Cognitive and functional changes with aging in schizophrenia

Lack of Efficacy of JNJ-18038683 on Cognitive Impairment in Patients With Stable Bipolar Disorder

BACKGROUND

The serotonin type 7 (5-HT7) receptor is one of 14 5-HT receptors. It has received attention for its possible role in mood disorders and cognition. The 5-HT7 receptor antagonist, JNJ-18038683, has been reported to be effective in rodent models of depression and REM sleep. Also, 5-HT7 receptor blockade has been postulated to be a key component of cognitive enhancement in a number of drugs. Bipolar disorder (BD) usually endures cognitive impairment (CI); however, no treatment for CI in BD has been approved. This study aimed to evaluate the efficacy of JNJ-18038683 to improve the CI of BD compared to a placebo.

METHODS

We conducted a placebo-controlled, 8-week trial of JNJ-18038683 in BD patients. Each patient's data were analyzed and reassessed blindly with a comprehensive neuropsychological battery, depression and hypomania ratings, and overall social and work function measures.

RESULTS

Of 60 patients, 38 (63%) were female, 43 (72%) had BD type 1, and most patients were Caucasian and married. The overall time effect for the combined group shows statistically significant improvement from baseline to week 8 for most of the neurocognitive battery measures. This indicates a significant improvement in psychopathology and cognition during the study time in both JNJ-18038683 and placebo groups, but no difference between groups.

CONCLUSIONS

This study showed no efficacy for the improvement of CIBD or mood symptoms with JNJ-18038683 compared to the placebo.

Disentangling age- and disease-related alterations in schizophrenia brain network using structural equation modeling: A graph theoretical study based on minimum spanning tree

Functional brain networks have been shown to undergo fundamental changes associated with aging or schizophrenia. However, the mechanism of how these factors exert influences jointly or interactively on brain networks remains elusive. A unified recognition of connectomic alteration patterns was also hampered by heterogeneities in network construction and thresholding methods. Recently, an unbiased network representation method regardless of network thresholding, so called minimal spanning tree algorithm, has been applied to study the critical skeleton of the brain network. In this study, we aimed to use minimum spanning tree (MST) as an unbiased network reconstruction and employed structural equation modeling (SEM) to unravel intertwined relationships among multiple phenotypic and connectomic variables in schizophrenia. First, we examined global and local brain network properties in 40 healthy subjects and 40 schizophrenic patients aged 21–55 using resting‐state functional magnetic resonance imaging (rs‐fMRI). Global network alterations are measured by graph theoretical metrics of MSTs and a connectivity‐transitivity two‐dimensional approach was proposed to characterize nodal roles. We found that networks of schizophrenic patients exhibited a more star‐like global structure compared to controls, indicating excessive integration, and a loss of regional transitivity in the dorsal frontal cortex (corrected p <.05). Regional analysis of MST network topology revealed that schizophrenia patients had more network hubs in frontal regions, which may be linked to the “overloading” hypothesis. Furthermore, using SEM, we found that the level of MST integration mediated the influence of age on negative symptom severity (indirect effect 95% CI [0.026, 0.449]). These findings highlighted an altered network skeleton in schizophrenia and suggested that aging‐related enhancement of network integration may undermine functional specialization of distinct neural systems and result in aggravated schizophrenic symptoms.

Early Identification and Intervention of Schizophrenia: Insight From Hypotheses of Glutamate Dysfunction and Oxidative Stress

Schizophrenia is a severe mental disorder which leads to functional deterioration. Early detection and intervention are vital for better prognosis. However, the diagnosis of schizophrenia still depends on clinical observation to date. Without reliable biomarkers, schizophrenia is difficult to detect in its early phase. Further, there is no approved medication for prodromal schizophrenia because current antipsychotics fail to show satisfactory efficacy and safety. Therefore, to develop an effective early diagnostic and therapeutic approach for schizophrenia, especially in its prodromal phase, is crucial. Glutamate signaling dysfunction and dysregulation of oxidative stress have been considered to play important roles in schizophrenic prodrome. The N-methyl-D-aspartate receptor (NMDAR) is one of three types of ionotropic glutamate receptors. In this article, we reviewed literature regarding NMDAR hypofunction, oxidative stress, and the linkage between both in prodromal schizophrenia. The efficacy of NMDAR enhancers such as D-amino acid oxidase inhibitor was addressed. Finally, we highlighted potential biomarkers related to NMDAR and oxidative stress regulation, and therefore suggested the strategies of early detection and intervention of prodromal schizophrenia. Future larger-scale studies combining biomarkers and novel drug development for early psychosis are warranted.

Schizophrenia and risk of dementia: a meta-analysis study

BACKGROUND

Evidence suggests that schizophrenia may be associated with an increased risk of dementia, but results from prior studies have been inconsistent. This study aimed to estimate the relationship between schizophrenia and incident dementia using a quantitative meta-analysis.

METHODS

Several databases were used to gather relevant information, including PubMed, Embase, and Web of Science, with the publication date of articles limited up to December 23, 2017. All studies reported a multivariate-adjusted estimate, represented as relative risk (RR) with 95% confidence intervals (CIs), for the association between schizophrenia and risk of dementia incidence. Pooled RRs were calculated using a random-effects model.

RESULTS

Six studies met our inclusion criteria for this meta-analysis, which included 206,694 cases of dementia and 5,063,316 participants. All individuals were without dementia at baseline. Overall, the quantitative meta-analysis suggested that subjects with schizophrenia were associated with a significantly greater risk of dementia incidence (RR 2.29; 95% CI 1.35-3.88) than those without.

CONCLUSION

The results of this meta-analysis indicate that individuals with schizophrenia may have an increased risk for the development of dementia. Future studies should explore whether schizophrenia is a modifiable risk factor for dementia.

The Etiology of Hoarding Disorder: A Review

This article will review the evidence of various proposed factors that contribute to the onset and maintenance of hoarding disorder (HD). Data suggests that hoarding is a chronic condition that starts early in life and does not remit if left untreated. There is emerging evidence that a number of factors contribute to the expression of HD symptoms, including genetics, neurocognitive functioning, attachments to possessions, beliefs, avoidance, personality factors, and life events. The extent to which each etiological factor uniquely contributes to hoarding is still unknown. Other demographic factors, such as socioeconomic status, age, and gender, may impact hoarding severity. Research on the causes and characteristics of hoarding has recently started making progress into understanding this newly recognized disorder, yet we still have a ways to go in understanding the biological and environmental causes. This paper will synthesize available literature on the etiology of HD.

Assessment of Lifespan Functioning Attainment (ALFA) scale: A quantitative interview for self-reported current and functional decline in schizophrenia

Schizophrenia has been characterized as a disorder with poor outcomes across various functional domains, especially social and occupational functioning. Although these outcomes have been investigated based on patients' current functioning, few studies have considered the assessment of functional outcomes across the lifespan in schizophrenia. We developed a novel and brief scale of adulthood lifespan functioning, the Assessment of Lifespan Functioning Attainment (ALFA). We assessed current functioning and percentage of pre- and post-psychosis onset engagement for five functional domains including paid employment, living independently, romantic partnerships, close friendships, and recreational engagement with others. Pre-to post-psychosis functional decline was observed for all domains, with paid employment having the greatest decline (d = 2.68) and living independently having the least decline (d = .59). Our exploratory factor analysis suggests that a single factor accounted for the most variance in Pre-Psychosis Functioning in ALFA domains. Two factors explain the majority of variance in Post-Psychosis Functioning and Pre-to-Post Psychosis Decline: a sociability factor (close friendships and recreational engagement with others) and an independence factor (paid employment, living independently, romantic relationships). To our knowledge, this is the first study to report on a self-reported quantitative assessment of adult lifespan functioning in schizophrenia. The ALFA scale may be a useful tool for future research on functional outcomes in schizophrenia.

Neurodevelopmental origin of cognitive impairment in schizophrenia

Cognitive impairment is a common feature of schizophrenia; however, its origin remains controversial. Neurodevelopmental abnormalities clearly play a role in pre-morbid cognitive dysfunction in schizophrenia, yet many authors believe that schizophrenia is characterized by illness-related cognitive decline before and after onset of the psychosis that can be the result of neurodegenerative changes. The main reasons behinds such arguments include, first, the evidence showing that effect sizes of the cognitive deficits in subjects who develop adult schizophrenia gradually increase in the first two decades of life and, second, the fact that there is functional decline in many patients with schizophrenia over the years. In this Editorial, I argue that current evidence suggests that illness-related cognitive impairment is neurodevelopmental in origin and characterized by slower gain (developmental lag) but not cognitive decline continuing throughout the first two decades of life. I introduce a model suggesting that neurodevelopmental abnormality can in fact explain the course of cognitive dysfunction and variations in the trajectory of functional decline throughout the life in individuals with schizophrenia. In this model, the severity of underlying neurodevelopmental abnormality determines the age that cognitive deficits first become apparent and contributes to the cognitive reserve of the individual. Interaction of neurodevelopmental abnormality with clinical symptoms, especially negative symptoms and aging, vascular changes, psychological and iatrogenic factors contributes to the heterogeneity of the functional trajectory observed in this disorder.

A longitudinal study of cognitive functioning in schizophrenia: clinical and biological predictors

BACKGROUND

Cognitive deficits are a central feature of schizophrenia but it is not certain how cognitive functioning changes over time. The purpose of this prospective longitudinal study was to determine the temporal change of cognitive functioning and the predictors of cognitive performance from among demographic, clinical, and biological variables.

METHODS

Participants were individuals with schizophrenia or schizoaffective disorder whose cognitive functioning was assessed at multiple time points with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). At the baseline visit participants had a blood sample drawn from which C-reactive protein, antibodies to Herpes Simplex Virus type 1, and selected genetic polymorphisms were measured. Repeated measures linear regression was used to determine whether cognitive measures changed over time and which variables predicted cognitive performance.

RESULTS

The sample consisted of 132 participants, mean age 43.7 years at baseline, who received a median of 3 cognitive assessments over a period averaging 2.8 years. The RBANS Total score and Language index showed no statistically significant temporal change; performance on two indices, Immediate Memory and Attention, showed modest but statistically significant improvements (gains of 0.89±0.33 and 0.76±0.29 points per year, respectively); Visuospatial/Constructional performance showed a modest but statistically significant decline (of 0.80±0.25 points per year). Few variables predicted cognitive performance; however greater psychiatric symptom severity was associated with worse cognitive performance for most cognitive measures.

CONCLUSIONS

Cognitive functioning in middle-aged persons with schizophrenia showed an absence of decline for most measures and modest gains in some measures.

Functional connectivity-based signatures of schizophrenia revealed by multiclass pattern analysis of resting-state fMRI from schizophrenic patients and their healthy siblings

BACKGROUND

Recently, a growing number of neuroimaging studies have begun to investigate the brains of schizophrenic patients and their healthy siblings to identify heritable biomarkers of this complex disorder. The objective of this study was to use multiclass pattern analysis to investigate the inheritable characters of schizophrenia at the individual level, by comparing whole-brain resting-state functional connectivity of patients with schizophrenia to their healthy siblings.

METHODS

Twenty-four schizophrenic patients, twenty-five healthy siblings and twenty-two matched healthy controls underwent the resting-state functional Magnetic Resonance Imaging (rs-fMRI) scanning. A linear support vector machine along with principal component analysis was used to solve the multi-classification problem. By reconstructing the functional connectivities with high discriminative power, three types of functional connectivity-based signatures were identified: (i) state connectivity patterns, which characterize the nature of disruption in the brain network of patients with schizophrenia; (ii) trait connectivity patterns, reflecting shared connectivities of dysfunction in patients with schizophrenia and their healthy siblings, thereby providing a possible neuroendophenotype and revealing the genetic vulnerability to develop schizophrenia; and (iii) compensatory connectivity patterns, which underlie special brain connectivities by which healthy siblings might compensate for an increased genetic risk for developing schizophrenia.

RESULTS

Our multiclass pattern analysis achieved 62.0% accuracy via leave-one-out cross-validation (p < 0.001). The identified state patterns related to the default mode network, the executive control network and the cerebellum. For the trait patterns, functional connectivities between the cerebellum and the prefrontal lobe, the middle temporal gyrus, the thalamus and the middle temporal poles were identified. Connectivities among the right precuneus, the left middle temporal gyrus, the left angular and the left rectus, as well as connectivities between the cingulate cortex and the left rectus showed higher discriminative power in the compensatory patterns.

CONCLUSIONS

Based on our experimental results, we saw some indication of differences in functional connectivity patterns in the healthy siblings of schizophrenic patients compared to other healthy individuals who have no relations with the patients. Our preliminary investigation suggested that the use of resting-state functional connectivities as classification features to discriminate among schizophrenic patients, their healthy siblings and healthy controls is meaningful.

The biology of schizophrenia

Schizophrenia is an illness where the clinical signs and symptoms, course, and cognitive characteristics are well described. Successful pharmacological treatments do exist, even though they are likely palliative. However, this broad knowledge base has not yet led to the identification of its pathophysiology or etiology The risk factors for schizophrenia are most prominently genetic and scientists anticipate that contributions from the new genetic information in the human genome will help progress towards discovering a disease mechanism. Brain-imaging techniques have opened up the schizophrenic brain for direct inquiries, in terms of structure, neurochemisiry, and function. New proposals for diagnosis include grouping schizophrenia together with schizophrenia-related personality disorders into the same disease entity, and calling this schizophrenia spectrum disorder. New hypotheses of pathophysiology do not overlook dopamine as playing a major role, but do emphasize the participation of integrative neural systems in the expression of the illness and of the limbic system in generating symptoms. Critical observations for future discovery are likely to arise from molecular genetics, combined with hypothesis-generating experiments using brain imaging and human postmortem tissue.

Schizophrenia: from epidemiology to rehabilitation

Purpose/Objective:

We discuss recent evidences about schizophrenia (frequency, onset, course, risk factors and genetics) and their influences to some epidemiological myths about schizophrenia diffuse between psychiatric and psychopathology clinicians. The scope is to evaluate if the new acquisitions may change the rehabilitation approaches to schizophrenia modifying the balance about the neurodevelopmental hypothesis of schizophrenia accepting that the cognitive deficits are produced by errors during the normal development of the brain (neurodevelopmental hypothesis) that remains stable in the course of illness and the neurodegenerative hypothesis according of which they derived from a degenerative process that goes on inexorably.

Research Method/Design:

A review of the literature about epidemiology of schizophrenia has been performed and the contributions of some of these evidence to neurodevelopmental hypothesis and to rehabilitation has been described.

Results:

It cannot be definitively concluded for or against the neurodevelopmental or degenerative hypothesis, but efforts in understanding basis of schizophrenia must go on. Until now, rehabilitation programs are based on the vulnerability-stress model: supposing an early deficit that go on stable during the life under favorable circumstances. So, rehabilitation approaches (as neuro-cognitive approaches, social skill training, cognitive-emotional training) are focused on the individual and micro-group coping skills, aiming to help people with schizophrenia to cope with environmental stress factors.

Conclusions/Implications:

Coping of cognitive deficits in schizophrenia may represents the starting-point for further research on schizophrenia, cohort studies and randomized trials are necessary to defined the range of effectiveness and the outcome of the treatments.

Abnormalities in the tricarboxylic acid (TCA) cycle in the brains of schizophrenia patients

Images of brain metabolism and measurements of activities of components of the electron transport chain support earlier studies that suggest that brain glucose oxidation is inherently abnormal in a significant proportion of persons with schizophrenia. Therefore, we measured the activities of enzymes of the tricarboxylic (TCA) cycle in dorsolateral-prefrontal-cortex from schizophrenia patients (N=13) and non-psychiatric disease controls (N=13): the pyruvate dehydrogenase complex (PDHC), citrate synthase (CS), aconitase, isocitrate dehydrogenase (ICDH), the alpha-ketoglutarate dehydrogenase complex (KGDHC), succinate thiokinase (STH), succinate dehydrogenase (SDH), fumarase and malate dehydrogenase (MDH). Activities of aconitase (18.4%, p<0.05), KGDHC (26%) and STH (28.2%, p<0.05), enzymes in the first half of the TCA cycle, were lower, but SDH (18.3%, p<0.05) and MDH (34%, p<0.005), enzymes in the second half, were higher than controls. PDHC, CS, ICDH and fumarase activities were unchanged. There were no significant correlations between enzymes of TCA cycle and cognitive function, age or choline acetyl transferase activity, except for aconitase activity which decreased slightly with age (r=0.55, p=003). The increased activities of dehydrogenases in the second half of the TCA cycle may reflect a compensatory response to reduced activities of enzymes in the first half. Such alterations in the components of TCA cycle are adequate to alter the rate of brain metabolism. These results are consistent with the imaging studies of hypometabolism in schizophrenia. They suggest that deficiencies in mitochondrial enzymes can be associated with mental disease that takes the form of schizophrenia.

Discriminative analysis of resting-state functional connectivity patterns of schizophrenia using low dimensional embedding of fMRI

Recently, a functional disconnectivity hypothesis of schizophrenia has been proposed for the physiological explanation of behavioral syndromes of this complex mental disorder. In this paper, we aim at further examining whether syndromes of schizophrenia could be decoded by some special spatiotemporal patterns of resting-state functional connectivity. We designed a data-driven classifier based on machine learning to extract highly discriminative functional connectivity features and to discriminate schizophrenic patients from healthy controls. The proposed classifier consisted of two separate steps. First, we used feature selection based on a correlation coefficient method to extract highly discriminative regions and construct the optimal feature set for classification. Then, an unsupervised-learning classifier combining low-dimensional embedding and self-organized clustering of fMRI was trained to discriminate schizophrenic patients from healthy controls. The performance of the classifier was tested using a leave-one-out cross-validation strategy. The experimental results demonstrated not only high classification accuracy (93.75% for schizophrenic patients, 75.0% for healthy controls), but also good generalization and stability with respect to the number of extracted features. In addition, some functional connectivities between certain brain regions of the cerebellum and frontal cortex were found to exhibit the highest discriminative power, which might provide further evidence for the cognitive dysmetria hypothesis of schizophrenia. This primary study demonstrated that machine learning could extract exciting new information from the resting-state activity of a brain with schizophrenia, which might have potential ability to improve current diagnosis and treatment evaluation of schizophrenia.

What do we know about neuropsychological aspects of schizophrenia?

Application of a neuropsychological perspective to the study of schizophrenia has established a number of important facts about this disorder. Some of the key findings from the existing literature are that, while neurocognitive impairment is present in most, if not all, persons with schizophrenia, there is both substantial interpatient heterogeneity and remarkable within-patient stability of cognitive function over the long-term course of the illness. Such findings have contributed to the firm establishment of neurobiologic models of schizophrenia, and thereby help to reduce the social stigma that was sometimes associated with purely psychogenic models popular during parts of the 20th century. Neuropsychological studies in recent decades have established the primacy of cognitive functions over psychopathologic symptoms as determinants of functional capacity and independence in everyday functioning. Although the cognitive benefits of both conventional and even second generation antipsychotic medications appear marginal at best, recognition of the primacy of cognitive deficits as determinants of functional disability in schizophrenia has catalyzed recent efforts to develop targeted treatments for the cognitive deficits of this disorder. Despite these accomplishments, however, some issues remain to be resolved. Efforts to firmly establish the specific neurocognitive/neuropathologic systems responsible for schizophrenia remain elusive, as do efforts to definitively demonstrate the specific cognitive deficits underlying specific forms of functional impairment. Further progress may be fostered by recent initiatives to integrate neuropsychological studies with experimental neuroscience, perhaps leading to measures of deficits in cognitive processes more clearly associated with specific, identifiable brain systems.

Neonatal lesions of the ventral hippocampus in rats lead to prefrontal cognitive deficits at two maturational stages

This experiment assessed the effect of neonatal ventral hippocampus lesions in rats, a heuristic approach to model schizophrenia, on continuous delayed alternation and conditional discrimination learning performance before and after complete cerebral maturation. Delays (0, 5, 15, and 30 s) were introduced in the tasks to help dissociate between a hippocampal and a prefrontal cortex dysfunction. At postnatal day (PND) 6 or 7, rats received bilateral microinjections of ibotenic acid or phosphate-buffered saline in the ventral hippocampus. From PND 26 to PND 35, rats were tested on the alternation task in a T-maze; from PND 47 to PND 85, the same rats were tested in the discrimination task where a stimulus and a response location had to be paired. Deficits in ventral hippocampus-lesioned rats were observed in both tasks whether a delay was introduced before a response or not. Impaired performance regardless of delay length, combined with high rates of perseverative errors, suggested a post-lesional prefrontal cortex dysfunction which persisted from the juvenile stage into adulthood. Premature cognitive impairments could not be predicted on the basis of the neurodevelopmental animal model of schizophrenia. Nevertheless, they appear consistent with accounts of premorbidly compromised memory, both immediate and delayed, in subgroups of schizophrenia patients.

The Primacy of Cognition in Schizophrenia

Cognitive tasks and concepts are used increasingly in schizophrenia science and treatment. Recent meta-analyses show that across a spectrum of research domains only cognitive measures distinguish a majority of schizophrenia patients from healthy people. Average effect sizes derived from common clinical tests of attention, memory, language, and reasoning are twice as large as those obtained in structural magnetic resonance imaging and positron emission tomography studies. Chronic stress, genes, brain disturbances, task structure, gender, and sociocultural background may all enhance the sensitivity of cognitive performance to schizophrenia. At the same time, disease heterogeneity and the presence of endophenotypes and subtypes within the patient population may place upper limits on the strength of any specific cognitive finding. Schizophrenia is a complex biobehavioral disorder that manifests itself primarily in cognition.

Differential effects of typical and atypical antipsychotics on nerve growth factor and choline acetyltransferase expression in the cortex and nucleus basalis of rats

Previously we reported that chronic exposure to haloperidol (HAL), but not the atypical antipsychotics risperidone (RISP) or clozapine (CLOZ), resulted in reductions in brain choline acetyltransferase (ChAT) immunoreactivity and impaired water maze task performance in rats. In the present study, we compared the effects of these antipsychotic drugs on the expression of nerve growth factor (NGF) as well ChAT the in the rat cortex and nucleus basalis of Meynert (NBM) in an effort to determine the underlying mechanism for the differential drug effects observed previously. We also evaluated the effects of these compounds in a crossover design to evaluate specific neurochemical consequences of switching between typical and atypical antipsychotics, a common practice observed in the clinical setting. Male Wistar rats (250-300 g) were exposed to HAL (2.0 mg/kg/day), RISP (2.5 mg/kg/day), or CLOZ (20 mg/kg/day) for 45 days or a pre-treatment regimen consisting of administering either RISP/HAL (i.e., RISP followed by HAL) or CLOZ/HAL, or a post-treatment regimen consisting of administering: HAL/RISP or HAL/CLOZ. The duration of each treatment in the crossover study was also 45 days. NGF and ChAT immunoreactivity were measured by quantitative immunohistochemistry in some sub-cerebral cortical regions and NBM after drug exposures. NGF protein was also measured by an enzyme-linked ImmunoSorbent assay (ELISA) in rat sensorimotor cortex. The results indicated that HAL (but not RISP or CLOZ) significantly reduced NGF levels in some sub-cortical regions and ChAT immunoreactivity in both cortex and NBM. However, pre-treatment with CLOZ prevented the HAL-associated decreases in NGF and ChAT, while post-treatment with either RISP or CLOZ (i.e., after the administration of HAL) appeared to restore NGF and ChAT to control levels. These data indicate that antipsychotic drugs exert dissimilar effects on the levels of NGF and ChAT in the brain, which may contribute to their differential effects on cognitive function. The crossover data further suggest that certain atypical antipsychotic drugs (e.g., clozapine) may have the potential to prevent or reverse the deleterious effects of HAL on important neurochemical substrates of cognitive function.

Review of cognition and brain structure in schizophrenia: profiles, longitudinal course, and effects of treatment

Research on the cognitive and brain structural correlates of schizophrenia has seen tremendous progress over the past decade. It has become increasingly clear that there is no pathognomic neuropsychological or structural neuroanatomic profile in schizophrenia, likely due in part to etiological heterogeneity within the disorder. Nonetheless, several studies have indicated that verbal episodic memory and vigilance deficits are particularly prominent, and are observed even in untreated patients in their first episode of the disorder. The course of schizophrenia appears to be somewhat variable, and factors that contribute to the development of the illness, and in some patients, deterioration of cognitive functioning, have not been elucidated clearly. Neurodevelopmental factors, however, likely play an important role in the diathesis of the disorder, while neuropathological processes contribute to deterioration and progression. At this time, there are relatively few controlled comparisons of the cognitive effects of atypical and conventional antipsychotic medications. Additional studies of the potential effects of antipsychotic medications on structural brain abnormalities are warranted. It is hoped that newer innovative psychopharmacological approaches and neuropsychological remediation programs will, in the not-too-distant future, provide clinicians with a variety of means to improve the cognitive and social functioning of their patients.

Neuropsychological differentiation of late-onset schizophrenia and dementia of the Alzheimer's type

Late-onset schizophrenia and dementia of the Alzheimer's type (DAT) often present with some pathological and behavioral commonalities. Specifically, both illnesses may involve varying degrees of delusional manifestation, apathy, lateral/third-ventricular enlargement, reduced frontal lobe activity, and hippocampal atrophy. Moreover, patients with either disease have shown comparable cognitive impairment on standardized neuropsychological tests. As such, a differential diagnosis of the 2 disorders on the basis of such testing can prove to be difficult. This study evaluated the neuropsychological test results of 32 patients with late-onset schizophrenia and 32 patients with DAT to distinguish the tests that best differentiate the 2 disorders. Results indicate that the Wechsler Adult Intelligence Scale-Revised Similarities subtest and the California Verbal Learning Test (both short- and long-delay free recall) correspond to sensitive diagnostic neuropsychological measures. This investigation was preliminary in nature, and should aid in the development of a definitive differential profile.

Does schizophrenia result from developmental or degenerative processes?

The debate as to whether schizophrenia is a neurodevelopmental or a neurodegenerative disorder has its roots in the latter part of the 19th century when authorities such as Clouston (1891) posited that at least some insanities were "developmental" in origin. These views were soon eclipsed by Kraepelin's (1896) concept of dementia praecox as a degenerative disease, and the latter view carried not only the day but also much of the 20th century. Then, in the 1980s several research groups again began to speculate that schizophrenia might have a significant developmental component (Feinberg, 1982-1983; Schulsinger et al., 1984; Murray et al., 1985; Murray and Lewis, 1987; Weinberger et al., 1987). What became known as the "neurodevelopmental hypothesis" received support from neuropathological studies implicating anomalies in early brain development such as aberrant migration of neurons. Unfortunately, these studies proved difficult, if not impossible, to replicate (Harrison, 1999). The pendulum, therefore, began to swing again, and in the latter part of the 1990s came renewed claims that the clinical progression of the illness was accompanied by continued cerebral ventricular enlargement and reduction in the volumes of certain brain structures. Nevertheless, since few doubt that there is a developmental component to schizophrenia, the question which we will address in this paper is whether schizophrenia is a) simply the final consequence of a cascade of increasing developmental deviance (Bramon et al., 2001), or b) whether there is an additional brain degeneration following onset of psychosis which is superimposed on the developmental impairment (Lieberman, 1999).

Differential effects of haloperidol, risperidone, and clozapine exposure on cholinergic markers and spatial learning performance in rats

Haloperidol (HAL), a potent typical antipsychotic, continues to be a frequently prescribed medication for behavioral disturbances associated particularly with schizophrenia despite well-documented adverse effects associated with its chronic use. Animal experiments have even indicated that HAL can damage cholinergic pathways and thus could be especially deleterious to those experiencing cognitive deficits. However, several recent clinical studies indicate that atypical antipsychotics may actually improve cognitive function in some patients, although this assertion requires further investigation. The purpose of this study was to compare the effects of prior chronic (45- or 90-day) oral exposure to HAL and the atypical antipsychotics risperidone (RISP) and clozapine (CLOZ) on cognitive performance and central cholinergic markers in rats. All analyses were done after 4 days of drug washout in order to minimize direct drug effects. Learning performance and choline acetyltransferase (ChAT) levels were assessed in a water maze task and with immunofluorescence staining, respectively. HAL significantly impaired learning performance after 90 but not after 45 days of treatment when compared to both vehicle controls and the atypical agents, while RISP slightly improved task performance. Both 45 and 90 days of previous HAL exposure reduced ChAT staining in several brain regions, including the cortex, caudate-putamen, and hippocampus. ChAT staining in the caudate-putamen and hippocampus was also decreased after 90 days of RISP exposure, raising the possibility of deleterious cognitive effects after exposure to this dosage for longer periods of time. The results suggest that antipsychotic drugs exert differential and temporally dependent effects on central cholinergic neurons and learning performance.