Altered modulation of prefrontal and subcortical brain activity in newly diagnosed schizophrenia and schizophreniform disorder. A regional cerebral blood flow study

The history of Danish neuroscience

The history of Danish neuroscience starts with an account of impressive contributions made at the 17th century. Thomas Bartholin was the first Danish neuroscientist, and his disciple Nicolaus Steno became internationally one of the most prominent neuroscientists in this period. From the start, Danish neuroscience was linked to clinical disciplines. This continued in the 19th and first half of the 20th centuries with new initiatives linking basic neuroscience to clinical neurology and psychiatry in the same scientific environment. Subsequently, from the middle of the 20th century, basic neuroscience was developing rapidly within the preclinical university sector. Clinical neuroscience continued and was even reinforced during this period with important translational research and a close co-operation between basic and clinical neuroscience. To distinguish 'history' from 'present time' is not easy, as many historical events continue in present time. Therefore, we decided to consider 'History' as new major scientific developments in Denmark, which were launched before the end of the 20th century. With this aim, scientists mentioned will have been born, with a few exceptions, no later than the early 1960s. However, we often refer to more recent publications in documenting the developments of initiatives launched before the end of the last century. In addition, several scientists have moved to Denmark after the beginning of the present century, and they certainly are contributing to the present status of Danish neuroscience-but, again, this is not the History of Danish neuroscience.

"Hyperfrontality" as seen on FDG PET in unmedicated schizophrenia patients with positive symptoms

INTRODUCTION

Decreased frontal activity has been reported widely in unmedicated schizophrenic patients with predominantly negative symptoms. Not many studies have assessed the frontal lobe status in unmedicated patients with positive symptoms.

PATIENTS AND METHODS

Fifty-one patients with schizophrenia (all unmedicated, 38 never medicated) and 12 healthy age-matched controls were evaluated with FDG PET CT. The patients met ICD-10 and DSM-IV criteria for schizophrenia, and all reported psychotic, "positive" symptoms when tested.

RESULTS

Schizophrenic patients with positive symptoms had a hypermetabolic frontal metabolic pattern on quantification by region to occipital ratio comparison. Associated statistically significant differences were also found when comparing ratios of occipital to thalamic, striatal and temporal cortex in schizophrenic patients.

CONCLUSION

The finding of a hyperfrontality in unmedicated and never medicated psychotic schizophrenic patients is observed when there is a predominance of positive symptoms. There could be a possible disruption of cortico-striato-thalamic feedback loops causing hyperfrontality as seen in experimentally induced models of psychosis .

Genetic influence on the working memory circuitry: behavior, structure, function and extensions to illness

Working memory is a highly heritable complex cognitive trait that is critical for a number of higher-level functions. However, the neural substrates of this behavioral phenotype are intricate and it is unknown through what precise biological mechanism variation in working memory is transmitted. In this review we explore different functional and structural components of the working memory circuitry, and the degree to which each of them is contributed to by genetic factors. Specifically, we consider dopaminergic function, glutamatergic function, white matter integrity and gray matter structure all of which provide potential mechanisms for the inheritance of working memory deficits. In addition to discussing the overall heritability of these measures we also address specific genes that may play a role. Each of these heritable components has the potential to uniquely contribute to the working memory deficits observed in genetic disorders, including 22q deletion syndrome, fragile X syndrome, phenylketonuria (PKU), and schizophrenia. By observing the individual contributions of disruptions in different components of the working memory circuitry to behavioral performance, we highlight the concept that there may be many routes to a working memory deficit; even though the same cognitive measure may be a valid endophenotype across different disorders, the underlying cause of, and treatment for, the deficit may differ. This has implications for our understanding of the transmission of working memory deficits in both healthy and disordered populations.

Executive function, neural circuitry, and genetic mechanisms in schizophrenia

After decades of research aimed at elucidating the pathophysiology and etiology of schizophrenia, it has become increasingly apparent that it is an illness knowing few boundaries. Psychopathological manifestations extend across several domains, impacting multiple facets of real-world functioning for the affected individual. Even within one such domain, arguably the most enduring, difficult to treat, and devastating to long-term functioning-executive impairment-there are not only a host of disrupted component processes, but also a complex underlying dysfunctional neural architecture. Further, just as implicated brain structures (eg, dorsolateral prefrontal cortex) through postmortem and neuroimaging techniques continue to show alterations in multiple, interacting signaling pathways, so too does evolving understanding of genetic risk factors suggest multiple molecular entry points to illness liability. With this expansive network of interactions in mind, the present chapter takes a systems-level approach to executive dysfunction in schizophrenia, by identifying key regions both within and outside of the frontal lobes that show changes in schizophrenia and are important in cognitive control neural circuitry, summarizing current knowledge of their relevant functional interactions, and reviewing emerging links between schizophrenia risk genetics and characteristic executive circuit aberrancies observed with neuroimaging methods.

Turning it upside down: areas of preserved cognitive function in schizophrenia

Patients with schizophrenia demonstrate marked impairments on most clinical neuropsychological tests. These findings suggest that patients suffer from a generalized form of cognitive impairment, with little evidence of spared performance documented in several large meta-analytic reviews of the clinical literature. In contrast, we review evidence for relative sparing of aspects of attention, procedural memory, and emotional processing observed in studies that have employed experimental approaches adapted from the cognitive and affective neuroscience literature. These islands of preserved performance suggest that the cognitive deficits in schizophrenia are not as general as they appear to be when assayed with clinical neuropsychological methods. The apparent contradiction in findings across methods may offer important clues about the nature of cognitive impairment in schizophrenia. The documentation of preserved cognitive function in schizophrenia may serve to sharpen hypotheses about the biological mechanisms that are implicated in the illness.

Cortical blood flow during rest and Wisconsin Card Sorting Test performance in schizophrenia

BACKGROUND

The aim of this study is to examine if patients with schizophrenia differ in prefrontal, orbitofrontal, temporal, parietal and occipital blood flow from healthy controls during performance of the Wisconsin Card Sorting Test (WCST).

METHODS

We conducted a 99mTc-hexamethylpropylene amine oxime-SPECT study in patients with schizophrenia (n = 21) and in healthy controls (n = 18). The assessment of relative regional cerebral blood flow (relCBF) was achieved by comparing blood flow of well-defined cortical regions to whole brain blood flow. relCBF at rest and during WCST was compared between the groups and in the groups.

RESULTS

Significant bilateral prefrontal and right-sided parietal increases of relCBF were found in patients (p < 0.05) during resting conditions, while prefrontal and parietal interhemispheric asymetry were higher in patients (p < 0.005). However, patients failed to increase right prefrontal and frontobasal relCBF as well as orbitofrontal interhemispheric asymetry during WCST performance in contrast to the control group (p < 0.05). The right occipital relCBF increased significantly in patients only (p < 0.05).

CONCLUSIONS

In our study we could confirm the common hypothesis of schizophrenic hypofrontality at rest and during WCST performance. Moreover, due to our method, we identified significant frontal and parietal interhemispheric asymmetries in schizophrenia at rest as well as right occipital hyperperfusion during WCST.

Differential effects of classical neuroleptics and a newer generation antipsychotics on the MK-801 induced behavioural primitivization in mouse

Cognitive dysfunction plays an important role in mental disorders like schizophrenia and may involve inadequate glutamatergic signalling in different regions of the brain, mediated by e.g. glutamatergic N-methyl-D-aspartate (NMDA) receptors. In rodents, NMDA receptor antagonists often increase motor activity; in addition they induce a more primitive and undifferentiated behavioural pattern, which we believe may correspond to some of the cognitive defects seen in schizophrenia. In the present study, the movement pattern of mice treated with the uncompetitive NMDA receptor antagonist MK-801 in conjunction with six antipsychotic agents, some with reported clinical effects on cognition, was characterised and quantified. The classical neuroleptic drugs chlorpromazine and trifluoperazine, the atypical antipsychotic agents ziprasidone and olanzapine, the gamma-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-receptor potentiator CX516 and the serotonin (5-HT)2A-antagonist M100907 were tested. In accordance with previous observations, MK-801 was found to induce a primitive and monotonous behavioural pattern dominated by forward locomotion; spatial movements, the number of switches between the states moving and stationary, and rearing frequency were reduced. All test substances counteracted MK-801-induced hyperactivity, but differed in their ability to improve behavioural quality. Chlorpromazine and trifluoperazine were unable to restore behavioural diversity while ziprasidone, olanzapine, CX516 and M100907 restored it to varying degrees. A striking similarity in movement pattern was seen between the hypoglutamatergic mice treated with the AMPA-receptor agonist CX516, and those receiving the 5HT2A-antagonist M100907.

Dorsolateral prefrontal cortex contribution to abnormalities of the P300 component of the event-related potential in schizophrenia

Abnormalities of the P300 component of the event-related potential are a common finding in schizophrenia. It seems possible that the dysfunction in the dorsolateral prefrontal (DLPF) region that has been reported in schizophrenia contributes to this finding. To explore this possibility, we calculated the relationship between, on the one hand, P300 latency and amplitude and, on the other hand, the degree of DLPF atrophy (as measured by magnetic resonance imaging) and metabolic activity during an attentional task (as measured by positron emission tomography). Seventeen schizophrenia patients with a brief duration of illness and minimal exposition to treatment and 25 healthy controls were studied. Patients exhibited significantly lower metabolic activity in the DLPF region, but they did not show cortical atrophy. P300 amplitude was also significantly reduced in the schizophrenia patients compared with the controls. Right DLPF region metabolic activity correlated significantly with P300 amplitude. This pattern remained after partialling out the influence of activity in the hippocampus, superior temporal gyrus and parietal lobe. It is therefore suggested that the prefrontal cortex could be implicated in the P300 amplitude reduction in schizophrenia.

Hypermetabolic pattern in frontal cortex and other brain regions in unmedicated schizophrenia patients. Results from a FDG-PET study

We report results of a FDG-PET study in 10 patients with schizophrenia (6 unmedicated, 4 never medicated) and 12 healthy age-matched controls. The patients met ICD-10 and DSM-IV criteria for schizophrenia and all reported psychotic, "positive" symptoms when tested. Schizophrenic patients had higher absolute CMRGlu values in almost all quantified regions compared to normal subjects. Using the occipital cortex as the reference region patients showed a hyperfrontal metabolic pattern. Other significant regional differences were found with respect to thalamus, striatum and temporal cortex. The finding of a hyperfrontality in un- and never medicated psychotic schizophrenic patients must be discussed in the light of the psychopathological symptoms of patients when tested, a possible disruption of cortico-striato-thalamic feedback loops and recent findings of a hyperfrontality in experimentally induced psychosis (ketamine- and psilocybin-model of schizophrenia).

Neural mechanisms of affective interference in schizotypy

Negatively valenced stimuli foster cognitive impairment in schizotypy and schizophrenia. To identify relevant brain mechanisms, the authors had 16 positive-schizotypy and 16 control participants perform an emotional Stroop task, judging the ink color of negative and neutral words during functional magnetic resonance imaging (fMRI) of regional brain activity. Schizotypy individuals showed increased right and decreased left activity in dorsolateral prefrontal cortex, indicating a deficit in maintenance of attentional set in the presence of negative emotional distractors. They also showed abnormal activity in ventral limbic areas, including decreased activity in nucleus accumbens and increased activity in hippocampus and amygdala, a circuit involved in the integration of cognitive and affective processes. These results indicate that aspects of emotion-cognition processes and the brain mechanisms that implement them are similar in schizotypy and schizophrenia.

Hypofrontality in men with first-episode psychosis

BACKGROUND

Decreased metabolic activity in the prefrontal cortex during cognitive activation is a recurrent finding and a likely functional marker of schizophrenia.

AIMS

To investigate the occurrence of hypofrontality in patients with first-episode psychosis, with or without evolution to schizophrenia.

METHOD

We used fluorodeoxyglucose positron emission tomography during the performance of an attention task and magnetic resonance imaging to study the dorsolateral prefrontal region in 13 men with a first episode of psychosis. Data from patients who progressed to schizophrenia were compared with those of patients who did not meet criteria for this diagnosis after 2 years.

RESULTS

Patients who developed schizophrenia demonstrated a significant hypofrontality in the dorsolateral prefrontal cortex in comparison with the non-schizophrenia and control groups.

CONCLUSIONS

Our results suggest that hypofrontality could be a marker of schizophrenia at the time of the first psychotic episode, in agreement with neurodevelopmental theories of schizophrenia.

Prefrontal atrophy in first episodes of schizophrenia associated with limbic metabolic hyperactivity

Reduced volume and activity of the prefrontal (PF) cortical gray matter (GM) and hippocampal hypermetabolism are repeated findings in schizophrenia. There is still an information deficit about the significance of reduction of PF GM in schizophrenia, and a simultaneous study of PF anatomy and activity and limbic metabolism can contribute to fill that deficit. In order to do so, we used positron emission tomography (PET) with 18-fluoro-deoxy-glucose (FDG) during an attention task and magnetic resonance imaging (MRI) to study a sample of first episodes of psychosis. We included 21 first episodes (FE) of psychosis and 16 healthy controls. A diagnosis of schizophrenia was confirmed in the follow-up in eleven of these patients and ruled out in the remaining 10 cases. Volumes of PF GM were determined and also activity in the same region and in the hippocampus. Residual GM was estimated in the PF region as a quantitative measurement of the degree of atrophy in each individual, using age and intracranial volume data from a set of 45 healthy controls and linear regression. Patients with schizophrenia had lower PF metabolic activation and greater hippocampal activity than controls. FE patients without schizophrenia were no different in any parameter as compared to controls. Patients with schizophrenia presented an inverse and significant association between GM deficit and hippocampal activity that was not observed in controls or in patients without schizophrenia. The same association was previously described by our group using PET in the resting state in recent-onset and chronic patients with schizophrenia. These findings support a loss in PF inhibitory capacity as a possible link between anatomical and functional alterations in schizophrenia.

Do schizophrenia patients make more perseverative than non-perseverative errors on the Wisconsin Card Sorting Test? A meta-analytic study

The Wisconsin Card Sorting Test (WCST) is widely used to explore executive functions in patients with schizophrenia. Among other findings, a higher number of perseverative errors has been suggested to implicate a deficit in task switching and inhibitory functions in schizophrenia. Many studies of patients with schizophrenia have focused on perseverative errors as the primary performance index in the WCST. However, do schizophrenia patients characteristically make more perseverative than non-perseverative errors compared with healthy controls? We reviewed the literature where schizophrenia patients were engaged in the WCST irrespective of the primary goal of the study. The results showed that while both schizophrenia patients and healthy participants made more perseverative than non-perseverative errors, the contrast between perseverative and non-perseverative errors is higher in schizophrenia patients only at a marginal level of significance. This result suggests that schizophrenia patients do make a comparable number of non-perseverative errors and cautions against simplistic interpretation of poor performance of schizophrenia patients in WCST as entirely resulting from impairment in set-shifting or inhibitory functions.

Procedural learning in schizophrenia can reflect the pharmacologic properties of the antipsychotic treatments

BACKGROUND

Conventional and atypical antipsychotics have different affinities for D2 receptors, and these receptors are principally located in the striatum. Given that this cerebral structure was previously found to play a major role in procedural learning, the antipsychotic treatment in schizophrenia may be determinant for the procedural learning profile of these patients.

OBJECTIVE

The current study was aimed at verifying whether procedural learning differs in patients with schizophrenia treated with conventional antipsychotics and patients treated with atypical antipsychotics.

METHOD

Forty-five patients with schizophrenia were divided into 3 different groups according to their pharmacologic treatment: (1) haloperidol, a classical neuroleptic with high D2 receptor affinity; (2) clozapine, an atypical neuroleptic with practically no D2 receptor affinity; and (3) risperidone, an atypical neuroleptic that nevertheless shows high D2 receptor affinity. Patients were compared to 35 control subjects on a visuomotor procedural learning task (mirror drawing).

RESULTS

All patients were able to learn the task. However, those treated with haloperidol showed some degree of learning impairment, while those treated with clozapine or risperidone did not show this impairment. In addition, performance per se, regardless of the learning, was found to be affected in the haloperidol and risperidone, but not in the clozapine groups.

CONCLUSION

Procedural learning in schizophrenia may be differentially affected, depending on the pharmacologic profiles of the antipsychotics used for the treatment of this illness.

The impact of frontal and non-frontal brain tumor lesions on Wisconsin Card Sorting Test performance

Several lesion and imaging studies have suggested that the Wisconsin Card Sorting Test (WCST) is a measure of executive dysfunction. However, some studies have reported that this measure has poor anatomical specificity because patients with either frontal or non-frontal focal lesions exhibit similar performance. This study examined 25 frontal, 20 non-frontal low-grade brain tumor patients, and 63 normal controls (NC) on the WCST. The frontal patients were also assigned to either a left frontal (n=10) group or a right frontal group (n=15) and compared with the non-frontal group and NC. It was hypothesized that the frontal brain tumor patients would display greater deficits on categories achieved and a higher number of perseverative errors than non-frontal brain tumor patients on the WCST. Finally, it was predicted that right frontal brain tumors would result in greater executive functioning deficits than left frontal or non-frontal brain tumors. Results indicated that the left frontal group achieved the fewest categories and committed the most perseverative errors compared to the other patient and normal control groups. In addition, the left frontal group committed significantly more perseverative errors than the right frontal group. These results suggest that the WCST is sensitive to the effects of low-grade brain tumors on executive functioning.

The Danish PET/depression project: performance on Stroop's test linked to white matter lesions in the brain

The Stroop test (ST) assesses the integrity of prefrontal and cingulate functioning. Patients with major depression perform poorly on the ST, pointing to disturbed function in these areas. We therefore used positron emission tomography to study 41 in-patients with major depression and 46 age- and gender-matched controls during neuropsychological activation with the ST. Magnetic resonance imaging was used for coregistration and for description of the localization of white matter lesions (WML). The cerebral blood flow (CBF) changes during ST were mapped for each of the two study groups, and inter-group differences were calculated on a voxel-by-voxel basis. The patients were followed for 3 to 5 years to ensure diagnostic stability. The control group activated anterior cingulate regions, prefrontal cortices, insula, thalamus and cerebellum. Despite the patients' slower performance with more errors, no significant differences were found comparing the activations in the two groups. The performance was, however, correlated to the number of WML in frontal lobes, insula and adjacent to the basal ganglia, whereas WML in other locations was not related to performance. We thus partly explain the poorer performance by increased frequency of WML in frontostriatal pathways in the depressed patients, impairing neurotransmission.

GABA and schizophrenia: a review of basic science and clinical studies

BACKGROUND

A converging body of evidence implicates the gamma-aminobutyric acid (GABA) neurotransmitter system in the pathogenesis of schizophrenia.

METHODS

The authors review neuroscience literature and clinical studies investigating the role of the GABA system in the pathophysiology of schizophrenia. First, a background on the GABA system is provided, including GABA pharmacology and neuroanatomy of GABAergic neurons. Results from basic science schizophrenia animal models and human studies are reviewed. The role of GABA in cognitive dysfunction in schizophrenia is then presented, followed by a discussion of GABAergic compounds used in monotherapy or adjunctively in clinical schizophrenia studies.

RESULTS

In basic studies, reductions in GABAergic neuronal density and abnormalities in receptors and reuptake sites have been identified in several cortical and subcortical GABA systems. A model has been developed suggesting GABA's role (including GABA-dopamine interactions) in schizophrenia. In several clinical studies, the use of adjunctive GABA agonists was associated with greater improvement in core schizophrenia symptoms.

CONCLUSIONS

Alterations in the GABA neurotransmitter system are found in clinical and basic neuroscience schizophrenia studies as well as animal models and may be involved in the pathophysiology of schizophrenia. The interaction of GABA with other well-characterized neurotransmitter abnormalities remains to be understood. Future studies should elucidate the potential therapeutic role for GABA ligands in schizophrenia treatment.

Altered auditory processing in acutely psychotic never-medicated first-episode patients

Individuals with psychosis fail to differentiate external impulses and suffer from distortions of reality testing. Schizophrenia group illnesses are also associated with deficits in working memory and perception. We examined the manifestations of a very early phase of psychotic illness to automatic auditory deviance detection to clarify the basic mechanisms underlying misinterpretations of perception.

METHODS

Twenty-five never-medicated patients admitted for hospital evaluation of acute psychosis were studied. Fifty-eight EEG channels were recorded during an auditory oddball paradigm. Event-related potentials (ERPs) time-locked to non-attended deviant auditory stimuli were studied in patients and compared with healthy controls. Auditory processing was examined both at the level of the measured biosignals (standard and deviant responses) and with subtraction waveforms. Topographical differences were characterized using global field power (GFP) and minimum norm estimates.

RESULTS

The maximum GFP amplitudes and mean amplitudes of the 58 channels within the time windows corresponding to the previously known 'N2b', 'P3a' and 'P3b' components were clearly reduced in patients when compared to healthy controls. However, the groups did not differ during attention-independent automatic processing corresponding to the 'N1' and 'MMN' components, or with respect to the peak latencies of the GFP maxima.

CONCLUSIONS

Impairment of the processing of a deviance in simple auditory input in acutely ill drug-naive first-episode psychotic patients only appears in attention-dependent processing after about 250 ms. The alterations in auditory processing differed between stimulus types, suggesting at least two mechanisms underlying the auditory discrimination impairments in acute psychosis. After 250 ms there was a linear and gradually increasing difference in magnitude between the groups in their responses to deviant stimuli, probably related to arousal. In addition, however, there was a striking difference between the groups in the processing of standard stimuli. The early processing was similar in patients and controls, but the striking difference appeared in later processing. The sensory memory deficits associated with psychosis may be explained by an abnormality in sensory model formation rather than by impaired deviant detection.

The Danish PET/depression project: poor verbal fluency performance despite normal prefrontal activation in patients with major depression

The verbal fluency (VF) test is associated with prefrontal and cingulate functioning. We used positron emission tomography (PET) to test the hypothesis that inactivity in these regions can explain why patients with depression often perform poorly on this test. Forty-one patients with major depression and 46 controls were scanned during rest and during activation with the VF test. The differences between the two conditions were mapped for each of the two groups, and between-group differences in the activation pattern were calculated on a voxel-by-voxel basis. As predicted, the patients performed significantly more poorly on the test. In both groups activations were seen in the left anterior cingulate region, the left dorsolateral prefrontal cortex, the left medial prefrontal cortex, and the right cerebellum. Performance was correlated to the cerebral perfusion in to the left occipitotemporal gyrus and the left cerebellum. However, no difference in activation between the two groups was significant. The present study had sufficient power to detect potential differences between the two groups, and the subtraction tasks were appropriate. Therefore, the result supports the notion that abnormalities in the prefrontal cortex in depression are qualitative in nature rather than quantitative; this suggests depression involves dys-coordination of neural activity in the frontal lobes rather than a simple reduction in activity.

Neuroactivación con torre de Hanoi en pacientes con trastorno obsesivo-compulsivo y voluntarios sanos

The aim of the study was to evaluate changes in regional cerebral blood flow (rCBF) in obsessive-compulsive disorder (OCD) patients and healthy controls during performance of Tower of Hanoi (TOH) test (cognitive task).

MATERIAL AND METHODS

We compared TOH test performance in 30 OCD patients and 30 individually matched healthy volunteers. Intelligence and anxiety measurements were taken into account for all participants. Within the patient group, factors such as duration and severity of symptoms and low mood were considered. rCBF was estimated through the uptake of 99mTc-hexamethylpropylamine-oxime (HMPAO) on single photon emission computerised tomography (SPECT). Regional values were quantified as ratios of cortical blood flow.

RESULTS

OCD patients and volunteers differed significantly in terms of subjective anxiety during procedures. TOH test performance was significantly impaired in OCD patients when compared with matched controls. 2-tailed t tests for repeated measures suggested that there were overall significant differences (p = 0.039) between both groups (OCD patients and controls) confined to left caudate activation. There was increased activity after activation in control subjects, but not in OCD patients. No differences in other regions were observed.

CONCLUSIONS

These results suggest a modification of the activating systems of basal ganglia functions in OCD compared with normal subjects.

Cerebral correlates of selective attention in schizophrenic patients with formal thought disorder: a controlled H2 15O-PET study

There is a widespread belief that formal thought disorders may be associated with disturbed selective attention in schizophrenia. Two hypotheses are derived: (1) patients with slightly pronounced formal thought disorders should differ from those with severely expressed formal thought disorders in terms of selective attention; and (2) the cerebral correlates of selective attention should be organised differently in mildly versus severely thought-disordered patients. We compared 20 female schizophrenic patients, one-half with mild, one-half with obvious formal thought disorders, and 10 control subjects on a neuropsychological battery and a cognitive activation task for selective attention (Go/NoGo) for the assessment of rCBF using H2 15O-PET. While the first hypothesis has not been confirmed, we found that the cerebral regions activated by selective attention in the two patient groups showed completely differing organisations. Low degrees of formal thought disorders were associated with significant activations in frontal superior gyrus and ventral anterior thalamic nucleus whereas high degrees of formal thought disorders were accompanied by significant activations in fusiform gyrus and precuneus. We suggest that differing task-solving strategies are applied by both clinical subgroups to achieve comparable results on the selective attention paradigm.

Procedural learning in schizophrenia: a functional magnetic resonance imaging investigation

Procedural learning (PL) is a type of rule-based learning in which performance facilitation occurs with practice on task without the need for conscious awareness. Schizophrenic patients have often (though not invariably) been found to show impaired PL. We performed functional magnetic resonance imaging (fMRI) during a blocked, periodic sequence-learning task with groups of: (i) healthy subjects, and (ii) schizophrenic patients on conventional antipsychotics. Healthy subjects showed significant PL, but patients did not. In healthy subjects, PL was associated with increased activation in the striatum, thalamus, cerebellum, precuneus, medial frontal lobe, and cingulate gyrus. The power of activation in the thalamus, striatum, precuneus, cingulate gyrus and BA 6 was related to the magnitude of PL in these subjects. No regions, except the anterior inferior gyrus, were significantly activated in patients. The caudate nucleus, thalamus, precuneus, and sensorimotor regions were activated significantly differently between the two groups. The findings demonstrate the involvement of the striatum, cerebellum, thalamus, cingulate gyrus, precuneus, and sensorimotor regions in PL. Further fMRI studies of PL in normal subjects treated with conventional antipsychotics, drug naïve patients, and patients given atypical antipsychotics would help to clarify the roles of schizophrenic disease processes and antipsychotic medication in impaired PL and associated brain abnormalities in schizophrenia.

An fMRI study of reduced left prefrontal activation in schizophrenia during normal inhibitory function

Functional magnetic resonance imaging (fMRI) was used to investigate the hypothesis that schizophrenia is associated with a dysfunction of prefrontal brain regions during motor response inhibition. Generic brain activation of six male medicated patients with schizophrenia was compared to that of seven healthy comparison subjects matched for sex, age, and education level while performing 'stop' and 'go-no-go' tasks. No group differences were observed in task performance. Patients, however, showed reduced BOLD signal response in left anterior cingulate during both inhibition tasks and reduced left rostral dorsolateral prefrontal and increased thalamus and putamen BOLD signal response during stop task performance. Despite good task performance, patients with schizophrenia thus showed abnormal neural network patterns of reduced left prefrontal activation and increased subcortical activation when challenged with motor response inhibition.

Bimanual coordination in chronic schizophrenia

Anomalies of movement are observed both clinically and experimentally in schizophrenia. While the basal ganglia have been implicated in its pathogenesis, the nature of such involvement is equivocal. The basal ganglia may be involved in bimanual coordination through their input to the supplementary motor area (SMA). While a neglected area of study in schizophrenia, a bimanual movement task may provide a means of assessing the functional integrity of the motor circuit. Twelve patients with chronic schizophrenia and 12 matched control participants performed a bimanual movement task on a set of vertically mounted cranks at different speeds (1 and 2 Hz) and phase relationships. Participants performed in-phase movements (hands separated by 0 degrees ) and out-of-phase movements (hands separated by 180 degrees ) at both speeds with an external cue on or off. All participants performed the in-phase movements well, irrespective of speed or cueing conditions. Patients with schizophrenia were unable to perform the out-of-phase movements, particularly at the faster speed, reverting instead to the in-phase movement. There was no effect of external cueing on any of the movement conditions. These results suggest a specific problem of bimanual coordination indicative of SMA dysfunction per se and/or faulty callosal integration. A disturbance in the ability to switch attention during the out-of-phase task may also be involved.

No deficit in total number of neurons in the prefrontal cortex in schizophrenics

The prefrontal cortex (PFC), defined as the cortical region which has the major reciprocal connections with the mediodorsal thalamic nucleus (MD), has often been implicated in schizophrenia. Morphometric studies have shown altered neuronal density and structure in parts of the PFC in schizophrenic brains. In addition, the MD and nucleus accumbens have shown a significant deficit in total neuron number. The purpose of the present study was to estimate the total neuron number in the PFC in schizophrenics and controls. Using a stereological design, the PFC was studied in eight brains from schizophrenic patients and 10 age-matched control brains. The bilateral average total number of neurons in the PFC was estimated to be 2.76 x 10(9) (CV=S.D./mean=0.15) in the schizophrenic brains whereas that of controls was a non-significantly different value of 3.11 x 10(9) (CV=0.22; P=0.23). Furthermore, no significant differences were found between the two groups in neuronal density (P=0.10) or volume of the PFC (P=0.49). It is of course possible that a neuronal deficit, which cannot be revealed when estimating the total global number of neurons in the whole PFC, might exist in a subregion of the PFC. In conclusion, uniform loss of neuronal soma in the PFC does not appear to constitute the neural substrate of the pathological process in schizophrenia.

Unawareness of illness in chronic schizophrenia and its relationship to structural brain measures and neuropsychological tests

The present study seeks to elucidate the relationship between unawareness of illness in schizophrenia and frontal lobe dysfunction, in addition to investigating the relationship between lack of insight and sociodemographic and clinical variables. Twenty-one medicated schizophrenic patients, recruited from in- and out-patient wards at Ullevâl Hospital, underwent the Scale to Assess Unawareness of Mental Disorder (SUMD), neuropsychological testing, psychiatric symptom ratings and neuroimaging procedures (CT). Also, 21 matched normal controls were neuropsychologically tested. CT data were assessed blindly by two experienced neuroradiologists, according to the degree of ventricular enlargement and/or sulcal widening, and an assessment of localisation of atrophy was made. Unawareness of illness was correlated with neuropsychological measures related to executive functioning, but not with other neuropsychological measures. Five patients showed slight frontal atrophy, while two showed moderate frontal atrophy. The remaining 13 patients did not show signs of frontal lobe atrophy. Frontal lobe atrophy documented by structural brain measures was associated with poor insight in schizophrenia. Furthermore, Anergia (BPRS), GAF score and 'undifferentiated' sub-diagnosis correlated with SUMD scores. Unawareness of illness in schizophrenia may be related to frontal lobe deficit. Also, awareness of illness may not be related to general psychopathology, but rather to specific aspects.

Neural models of schizophrenia

Hallucinations and delusions - two diagnostic features of psychosis shared across the spectrum of heterogeneous schizophrenia constructs - can be described in terms of the pathophysiology of sensory information processing: hallucination is the impaired ability to classify representations as internally or externally generated, while delusion is the immutable linking of representations with each other in the absence of external dependency. The key anatomical systems in higher-order information processing are the cortex, thalamus, basal ganglia, and medial temporal lobe, each of which is modulated by neurotransmitter projection systems. Preliminary evidence, concentrating to date on the dorsolateral prefontal cortex, thalamus, and hippocampal region of the medial temporal lobe, points to neural circuitry dysfunction within and between each system in psychosis. This may account for specific symptoms and associated cognitive deficits such as memory impairment, attention deficit, and language disturbance.

Schizophrenic subjects show aberrant fMRI activation of dorsolateral prefrontal cortex and basal ganglia during working memory performance

BACKGROUND

Working memory (WM) deficits in schizophrenia have been associated with dorsolateral prefrontal cortex (DLPFC) dysfunction in neuroimaging studies. We previously found increased DLPFC activation in schizophrenic versus normal subjects during WM performance (Manoach et al 1999b). We now have investigated whether schizophrenic subjects recruit different brain regions, particularly the basal ganglia and thalamus, components of frontostriatal circuitry thought to mediate WM.

METHODS

We examined regional brain activation in nine normal and nine schizophrenic subjects during WM performance using functional magnetic resonance imaging. Subjects performed a modified version of the Sternberg Item Recognition Paradigm that included a monetary reward for correct responses. We compared high and low WM load conditions to each other and to a non-WM baseline condition. We examined activation in both individual subjects and averaged group data.

RESULTS

Relative to normal subjects, schizophrenic subjects exhibited deficient WM performance, at least an equal magnitude of right DLPFC activation, significantly greater left DLPFC activation, and increased spatial heterogeneity of DLPFC activation. Furthermore, only the schizophrenic group activated the basal ganglia and thalamus, even when matched for task performance with the normal group.

CONCLUSIONS

Aberrant WM performance and brain activation in schizophrenia may reflect dysfunction of frontostriatal circuitry that subserves WM. Future studies will elucidate the contribution of the anatomical components of this circuitry to WM deficits.

Neural correlates of memory organization deficits in schizophrenia. A single photon emission computed tomography study with 99mTc-ethyl-cysteinate dimer during a verbal learning task

Regional cerebral blood flow (rCBF) during a verbal learning task was measured using 99mTc-ethyl-cysteinate dimer and single photon emission computed tomography in 10 patients with schizophrenia and nine normal controls. Verbal repetition was used as a control task. The schizophrenic patients showed failure to spontaneously utilize implicit category information to learn the word lists. In the normal controls, rCBF in the left inferior frontal and left anterior cingulate regions was significantly increased during the verbal learning task, compared with the verbal repetition task. In contrast, there was no significant frontal lobe activation by the verbal learning in the schizophrenic patients. The patients had lower rCBF during the verbal learning task than the controls in the bilateral inferior frontal, left anterior cingulate, right superior frontal, and bilateral middle frontal regions. Activation in the left inferior frontal region was significantly positively correlated with categorical clustering in the task in the controls, but no such correlation was found in the patients. These results indicate that memory organization deficits in schizophrenia may be related to dysfunction in the prefrontal areas, especially in the left inferior frontal region.

Regional cerebral blood flow in male schizophrenic patients performing an auditory discrimination task

Regional cerebral blood flow (rCBF) was measured in 11 schizophrenic patients amid 10 normal controls, both at rest and while performing an auditory discrimination task. Single photon emission computed tomography with technetium-99m hexamethylpropylene amine oxime was used for quantitative evaluation of rCBF. The schizophrenic patients showed greater rCBF in the temporal and parietal regions at rest than the controls, but no abnormalities were found in frontal perfusion. During task performance. on the other hand, the patients showed a reduced frontal rCBF. whereas there was no group difference in rCBF in the temporal and parietal regions. In addition, the left> right hemisphere asymmetries of rCBF observed in the controls during task performance were not present in the patients. although there was no group difference in hemisphere laterality in rCBF at rest. These findings suggest that the employment of a cognitive task for neuroimaging studies is useful for detecting abnormalities of brain activation. such as hypofrontality and altered hemisphere laterality. in patients with schizophrenia.

Working memory constrains abstraction in schizophrenia

BACKGROUND

Abstraction has long been considered an area of differential cognitive deficit in schizophrenia, primarily because of patients' poor performance on the Wisconsin Card Sorting Test (WCST). Yet, the complexity and multidimensional nature of the WCST increases the likelihood that several different cognitive processes, perhaps mediated by different neural systems, are being tapped.

METHODS

In the current study, the Abstraction and Working Memory (AIM) task was designed to disentangle abstraction and working memory so that the effects of each cognitive domain could be independently analyzed. The AIM task and a battery of neuropsychological tests were administered to 62 patients with schizophrenia and 62 matched healthy volunteers.

RESULTS

Whereas patients with schizophrenia demonstrated deficits in simple abstraction, they were disproportionately impaired with the addition of a minimal memory requirement.

CONCLUSIONS

Group differences on WCST performance appear to be attributable to patients' inability to maintain information over a short delay, before that information is used for more complex cognitive operations.

Auditory hallucinations: phenomenology, neuropsychology and neuroimaging update

Auditory verbal hallucinations (AVHs) are a cardinal feature of psychosis. Recent research is reviewed which has attempted to advance our knowledge of the mechanisms underlying this symptom. Phenomenological surveys have confirmed the importance of the content of such hallucinations and their meaning to the voice-hearer. Psychological and neuroimaging studies of inner speech and source monitoring have provided a neuropsychological framework for AVHs as well as some novel therapeutic strategies. There have also been successful attempts to 'capture' neural activity coincident with the experience of hallucinations using PET, SPECT and functional magnetic resonance imaging (MRI). This body of knowledge in combination with work on in-vivo receptor binding (dopamine and GABA) provides the beginnings of a cognitive and neurophysiological understanding of this complex and intriguing phenomenon.

Schizophrenic subjects activate dorsolateral prefrontal cortex during a working memory task, as measured by fMRI

BACKGROUND

Neuroimaging studies of schizophrenic subjects performing working memory (WM) tasks have demonstrated a relative hypoactivity of prefrontal cortex compared with normal subjects.

METHODS

Using functional magnetic resonance imaging (fMRI), we compared dorsolateral prefrontal cortex (DLPFC) activation in 12 schizophrenic and 10 normal subjects during rewarded performance of a WM task. Subjects performed a modified version of the Sternberg Item Recognition Paradigm (SIRP), a continuous performance, choice reaction time (RT) task that requires WM. We compared a high WM load condition with a nonWM choice RT condition and with a low WM load condition.

RESULTS

Schizophrenic subjects performed the tasks better than chance but worse than normal subjects. They showed greater activation than normal subjects in the left DLPFC but did not differ in the right DLPFC or in the control region. In the schizophrenic group, left DLPFC activation was inversely correlated with task performance, as measured by errors.

CONCLUSIONS

These findings contrast with previous studies that demonstrated task-related hypofrontality in schizophrenia. Task parameters that may contribute to this difference are discussed. We hypothesize that the performance and activation differences we observed are also manifestations of prefrontal dysfunction in schizophrenia. They reflect inefficient functioning of the neural circuitry involved in WM.

Regional cerebral blood flow in Down syndrome adults during the Wisconsin Card Sorting Test: exploring cognitive activation in the context of poor performance

BACKGROUND

Prior studies have indicated abnormal frontal lobes in Down syndrome (DS). The Wisconsin Card Sorting Test (WCST) has been used during functional brain imaging studies to activate the prefrontal cortex. Whether this activation is dependent on successful performance remains unclear. To determine frontal lobe regional cerebral blood flow (rCBF) response in DS and to further understand the effect of performance on rCBF during the WCST, we studied DS adults who perform poorly on this task.

METHODS

Initial slope (IS), an rCBF index, was measured with the 133Xe inhalation technique during a Numbers Matching Control Task and the WCST. Ten healthy DS subjects (mean age 28.3 years) and 20 sex-matched healthy volunteers (mean age 28.7 years) were examined.

RESULTS

Performance of DS subjects was markedly impaired compared to controls. Both DS and control subjects significantly increased prefrontal IS indices compared to the control task during the WCST.

CONCLUSIONS

Prefrontal activation in DS during the WCST was not related to performance of that task, but may reflect engagement of some components involved in the task, such as effort. Further, these results show that failure to activate prefrontal cortex during WCST in schizophrenia is unlikely to be due to poor performance alone.

The resting and activation issue of hypofrontality: a single photon emission computed tomography study in neuroleptic-naive and neuroleptic-free schizophrenic female patients

BACKGROUND

Functional neuroimaging findings of "hypofrontality" in schizophrenic patients is still controversial, due to the heterogeneity of methods and patient samples. This study tries to prevent some of these concerns by studying neuroleptic-naive (NN) and neuroleptic-free (NF) young female patients both in resting conditions and during a frontal cognitive activation task.

METHODS

Regional cerebral blood flow (rCBF) was studied at rest and during the Wisconsin Card Sorting Test (WCST) in 25 young acute unmedicated schizophrenic female patients (14 NN and 11 NF) and 15 female controls, using single photon emission computed tomography.

RESULTS

The schizophrenic and control groups did not differ in rCBF during the baseline condition, but the schizophrenic group failed to activate the frontal lobe during the WCST condition. In addition, the left anterior temporal rCBF at rest correlated with the Scale for the Assessment of Positive Symptoms total score.

CONCLUSIONS

The results suggest that hypofrontality in young acute unmedicated schizophrenic patients is a result of an inability to activate frontal regions during cognition, rather than a baseline decrease in frontal activity. Furthermore, positive symptoms seem to be associated with left temporal cortex activity.

Brain functions and psychiatric disorders. A clinical view

Psychiatric disorders are viewed as brain disorders affecting five circuits of the brain: the brainstem, the hypothalamus, the motor striatum, the limbic system (ventral striatum), and the neocortex. This five-circuit model combines neuroscientific, psychopharmacologic, evolutionary, introspective, and behavioral data. The article presents a broad speculative overview of some brain functions and dysfunctions relevant for clinicians.

Regional cerebral blood flow and comorbid diagnosis in abstinent opioid addicts

Studies using single photon emission computed tomography (SPECT) have found low cerebral blood flow (CBF) in frontal and parietal cortices in patients with chronic opiate dependence. In the present study, SPECT with 99mTc-HMPAO as tracer was used to compare 27 detoxified opiate addicts with nine healthy control subjects. All the subjects were evaluated with clinical psychiatric (DSM-IV), psychometric and neuropsychological measures. Compared with normal control subjects, the addicts showed a non-significant reduction of whole brain perfusion values. Significant hypoperfusion in the right frontal and left temporal lobes was found in addicts with comorbid depression, and a significant decrease in CBF in the right frontal lobe was observed in those with antisocial tendencies. A significant negative correlation emerged between Depression subscale scores on the Minnesota Multiphasic Personality Inventory and left temporal CBF in the patients. No significant correlations were found, however, between measures of cognition and CBF in opiate addicts. The asymmetrical findings in CBF that characterized the addicts relative to normal control subjects may be more closely related to mood and behavioral traits than to substance abuse, per se.

Role of the cingulate gyrus during the Wisconsin Card Sorting Test: a single photon emission computed tomography study in normal volunteers

The purpose of this study was to investigate the effect of the Wisconsin Card Sorting Test (WCST) on frontal regional cerebral blood flow (rCBF) in normal subjects, separating the cingulate gyrus from the prefrontal cortex. Two technetium-99m-hexamethyl-propylene-amine-oxime brain single photon emission computed tomography (SPECT) scans, at rest and during WCST performance, were performed in randomized order on 13 right-handed normal volunteers. A statistically significant rCBF increase was found in the left inferior cingulate and the left posterior frontal region, although rCBF ratios in the left and right prefrontal cortex, and in the right inferior cingulate, were slightly higher during WCST performance in nine of the 13 subjects studied. No differences in activation scores (activated-resting rCBF ratios) were found between subjects who had the resting SPECT first and subjects who had the resting condition second. These results suggest that the inferior cingulate cortex, a limbic region that has been implicated in attentional mechanisms, plays a significant role in WCST performance. Furthermore, the motor component of the WCST may account for the activation of the left posterior frontal region. In addition, no order effect was found in this study. These findings illustrate the advantage of independently evaluating the cingulate gyrus and the prefrontal cortex in SPECT studies of frontal cognitive function.

Regional cerebral blood flow in first-episode schizophrenia patients before and after antipsychotic drug treatment. Scottish Schizophrenia Research Group

A total of 38 patients in a first presentation of schizophrenia prior to drug treatment underwent a single photon emission computerized tomography (SPECT) scanning programme whilst undertaking a verbal fluency task. Their scans were compared with those of 38 normal volunteer controls matched for age, sex and father's social class. Schizophrenic patients displayed a trend towards a reduced blood flow in comparison with controls. Comparing right with left hemispheres, asymmetrical blood flow patterns were more likely to be found in patients in frontal regions than elsewhere. When 27 of the 38 patients underwent a repeat SPECT scanning programme after receiving 6 months of antipsychotic drug treatment, the hypofrontal blood flow pattern persisted. Increased blood flow was observed bilaterally in the putamen. The more symmetrical blood flow pattern of the patients compared to the control subjects did not alter substantially.

High-energy phosphates in the frontal lobe correlate with Wisconsin Card Sort Test performance in controls, not in schizophrenics: a 31phosphorus magnetic resonance spectroscopic and neuropsychological investigation

In recent years, a number of 31phosphorus magnetic resonance spectroscopy (P-MRS) studies on the frontal lobe of schizophrenics have been performed, reporting alterations of phospholipids and high-energy phosphates. Deicken et al. (1994b) recently found positive correlations between left frontal phosphomonoester% (PME%) levels and the performance of a specific frontal lobe task, the Wisconsin Card Sorting Test (WCST), in schizophrenics. In the present paper, the correlations between phospholipids and high-energy phosphates in the frontal lobe of 26 schizophrenics and 23 controls measured with a volume-selective P-MRS method were investigated. Overall, we could not find any correlations between WCST results and phospholipid levels, but in controls phosphocreatine% (PCr%) and PCr/adenenosine triphosphate (ATP) ratios were negatively correlated with test performance. Since PCr behaves as a buffer of ATP, in the sense that when ATP is consumed by neuronal activity PCr is catalysed rapidly to ATP, increased PCr% values and, moreover, increased PCr/ATP ratios point to a decreased ATP consumption. Thus, the correlations found between PCr% and PCr/ATP and test performance in controls point to an association between reduced performance in a specific frontal lobe task and decreased energy demanding processes at rest. This association was not found in schizophrenics, possibly due to the influence of neuroleptic medication or the disease process per se.

SPECT brain blood flow changes with continuous ligand infusion during previously learned WCST performance

Performance of the Wisconsin Card Sorting Test (WCST) and related brain-activation patterns reflect both task learning and execution. Normal subjects learned the WCST prior to performance during slow SPECT ligand infusion. Blood flow increased in bilateral inferior frontal, right middle and inferior parietal cortices. Activity decreased in hippocampi, temporal cortex, anterior cingulate and caudate.

Chemical and physiologic brain imaging in schizophrenia

Technologic advances in functional brain imaging have provided exciting and informative insights into the functional neuroanatomy and neurochemistry of schizophrenia. Using MR spectroscopy, it has been possible to examine in vivo brain metabolism and to relate observed changes to physiological processes occurring at a cellular level. Positron emission tomography and single photon emission computed tomography have revealed disturbances of cerebral blood flow and glucose metabolism in patients with schizophrenia. More recently, these tools have also proved most useful in studying the relative receptor occupancy of typical and atypical antipsychotic medications.

Hypofrontality in schizophrenia: influence of normalization methods

1. Studies with Single Photon Emission Computed Tomography (SPECT) in schizophrenia research have utilized different approaches to normalization of data, such as cerebellar ratio and whole brain ratio methods, leading to conflicting findings. 2. The authors compared these two methods to test the hypofrontality hypothesis of schizophrenia. 3. Eighteen chronic and medicated DSM-IV schizophrenic patients and 10 healthy controls underwent two SPECT examinations using 99mTc HMPAO as a tracer at baseline and during frontal activation while applying the Wisconsin Card Sorting Test. 4. The hypofrontality hypothesis was supported with both indexes of relative perfusion, although the whole brain ratio method appeared to be more reliable and specific than the cerebellar ratio method. 5. Further studies are required to confirm these preliminary results on the specificity and sensitivity of both methods.

Cerebral glucose metabolism in childhood onset schizophrenia

Decreased frontal cortical glucose metabolism has been demonstrated in adult schizophrenics both at rest and while engaging in tasks that normally increase frontal metabolism, such as the Continuous Performance Test (CPT). The authors tested the hypothesis that adolescents with childhood onset schizophrenia would also demonstrate hypofrontality while performing the CPT. Cerebral glucose metabolism was examined in 16 adolescents (mean age 14.1 +/- 1.7) with onset of schizophrenia by age 12 (mean age at onset 9.9 +/- 1.8) and 26 healthy adolescents selected to be similar in age, sex and handedness using positron emission tomography and 18F-fluorodeoxyglucose. Patients with childhood onset schizophrenia made fewer correct and more incorrect identifications on the CPT. Region of interest analysis revealed no significant group differences in global cerebral glucose metabolism, but increased metabolic rate in supramarginal gyrus (F = 6.74, P < 0.05) and inferior frontal gyrus/insula (F = 7.09, P < 0.05) and decreased metabolic rate in middle frontal gyrus (F = 6.72, P < 0.05) and superior frontal gyrus (t = 2.04, P < 0.05) in schizophrenics. Comparison of effect sizes with an identically designed study of adult schizophrenics did not indicate more severe hypofrontality in childhood onset schizophrenia. Pixel-based analyses indicated a more complex pattern of group differences in cerebral metabolism with bilaterally increased cerebellar metabolic rate in childhood onset schizophrenics. These findings suggest that childhood onset schizophrenia may be associated with a similar, but not more severe, degree of hypofrontality relative to that seen in adult onset schizophrenia.

Brain activation during cognitive stimulation with the Wisconsin Card Sorting Test--a functional MRI study on healthy volunteers and schizophrenics

It has been demonstrated by single photon emission computed tomography (SPECT) and positron emission tomography (PET) that frontal brain regions are stimulated during performance of the Wisconsin Card Sorting Test (WCST). The WCST is also regarded as one of the standard tests for the assessment of frontal activity in brain imaging studies of schizophrenia. In this study cerebral activation was assessed by means of functional magnetic resonance imaging (fMRI). In healthy volunteers WCST stimulation resulted in a right lateralized frontal activation. In 13 chronic schizophrenics on stable neuroleptic medication, a lack of activation in the right prefrontal cortex and--as a trend--an increased left temporal activity during execution of the WCST was noted compared to controls. Since a one-slice technique was used, no information about the activation pattern in adjacent brain regions was obtained. However, as fMRI possesses a superior spatial resolution compared to SPECT and PET, the anatomical localization of the activation effect in the measured slice can be defined more precisely. Beside these methodological considerations, the results are discussed in relation to prior findings of a reduced ability of schizophrenics to coordinate cerebral function.

Regional cerebral blood flow in late-onset schizophrenia: a SPECT study using 99mTc-HMPAO

Functional neuroimaging studies have been performed in many young patients with schizophrenia, but late-onset schizophrenia (LOS) remains largely unexamined by these techniques. We predicted that LOS would demonstrate regional cerebral blood flow (rCBF) abnormalities similar to those seen in early-onset schizophrenia (EOS), but with a basis in demonstrable coarse brain disease. The subjects were 15 LOS and 7 EOS patients and 27 healthy controls. Each was given a detailed clinical and neuropsychological assessment and underwent MRI and Tc99m-HMPAO single photon emission computed tomography (SPECT) scans. The LOS subjects had a significantly lower cerebral hemispheric perfusion than controls, with a lower perfusion in the frontal and temporal lobes bilaterally. The LOS group also had significantly lower left-to-right hemisphere blood flow ratios. EOS subjects had a lower frontal perfusion than the controls, which was significant in the left frontal region. The temporal perfusion in the EOS subjects was greater than in the LOS group, and not different from the control subjects. Left temporal perfusion was the most discriminating variable between LOS and control subjects on logistic regression. Correlations of perfusion with MRI were generally low with the exception that the asymmetry indices were significantly correlated, and basal ganglia perfusion correlated with basal ganglia hyperintensities on MRI. The total cerebral perfusion index correlated significantly with the mini-mental state examination (MMSE) score, and the temporal lobe perfusion correlated with MMSE scores and some verbal memory measures. In the schizophrenic groups, perfusion correlated nonsignificantly with symptom profiles. We conclude that our findings of temporal and frontal rCBF abnormalities, especially on the left side, in LOS are similar to those reported in schizophrenia in general. The results do not provide evidence for coarse brain disease underlying the rCBF abnormalities in LOS, or support the specificity of these abnormalities for particular subsyndromes of schizophrenia.

Psychopathological and SPECT findings in never-treated schizophrenia

A total of 24 never-treated (i.e. drug-naive) actively psychotic schizophrenic patients, operationalized according to DSM-III-R, were examined in a pre-post-treatment design using the Positive and Negative Syndrome Scale for Schizophrenia (PANSS) and 99mTc-HMPAO-single photon emission computed tomography (SPECT) to assess regional cerebral blood flow (rCBF). The control subjects were 20 patients free of neurological and psychiatric symptoms. Before treatment there was only a slight hypofrontality, and hypoperfusion was observed in the left temporal superior region. After treatment, hypofrontality was reduced to one region and temporal hypoperfusion disappeared. Formal thought disorders were accompanied by increased rCBF in the bilateral frontal interior and left temporal superior regions. Delusions were associated with hypoperfusion in the anterior cingulate cortex. Negative symptoms showed no linkage to hypofrontality, either before or after treatment. Factor analysis showed delusions and hallucinations loading on different dimensions. The disorganized dimension correlated positively with all regions of interest, whereas these were negatively correlated with reality distortion.