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

Mice lacking melatonin MT2 receptors exhibit attentional deficits, anxiety and enhanced social interaction

BACKGROUND

Aside from regulating circadian rhythms, melatonin also affects cognitive processes, such as alertness, and modulates the brain circuitry underlying psychiatric diseases, such as depression, schizophrenia and bipolar disorder, via mechanisms that are not fully clear. In particular, while melatonin MT1 receptors are thought primarily to mediate the circadian effects of the hormone, the contribution of the MT2 receptor to melatonin actions remains enigmatic.

AIMS

To characterise the contribution of MT2 receptors to melatonin's effects on cognition and anxiety/sociability.

METHODS

Mice with a genetic deletion of the MT2 receptor, encoded by the Mtnr1b gene, were compared with wild-type littermates for performance in a translational touchscreen version of the continuous performance task (CPT) to assess attentional processes and then monitored over 3 days in an ethological home-cage surveillance system.

RESULTS

Mtnr1b knockout (KO) mice were able to perform at relatively normal levels in the CPT. However, they showed consistent evidence of more liberal/risky responding strategies relative to control mice, with increases in hit rates and false alarm rates, which were maintained even when the cognitive demands of the task were increased. Assessment in the home-cage monitoring system revealed that female Mtnr1b KO mice have increased anxiety levels, whereas male Mtnr1b KO mice show increased sociability.

CONCLUSIONS

The results confirm that the MT2 receptor plays a role in cognition and also modulates anxiety and social interactions. These data provide new insights into the functions of endogenous melatonin and will inform future drug development strategies focussed on the MT2 receptor.

Sustaining attention to simple visual tasks: a central deficit in schizophrenia? A systematic review

Impairments in sustained attention, that is, the ability to achieve and maintain the focus of cognitive activity on a given stimulation source or task, have been described as central to schizophrenia. Today, sustained attention deficit is still considered as a hallmark of schizophrenia. Nevertheless, current findings on this topic are not consistent. To clarify these findings, we attempt to put these results into perspective according to the type of assessment (i.e., overall and over time assessment), the participants' characteristics (i.e., clinical and demographic characteristics), and the paradigms (i.e., traditionally formatted tasks, go/no-go tasks, and the sustained attention task) and measures used. Two types of assessment lead to opposite findings; they do not evaluate sustained attention the same way. Studies using overall assessments of sustained attention ability tend to reveal a deficit, whereas studies using over time assessments do not. Therefore, further research is needed to investigate the underlying cognitive control mechanisms of changes in sustained attention in schizophrenia.

Brain substrates of perceived spatial separation between speech sources under simulated reverberant listening conditions in schizophrenia

BACKGROUND

People with schizophrenia recognize speech poorly under multiple-people-talking (informational masking) conditions. In reverberant environments, direct-wave signals from a speech source are perceptually integrated with the source reflections (the precedence effect), forming perceived spatial separation (PSS) between different sources and consequently improving target-speech recognition against informational masking. However, the brain substrates underlying the schizophrenia-related vulnerability to informational masking and whether schizophrenia affects the unmasking effect of PSS are largely unknown.

METHOD

Using psychoacoustic testing and functional magnetic resonance imaging, respectively, the speech recognition under either the PSS or perceived spatial co-location (PSC) condition and the underlying brain substrates were examined in 20 patients with schizophrenia and 16 healthy controls.

RESULTS

Speech recognition was worse in patients than controls. Under the PSS (but not PSC) condition, speech recognition was correlated with activation of the superior parietal lobule (SPL), and target speech-induced activation of the SPL, precuneus, middle cingulate cortex and caudate significantly declined in patients. Moreover, the separation (PSS)-against-co-location (PSC) contrast revealed (1) activation of the SPL, precuneus and anterior cingulate cortex in controls, (2) suppression of the SPL and precuneus in patients, (3) activation of the pars triangularis of the inferior frontal gyrus and middle frontal gyrus in both controls and patients, (4) activation of the medial superior frontal gyrus in patients, and (5) impaired functional connectivity of the SPL in patients.

CONCLUSIONS

Introducing the PSS listening condition efficiently reveals both the brain substrates underlying schizophrenia-related speech-recognition deficits against informational masking and the schizophrenia-related neural compensatory strategy for impaired SPL functions.

Paying attention to MMN in schizophrenia

The aim of this review is to explore the phenomenon of reduced mismatch negativity (MMN) in persons with schizophrenia and the possible relationship it has with attention impairments. In doing so we discuss (i) the prediction error account of MMN, (ii) reduced MMN as a faulty predictive processing system in persons with schizophrenia, (iii) the role of these systems in relevance filtering and attentional resource protection, (iv) attentional impairments in persons with schizophrenia, and (v) research that has explored MMN and attention in schizophrenia groups. Our review of the literature suggests that no study has appropriately examined the functional impact of smaller MMN in schizophrenia on the performance of a concurrent attention task. We conclude that future research should explore this notion further in the hope that it might embed MMN findings within outcomes of functional significance to individuals with the illness and those providing treatment. This article is part of a Special Issue entitled SI: Prediction and Attention.

A meta-analysis of decision-making and attention in adults with ADHD

OBJECTIVE

Deficient reward processing has gained attention as an important aspect of ADHD, but little is known about reward-based decision-making (DM) in adults with ADHD. This article summarizes research on DM in adult ADHD and contextualizes DM deficits by comparing them to attention deficits.

METHOD

Meta-analytic methods were used to calculate average effect sizes for different DM domains and continuous performance task (CPT) measures.

RESULTS

None of the 59 included studies (DM: 12 studies; CPT: 43; both: 4) had indications of publication bias. DM and CPT measures showed robust, small to medium effects. Large effect sizes were found for a drift diffusion model analysis of the CPT.

CONCLUSION

The results support the existence of DM deficits in adults with ADHD, which are of similar magnitude as attention deficits. These findings warrant further examination of DM in adults with ADHD to improve the understanding of underlying neurocognitive mechanisms.

Neuropsychologically informed strategic psychotherapy in teenagers and adults with ADHD

Stimulants are the primary treatment for ADHD. Psychotherapy may augment pharmacologic treatment. In this article, we discuss strategies psychotherapists may use in working with teenagers and adults, including individuals who reject medications or take them suboptimally. Individuals with ADHD often have other psychiatric issues, including affective or cognitive comorbidities. Having ADHD does not protect people from the difficulties of life, and psychotherapy can help to disentangle "ADHD" from other issues. A psychotherapist knowledgeable about ADHD assessment can improve diagnostic precision. Psychotherapy can integrate forms of treatment in which the central goal is increasing mastery and competence of the individual.

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.

Dissociation of acute and chronic intermittent phencyclidine-induced performance deficits in the 5-choice serial reaction time task: influence of clozapine

BACKGROUND

Cognitive deficits are a core feature of schizophrenia that respond minimally to existing drugs. PCP is commonly used to model schizophrenia-like deficits preclinically although different dosing protocols may affect different domains. Here we characterise the acute, and chronic intermittent effects of PCP in the 5-choice serial reaction time task (5-CSRTT) in rats, and assess the effects of clozapine. In a novel approach, we also assess the effects of increased inhibitory load and conduct clinically relevant signal detection analysis (SDA).

MATERIALS AND METHODS

The effects of acute and repeated PCP (2.58 mg/kg) treatment on attentional processes and inhibitory control were assessed during and following the chronic treatment regime in the presence or absence of chronic clozapine (20 mg/kg/day).

RESULTS

Thirty minutes post-PCP injection, there was an increase in anticipatory responding which disappeared after 24 h. Although, acute PCP did not change accuracy of responding or processing speed, repeated PCP revealed delayed deficits in cognitive processing speed which were partly ameliorated by clozapine. Extended inter-trial intervals increased premature responding, while SDA revealed that clozapine modified persistent PCP-induced deficits in lnBeta (a composite measure of risk taking versus caution).

CONCLUSION

Acute NMDA receptor antagonism impairs inhibitory control, whereas repeated treatment produces delayed deficits in cognitive processing speed. The ability of clozapine partially to restore persistent PCP-induced deficits in processing speed and in lnBeta is consistent with clinical findings. This suggests that the enduring effects of repeated PCP treatment, combined with SDA, offers a useful, translational, approach to evaluate novel cognitive enhancers in the 5-CSRTT.

Impaired response inhibition in ill Gulf War veterans

Poor performance on tasks requiring response inhibition has been observed among chronically ill veterans of the 1991 Persian Gulf War. Semantic difficulties have also been reported. We collected event-related potential (ERP) and behavioral data from 25 Gulf War veterans who complained of cognitive difficulties and from 23 matched controls, who were deployed but not symptomatic, while they performed a GO-NOGO task that required both a semantic decision and inhibitory processing. A significantly greater false-alarm rate among the ill veterans was accompanied in the ERP data by significantly reduced amplitude in the NOGO P3, consistent with previous ERP studies of other patient groups that have shown poor inhibitory response performance. This supports the contention that the ill veterans' deficit lies more in inhibiting than in detecting task-related differences in the stimuli.

A neurocognitive animal model dissociating between acute illness and remission periods of schizophrenia

RATIONALE

The development and validation of animal models of the cognitive impairments of schizophrenia have remained challenging subjects.

OBJECTIVE

We review evidence from a series of experiments concerning an animal model that dissociates between the disruption of attentional capacities during acute illness periods and the cognitive load-dependent impairments that characterize periods of remission. The model focuses on the long-term attentional consequences of an escalating-dosing pretreatment regimen with amphetamine (AMPH).

RESULTS

Acute illness periods are modeled by the administration of AMPH challenges. Such challenges result in extensive impairments in attentional performance and the "freezing" of performance-associated cortical acetylcholine (ACh) release at pretask levels. During periods of remission (in the absence of AMPH challenges), AMPH-pretreated animals' attentional performance is associated with abnormally high levels of performance-associated cortical ACh release, indicative of the elevated attentional effort required to maintain performance. Furthermore, and corresponding with clinical evidence, attentional performance during remission periods is exquisitely vulnerable to distractors, reflecting impaired top-down control and abnormalities in fronto-mesolimbic-basal forebrain circuitry. Finally, this animal model detects the moderately beneficial cognitive effects of low-dose treatment with haloperidol and clozapine that were observed in clinical studies.

CONCLUSIONS

The usefulness and limitations of this model for research on the neuronal mechanisms underlying the cognitive impairments in schizophrenia and for drug-finding efforts are discussed.

Advances in endophenotyping schizophrenia

The search for the genetic architecture of schizophrenia has employed multiple, often converging strategies. One such strategy entails the use of tracing the heritability and neurobiology of endophenotypes. Endophenotypes are quantifiable traits not visible to the eye, which are thought to reflect an intermediate place on the path from genes to disorder. Endophenotype abnormalities in domains such as neurophysiology or neurocognition occur in schizophrenia patients as well as their clinically "unaffected" relatives, and reflect polymorphisms in the DNA of schizophrenia spectrum subjects which create vulnerability to developing schizophrenia. By identifying the single nucleotide polymorphisms (SNPs) associated with endophenotypes in schizophrenia, psychiatric neuroscientists can select new strong inference based molecular targets for the treatment of schizophrenia.

Attention-deficit/hyperactivity disorder: a neuropsychological perspective towards DSM-V

Neuropsychological methods and techniques have much to offer in the evaluation of the individual suspected as having Attention-Deficit/Hyperactivity Disorder (ADHD). After a review of the historical evolution of the ADHD concept, incidence and prevalence, and DSM-IV criteria for diagnosis, especially as regards omission related to gender differences, and other associated cultural, familial, socioenvironmental, and subject influences, this paper describes a number of dilemmas and obstacles encountered in clinical practice. Included are the confounds associated with the wide range of possible comorbidities, the insufficiency of current DSM-IV criteria, the emergence of subtype differentiation and its impact on diagnosis and treatment. The complex relationship between neuropsychological constructs and ADHD, and obstacles to valid assessment are also addressed. The complexities associated with a thorough ADHD evaluation are viewed within an impressive and expansive existing scientific framework and recommendations are made for future directions.

Response selection in schizophrenia

Schizophrenia patients tend to have longer and more variable latencies of response than healthy control subjects. However, the distributions of data from the two groups overlap to a large extent. Therefore, we investigated (1) whether the process of response selection in schizophrenia patients is like that of slow control subjects or has different properties, and (2) whether the intra-individual variability of schizophrenia patients is intrinsically greater than that of control subjects or reflects their longer mean latency. To answer these questions we tested schizophrenia patients and healthy control subjects in a choice reaction time (RT) task with 2-choice and 4-choice conditions. We analyzed how mean RT in the 2-choice condition predicted mean RT in the 4-choice condition and found that the relation was significantly different between the two groups. In contrast, the intra-individual variability of RT was related to mean RT in the same way for schizophrenia patients and control subjects. These results indicate that the response selection process of schizophrenia patients was not simply a slower version of the same process engaged by control subjects, but it was a selection process with different dynamic properties. In contrast, schizophrenia patients did not have a greater intrinsic variability than control subjects. Furthermore, we found that the difference Deltat between RT measured in the 4-choice condition and RT predicted for the control group in the same condition could be used to discriminate effectively patients and control subjects. However, there was no significant association between Deltat and clinical variables. These results suggest that Deltat could reflect a trait impairment of schizophrenia independent from symptom profile. Finally, we suggest that the impairment of the process of selection of the motor response in schizophrenia reflects the alteration of the time-dependent patterns of neural activity that result from anomalies in the connectivity of the brain areas engaged for the selection of the motor response.

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.

More severe sustained attention deficits in nonpsychotic siblings of multiplex schizophrenia families than in those of simplex ones

Sustained attention deficits measured by the Continuous Performance Test (CPT) have been proposed as an endophenotype of schizophrenia. However, little is known about whether sustained attention deficits in first-degree relatives of schizophrenic patients are associated with familial loading for schizophrenia. We examined 107 parents and 84 siblings of simplex schizophrenia families as well as 72 parents and 56 siblings of multiplex schizophrenia families, all nonpsychotic, using the Diagnostic Interview for Genetic Studies and two sessions of the CPT (undegraded and degraded). The effect of perceptual load was assessed using the residual of the regression of the degraded score on the undegraded one. Statistical models that can adjust for familial correlations were used to compare the CPT performance of relatives between the two types of families. Siblings from multiplex families exhibited worse performance on the degraded CPT and less proficiency in processing the perceptual load than those from simplex families. No such difference was observed for the parents on either CPT version. We concluded that sustained attention along with perceptual load processing is more impaired in the siblings of schizophrenic patients with high familial loading and that this finding might be useful for future genetic dissection of schizophrenia.

Pathophysiology of mental illness: A view from the fourth ventricle

The concept of mental disorders as diseases of the brain is as old as the ancient Greek philosopher-physicians. However, for thousands of years, the majority of doctors, as well as laypersons, held strongly to the belief that epilepsy and "madness" (i.e., schizophrenia)--the major disorders discussed in this paper--were caused by demonic "possession." As always, the theory of causation led to apposite therapies: Cast out the devil by whatever means necessary. Later, more enlightened views of etiology led to less punitive "cures," which, to modern sensibilities, still seem barbaric. The 20th century saw the introduction of medications that provide symptomatic relief, if not cures, for seizure disorders and schizophrenia. In this paper, we consider the etiology of absence (petit mal) epilepsy and schizophrenia based on the pathophysiology underlying the shared symptom of impaired sustained attention. We emphasize the role of abnormal functioning of brainstem structures in the region of the fourth ventricle, whether caused by genetic or environmental factors or a combination thereof. Our theorizing relies on the findings of Lindsley, Magoun, and Moruzzi, who delineated the role of the brainstem reticular activating system in sleep, wakefulness, and consciousness. It also relies on the work of Penfield, Jasper, and Gloor, who sought to illuminate the role of brainstem-thalamus-cortical dysfunction in idiopathic generalized epilepsies. We consider evidence from recent studies that emphasize the phasic attentional functions supported by brainstem structures in the region of the fourth ventricle, and possible genetic links among disorders in which impaired attention is a prominent symptom.

Searching for the liability to schizophrenia: concepts and methods underlying genetic high-risk studies of adolescents

Conceptualizations of the liability for schizophrenia help guide the development of research protocols, which, in turn, provide empirical confirmations or disconfirmations of the conceptualization's tenets. This paper focuses on a conception of liability and its relationships to genetic adolescent high-risk studies. Specifically, the derivation and nature of a proposed multidimensional syndrome of liability to schizophrenia ("schizotaxia") are outlined, followed by a representative review of features reported in previous high-risk studies that may be related to schizotaxia, and a perspective on future high-risk investigations. Overall, genetic high-risk studies generally confirm the concept of liability in the offspring of parents with schizophrenia, as expressed by deficits or abnormalities in multiple dimensions. It is concluded that high-risk studies on the liability to schizophrenia provide an important tool with which to explore the etiology and development of schizophrenia, in part by contributing to the identification and validation of specific liability syndromes.

The effect of sulpiride on amphetamine-induced disruption of overshadowing in the rat

Previous studies have demonstrated dopaminergic (DA) modulation of stimulus selection performance in the overshadowing and Kamin blocking (KB) tasks. Systemic administration of the DA agonist D-amphetamine selectively disrupted overshadowing in the rat. In the present study, we examined the ability of the selective DA D2 receptor antagonist sulpiride to reverse amphetamine-induced disruption of overshadowing, in the conditioned emotional response (CER) procedure. In the overshadowing task, two stimuli (light and tone) are presented simultaneously alongside an aversive unconditioned stimulus (CS) (mild footshock); overshadowing consists in the decrease in learning to the less salient stimulus, as compared to when it is conditioned alone. Systemic D-amphetamine (1 mg/kg, i.p.) prevented overshadowing, while having no effect on control learning. Pre-administration of sulpiride (50 and 100 mg/kg, i.p.) did not prevent the ability of D-amphetamine to impair overshadowing. In addition, sulpiride had no significant effect on overshadowing when administered alone. The results are in agreement with previous data indicating that DA modulation of stimulus selection performance is mediated by activation of the DA D1 rather than DA D2 receptor subtype.

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.

Sustained attention deficits in nonpsychotic relatives of schizophrenic patients: a recurrence risk ratio analysis

BACKGROUND

In nonpsychotic parents and siblings of schizophrenic patients, the recurrence risk ratios of sustained attention deficits, as measured by the continuous performance test (CPT), were examined with a series of cut-off points.

METHODS

Among 116 parents and 95 siblings of 91 schizophrenic probands in northern Taiwan, both undegraded and degraded sessions of the CPT were administered. Subjects' signal detection sensitivity of CPT performance (d') was standardized against a community sample without (unadjusted z score) or with (adjusted z score) adjustment for age, gender, and educational level.

RESULTS

Differences in the risk ratios between the parents and siblings that were based on the unadjusted z scores of CPT d' diminished markedly if the adjusted z scores were used. As the cut-off point in the adjusted z score decreased from -2.5 to -3.0, the risk ratio increased continually for both the undegraded (10.1-18.8 for parents, 10.0-16.7 for siblings) and degraded (12.4-102.7 for parents, 8.6-72.0 for siblings) test.

CONCLUSIONS

Stringent cut-off criteria of CPT deficits with adjustment for demographic features leads to recurrence risk ratios greater than those based on schizophrenia alone in both parents and siblings of schizophrenic patients.

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.

Effects of a neurosteroid, pregnenolone, during the neonatal period on adenosine A1 receptor, dopamine metabolites in the fronto-parietal cortex and behavioral response in the open field

Neuronal dysfunction in the frontal cortex has been reported in the etiology of mental disorders, including schizophrenia. The adenosine A(1) receptor system, as well as the dopaminergic system, are important in the control of cortical neuronal activity. We hypothesize that neuroexcitability in early life is critical to the normal development of the brain, and neurosteroids are factors that modulate neuroexcitability during the development period. In this study, we treated neonatal rats with a neurosteroid, pregnenolone (10 microg/g) from postnatal day (PD) 3 until PD 7. In pregnenolone-treated male and female rats, adenosine A(1) receptor density, the amount of dopamine (DA), serotonin (5-HT) and their metabolites in the fronto-parietal cortex and behavioral responses in the open field were examined pre- and post-puberty. A decrease in K(d) values for the adenosine A(1) receptor binding assay using [(3)H]1,3-dipropyl-8-cyclopentylxanthine (DPCPX), increased formation of DA metabolites and hyper-locomotor activity in the open field were found in pregnenolone-treated rats compared with controls in pre- and post-puberty. An increase in 5-HT metabolites was found in the pregnenolone-treated rats in pre-puberty, but not post-puberty. These effects of pregnenolone were not different between males and females. However, correlations between horizontal and vertical activities in the open field were disrupted only in pregnenolone-treated females. The present results indicate that pregnenolone treatment during the neonatal period influences the cortical dopaminergic and adenosinergic systems as well as behavioral responses in the open field.

Reduced or increased influence of non-pertinent information in patients with schizophrenia?

We tested the ability of 18 patients with schizophrenia and 18 matched controls to filter non-pertinent information in orientation matching tasks. The non-pertinent information consisted of pictures conveying semantic information. The pertinent information consisted of oriented line-segments drawn inside pictures or was represented by the overall orientation of the picture itself. The results showed that non-pertinent information interfered with performance of control subjects in all tasks. In contrast, non-pertinent information interfered with the performance of patients with schizophrenia to the same extent as that of matched controls only when non-pertinent and pertinent information was physically mingled, but not when they were separated. Yet, patients processed non-pertinent information in all experiments, as shown by reversed interference effects when non-pertinent and pertinent information was physically separated. These results suggest a deficit at linking physically distinct visual information in patients with schizophrenia. Additionally, performance was more impaired in patients with schizophrenia than in control subjects when the amount of displayed information increased. The results suggest the coexistence, and a possible relationship between attentional deficits and impairments at linking distinct visual information in patients with schizophrenia.

A comparative profile analysis of neuropsychological functioning in patients with schizophrenia and bipolar psychoses

Evidence for neuropsychological deficits in schizophrenia is substantial whereas evidence for the specificity of dysfunction is relatively sparse. To assess specificity, we compared neuropsychological function in patients with chronic schizophrenia, patients with chronic psychotic bipolar disorder and normal controls. Groups were comparable on age, ethnicity and expected intellectual ability (based on single word reading). Patients with schizophrenia and bipolar psychoses were also relatively similar on age at onset and number of hospitalizations. Using multivariate analyses of variance with sex and parental SES as covariates (our primary analyses), patients with schizophrenia were significantly more impaired than controls on seven of eight neuropsychological functions (all but verbal ability), and were significantly more impaired than bipolar patients on abstraction, perceptual-motor speed and vigilance. Bipolar patients were significantly impaired compared to controls on declarative verbal memory, and showed moderate-to-large effect size decrements on abstraction, perceptual-motor speed and vigilance. Results were not attenuated when IQ was controlled, which was significantly lower in patients with schizophrenia. Analyses indicated that the two psychiatric groups had similar profile patterns, but that patients with schizophrenia had a more severe impairment than patients with bipolar psychoses. Further research is required to determine whether similar mechanisms underly the neurocognitive deficits in these disorders.

Continuous performance tests are sensitive to ADHD in adults but lack specificity. A review and critique for differential diagnosis

Historically, the focus for Attention Deficit Hyperactivity Disorder (ADHD) has been on children, with considerable research and many opinions available in this area. More recently, the focus has been expanded to include ADHD in adults. Assessment of ADHD in adults is complicated by the high rate of co-occurring disorders as well as symptom overlap with a number of disorders. One popular family of measures for the assessment of attention and executive control is the continuous performance test (CPT). A review of the available research on CPTs reveals that they are quite sensitive to CNS dysfunction. This is both a strength and a limitation of CPTs in that multiple disorders can result in impaired performance on a CPT. The high sensitivity of CPTs is further complicated by the multiple variations of CPTs available, some of which may be more sensitive or demonstrate better specificity to ADHD in adults than others. If CPTs are to be used clinically, further research will be needed to answer the questions raised by this review.

Cortical cholinergic inputs mediating arousal, attentional processing and dreaming: differential afferent regulation of the basal forebrain by telencephalic and brainstem afferents

Basal forebrain corticopetal neurons participate in the mediation of arousal, specific attentional functions and rapid eye movement sleep-associated dreaming. Recent studies on the afferent regulation of basal forebrain neurons by telencephalic and brainstem inputs have provided the basis for hypotheses which, collectively, propose that the involvement of basal forebrain corticopetal projections in arousal, attention and dreaming can be dissociated on the basis of their regulation via major afferent projections. While the processing underlying sustained, selective and divided attention performance depends on the integrity of the telencephalic afferent regulation of basal forebrain corticopetal neurons, arousal-induced attentional processing (i.e. stimulus detection, selection and processing as a result of a novel, highly salient, aversive or incentive stimuli) is mediated via the ability of brainstem ascending noradrenergic projections to the basal forebrain to activate or "recruit" these telencephalic afferent circuits of the basal forebrain. In rapid eye movement sleep, both the basal forebrain and thalamic cortiocopetal projections are stimulated by cholinergic afferents originating mainly from the pedunculopontine and laterodorsal tegmenta in the brainstem. Rapid eye movement sleep-associated dreaming is described as a form of hyperattentional processing, mediated by increased activity of cortical cholinergic inputs and their cortical interactions with activated thalamic efferents. In this context, long-standing speculations about the similarities between dreaming and psychotic cognition are substantiated by describing the role of an over(re)active cortical cholinergic input system in either condition. Finally, while determination of the afferent regulation of basal forebrain corticopetal neurons in different behavioral/cognitive states assists in defining the general cognitive functions of cortical acetylcholine, this research requires a specification of the precise anatomical organization of basal forebrain afferents and their interactions in the basal forebrain. Furthermore, the present hypotheses remain incomplete because of the paucity of data concerning the regulation and role of basal forebrain non-cholinergic, particularly GABAergic, efferents.