives and clinical heterogeneity among probands, which could have reduced our power to detect effects.

Overall vigilance and sustained attention decrements in healthy aging

Age differences in sustained attention were investigated using a high-event rate digit-discrimination task at 6 levels of stimulus degradation (lasting 8.1 min each). Twenty-one young, 21 middle-aged, and 20 old healthy subjects were studied. Overall sensitivity (d') was equivalent in all groups. Although all subjects showed a sensitivity decrement over blocks, there were no age-related differences in sustained attention capacity. All subjects had larger decrements in d' over blocks at higher degradation levels. However, the performance decrement at higher degradation levels was equivalent in all groups, indicating similar decrement rates in sensitivity with increasing demands on effortful processing. These results indicate that overall levels of vigilance and the ability to sustain attention over time are equivalent in all groups under conditions requiring both automatic (low-degradation) and effortful (high-degradation) stimulus processing.

Age differences in vigilance as a function of health-related physical fitness and task demands

The influence of health-related physical fitness on age differences in vigilance as a function of the level of task complexity was examined in a group of 24 younger women aged 21-30 years (M = 24.04, S.D. = 2.51), and 23 older women aged between 61 and 83 years (M = 68.70, S.D. = 6.38). In the high event rate vigilance task, task demands were manipulated by degrading stimuli by 10, 20, and 30%. Age variation in performance was found in respect to time-on-task and level of stimulus degradation. As predicted, physical fitness moderated that age variance. It is concluded that physical fitness has greater influence on age differences in vigilance in situations placing high demands on attentional resources. The theoretical implications of the findings are discussed with emphasis upon the possible mediating role of the frontal cortex.

Sustained attention in patients with obsessive-compulsive disorder: a controlled study

Studies on attentional processes in obsessive-compulsive disorder (OCD) have been inconsistent. The present study focused on the question of sustained attention in OCD, using the 'Degraded Stimulus Continuous Performance Test' (DS-CPT) sensitivity index over time. This study included 20 OCD patients and 25 control subjects, comparable in sex, age and educational level. All subjects had a neuropsychiatric structured diagnostic interview, as well as a psychometric battery. The DS-CPT evaluated sustained attention. The sensitivity decrement during DS-CPT was significant in both controls and OCD subjects. Contrary to our expectations, OCD patients did not show a greater decrease in sensitivity over time, compared to controls: thus, OCD patients presented a no more important attention decrease than controls. Controls and OCD subjects became more conservative in their response criteria throughout the DS-CPT test. Comparing OCD with and without pharmacological treatment did not reveal any difference in CPT outcome. Moreover, we observed, in OCD, a positive significant correlation between the Y-BOCS compulsion score and the CPT sensitivity index. A significant negative correlation of the Y-BOCS compulsive score with the CPT false alarm score was also found. In conclusion, OCD patients did not present any disturbance in sustained attention during a task requiring an increased processing load.

Genetics and visual attention: selective deficits in healthy adult carriers of the epsilon 4 allele of the apolipoprotein E gene

The epsilon4 allele of the apolipoprotein E (APOE) gene is associated with altered brain physiology in healthy adults before old age, but concomitant deficits in cognition on standardized tests of cognitive function have not been consistently demonstrated. We hypothesized that sensitive and specific assessment of basic attentional functions that underlie complex cognition would reveal evidence of impairment in otherwise asymptomatic individuals. We found that as early as middle age, nondemented carriers of the varepsilon4 allele of the APOE gene showed deficits when visual attention was spatially directed by cues in tasks of visual discrimination and visual search, in comparison to those without the epsilon4 allele (epsilon2 and epsilon3 carriers). Two component attentional operations were selectively affected: (i) shifting spatial attention following invalid location cues, and (ii) adjusting the spatial scale of attention during visual search. These changes occurred only in the presence of the epsilon4 allele and without decline in other aspects of attention (vigilance), memory, or general cognition. The results show that specific components of visual attention are affected by APOE genotype and that the course of cognitive aging is subject to selective alteration by a genetic trait.

Correlation of intellectual impairment in Parkinson's disease with FDG PET scan

This study investigated the relationship between regional glucose metabolism with intellectual impairment in patients with Parkinson's disease using statistical parametric mapping. Regional cerebral glucose metabolism using [18F]deoxyglucose (FDG) PET scans were performed on 10 patients with Parkinson's disease. We used the intellectual impairment score from the UPDRS. PET scans were analyzed with SPM96. Patients showed significant positive correlations with left limbic structures such as the cingulate gyrus, parahippocampal gyrus, and medial frontal gyrus. Patients showed significant negative correlations with associative neocortical posterior structures such as bilateral parietal and occipital gyrus. There were significant relationships between regional glucose metabolism and intellectual impairment.

The effects of signal salience and caffeine on performance, workload, and stress in an abbreviated vigilance task

In 2 experiments, a 12-min computerized vigilance task was demonstrated to reproduce the vigilance decrement, high workload (NASA-TLX), and stressful character (Dundee Stress State Questionnaire) of vigilance tasks lasting 30 min or more. In Experiment 1, the abbreviated task was also shown to duplicate the signal salience effect, a major finding associated with long-duration vigilance tasks. Moreover, Experiment 2 showed that performance on the abbreviated task can be enhanced by caffeine - a drug that benefits long-duration tasks. This enhancement effect was limited to performance, however, suggesting that caffeine influences factors that control signal detection but not those that control task-induced stress. The results parallel those obtained with long-duration tasks and support a resource-depletion model of the vigilance decrement. The abbreviated task might be useful in situations in which long-duration tasks are precluded (e.g., performance assessment batteries, neuropsychological testing, and brain imaging).

Development of sustained attention assessed using the continuous performance test among children 6-15 years of age

The Continuous Performance Test (CPT) is a widely used measure of sustained attention, which may rely on the efficiency of cognitive inhibition. We examined the relationships of age and sex with CPT performance among 341 randomly selected school children 6-15 years of age. Multiple regression analyses revealed that the hit rate, false alarm rate, and sensitivity of both the undegraded and the degraded CPT were associated with age by a quadratic relationship. The age-development curves for the hit rate and sensitivity were convex, whereas that for the false alarm rate was concave. Sex was associated with the hit rate and sensitivity on the degraded CPT only. Our findings are consistent with the hypothesis that sustained attention develops during the primary school ages. The data reported are essential for identifying children with conditions associated with sustained attention deficit, such as attention-deficit hyperactivity disorder, as well as those at an increased risk for developing schizophrenia.

Vigilance in schizophrenia and its disruption by impaired pre-attentive selection: a dysintegration hypothesis

INTRODUCTION

The study determined, simultaneously, whether major deficits of schizophrenia (sustained and selective attention, slow information processing, slow motor responding) are independent or related to each other.

METHODS

An auditory vigilance task (Pigache Attention Task, PAT) required a button-press to targets during four 5-minute subtests (slow diotic, fast diotic, slow dichotic, fast dichotic, analogous to four versions of the continuous performance test). Twenty schizophrenics on the first test-occasion of a double-blind, placebo controlled, crossover study were compared to 11 healthy subjects. Also, all 28 fortnightly test occasions were analysed to quantify the schizophrenia deficits more precisely and the PAT was evaluated in a larger group of 86 healthy subjects.

RESULTS

Schizophrenics were significantly impaired on all task parameters versus healthy subjects. The patients' errors were independent and additive (grand mean components: basic task 36%, including a 9% time-on-task component; speed increment 26%; dichotic increment 38%). Errors, latencies, and psychosis severity were mutually correlated.

CONCLUSIONS

The performance of all subjects confirmed a quantitative Vigilance Decision Model. The PAT impairments in schizophrenia suggested that rival options (e.g. thoughts) redeployed or suppressed attention away from the task , indicating a dysfunction of pre-attentive selection processes. Brain mechanisms are discussed and a new dys integration hypothesis of schizophrenia is proposed.

A new visual performance test offers new variables for assessing daytime vigilance: short pauses in performance

A new visual performance test, VigiMouse, was evaluated with the aid of 6 volunteering pediatry residents. The results were compared with a visual analogue scale in differentiating four different states: mild sleep deprivation, low blood alcohol level, a combination of both, and the normal state. A normal night shift at a busy pediatric ward was chosen to represent sleep deprivation. A new set of parameters based on short pauses in performance proved to be more sensitive in detecting small changes in performance than parameters based on reaction times.

The effects of increasing resource demand on vigilance performance in adults with schizophrenia or developmental attentional/learning disorders: a preliminary study

The goal of this study was to assess whether degree of information processing load differentially affects vigilance performance in patients with schizophrenia as compared to normal controls or patients with other attentional disorders. We contrasted the performance of clinically stable outpatients with schizophrenia (n = 18), with that of normal controls (n = 17), and adults with developmental attentional/learning disorders (n = 13) on simple and demanding versions of a visual continuous performance test (CPT). Patients with schizophrenia were significantly impaired on both versions of the CPT compared to normal controls, and showed a significant decline in perceptual sensitivity and significantly more omission errors with increased processing demands. Compared to adults with developmental attentional/learning disorders, patients with schizophrenia manifested a tendency toward a decline in perceptual sensitivity. There were no significant differences between groups on a measure of response bias. The data support the hypothesis that patients with schizophrenia have insufficient information processing resources to cope with higher processing demands on effortful attention tasks. Further study comparing schizophrenic patients with patients who have other neuropsychiatric disorders, controlling for severity of illness, is required to determine the specificity of this deficit in schizophrenia.

Effects of meals on objective and subjective measures of daytime sleepiness

Effects of recent food ingestion on daytime sleepiness were assessed in 16 subjects (8 men and 8 women) who were each studied on two occasions, 28 days apart. On each occasion, subjects ate a high-fat low-carbohydrate (CHO) (fat/CHO energy ratio 54:41) meal and an isoenergetic low-fat high-CHO meal (fat/CHO energy ratio 7:88) 4 h apart in a counterbalanced order. Sleepiness was measured at 2-hr intervals by using the Multiple Sleep Latency Test and the Akerstedt electroencephalograph sleepiness test. To control for circadian factors, one group (4 men, 4 women) ate the meals 2 h later than did the other group of subjects. There were no differences in sleepiness according to the composition of the meal. Sleepiness in the Multiple Sleep Latency Test was significantly greater 1.5 h after the meals were eaten than before (F 11.37; df 1,15; P = 0.004). Sleepiness was also enhanced in the Akerstedt sleepiness test 3 h 20 min after the meals. The results suggest that the meals induced an enhancement in sleepiness that was not solely due to circadian rhythms.

Effects of a specific CCK-A antagonist, Loxiglumide, on postprandial mood and sleepiness

Previous studies have demonstrated that feelings of sleepiness increase after ingestion of a fat-rich meal. The aim of the study was to test the hypothesis that postprandial sleepiness is mediated by cholecystokinin (CCK) acting on CCK-A receptors. A double-blind crossover study was conducted. Twelve male volunteers ate a high-fat morning meal [54% energy fat, 41% energy carbohydrate (CHO)]. On one day they received an i.v. infusion of Loxiglumide, a CCK-A receptor antagonist (30 mg/kg/h for 10 min then 10 mg/kg/h for 3 h 10 min). On another day the protocol was repeated except a saline placebo infusion was given at similar rates as the Loxiglumide, starting 20 min before the meal. Subjects' mood and sleepiness were monitored throughout using questionnaires and performance tasks. The results indicate that ratings of vigour were significantly lower during the Loxiglumide infusion than during the saline infusion, [F(1,10) = 6.65; p = 0.027]. Subjects who were infused with Loxiglumide on their first test day felt significantly (p < 0.05) more fatigued, sleepy and tense and less vigorous, less efficient and had lower energetic arousal during the Loxiglumide infusion than during the saline infusion. In conclusion, the results suggest that the postprandial decline in feelings of alertness after a fat-rich meal is not mediated solely by CCK acting through CCK-A receptors.

Brain abnormalities in murderers indicated by positron emission tomography

Murderers pleading not guilty by reason of insanity (NGRI) are thought to have brain dysfunction, but there have been no previous studies reporting direct measures of both cortical and subcortical brain functioning in this specific group. Positron emission tomography brain imaging using a continuous performance challenge task was conducted on 41 murderers pleading not guilty by reason of insanity and 41 age- and sex-matched controls. Murderers were characterized by reduced glucose metabolism in the prefrontal cortex, superior parietal gyrus, left angular gyrus, and the corpus callosum, while abnormal asymmetries of activity (left hemisphere lower than right) were also found in the amygdala, thalamus, and medial temporal lobe. These preliminary findings provide initial indications of a network of abnormal cortical and subcortical brain processes that may predispose to violence in murderers pleading NGRI.

Age-related changes in cognitive ERPs of attenuation

This investigation explored developmental changes in passive and effortful components of ERPs associated with a visual attention task in children, adolescents, and adults. The task was a 'go-go' version of a continuous performance task, coupled with a passive attending phase in which the subjects merely watched the stimuli of the task. The three age groups featured a constellation of ERP components that shared the same general morphological appearance and distribution, but differences were seen with respect to latencies and amplitudes. Consistent with other studies, there was an inverse relationship with respect to age and peak latencies of the major passive and effortful components. With respect to peak amplitudes, however, the most impressive changes with age were observed in the passive processing components. For example, the P150 and P250 components presented greater amplitudes in children, whereas the N200 component presented its greatest amplitude in adults. While passive in the sense that their appearances were independent of the 'decision-making' process, these components were found to be upwardly adjustable by effort. The late positive component was found to be a combination of a passive P350 and an effortful P450. The P350 component was judged to be largely passive in character as it was well developed in subjects of all age groups when passively attending to the visual stimuli. There was no marked amplitude difference between the child and adult P450 components, but the components peaked in amplitude later in the children. Finally, the children's ERPs featured a distinct frontal negativity (FN) that was present in the Passive phase, but greatly enhanced during the Effortful phase. This study, as have many others, showed that there are reliable developmental changes in the components of visual ERPs. Therefore, the characteristics of the various components of cognitive ERPs may be effective markers of neurodevelopmental status, especially of those neuronal systems vital to attentional processing and effort regulation.

Effect of sertraline on regional metabolic rate in patients with affective disorder

Seventeen patients with major affective disorder completed a 10-week, placebo-controlled, randomized trial of the serotonin reuptake inhibitor sertraline. Patients underwent positron emission tomography with 18F-deoxyglucose and were assessed with the Hamilton Depression Rating Scale at baseline and 10 weeks after treatment with sertraline or placebo. The middle frontal gyrus, an area previously characterized by decreased metabolic activity in depressive patients, showed relatively increased activity on both sides after sertraline when contrasted with temporal and some occipital areas. Sertraline was associated with a significantly increased relative metabolic rate in right parietal lobe and in left occipital area 19, and a decreased metabolic rate in right occipital area 18. Other areas that differed between controls and a larger cohort of 39 depressive patients--including medial frontal lobe, cingulate gyrus, and thalamus--also showed a normalization of metabolic rate after sertraline.

Topographical analyses of attention disorders of childhood

Cognitive ERPs and EEG spectral differences were compared in three groups of children: nonreferred controls, those with a dominant hyperactivity/impulsivity factor (ADHD-Im), and those with a dominant inattentive factor (ADHD-Ia). The results from the ERP analyses indicated that the P250, P350, and P500 components differed between the groups. The most marked differences were seen with respect to the amplitude of the P500 components. In addition, the topographic foci of the P500 components for the CON and ADHD-Im groups were symmetrical, but the ADHD-Ia group featured P250 and P350 components that were biased away from the right hemisphere. Nevertheless, the P500 was found to be an effective discriminator between the groups. The combined spectral and ERP results suggest that the attention disordered children have difficulty adjusting their level of physiological arousal, and are defective with respect to controlled (or effortful) processing.

Topographical analysis of adolescent affective disorders

This study evaluated the EEG spectral content and the components of the cognitive ERPs evoked by a visual sustained-selective attention task from adolescents diagnosed as having an affective disorder and those who did not (nonreferred controls, CON) to determine if there were different electrophysiological profiles associated with major subtypes of affective disorders; i.e., Dysthymic Disorder (DysD) and Cyclothymic Disorder (CycD). Distinctive ERP and EEG profiles were found to be associated with the DysD and CycD groups. While both groups of depressives presented diminished P3b amplitudes, the DysD group showed a relatively greater suppression over the right temporal regions, whereas the CycD group exhibited relatively greater suppression over the left temporal region. In addition, there were differences with respect to the earlier components associated with information processing. For instance, the P1 was found deficient in the DysD group as compared to the other groups, whereas the N2 component was deficient in the CycD groups as compared to CON and DysD groups. In contrast to these amplitude differences, no significant latency differences were seen with respect to any component elicited by this paradigm. With respect to the EEG spectra, the CON group showed greater relative power in the Beta range than either the CycD or the DysD group, with the depressives featuring more midline frontal Theta activity. Characteristically, both depressant groups showed a greater anterior distribution of Alpha activity. In addition, the foci of the various spectral bands for the DysD subjects were shifted away from the right hemisphere as was the case for the P3b. Overall, the profiles suggested that those who fit the diagnostic classification of DysD have deficit function in right post-Rolandic zones, along with anomalous frontal function. It was also suggested that there may be a core disturbance of physiological arousal in unipolar depression. The CycD subjects, on the other hand, featured no hemispheric bias with respect to the P3b components or spectral foci, but did not show similar features of being cortically "hypoaroused" so that actively depressed adolescent CycD subjects did share certain physiological features with unipolar subjects.

Brain metabolism patterns are sensitive to attentional effort associated with a tone recognition task

Using positron emission tomography with the tracer 18-fluoro-D-deoxyglucose, we assessed regional cerebral glucose utilization patterns (rCMRglu) associated with three performance levels in a forced choice, tone recognition task. Four normal subjects responded with one hand when they heard a high-frequency tone (1500 Hz), and with the other hand when they recognized a low-frequency tone (750 Hz). The EASY (EAS) condition accuracy average was 96%, the INTERMEDIATE level accuracy averaged 89%, and the DIFFICULT (DIF) recognition task accuracy average was 77%. Statistical parametric mapping (SPM94) analysis revealed that the DIF minus EAS contrast is associated with a marked metabolic elevation in the right middle and inferior temporal gyri and the gyrus fusiformis. The EAS minus DIF contrast revealed greater rCMRglu in the right medial geniculate body. Enhanced activity in right temporal lobe structures may reflect a role in auditory memory and "image" visualization. The medial geniculate enhancement may reflect tone frequency assessment.

Auditory sustained attention in schizophrenia: a comparison of the Continuous Performance Test and the Pigache Attention Task

An auditory version of the Continuous Performance Test (CPT) was compared with the Pigache Attention Task (PAT) to evaluate relative sensitivities in schizophrenia. Digits spoken seamlessly for 5 min required a button-press response to each of 50 targets. Diotic and dichotic event rates were 1/s for the CPT and 0.5/s and 2/s for the PAT. 'Correct' responses were restricted to the interstimulus interval (CPT) or to longer intervals (PAT). This study demonstrated that the CPT method of scoring is invalid since significant numbers of late responses counted as both omission and commission errors. The CPT was significantly easier than the PAT, which provided a more appropriate range of difficulty. The PAT again discriminated between healthy subjects and schizophrenic patients.

Cerebral metabolic activity correlates of subsyndromes in chronic schizophrenia

Seventy-nine patients with schizophrenia and 47 healthy controls received positron-emission tomography (PET) with 18F-2-deoxyglucose uptake while executing the Continuous Performance Test (CPT). Patients had been off all psychoactive medication for at least four weeks. Patients' symptoms were assessed with the Brief Psychiatric Rating Scale and factor scale scores were obtained. These scores were used in cluster analysis to identify patients with predominantly delusional, negative, disorganized, and remitted symptoms. To address the interconnective nature of cerebral functioning, regions of interest were defined on the basis of the results of a factor analysis of metabolic rate in selected brain regions. This procedure identified six cortical and eight subcortical region of interest factors. Metabolic rate factor scale scores were compared between the patients' clusters and the healthy controls. The delusional cluster showed a significantly reduced hippocampal activity, while the negative symptoms cluster presented with a prominent hypofrontality and significantly increased left temporal cortex values. Concurrently, both clusters were associated with a decreased activity on the factor 'anterior cingulum and medial frontal gyrus'. The disorganized cluster was characterized by a significant overactivity in the parietal cortex and motor strip and a decreased activity in the corpus callosum. The subsyndromes of chronic schizophrenia are therefore characterized by deviant patterns of cerebral activity rather than deficits in a single location.

Glucose metabolic correlates of continuous performance test performance in adults with a history of infantile autism, schizophrenics, and controls

Twenty-five schizophrenic patients, fourteen adults with a history of infantile autism, and twenty normal controls performed a test of sustained attention, the degraded stimulus continuous performance test (CPT), during the 35 minute 18-fluoro-2-deoxyglucose uptake period preceding positron emission tomographic (PET) scan acquisition. This is the first analysis comparing correlations between glucose metabolic rate (GMR) for selected regions and CPT performance. CPT performance differed in controls and schizophrenics, but autistics did not differ from either group. In controls and schizophrenic patients, task performance correlated with GMR in medial superior frontal gyrus and lateral inferior temporal gyrus, suggesting that activation of those regions is important in the normal performance of the task and that damage to those regions, which also showed low GMR in schizophrenics, contributes to the attentional dysfunction in schizophrenia. Also, schizophrenics showed negative correlations of task performance with anterior cingulate activity suggesting that overactivity of that region, which is involved in mental effort and whose GMR was low in our larger study of schizophrenia, impairs task performance in schizophrenics. Autistic patients showed negative correlations of medial frontal cortical GMR with attentional performance, suggesting that neuronal inefficiency in that region may contribute to poor performance.

Influences of dietary and intraduodenal lipid on alertness, mood, and sustained concentration

The effects of intraduodenal and dietary lipid on alertness, mood and performance in a task requiring sustained attention were investigated in two studies. The first experiment compared the effect of duodenal infusion of either 100 g/l Intralipid (8.36 kJ/min) or isotonic saline (9 g NaCl/l) in paired studies carried out on two non-consecutive days on five male volunteers. Two consecutive 3 h infusions, one of lipid, the other saline, were given blind on each day using a crossover design. Analysis of variance indicated that lipid significantly reduced alertness (P < 0.05) and affected the speed and accuracy of performance in a sustained attention task (P < 0.05). A second experiment compared the effects on eight male volunteers of two isoenergetic lunches of similar appearance, taste and protein content but differing fat and carbohydrate (CHO) contents (fat energy:CHO, 64:18 v. 7:76). Alertness was lower (P < 0.05) and responses to stimuli in a sustained attention task were slower after the high-fat meal than after the low-fat meal (P < 0.05). In conclusion, infusion of lipid into the small intestine, and the substitution of fat for carbohydrate while keeping energy and protein constant in a lunch, both cause an enhanced postprandial decline in alertness and concentration. This may be related to the presence of lipid in the small intestine.

Tone discrimination performance in schizophrenic patients and normal volunteers: impact of stimulus presentation levels and frequency differences

Psychophysical and cognitive studies carried out in schizophrenic patients show high within-group performance variance and sizable differences between patients and normal volunteers. Experimental manipulation of a target's signal-to-noise characteristics can, however, make a given task more or less difficult for a given subject. Such signal-to-noise manipulations can substantially reduce performance differences between individuals. Frequency and presentation level (volume) changes of an auditory tone can make a sound more or less difficult to recognize. This study determined how the discrimination accuracy of medicated schizophrenic patients and normal volunteers changed when the frequency difference between two tones (high frequency vs. low frequency) and the presentation levels of tones were systematically degraded. The investigators hypothesized that each group would become impaired in its discrimination accuracy when tone signals were degraded by making the frequencies more similar and the presentation levels lower. Schizophrenic patients were slower and less accurate than normal volunteers on tests using four tone levels and two frequency differences; the schizophrenic patient group showed a significant decrement in accuracy when the signal-to-noise characteristics of the target tones were degraded. The benefits of controlling stimulus discrimination difficulty in functional imaging paradigms are discussed.

Alzheimer patients show a sensitivity decrement over time on a tonic alertness task

Tonic alertness was investigated in Alzheimer patients and normal elderly subjects. Sensitivity and criterion shifts were investigated across 45 min of continuous testing using a high event rate test with very low target probability. Alzheimer patients showed a significant sensitivity decrement over time that was unrelated to dementia severity. These results suggest that tonic alertness is impaired by Alzheimer's disease even in its early stages.

Patterns of cortical activity in schizophrenia

Eighty-three patients with schizophrenia and 47 healthy controls received positron emission tomography (PET) with 18F-2-deoxyglucose uptake while they were executing the Continuous Performance Test (CPT). The entire cortex was divided into 16 regions of interest in each hemisphere, four in each lobe of the brain, and data from corresponding right and left hemispheric regions were averaged. Data from the schizophrenic patients were subjected to a factor analysis, which revealed five factors that explained 80% of the common variance. According to their content, the factors were identified and labelled 'parietal cortex and motor strip', 'associative areas', 'temporal cortex', 'hypofrontality' (which included midfrontal and occipital areas) and 'frontal cortex'. Hemispheric asymmetry was only confirmed for the temporal cortex. Factor weights obtained in the schizophrenic group were applied to the metabolic data of the healthy controls and factors scales computed. Schizophrenics were significantly more hypofrontal than the controls, with higher values on the 'parietal cortex and motor strip' factor and a trend towards higher values in the temporal cortex. A canonical discriminant analysis confirmed that the 'hypofrontality' and 'parietal cortex and motor strip' factors accurately separated the schizophrenic group from the healthy controls. Hemispheric asymmetry was only confirmed for the temporal lobe. Significantly higher factor scores for the left temporal lobe in schizophrenics than in normals were obtained when calculated for the right and left hemisphere separately. Taken together, our results confirm the importance of hypofrontality as a pattern of cortical metabolic rate and point to the potential importance of parietal and motor strip function in schizophrenia.

Cognitive disorders and negative symptoms as correlates of motivational deficits in psychotic patients

The problem of a possible lack of motivation to perform cognitive tasks, which is often encountered in psychotic patients, has been approached from the perspective of the 'energetics' of cognition (Hockey et al. 1986) and from the broader clinical context of psychosis as an 'amotivational syndrome' and its related negative symptoms. The presence of motivational deficits was investigated in a group of psychotic in-patients (N = 73, and 40 had schizophrenia) compared with a control group of non-psychotic psychiatric in-patients (N = 23). The motivational deficit was operationalized in terms of Sanders's (1983) cognitive-energetic model as a large effect of 'time-on-task' during a simple, monotonous reaction test. Significantly more psychotic patients than control patients showed evidence of this type of motivational deficit. The deficit appeared to be related with negative but not with positive symptoms of psychosis. Furthermore, the deficit was shown to be related to the cognitive disorders of psychosis, which have been amply documented in the literature, i.e. disorders of vigilance, verbal memory and distractibility. These results suggest that the cognitive disorders of psychosis are not of a 'computational' but of an 'energetical', i.e. motivational nature.

Effects of mizolastine and clemastine on actual driving and psychomotor performance in healthy volunteers

The acute effect of doses of mizolastine 5, 10, 20 and 40 mg, an active control (clemastine 2 mg) and placebo on actual car driving and psychomotor performance have been compared. Twenty four healthy volunteers were treated according to a double-blind, 6-way cross-over design. In the driving test, lasting about 1 h, lateral position control and speed were continuously measured; the psychomotor test battery, lasting 50 min, comprised critical flicker-fusion frequency, critical instability tracking, divided attention, memory search and choice reaction time, and vigilance studies; and mood changes and possible adverse-effects were rated on visual analogue scales. The results showed a dose-response relationship: mizolastine 40 and 20 mg impaired driving and psychomotor performance. The effect of mizolastine 40 mg on driving was strongly correlated with that of clemastine (r = 0.78) and was comparable to the effect of a blood ethanol level of 0.8 mg.ml-1. Mizolastine 5 mg and 10 mg did not have a significant effect on driving performance and psychomotor tests. It was concluded that at a 10 mg dose of mizolastine, the therapeutic dose, it could be considered a safe anti-histamine, although individual adverse reactions cannot be completely ruled out.

Selective reductions in prefrontal glucose metabolism in murderers

This study tests the hypothesis that seriously violent offenders pleading not guilty by reason of insanity or incompetent to stand trial are characterized by prefrontal dysfunction. This hypothesis was tested in a group of 22 subjects accused of murder and 22 age-matched and gender-matched controls by measuring local cerebral uptake of glucose using positron emission tomography during the continuous performance task. Murderers had significantly lower glucose metabolism in both lateral and medial prefrontal cortex relative to controls. No group differences were observed for posterior frontal, temporal, and parietal glucose metabolism, indicating regional specificity for the prefrontal deficit. Group differences were not found to be a function of raised levels of left-handedness, schizophrenia, ethnic minority status, head injury, or motivation deficits in the murder group. These preliminary results suggest that deficits localized to the prefrontal cortex may be related to violence in a selected group of offenders, although further studies are needed to establish the generalizability of these findings to violent offenders in the community.

The expression of the 'pre-menstrual syndrome' in measures of mood and sustained attention

Twenty-eight women performed two demanding sustained attention tasks in the premenstrual and intermenstrual phases of the menstrual cycle. Mood was assessed before and after performance. No effects of phase were found on perceptual sensitivity and response criterion, but response time on the less demanding of the two tasks was slower in the premenstrual phase. There were no effects of phase on pre-task mood, but following performance, premenstrual women were lower in energy and in pleasantness of mood. Moods varied with phase irrespective of usage of the contraceptive pill, but effects on response time were stronger in non-pill users. Performance data suggest that speed of visual discrimination varies with the cycle, but this finding is of little practical significance. The mood data suggest that the affective correlates of the cycle vary with situational stress, and, in the workplace, it may be desirable to reduce stress and workload during the premenstrual phase.