Visual object processing in schizophrenia: evidence for an associative agnosic deficit

Validity of the Test of Visual Perceptual Skills-Fourth Edition in People With Schizophrenia

IMPORTANCE

The Test of Visual Perceptual Skills-Fourth Edition (TVPS-4), which utilizes seven subscales, comprehensively assesses visual perception.

OBJECTIVE

To examine the ecological, convergent, and discriminative validities of the TVPS-4 in the assessment of people with schizophrenia.

DESIGN

Prospective and observational study.

SETTING

Community rehabilitation facilities.

PARTICIPANTS

Eighty people with schizophrenia.

OUTCOMES AND MEASURES

To examine ecological validity, we estimated correlations (Pearson's r) between the TVPS-4 scores (i.e., overall scale and subscales) and the Activities of Daily Living Rating Scale-III (ADLRS-III). To examine convergent validity, we computed the correlations (r) between the TVPS-4 scores and two cognitive measures. An analysis of variance was applied to compare the TVPS-4 scores in groups with different disease severities to examine discriminative validity.

RESULTS

Moderate to strong correlations were found between TVPS-4 scores and ADLRS-III scores (rs = .33-.61) and between TVPS-4 scores and two cognitive measures (rs = .44-.70). TVPS-4 scores could discriminate among the three groups with different severities of psychiatric illnesses (p < .05), except for two subscales (Visual Memory and Spatial Relationships).

CONCLUSIONS AND RELEVANCE

The TVPS-4 has sufficient ecological validity, good convergent validity, and acceptable discriminative validity in assessing people with schizophrenia. The Spatial Relationships subscale, which displays a strong correlation with the ADLRS-III, can reveal the status of daily living in people with schizophrenia. Two subscales showing inadequate discriminative validity should be used cautiously to discriminate people with different severities of schizophrenia. What This Article Adds: The TVPS-4 showed three sound validities (ecological, convergent, and discriminative) for assessing visual perception in people with schizophrenia.

Visual processing deficits in patients with schizophrenia spectrum and bipolar disorders and associations with psychotic symptoms, and intellectual abilities

Objective

Low-level sensory disruption is hypothesized as a precursor to clinical and cognitive symptoms in severe mental disorders. We compared visual discrimination performance in patients with schizophrenia spectrum disorder or bipolar disorder with healthy controls, and investigated associations with clinical symptoms and IQ.

Methods

Patients with schizophrenia spectrum disorder (n = 32), bipolar disorder (n = 55) and healthy controls (n = 152) completed a computerized visual discrimination task. Participants responded whether the latter of two consecutive grids had higher or lower spatial frequency, and discrimination thresholds were estimated using an adaptive maximum likelihood procedure. Case-control differences in threshold were assessed using linear regression, F-test and post-hoc pair-wise comparisons. Linear models were used to test for associations between visual discrimination threshold and psychotic symptoms derived from the PANSS and IQ assessed using the Matrix Reasoning and Vocabulary subtests from the Wechsler Abbreviated Scale of Intelligence (WASI).

Results

Robust regression revealed a significant main effect of diagnosis on discrimination threshold (robust F = 6.76, p = .001). Post-hoc comparisons revealed that patients with a schizophrenia spectrum disorder (mean = 14%, SD = 0.08) had higher thresholds compared to healthy controls (mean = 10.8%, SD = 0.07, β = 0.35, t = 3.4, p = .002), as did patients with bipolar disorder (12.23%, SD = 0.07, β = 0.21, t = 2.42, p = .04). There was no significant difference between bipolar disorder and schizophrenia (β = -0.14, t = -1.2, p = .45). Linear models revealed negative associations between IQ and threshold across all participants when controlling for diagnostic group (β = -0.3, t = -3.43, p = .0007). This association was found within healthy controls (t = -3.72, p = .0003) and patients with bipolar disorder (t = -2.53, p = .015), and no significant group by IQ interaction on threshold (F = 0.044, p = .97). There were no significant associations between PANSS domain scores and discrimination threshold.

Conclusion

Patients with schizophrenia spectrum or bipolar disorders exhibited higher visual discrimination thresholds than healthy controls, supporting early visual deficits among patients with severe mental illness. Discrimination threshold was negatively associated with IQ among healthy controls and bipolar disorder patients. These findings elucidate perception-related disease mechanisms in severe mental illness, which warrants replication in independent samples.

Retinal ganglion cell dysfunction is correlated with disturbed visual cognition in schizophrenia patients with visual hallucinations

Patients with schizophrenia have altered visual cognition and retinal functions. No studies have explored if retinal anomalies are related to visual cognition and the presence of visual hallucinations (VH). We explored functional responses of the retinal ganglion cells in schizophrenia patients with or without VH and conducted a neuropsychological evaluation to explore the links between cognition and retinal function. The VH+ group showed poorer visual cognition and we found correlations between the amplitudes of the P50 and the N95 waves and visual cognition. Our results provide arguments for a link between retinal dysfunction, impaired visual processing and VH in schizophrenia.

A Natural Product with High Affinity to Sigma and 5-HT7 Receptors as Novel Therapeutic Drug for Negative and Cognitive Symptoms of Schizophrenia

Dehydrocorybulbine (DHCB), an alkaloid from Corydalis yanhusuo. W.T, has been identified as a dopamine receptor antagonist. We extended our assessment of its pharmacological profile and found that DHCB exhibits high to moderate binding affinities to sigma 1 and 2 receptors, serotonin 5-HT7 receptor, and histamine H2 receptors. This led us to evaluate DHCB properties in pharmacological (apomorphine and MK-801) animal models of schizophrenia in mice. The pharmacological profile of DHCB was screened through radioligand receptor binding assays. Single dose of DHCB reversed the locomotor hyperactivity, stereotypy, and prepulse inhibition deficits induced by the dopaminergic agonist apomorphine. DHCB also reversed the depressive-like behavior and memory deficit induced by the glutamatergic antagonist MK-801 in the forced swim and the novel object recognition assays, respectively. These results indicate that DHCB effectively improves schizophrenia-like behavioral deficits that are induced by the disruption of dopaminergic and glutamatergic systems. The effectiveness of DHCB in reversing responses that mimic negative and cognitive deficits of schizophrenia might suggest that its anti-schizophrenia effects are mediated through modulating the activities of several receptor particularly sigma 1, sigma 2, 5-HT7 and dopamine receptors. Our study casts DHCB as a promising lead for therapeutic treatment of schizophrenia.

Development and preliminary validation of a brief behavioral measure of psychotic propensity

Extensive research demonstrates that the dimensional assessment of psychotic manifestations is a primary strength of the Rorschach inkblot task, which provides an in vivo sample of problem-solving behavior and normative standards concerning the logic and coherence of thought processes and the typicality of perceptual representations. This article presents foundational research for the Thought and Perception Assessment System (TPAS), a Rorschach-based system designed to assess solely for disordered thinking and perceptual aberrations using either the standard 10-card set of inkblots or alternative 3-, 4-, and 5-card short forms. Using data from three patient samples (ns = 61, 93, and 133) and one nonpatient sample (n = 118), we document the equivalence of mean scores across the full and short-form card sets. We also document satisfactory interrater reliability and validity for the full and short forms, as well as strong part-whole reliability coefficients between the short forms and the full form. Consistent with psychometric theory and the principle of aggregation, each type of coefficient decreased as a function of decreasing the number of cards. We discuss implications and future applications in research and clinical assessment.

Albizia zygia root extract exhibits antipsychotic-like properties in murine models of schizophrenia

BACKGROUND

The root extract of Albizia zygia (DC.) J.F. Macbr. (Leguminosae) is used to manage mental disorders in African traditional medicine. However, its value, particularly, against negative and cognitive symptoms of schizophrenia have not been evaluated.

AIM

The aim of this study was to evaluate the antipsychotic properties of the hydroethanolic root extract of Albizia zygia (AZE) against positive, negative and cognitive symptoms of schizophrenia in animal models.

MATERIALS AND METHODS

The effects of AZE (30-300 mg kg^-1) were evaluated against apomorphine-induced cage climbing as well as ketamine -induced hyperlocomotion, -enhanced immobility, -impaired social interaction and novel object recognition. The propensity of AZE to induce catalepsy and to attenuate haloperidol-induced catalepsy were also investigated.

RESULTS

AZE 30-300 mg kg^-1 significantly reduced apomorphine-induced climbing behaviour as well as ketamine-induced hyperlocomotion, immobility and object recognition deficits (at least P < 0.05). Moreover, the extract showed no cataleptic effect but significantly inhibited haloperidol-induced catalepsy at a dose of 30 mg kg^-1 (P < 0.05).

CONCLUSION

The root extract of Albizia zygia exhibited an antipsychotic-like activity in mice with potential to alleviate positive, negative and cognitive symptoms of schizophrenia.

Is Forced Swimming Immobility a Good Endpoint for Modeling Negative Symptoms of Schizophrenia? - Study of Sub-Anesthetic Ketamine Repeated Administration Effects

Immobility time in the forced swimming has been described as analogous to emotional blunting or apathy and has been used for characterizing schizophrenia animal models. Several clinical studies support the use of NMDA receptor antagonists to model schizophrenia in rodents. Some works describe the effects of ketamine on immobility behavior but there is variability in the experimental design used leading to controversial results. In this study, we evaluated the effects of repeated administration of ketamine sub-anesthetic doses in forced swimming, locomotion in response to novelty and novel object recognition, aiming a broader evaluation of the usefulness of this experimental approach for modeling schizophrenia in mice. Ketamine (30 mg/kg/day i.p. for 14 days) induced a not persistent decrease in immobility time, detected 24h but not 72h after treatment. This same administration protocol induced a deficit in novel object recognition. No change was observed in mice locomotion. Our results confirm that repeated administration of sub-anesthetic doses of ketamine is useful in modeling schizophrenia-related behavioral changes in mice. However, the immobility time during forced swimming does not seem to be a good endpoint to evaluate the modeling of negative symptoms in NMDAR antagonist animal models of schizophrenia.

Estradiol and raloxifene modulate hippocampal gamma oscillations during a spatial memory task

Previous work suggests that estradiol regulates the expression of hippocampal parvalbumin as well as hippocampus-dependent spatial memory in mice. Parvalbumin interneurons generate neuronal oscillatory activity in the gamma frequency range (30-80Hz) and gamma oscillations are closely linked with higher cognitive functions. Raloxifene, a selective estrogen receptor modulator, shows beneficial effects on human cognitive performance, and has few peripheral side effects unlike estradiol, but the biological mechanisms which underpin these benefits are not clear. This study aimed to investigate whether estradiol and raloxifene modulate hippocampal gamma-band oscillations during spatial memory performance. Prepubescent female mice were ovariectomized (OVX) and implanted with a subcutaneous pellet of either estradiol (E2), raloxifene or placebo. During adulthood, local field potentials were recorded from the dorsal hippocampus while mice were performing the Y-maze hippocampus-dependent spatial memory task. Ovariectomy caused deficits in spatial memory, accompanied by a significant reduction in hippocampal gamma oscillations, specifically during decision making. Estradiol as well as raloxifene rescued both behavioural and electrophysiological deficits. These data have significant implications for disorders of cognitive impairment where altered gamma oscillations are apparent, such as schizophrenia.

A Methionine-Induced Animal Model of Schizophrenia: Face and Predictive Validity

BACKGROUND

Modulating the methylation process induces broad biochemical changes, some of which may be involved in schizophrenia. Methylation is in particular central to epigenesis, which is also recognized as a factor in the etiology of schizophrenia. Because methionine administration to patients with schizophrenia has been reported to exacerbate their psychotic symptoms and because mice treated with methionine exhibited social deficits and prepulse inhibition impairment, we investigated whether methionine administration could lead to behavioral changes that reflect schizophrenic symptoms in mice.

METHODS

l-Methionine was administered to mice twice a day for 7 days.

RESULTS

We found that this treatment induces behavioral responses that reflect the 3 types of schizophrenia-like symptoms (positive, negative, or cognitive deficits) as monitored in a battery of behavioral assays (locomotion, stereotypy, social interaction, forced swimming, prepulse inhibition, novel object recognition, and inhibitory avoidance). Moreover, these responses were differentially reversed by typical haloperidol and atypical clozapine antipsychotics in ways that parallel their effects in schizophrenics.

CONCLUSION

We thus propose the l-methionine treatment as an animal model recapitulating several symptoms of schizophrenia. We have established the face and predictive validity for this model. Our model relies on an essential natural amino acid and on an intervention that is relatively simple and time effective and may offer an additional tool for assessing novel antipsychotics.

Redox dysregulation in the pathophysiology of schizophrenia and bipolar disorder: insights from animal models

SIGNIFICANCE

Schizophrenia (SZ) and bipolar disorder (BD) are classified as two distinct diseases. However, accumulating evidence shows that both disorders share genetic, pathological, and epidemiological characteristics. Based on genetic and functional findings, redox dysregulation due to an imbalance between pro-oxidants and antioxidant defense mechanisms has been proposed as a risk factor contributing to their pathophysiology.

RECENT ADVANCES

Altered antioxidant systems and signs of increased oxidative stress are observed in peripheral tissues and brains of SZ and BD patients, including abnormal prefrontal levels of glutathione (GSH), the major cellular redox regulator and antioxidant. Here we review experimental data from rodent models demonstrating that permanent as well as transient GSH deficit results in behavioral, morphological, electrophysiological, and neurochemical alterations analogous to pathologies observed in patients. Mice with GSH deficit display increased stress reactivity, altered social behavior, impaired prepulse inhibition, and exaggerated locomotor responses to psychostimulant injection. These behavioral changes are accompanied by N-methyl-D-aspartate receptor hypofunction, elevated glutamate levels, impairment of parvalbumin GABA interneurons, abnormal neuronal synchronization, altered dopamine neurotransmission, and deficient myelination.

CRITICAL ISSUES

Treatment with the GSH precursor and antioxidant N-acetylcysteine normalizes some of those deficits in mice, but also improves SZ and BD symptoms when given as adjunct to antipsychotic medication.

FUTURE DIRECTIONS

These data demonstrate the usefulness of GSH-deficient rodent models to identify the mechanisms by which a redox imbalance could contribute to the development of SZ and BD pathophysiologies, and to develop novel therapeutic approaches based on antioxidant and redox regulator compounds.

A conceptual and practical guide to the behavioural evaluation of animal models of the symptomatology and therapy of schizophrenia

Schizophrenia is a chronic debilitating brain disorder characterized by a complex set of perceptual and behavioural symptoms that severely disrupt and undermine the patient's psychological well-being and quality of life. Since the exact disease mechanisms remain essentially unknown, holistic animal models are indispensable tools for any serious investigation into the neurobiology of schizophrenia, including the search for remedies, prevention of the disease and possible biological markers. This review provides some practical advice to those confronted with the task of evaluating their animal models for relevance to schizophrenia, a task that inevitably involves behavioural tests with animals. To a novice, this challenge not only is a technical one but also entails attention to interpretative issues concerning validity and translational power. Here, we attempt to offer some guidance to help overcome these obstacles by drawing on our experience of diverse animal models of schizophrenia based on genetics, strain difference, brain lesions, pharmacological induction and early life developmental manipulations. The review pays equal emphasis to the general (theoretical) considerations of experimental design and the illustration of the problems related to critical test parameters and the data analysis of selected exemplar behavioural tests. Finally, the individual differences of behavioural expression in relevant tests observed in wild-type animals might offer an alternative approach in order to explore the mechanism of schizophrenia-related behavioural dysfunction at the molecular, cellular and structural levels, all of which are of more immediate relevance to cell and tissue research.

Egis-11150: a candidate antipsychotic compound with procognitive efficacy in rodents

Classical antipsychotics, e.g. haloperidol, chlorpromazine, are potent at controlling the positive symptoms of schizophrenia but frequently elicit extrapyramidal motor side-effects. The introduction of atypical antipsychotics such as risperidone, olanzapine and clozapine has obviated this problem, but none of the current drugs seem to improve the cognitive deficits accompanying schizophrenia. Thus there is an unmet need for agents that not only suppress the psychotic symptoms but also ameliorate the impairment of cognition. Here, we report the preclinical properties of a candidate antipsychotic, Egis-11150, that shows marked pro-cognitive efficacy. Egis-11150 displayed high affinity for adrenergic α(1), α(2c), 5-HT(2A) 5-HT₇, moderate affinity for adrenergic α(2a) and D₂ receptors. It was a functional antagonist on all of the above receptors, with the exception of 5-HT₇ receptors, where it was an inverse agonist. Phencyclidine-induced hypermotility in mice and inhibition of conditioned avoidance response in rats were assessed to estimate efficacy against the positive and social withdrawal test in rats was used to predict efficacy against the negative symptoms of schizophrenia. Passive-avoidance learning, novel object recognition and radial maze tests in rats were used to assess pro-cognitive activity, while phencyclidine-induced disruption of prepulse inhibition in mice was examined to test for effects on attention. Egis-11150 (0.01-0.3 mg/kg, ip.) was effective in all of the preclinical models of schizophrenia examined. Moreover, a robust pro-cognitive profile was apparent. In summary, work in preclinical models indicates that Egis-11150 is a potential treatment for controlling the psychosis as well as the cognitive dysfunction in schizophrenia. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Visuo-perceptual organization and working memory in patients with schizophrenia

We explore the mechanisms sub-tending the re-organization and memorization of visual information by studying how these mechanisms fail in patients with schizophrenia. Several studies have suggested that patients have difficulties in organizing information in perception and memory. We explore to what extent prompting patients to group items influences memory performance. We distinguish automatic grouping from top-down grouping processes, which are especially involved in re-organizing information. The main task was to memorize pairs of figures. Following manipulation of proximity, pairs of figures were part of the same perceptual group (within-group pair, formed on the basis of automatic grouping) or belonged to different groups (between-group pairs, re-grouped through top-down processes). Prior to the memory task, subjects ran a perception task prompting them to prioritize either within-group or between-group pairs. Unlike patients, controls globally benefited from grouping by proximity in the memory task. In addition, the results showed that prioritizing between-group pairs had a deleterious effect in patients, but with a large decrement in memory performance in the case of within-group rather than between-group figures. This occurred despite preserved focalization on within-group figures, as shown by eye-movement recordings. The suggestion is that when patients are prompted to re-group separate items, they can do so, but the benefit derived from automatic grouping is then not only lost but also reversed. This suggests re-organizing visual information not only involves re-grouping separate items but also integrating these new groups in a unified representation, which is impaired in patients with schizophrenia.

Investigating the mechanisms of hallucinogen-induced visions using 3,4-methylenedioxyamphetamine (MDA): a randomized controlled trial in humans

BACKGROUND

The mechanisms of drug-induced visions are poorly understood. Very few serotonergic hallucinogens have been studied in humans in decades, despite widespread use of these drugs and potential relevance of their mechanisms to hallucinations occurring in psychiatric and neurological disorders.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated the mechanisms of hallucinogen-induced visions by measuring the visual and perceptual effects of the hallucinogenic serotonin 5-HT2AR receptor agonist and monoamine releaser, 3,4-methylenedioxyamphetamine (MDA), in a double-blind placebo-controlled study. We found that MDA increased self-report measures of mystical-type experience and other hallucinogen-like effects, including reported visual alterations. MDA produced a significant increase in closed-eye visions (CEVs), with considerable individual variation. Magnitude of CEVs after MDA was associated with lower performance on measures of contour integration and object recognition.

CONCLUSIONS/SIGNIFICANCE

Drug-induced visions may have greater intensity in people with poor sensory or perceptual processing, suggesting common mechanisms with other hallucinatory syndromes. MDA is a potential tool to investigate mystical experiences and visual perception.

TRIAL REGISTRATION

Clinicaltrials.gov NCT00823407.

Facial emotion processing in schizophrenia: a non-specific neuropsychological deficit?

BACKGROUND

Identification of facial emotions has been found to be impaired in schizophrenia but there are uncertainties about the neuropsychological specificity of the finding.

METHOD

Twenty-two patients with schizophrenia and 20 healthy controls were given tests requiring identification of facial emotion, judgement of the intensity of emotional expressions without identification, familiar face recognition and the Benton Facial Recognition Test (BFRT). The schizophrenia patients were selected to be relatively intellectually preserved.

RESULTS

The patients with schizophrenia showed no deficit in identifying facial emotion, although they were slower than the controls. They were, however, impaired on judging the intensity of emotional expression without identification. They showed impairment in recognizing familiar faces but not on the BFRT.

CONCLUSIONS

When steps are taken to reduce the effects of general intellectual impairment, there is no deficit in identifying facial emotions in schizophrenia. There may, however, be a deficit in judging emotional intensity. The impairment found in naming familiar faces is consistent with other evidence of semantic memory impairment in the disorder.

Action and object naming in schizophrenia

Patients with schizophrenia demonstrate impaired action verbal fluency, but no study has examined verb-noun differences using picture naming. The present study compared object and action naming in 20 adult patients diagnosed with schizophrenia (DSM-IV-TR, Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition, Text Revision; American Psychiatric Association, 2000) criteria, and 20 demographically matched healthy controls, using pictures. Overall, schizophrenic patients showed poorer naming than controls on all measures of object and action lexical semantic access and retrieval despite normal comprehension for action and object names. Results further indicated that action names were significantly more difficult to retrieve than object names in schizophrenic patients. The absence of dissociation in comprehension of action and object names but semantic errors in naming both classes suggests intact conceptual-semantic stores among middle-aged community-dwelling outpatients with schizophrenia but difficulties mapping semantics onto the lexicon. Action-naming impairments can arise from both semantic and postsemantic origins in schizophrenia. These results have implications for the neurobiology of language given the association between both schizophrenia and verb processing and frontal damage. Moreover, the issue being addressed is important for a cognitive characterization of schizophrenia and for an understanding of the representations of action and object names in the brain.

Neurological disorders in schizophrenia

Schizophrenia (SZ) is a complex, heterogeneous, and disabling psychiatric disorder that impairs multiple aspects of human cognitive, perceptual, emotional, and behavioral functioning. SZ is relatively frequent (prevalence around 1%), with onset usually during adolescence or early adulthood, and has a deteriorating course. The rapidly growing area of neuroimaging research has has found clear evidence of many cortical and subcortical abnormalities in individuals with SZ. In this article the most recent findings from multiple studies on neurological disorders in SZ are reviewed, and the authors make a strong argument for a neurological basis of the schizophrenic process.

Preclinical behavioral models for predicting antipsychotic activity

Schizophrenia is a major psychiatric disease that is characterized by three distinct symptom domains: positive symptoms, negative symptoms, and cognitive impairment. Additionally, treatment with classical antipsychotic medication can be accompanied by important side effects that involve extrapyramidal symptoms (EPS). The discovery of clozapine in the 1970s, which is efficacious in all three symptom domains and has a reduced propensity to induce EPS, has driven research for new antipsychotic agents with a wider spectrum of activity and a lower propensity to induce EPS. The following chapter reviews existing behavioral procedures in animals for their ability to predict compound efficacy against schizophrenia symptoms and liability to induce EPS. Rodent models of positive symptoms include procedures related to hyperfunction in central dopamine and serotonin (5-hydroxytryptamine) systems and hypofunction of central glutamatergic (N-methyl-d-aspartate) neurotransmission. Procedures for evaluating negative symptoms include rodent models of anhedonia, affective flattening, and diminished social interaction. Cognitive deficits can be assessed in rodent models of attention (prepulse inhibition (PPI), latent inhibition) and of learning and memory (passive avoidance, object and social recognition, Morris water maze, and operant-delayed alternation). The relevance of the conditioned avoidance response (CAR) is also discussed. A final section reviews animal procedures for assessing EPS liability, in particular parkinsonism (catalepsy), acute dystonia (purposeless chewing in rodents, dystonia in monkeys), akathisia (defecation in rodents), and tardive dyskinesia (long-term antipsychotic treatment in rodents and monkeys).

The head-centered meridian effect: Auditory attention orienting in conditions of impaired visuo-spatial information

This paper examines the characteristics of spatial attention orienting in situations of visual impairment. Two groups of subjects, respectively schizophrenic and blind, with different degrees of visual spatial information impairment, were tested. In Experiment 1, the schizophrenic subjects were instructed to detect an auditory target, which was preceded by a visual cue. The cue could appear in the same location as the target, separated from it respectively by the vertical visual meridian (VM), the vertical head-centered meridian (HCM) or another meridian. Similarly to normal subjects tested with the same paradigm (Ferlazzo, Couyoumdjian, Padovani, and Olivetti Belardinelli, 2002), schizophrenic subjects showed slower reactions times (RTs) when cued, and when the target locations were on the opposite sides of the HCM. This HCM effect strengthens the assumption that different auditory and visual spatial maps underlie the representation of attention orienting mechanisms. In Experiment 2, blind subjects were asked to detect an auditory target, which had been preceded by an auditory cue, while staring at an imaginary point. The point was located either to the left or to the right, in order to control for ocular movements and maintain the dissociation between the HCM and the VM. Differences between crossing and no-crossing conditions of HCM were not found. Therefore it is possible to consider the HCM effect as a consequence of the interaction between visual and auditory modalities. Related theoretical issues are also discussed.

Reduced neuron density, enlarged minicolumn spacing and altered ageing effects in fusiform cortex in schizophrenia

Structural and functional MRI studies report reduced volume and activation of the fusiform gyrus in schizophrenia. The fusiform cortex is involved in object naming and face recognition. Neuron cell size, shape and density, glial cell density and minicolumn spacing in layers III and V of the fusiform cortex were assessed following systematic random sampling from 13 controls and 11 schizophrenic patients. Pyramidal cell density was reduced in schizophrenia. Non-pyramidal cell density was reduced in layer III of the left hemisphere in schizophrenia, mostly in females. Non-pyramidal cells were larger in schizophrenia. Glial cell density was unaltered. Fusiform minicolumn spacing was asymmetrically wider in the right hemisphere of normal control subjects. Minicolumns were less dense in schizophrenia, particularly in the left hemisphere of females and the right hemisphere of males. Reduced neuron density in the fusiform cortex in schizophrenia contributes to evidence of functional-anatomical abnormalities from neuroimaging and neuropathology studies. Anatomical sex differences in schizophrenia may relate to anatomical and cognitive sex differences associated with fusiform cortex in the normal population. Wider minicolumn spacing is consistent with reduced cell density and is linked to altered ageing in schizophrenia.

Seeing is remembering: do deficits in closure affect visual memory recognition in schizophrenia?

INTRODUCTION

Episodic memory is significantly impaired in people with schizophrenia. The precise cause of this impairment has yet to be determined, as the formation of episodic memories is dependent on other processes, some of which also show impairment in schizophrenia. One such process is closure, that is, the filling-in of missing information. Failure to close adequately incomplete stimuli may cause people with schizophrenia to store inadequate or piecemeal representations in memory.

METHODS

Forty people with schizophrenia and 21 healthy comparison subjects participated in the study. The experiment was divided into six blocks, each of which involved both an encoding and a recognition phase. During the encoding phase, 20 figures were presented sequentially and participants had to determine whether each was symmetric or asymmetric. These figures were either complete or fragmented at three different levels. In subsequent recognition phase, 40 abstract figures (20 new and 20 old) were presented. All figures were complete in this phase.

RESULTS

Memory performance of both groups was affected similarly by fragmentation, with an additional increase in performance afforded by a slight fragmentation for participants with schizophrenia.

CONCLUSION

Slight fragmentation may have induced a perceptual difficulty that was mild enough to increase visual processing without compromising it. Closure was thus not involved in the episodic memory deficit of people with schizophrenia.

Visual form perception: a comparison of individuals at high risk for psychosis, recent onset schizophrenia and chronic schizophrenia

Schizophrenia has been associated with deficits in visual perception and processing, but there is little information about their temporal development and stability. We assessed visual form perception using the Rorschach Comprehensive System (RCS) in 23 individuals at clinical high risk for psychosis, 15 individuals with recent onset schizophrenia (< or =2 years since onset), and 34 with chronic schizophrenia (> or =3 years since onset). All three groups demonstrated reduced conventional form perception (X+%), as compared with published norms, but did not differ significantly from one another. In contrast, the high-risk group had significantly better performance on an index of clarity of conceptual thinking (WSUM6) compared to the chronic schizophrenia patients, with the recent onset group scoring intermediate to the high-risk and chronic schizophrenia groups. The results suggest that individuals at clinical high risk for psychosis display substantial deficits in visual form perception prior to the onset of psychosis and that these deficits are comparable in severity to those observed in individuals with schizophrenia. Therefore, visual form perception deficits may constitute a trait-like risk factor for psychosis in high-risk individuals and may potentially serve as an endophenotype of risk for development of psychosis. Clarity of conceptual thinking was relatively preserved among high-risk patients, consistent with a relationship to disease expression, not risk. These deficits are discussed in the context of the putative neurobiological underpinnings of visual deficits and the developmental pathophysiology of psychosis in schizophrenia.

Formal thought disorder is characterised by impaired lexical access

Recent studies have proposed that difficulty with accessing the lexical-semantic memory store may underpin some of the specific linguistic problems associated with formal thought disorder (FTD). We examined the consistency of name retrieval as an indicator of the ability to access lexical-semantic knowledge in patients with and without marked FTD to see if problems are specific to the former or common to schizophrenic patients in general. A graded naming test was administered on two separate occasions 8-16 weeks apart to 48 participants in three groups: 16 schizophrenic patients with high ratings of FTD, 16 schizophrenic patients with low ratings of FTD and 16 healthy controls. We compared the groups for naming consistency across time and the relationship between naming consistency and specific symptoms of FTD. Both patient groups had impaired naming and this was significantly greater in high than low FTD patients. The high FTD patients showed a profile that differed from both low FTD patients and healthy controls insofar as their naming was inconsistent across time, characteristic of an access disorder. Specifically, the FTD symptoms of derailment, tangentality and incoherence were related to the ability to access the lexical-semantic store. In conclusion, most patients with schizophrenia show an impaired semantic memory store. Nevertheless, FTD is associated with additional lexical-semantic difficulties that are quantitatively different to those seen in patients without FTD, and which may reflect disorganized semantic access.

Domain-specific deficits in schizophrenia

INTRODUCTION

Object recognition deficits are well documented in certain neurological disorders (e.g., Alzheimer's disease, herpes simplex encephalitis). Although agnosic problems have been documented in some patients with schizophrenia (Gabrovska et al., 2003), no study has investigated whether such deficits differentially affect specific categories of information (as they sometimes do in neurological cases).

METHOD

In Part I of this study, we compared object recognition in 55 patients with chronic schizophrenia and 22 age- and NART IQ-matched healthy controls. In Part II, we present a detailed case study of one patient with schizophrenia (DH) who displays a severe category specific semantic knowledge for living things.

RESULTS

Of the patients with schizophrenia, 75% had object recognition below the 5th percentile, and in 11% of cases, a highly specific classical category dissociation emerged (5 cases with nonliving deficit and 1 with living deficit); and two other patients showed strong dissociation for living things. These findings provide convincing evidence of a classical double dissociation across the two categories. In Part II, the in-depth case study of one schizophrenic patient (DH), documented a profound agnosia for living things. While DH displayed intact low level perceptual and spatial ability and could copy drawings, he was severely impaired at naming, picture-name matching, semantic fluency, and could not describe or draw items from memory.

CONCLUSIONS

The presence of impaired object recognition in most schizophrenic patients, along with highly selective category specific deficits in a minority, is discussed with reference to similar findings in neurological patients.

A longitudinal analysis of memory in patients with schizophrenia

Memory deficits are widely reported in patients with schizophrenia, but uncertainties remain about the extent and the longitudinal course of these deficits. Twenty-eight patients with a DSM-IV diagnosis of schizophrenia were tested on multiple aspects of memory at baseline, 9- and 18-month follow-up. Measures included: digit span, the Rivermead Behavioural Memory test (RBMT) battery, the Graded Naming Test (GNT) and several computerized memory tests from the Cambridge Automated Neuropsychological Testing Battery (CANTAB). A group of healthy controls (N=17) was tested on the CANTAB battery at baseline and 9-month follow up. The patients performed significantly poorer than controls on all CANTAB measures; however, there was no difference in change between groups over a 9-month period. Within-group patient comparisons revealed that symptoms reduced significantly over the study period, but had no association with memory. Significant improvements were observed for patients on two verbal memory tasks: the GNT and digit span, but not on any other measure. Interestingly, these were the only two tests on which patients were within normal limits at baseline. This study shows that patients with schizophrenia have deficits in multiple aspects of memory which remain stable over long periods of time. In addition, patients showed a tendency to improve on memory tasks which contained a verbal component.

Storage and access procedures in schizophrenia: evidence for a two phase model of lexical impairment

Evidence has accumulated to show that schizophrenia is characterized by lexical-semantic difficulties; however, questions remain about whether schizophrenics have problems in accessing intact representations or a loss of the representations themselves. Both access and storage types of disorder have been reported and it has been speculated that this may reflect a transition from the former to latter with increasing length of illness. This study investigated whether illness duration, age or estimated premorbid IQ predict the size and accessibility of the lexical store. Fifty-six schizophrenic patients (chosen to represent a wide range of illness duration from 3-40 years) and 24 matched healthy controls were asked to name 120 pictures on two occasions. Estimates of store size and retrieval probability were derived from a two parameter stochastic Markov chain model. This revealed that even early in the course of illness, schizophrenics appear to have suffered a reduction in lexical store size and that those with longer length of illness show deficits in both their store size and their ability to retrieve names from that store.

Cortical intercorrelations of temporal area volumes in schizophrenia

BACKGROUND

Abnormal temporal connections with other cortical areas may underlie some of the most prominent cognitive deficits described in schizophrenia. In order to evaluate the relationship between temporal and other cortical regions in schizophrenia, we examined the intercorrelations of volumetric measures of gray and white matter for each Brodmann's area of the temporal lobe with volumes in the rest of the cortex in patients with schizophrenia and normal comparison subjects.

METHODS

MR images were acquired in normal subjects (n=46) and patients with schizophrenia (n=106), divided into good-outcome (n=52) and poor-outcome (Kraepelinian; n=54) subtypes; and correlational patterns between the volumes of individual Brodmann's areas were compared and examined in relation to outcome.

RESULTS

Positive frontotemporal intercorrelations were significantly stronger while negative frontotemporal intercorrelations were weaker in schizophrenia patients as compared to normal subjects. Correlations between the right temporal pole and other temporal regions were significantly weaker in schizophrenia patients than in controls. When compared to normal controls and good-outcome patients, schizophrenia patients with poor outcomes showed a selective pattern of stronger gray matter correlations between the medial temporal vs. primary visual and between primary auditory vs. dorsolateral prefrontal cortices, all in the left hemisphere.

CONCLUSIONS

Strengthening of positive associations among the temporal and extratemporal (mainly frontal and occipital) regions as well as weakening of regional intercorrelations within the temporal lobe in patients appear to constitute the major differences of correlational patterns in schizophrenia patients and normal subjects. Present findings may be implicated in object recognition deficits seen in patients with schizophrenia, as well as in purportedly deficient spatial and semantic processing of both auditory and visual information that may be associated with poor outcome.

Visual agnosia

The visual agnosias are an intriguing class of clinical phenomena that have important implications for current theories of high-level vision. Visual agnosia is defined as impaired object recognition that cannot be attributed to visual loss, language impairment, or a general mental decline. At least in some instances, agnostic patients generate an adequate internal representation of the stimulus but fail to recognize it. In this review, we begin by describing the classic works related to the visual agnosias, followed by a description of the major clinical variants and their occurrence in degenerative disorders. In keeping with the theme of this issue, we then discuss recent contributions to this domain. Finally, we present evidence from functional imaging studies to support the clinical distinction between the various types of visual agnosias.

An animal model with relevance to schizophrenia: sex-dependent cognitive deficits in osteogenic disorder-Shionogi rats induced by glutathione synthesis and dopamine uptake inhibition during development

Low glutathione levels have been observed in the prefrontal cortex and the cerebrospinal fluid of schizophrenic patients, possibly enhancing the cerebral susceptibility to oxidative stress. We used osteogenic disorder Shionogi mutant rats, which constitute an adequate model of the human redox regulation because both are unable to synthesize ascorbic acid. To study the long-term consequences of a glutathione deficit, we treated developing rats with L-buthionine-(S,R)-sulfoximine (BSO), an inhibitor of glutathione synthesis, and later investigated their behavior until adulthood. Moreover, some rats were treated with the dopamine uptake inhibitor GBR 12909 in order to elevate dopamine extracellular levels, thereby mimicking the dopamine hyperactivity proposed to be involved in schizophrenia. BSO and GBR 12909 alone or in combination minimally affected the development of spontaneous alternation or basic sensory and motor skills. A major effect of BSO alone or in combination with GBR 12909 was the induction of cataracts in both sexes, whereas GBR 12909 induced an elevation of body weight in females only. Sex and age-dependent effects of the treatments were observed in a test of object recognition. At postnatal day 65, whereas male rats treated with both BSO and GBR 12909 failed to discriminate between familiar and novel objects, females were not affected. At postnatal day 94, male object recognition capacity was diminished by BSO and GBR 12909 alone or in combination, whereas females were only affected by the combination of both drugs. Inhibition of brain glutathione synthesis and dopamine uptake in developing rats induce long-term cognitive deficits occurring in adulthood. Males are affected earlier and more intensively than females, at least concerning object recognition. The present study suggests that the low glutathione levels observed in schizophrenic patients may participate in the development of some of their cognitive deficits.