Schizophrenia research: the problem of controls

A comparative study of the working memory multicomponent model in psychosis and healthy controls

Working memory deficits are considered nuclear deficits in psychotic disorders. However, research has not found a generalized impairment in all of the components of working memory. We aimed to assess the components of the Baddeley and Hitch working memory model: the temporary systems-the phonological loop, the visuospatial sketchpad and the episodic buffer (introduced later by Baddeley)-and the central executive system, which includes four executive functions: divided attention, updating, shifting and inhibition. We assessed working memory performance in a sample of 21 patients with a psychotic disorder and 21 healthy controls. Patients also underwent a clinical assessment. Both univariate and repeated measures ANOVAs were applied to analyze performance in the working memory components between groups. Patients with a psychotic disorder underperformed compared to the controls in all of the working memory tasks, but after controlling for age and premorbid IQ, we only found a difference in performance in the N-Back task. Repeated measures ANCOVAs showed that patients also underperformed compared to the controls in the Digit span test and the TMT task. Not all of the components of working memory were impaired in the patients. Specifically, patients' performance was impaired in the tasks selected to assess the phonological loop and the shifting executive function. Patients' also showed worse performance than controls in the N-Back task, representative of the updating executive function. However, we did not find higher impairment in the patients' performance respect to controls when increasing the loading of the task.

A new developmental epidemiology of schizophrenia: the HRB Schizophrenia Research Unit, 1991-92, and contemporary perspectives of the disease

General aspects of research funding in the biomedical sciences are briefly discussed and some specific issues of policy considered, as they relate particularly to the Health Research Board's Unit strategy. The origins, objectives and workings of the Board's Schizophrenia Research Unit are elaborated, in relation to contemporary perspectives of this illness as a neuro-developmental disorder, and the extent of progress made over it's first year of operation is outlined. It is argued that the ‘neurodevelopmental hypothesis’ now has substantial foundations; it provides an important conceptual focus, both for the field in general and for the Health Research Board's Schizophrenia Research Unit in particular.

Abnormal temperament in patients with morbid obesity seeking surgical treatment

BACKGROUND

Obesity and its related disorders are growing epidemic across the world. Research on links between the bipolar spectrum and obesity has proliferated in the last few years. As some forms of abnormal temperament are considered as subtypes of the soft bipolar spectrum, we aimed to evaluate abnormal temperaments in morbidly obese patients.

METHODS

Using a short version of the Temperament Evaluation of Memphis, Pisa, Paris and San Diego, we investigated abnormal depressive, cyclothymic, hyperthymic, irritable or anxious temperament in 213 patients with morbid obesity compared to a control group of 90 patients admitted prior to organ transplantation. Additionally, the Beck-Depression Inventory (BDI) and the Self-Report Manic Inventory (SRMI) were applied to assess current mood status.

RESULTS

The obese group showed statistically significantly more psychiatric comorbidities compared to the control group. Abnormal temperaments were significantly more often observed in patients with morbid obesity rather than in controls. Cyclothymic, irritable and anxious temperaments showed specificity to obesity. Obese patients had significantly higher scores on the BDI, while no difference for SRMI scores was found among the whole groups. All temperaments were positively correlated with BDI and SRMI in the obese group.

LIMITATIONS

The control group was not matched for demographic characteristics.

CONCLUSIONS

Our results need replication but indicate an affective overlap in the form of abnormal temperament and depressive symptoms in obese patients, whereas mood swings should be evaluated and early mood stabilization considered for patients with significant weight gain to prevent obesity or to reduce already existing overweight. Studies of mood stabilizers and prospective observations would shed further insight on this complex interface of a major clinical and public health issue.

Working memory in schizophrenia: a meta-analysis

BACKGROUND

Memory impairment is being recognized increasingly as an important feature of the neuropsychology of schizophrenia. Dysfunction of working memory, a system for the short-term storage and manipulation of information, may relate to a number of core symptoms of schizophrenia. Many studies have examined working memory function in schizophrenia but a clear understanding of the nature and extent of any deficit has been elusive.

METHOD

A systematic review and meta-analysis of studies comparing working memory function in subjects with schizophrenia and healthy controls was performed. Following a comprehensive literature search, meta-analyses were conducted on 36 measures of phonological, visuospatial and central executive working memory functioning, encompassing 441 separate results from 187 different studies.

RESULTS

Statistically significant effect sizes were found for all working memory measures, indicating deficits in schizophrenia groups. Some of these were robust findings in the absence of evidence of significant heterogeneity or publication bias. Meta-regression analyses showed that the working memory deficit was not simply explained by discrepancies in current IQ between schizophrenia and control groups.

CONCLUSIONS

Large deficits in working memory were demonstrated in schizophrenia groups across all three working memory domains. There were, however, no clear differences across subdomains or between particular working memory tasks. There was substantial heterogeneity across results that could only be partly explained.

Head size and schizophrenia

There is a small but intriguing body of literature which suggests that head size may be reduced in patients with schizophrenia. This literature sits alongside more substantial and compelling evidence that there is a reduction in cerebral volume in schizophrenia. As an extension of earlier work, measures of extracranial head size derived from standard anthropometric approaches were assessed in 44 patients and 46 control subjects. Head size was found to be normal in schizophrenia. The relationship of brain size to head size is elaborated.

Thalamic and amygdala-hippocampal volume reductions in first-degree relatives of patients with schizophrenia: an MRI-based morphometric analysis

BACKGROUND

Schizophrenia is characterized by subcortical and cortical brain abnormalities. Evidence indicates that some nonpsychotic relatives of schizophrenic patients manifest biobehavioral abnormalities, including brain abnormalities. The goal of this study was to determine whether amygdala-hippocampal and thalamic abnormalities are present in relatives of schizophrenic patients.

METHODS

Subjects were 28 nonpsychotic, and nonschizotypal, first-degree adult relatives of schizophrenics and 26 normal control subjects. Sixty contiguous 3 mm coronal, T1-weighted 3D magnetic resonance images of the brain were acquired on a 1.5 Tesla magnet. Cortical and subcortical gray and white matter and cerebrospinal fluid (CSF) were segmented using a semi-automated intensity contour mapping algorithm. Analyses of covariance of the volumes of brain regions, controlling for expected intellectual (i.e., reading) ability and diagnosis, were used to compare groups.

RESULTS

The main findings were that relatives had significant volume reductions bilaterally in the amygdala-hippocampal region and thalamus compared to control subjects. Marginal differences were noted in the pallidum, putamen, cerebellum, and third and fourth ventricles.

CONCLUSIONS

Results support the hypothesis that core components of the vulnerability to schizophrenia include structural abnormalities in the thalamus and amygdala-hippocampus. These findings require further work to determine if the abnormalities are an expression of the genetic liability to schizophrenia.

Structural brain imaging in schizophrenia

The subtle pathomorphology of schizophrenia is gradually being unraveled through the application of increasingly sophisticated brain imaging techniques. There is now compelling evidence of subtle brain abnormalities in patients with schizophrenia. It less clear, however, whether these reflect a widespread cortical involvement, or more selective involvement among interconnected neural systems, or more focal pathology. The extent of brain changes, their etiopathologic significance, and putative clinical correlates are reviewed in this article.

Sleep-onset rapid eye movement periods in neuropsychiatric disorders: implications for the pathophysiology of psychosis

This paper reviews the literature describing the occurrence of sleep-onset rapid eye movement periods in narcolepsy, schizophrenia, psychotic depression, and delirium tremens; the association of narcolepsy with psychotic disorders; the neuropathology of the brainstem in narcolepsy and schizophrenia; and other behavioral disorders resulting from probable brainstem pathology. These findings suggest that some forms of psychosis are a manifestation of pathophysiological changes in the brainstem. Some implications of this hypothesis for the treatment of psychoses are discussed. Future research should investigate psychoses and the psychobiological correlates of such biological markers as sleep-onset rapid eye movement periods across diagnostic categories.

Neurocognitive correlates of positive and negative syndromes in schizophrenia

OBJECTIVE

To identify the neurocognitive correlates of positive and negative schizophrenic syndromes using a battery of information-processing measures as the principal method of evaluation.

METHOD

Fifty-two treated, symptomatically stable, schizophrenic (DSM-III-R) patients and 24 age-matched, healthy volunteers were administered a computerized cognitive test battery (COGLAB). The battery included measures of preattentional, attentional, conceptual, and psychomotor performance. The patients' psychopathology was rated with the positive and negative syndromes scale (PANSS), which derived scores for positive symptoms, negative symptoms, general psychopathology, and insight.

RESULTS

Compared with controls, schizophrenic patients, as a group, showed significant deficits on all of the neurocognitive tasks. Impaired performance on the backward masking, span of apprehension, and Wisconsin card sorting tasks correlated significantly with negative symptoms (r = 0.27-0.40), general psychopathology (r = 0.29-0.42) and impaired insight (r = 0.34-0.52), but no clear association was found between positive symptom scores and neurocognitive deficits.

CONCLUSIONS

Schizophrenic patients with predominantly negative symptoms and impaired insight seem to exhibit more severe neurocognitive deficits, which lends support to the evolving concept of schizophrenia subtypes and their distinctive neurobiological mechanisms.

Functional magnetic resonance imaging in schizophrenia: initial methodology and evaluation of the motor cortex

The purpose of the present study was to evaluate the differential activation of the motor cortex during finger tapping in patients with schizophrenia using the newly available imaging method of functional magnetic resonance imaging (fMRI). Nine patients with DSMIII-R schizophrenia and 9 well-matched healthy volunteer subjects underwent fMRI examination on a conventional MR unit; activation of the primary motor cortex was evaluated during performance of a finger motion task. Localized activation of the motor cortex was observed in 17 of 18 subjects during fMRI. Patients and controls were, however, indistinguishable with respect to signal intensity or area thereof within the motor cortex. fMRI did not reveal motor cortical dysfunction in schizophrenia. Despite its infancy, fMRI holds considerable promise to advance understanding of the neurodynamics of psychiatric disorders, particularly schizophrenia.

Sex differences in neuropsychological function in non-psychotic relatives of schizophrenic probands

Some recent studies suggest that men with schizophrenia may have greater neuropsychological deficits than women. It is not known, however, whether similar sex differences may be present in biological relatives of schizophrenic patients. We evaluated neuropsychological functioning of 54 relatives of schizophrenic patients and 72 normal volunteers. It was hypothesized that, if sex differences were present, they would be accounted for largely by deficits in male relatives. We were particularly interested in three neuropsychological functions that we previously identified as putative neuropsychological vulnerability indicators for schizophrenia: (1) abstraction/executive function; (2) verbal memory; and (3) auditory attention. There were significant group x sex interactions for verbal memory and motor function, and trends toward significant interactions for auditory attention and mental control/encoding. However, with the exception of motor function, it was the female relatives who accounted for most of the impairment. A speculative explanation for the findings is that women may have a higher threshold than men for developing schizophrenia. If so, female relatives might be able to withstand greater impairments than men before developing psychotic symptoms. Consequently, in a sample that was limited to non-psychotic relatives--as in the present study--there could be over-representation of both less impaired men and more impaired women. Alternative explanations and limitations of the study are also discussed.

Neuropsychological functioning among the elderly nonpsychotic relatives of schizophrenic patients

In our prior work with a young sample (age < 60), we showed that three neuropsychological functions were impaired among relatives of schizophrenic patients: abstraction, verbal memory, and auditory attention. In the present work we show that these results do not generalize to an older sample aged 60 years and greater. Thus, although we and others have put forth measures of neuropsychological function as indicators of the schizophrenia genotype, the present study suggests that conclusions may be limited to non-elderly samples. Further work is needed to address this issue definitively.

The '3 Rs' and neuropsychological function in schizophrenia: a test of the matching fallacy in biological relatives

The 'matching fallacy' suggests that matching schizophrenic patients and normal control subjects on education or IQ may cause systematic mismatching of theoretically expected ability. This study supports a modest version of the matching fallacy effect in nonpsychotic biological relatives of schizophrenic patients. At equivalent levels of education, relatives and control subjects had similar Reading and Spelling scores on the Wide Range Achievement Test-Revised--measures that are largely unimpaired by schizophrenia-related processes. However, relatives showed a deficit in IQ (primarily verbal IQ) compared with what would be predicted from their Reading scores. A similar deficit in Arithmetic scores was found in non-college-educated relatives, but college-educated relatives showed an advantage. We discuss possible implications of the findings with regard to genetic and environmental factors.

1H-magnetic resonance spectroscopy of the left temporal and frontal lobes in schizophrenia: clinical, neurodevelopmental, and cognitive correlates

Twenty eight schizophrenic patients and 20 normal volunteers underwent proton magnetic resonance spectroscopy (MRS) on the left temporal and frontal lobe regions. Male patients showed a significant reduction in frontal but not temporal n-acetylaspartate (an intraneuronally distributed metabolite) in comparison with either male controls or female patients; frontal choline was raised in male patients relative to these groups. Putative neurodevelopmental indices, including obstetric complications, family history of schizophrenia, and minor physical anomalies, proved unrelated to MRS resonances. However, multiple aspects of memory function in patients were related to temporal but not frontal creatine, a pattern that was not apparent among controls. These MRS findings complement some previous structural MRI studies and much clinical and epidemiological evidence of important gender differences in schizophrenia. The findings also suggest that memory dysfunction in patients with schizophrenia may be associated with a particular pattern of temporal lobe metabolism on MRS.

Improvement in cognitive functions and psychiatric symptoms in treatment-refractory schizophrenic patients receiving clozapine

Cognitive functions and psychopathology were assessed in 36 treatment-refractory schizophrenic patients before initiation of clozapine, and at 6 weeks and 6 months, thereafter. Before treatment, cognitive impairment was found in each measure of memory, attention, and executive function as compared with 26 normal controls. After both 6 weeks and 6 months of treatment, significant improvement occurred in the Controlled Oral Word Association Test, a measure of retrieval from reference memory. Improvement was also noted at 6 months in the Category Instance Generation Test, another measure of retrieval from reference memory, and in some, but not all, tests of executive function, attention, and recall memory. Clozapine treatment also resulted in significant improvement in Brief Psychiatric Rating Scale (BPRS) Total and Positive symptom scores at both 6-week and 6-month assessment points. There was some evidence for a relationship between improvement in psychopathology and cognitive function. The improvement in cognitive function during clozapine treatment could have consequences for capacity to work and social function.