Single-photon emission computed tomography with 99mTc-exametazime in unmedicated schizophrenic patients

Abnormalities of auditory event-related potentials in schizophrenia prior to treatment

BACKGROUND

P300 amplitude reduction is a consistent finding in schizophrenic patients, but it is unclear if this abnormality predates neuroleptic treatment or is present at onset of illness.

METHODS

Auditory event-related potentials (ERPs), during a standard oddball paradigm, were recorded from 45 neuroleptic-naive schizophrenics, 56 drug-free, previously treated schizophrenics, and 73 healthy normal controls. Forty-seven of the schizophrenic subjects had their first episode within the past year.

RESULTS

N200 amplitude did not differ among groups. P300 amplitude was significantly smaller in both neuroleptic-naive and previously treated schizophrenic groups compared to the control groups. There were no significant differences between the two schizophrenic groups in P300 amplitude. N200 and P300 latency were prolonged in previously treated schizophrenics compared to neuroleptic-naive schizophrenics and normal controls.

CONCLUSIONS

The present study suggests that ERP abnormalities, especially P300 amplitude reduction, are already present prior to the administration of neuroleptic medication in the earliest stage of schizophrenia.

Multiple regression analysis of relationship between frontal lobe phosphorus metabolism and clinical symptoms in patients with schizophrenia

We investigated the differences among diagnostic types of 36 schizophrenic patients in the brain phosphorus metabolism in the frontal lobe. We performed phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in the frontal region in patients with schizophrenia of the catatonic (n = 4), disorganized (n = 8), paranoid (n = 10) and undifferentiated (n = 14) types. In the disorganized type, the PME level was significantly decreased compared to those in the other three types, while the phosphodiester (PDE) level tended to be higher, although not significantly, than those in the other types. Using multiple regression analysis, we investigated whether or not the clinical symptoms were correlated with the brain phosphorus metabolism. An increased motor retardation factor score was significantly correlated with decreased PME level, whereas more severe emotional withdrawal and blunted affect were associated with increased PDE level. These results suggest that altered membrane phospholipid metabolism in the frontal region may be associated with negative symptoms and that schizophrenia of the disorganized type is associated with more severe negative symptoms and may present more severe brain abnormalities compared to the other types.

Decreased energy demanding processes in the frontal lobes of schizophrenics due to neuroleptics? A 31P-magneto-resonance spectroscopic study

In the present investigation on 31P-magneto-resonance spectroscopic parameters in the frontal lobe, we found phosphocreatine levels and the ratio phosphocreatine/adenosine triphosphate to be increased (12.62 +/- 1.98% resp. 0.31 +/- 0.06) in 50 neuroleptic-treated schizophrenics, whereas no differences were detected in 10 neuroleptic-free patients (11.66 +/- 2.57% resp. 0.29 +/- 0.08) compared to 36 controls (11.37 +/- 1.45 resp. 0.29 +/- 0.04). This result points to a major role of neuroleptics in the metabolism of high-energy phosphates.

Schizophrenia, psychosis, and the basal ganglia

Schizophrenia is one of the most common and perhaps the most disabling of mental disorders, for which effective forms of treatment have not yet been established definitively. The findings reviewed in this article strongly suggest that basal ganglia abnormalities are involved in the pathophysiology of psychotic syndromes in general, and schizophrenia in particular.

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.

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.

Correlation of positive symptoms exclusively to hyperperfusion or hypoperfusion of cerebral cortex in never-treated schizophrenics

BACKGROUND

Studies of schizophrenia by single photon emission computed tomography (SPECT) and positron emission tomography (PET) have shown both regional cerebral hyperperfusion and hypoperfusion. The aim of this study was to examine the inter-relations between regional cerebral blood flow (rCBF), psychopathology, and effects of neuroleptic therapy.

METHODS

24 never-treated patients with acute schizophrenia were examined with hexamethylpropyleneamine-oxime brain SPECT and assessed psychopathologically according to the positive and negative syndrome scale; they were studied again after neuroleptic treatment and psychopathological remission. rCBF values that deviated from those of 20 controls by more than 2 SD were regarded as abnormal.

FINDINGS

Both hyperperfused and hypoperfused patterns were found among schizophrenia patients during acute illness. The seven positive symptoms on the symptom scale showed different correlations with rCBF: formal thought disorders and grandiosity correlated positively (and strongly) with bifrontal and bitemporal rCBF; delusions, hallucinations, and distrust correlated negatively (and strongly) with cingulate, left thalamic, left frontal, and left temporal rCBF. Stereotyped ideas as a negative symptom correlated negatively (and strongly) with left frontal, cingulate, left temporal, and left parietal rCBF. After neuroleptic treatment (and reduction of positive symptoms), only negative symptoms correlated exclusively with bifrontal, bitemporal, cingulate, basal ganglia, and thalamic hypoperfusion.

INTERPRETATION

Different positive symptoms are accompanied by different rCBF values--some related to hyperperfusion, others to hypoperfusion. This finding may help to explain observed inconsistencies of perfusion patterns in drug-naïve schizophrenics.

Differential relationships between positive and negative symptoms and neuropsychological deficits in schizophrenia

This study assessed the relationships between positive and negative clinical symptoms and specific neuropsychological deficits in a group of stable schizophrenic patients.

METHOD

Thirty patients were assessed using the Positive and Negative Syndrome Scale (PANSS) for schizophrenia and a battery of cognitive tests. The PANSS assessments were done by a group of raters blind to the results of cognitive tests, while the cognitive tests were conducted by a different group of raters who remained blind to the PANSS scores.

RESULTS

We found that, although positive and negative symptoms showed a trend toward direct correlation with each other, they correlated with distinct cognitive deficits. Patients with higher negative scores had more perseverative responses, perservative errors, and completed fewer categories on the Wisconsin Card Sorting Test; they also experienced more difficulties on trail making and verbal fluency tests. On the other hand, positive symptoms were associated with poor performance on the Digit Span, particularly the Digit Span Forward.

CONCLUSIONS

Our findings are in agreement with previous reports that negative symptoms may be associated with poor performance on cognitive tests reflecting particularly frontal function. Positive symptoms, on the other hand, seem to be associated with poor attention, specifically of auditory type, and thus, possibly with dysfunction within the more widespread neural networks underlying attention. Our findings support the hypothesis that positive and negative symptoms may be associated with distinct neuropsychological deficits and thus with distinct neurological substrates and point to the need to address both positive and negative dimensions when studying schizophrenia.

Factor-derived subsyndromes of schizophrenia and familial morbid risks

Factor analysis was performed on OPCRIT checklist ratings from 66 patients with RDC schizophrenia. Eight substantive factors were found, characterised respectively by: positive formal thought disorder; first rank delusions; first rank hallucinations; inappropriate affect/bizarre behaviour; negative symptoms; grandiose/bizarre delusions; delusions of influence/persecution; and other hallucinations. A history of schizophrenia and other non-affective psychoses was ascertained in the probands' first-degree relatives using a family history approach. Illness in relatives was best predicted by probands' scores on subsyndromes derived from the inappropriate affect/bizarre behaviour and positive formal thought disorder factors.

Metabolic hyperfrontality and psychopathology in the ketamine model of psychosis using positron emission tomography (PET) and [18F]fluorodeoxyglucose (FDG)

To date, the ketamine/PCP model of psychosis has been proposed to be one of the best pharmacological models to mimic schizophrenic psychosis in healthy volunteers, since ketamine can induce both positive and negative symptoms of schizophrenia. At subanesthetic doses, ketamine has been reported to primarily block N-methyl-D-aspartate (NMDA) receptor complex giving support to a glutamate deficiency hypothesis in schizophrenia. Positron emission tomography was used to study ketamine-induced psychotic symptom formation in relation to cerebral metabolic alterations in healthy volunteers. Our study shows that NMDA receptor blockade results in a hyperfrontal metabolic pattern. Increased metabolic activity in the frontomedial and anterior cingulate cortex correlated positively with psychotic symptom formation, in particular with ego pathology. Analysis of correlations between syndrome scores and metabolic rate of glucose (CMRglu) or metabolic gradients (ratios) revealed that each psychopathological syndrome was associated with a number of metabolic alterations in cortical and subcortical brain regions, suggesting that not a single brain region, but distributed neuronal networks are involved in acute psychotic symptom formation.

Differential psychopathology and patterns of cerebral glucose utilisation produced by (S)- and (R)-ketamine in healthy volunteers using positron emission tomography (PET)

Until recently, racemic ketamine (S-ketamine/R-ketamine = 50:50) has been used to study NMDA receptor hypofunction in relation to pathophysiological models of schizophrenia. Ketamine given to normal humans in subanesthetic doses produces a model psychosis including both positive and negative symptoms of schizophrenia. More recently it has been shown that at subanesthetic doses the pure (S)- and (R)-ketamine enantiomeres interact differently with the NMDA and sigma receptor sites in human brain. It was found that (S)-ketamine binds with a 3-4 time higher affinity to the PCP binding site of the NMDA receptor than (R)-ketamine, and that at these concentrations (R)-ketamine interacts also weakly with the sigma receptor sites, where (S)-ketamine binds only negligibly. To further investigate the role of NMDA-receptor mediated neurotransmission in schizophrenic psychosis, the effects of pure (S)- and (R)-ketamine enantiomeres on brain energy metabolism in normal humans using positron emission tomography and [18F]fluorodeoxyglucose (FDG) are reported here. Psychotomimetic doses of (S)-ketamine increased cerebral metabolic rates of glucose (CMRglu) markedly in the frontal cortex including the anterior cingulate, parietal and left sensorimotor cortex, and in the thalamus. The metabolic changes in the frontal and left temporal cortex correlated with ego-disintegration and hallucinatory phenomena. Equimolar doses of (R)-ketamine tended to decrease CMRglu across brain regions and significantly suppressed CMRglu in the temporomedial cortex and left insula. (R)-ketamine did not produce psychotic symptoms, but a state of relaxation. The (S)-ketamine-induced metabolic hyperfrontality appears to parallel similar metabolic findings in acute psychotic schizophrenic patients and encourages further investigations of glutamatergic disturbances in schizophrenia.

Factor analysis of schizophrenic symptoms using the OPCRIT checklist

Factor analysis was performed on OPCRIT checklist psychotic symptoms rated on 102 patients with DSM-III-R schizophrenia. An initial three-factor solution produced positive, negative, and disorganisation factors. However, application of the scree test suggested five substantive factors, with the positive factor dividing into three factors characterised, respectively, by paranoid symptoms, first rank delusions and first rank hallucinations.

Expanded CAG/CTG repeats in schizophrenia. A study of clinical correlates

BACKGROUND

Schizophrenia is associated with expanded CAG/CTG trinucleotide repeats. We wished to determine whether the presence of such expansions correlated with specific subsyndromes or other clinical features of schizophrenia.

METHOD

Seventy patients from England and Wales and 44 patients from Portugal with a DSM-III-R diagnosis of schizophrenia were rated on the OPCRIT checklist. Patient's maximum CAG/CTG repeat length was measured using repeat expansion detection (RED). Significant differences were sought for repeat lengths in subjects categorised according to dimensional and categorical schizophrenia subsyndromes, affective episodes, individual symptoms, and a range of demographic variables.

RESULTS

Maximum CAG/CTG repeat length did not differ significantly for any of the clinical or demographic variables studied.

CONCLUSION

There are no subsyndromes or other clinical features of schizophrenia associated with CAG/CTG repeat expansion. Therefore, the identification of the gene(s) that contain expanded CAG/CTG repeats and which are associated with schizophrenia is unlikely to be facilitated at present by using any subsyndromes of schizophrenia as phenotypes.

Prefrontal function in schizophrenia: confounds and controversies

A wealth of clinical data indirectly implicate dysfunction of frontal cortex in schizophrenia, including negative symptoms, the pattern of neuropsychological deficits, and abnormal eye movements. Neuroimaging studies have provided direct evidence of frontal, particularly prefrontal, malfunction, but the results have been inconsistent and controversial. The burning question is whether prefrontal hypofunction is a pathophysiological characteristic of schizophrenia per se or an artifact of the imaging protocol. In studies of patients at rest, 'hypofrontality' has been an inconsistent finding, probably because resting is physiologically and psychologically variable. Cognitive activation paradigms, especially during working memory tasks, have been reliable in showing prefrontal hypofunction in patients, but these results have been challenged as artifacts of poor performance. Performance differences have been addressed by studying patients and controls matched either for poor performance or for normal performance. The former approach, which has the potential of elucidating the specificity of physiological mechanisms associated with poor performance, has shown that prefrontal activity in patients with schizophrenia differs quantitatively and qualitatively from that of normals and of other patient populations who perform at a comparable level. The latter approach, which tends not to find prefrontal differences between patients and controls, may be selecting out important aspects of the disease by focusing on unaffected neural functions. While there are pitfalls to each approach and no single study can address all the potential phenomenological confounds, overall, the functional neuroimaging database in patients with schizophrenia suggests that prefrontal cognitive deficits are because of prefrontal pathophysiology and not the inverse.

The role of the prefrontal cortex in self-consciousness: the case of auditory hallucinations

Many patients with schizophrenia report hallucinations in which they hear voices talking to them or about them. Behavioural and physiological studies show that this experience is associated with processes occurring in auditory language systems associated with both the production and the reception of speech. I propose that hallucinations are experienced because patients have difficulty in distinguishing sensations caused by their own actions from those that arise from external influences. This distinction can be made by predicting the sensations that will result from executive commands (forward modelling). If the predicted sensation matches the actual sensation then no outside influences have occurred and perception of change can be 'cancelled'. At the physiological level this mechanism depends upon interactions between the prefrontal areas where the executive commands originate and posterior brain regions concerned with the resultant sensations. Evidence from functional brain imaging confirms that interactions between prefrontal (executive) areas and auditory association areas are abnormal in schizophrenia. However, this account needs to be extended before we can understand why patients experience the voices as emanating, not just from an external source, but from agents who are trying to influence their behaviour. Recent imaging studies suggest that medial prefrontal cortex is engaged when we think about other people, but the precise nature of the interaction of this brain area with other regions remains to be established.

Limbic dysfunction in schizophrenia and mania. A study using 18F-labelled fluorodeoxyglucose and positron emission tomography

BACKGROUND

Diagnostic classes (derived from CATEGO) can be correlated with regional brain metabolism in patients with major psychiatric disorders.

METHOD

Seventeen patients with schizophrenia, 15 with mania, 10 with depression and 10 healthy Volunteers were examined with positron emission tomography (PET) and 18F-labelled fluorodeoxyglucose, as a marker for glucose metabolism. The number of possible comparisons of regions of interest was reduced by principal-components analysis, and differences in factor scores were determined between diagnostic groups.

RESULTS

Four independent factors, representing distributed brain systems, emerged: an anterior-posterior (1), a left-right temporal (2), a temporofrontal (3), and a mediofrontal (4) system, of which (1), (2) and (3) were abnormal in schizophrenia, (1) and (2) in mania, and (1) in depression.

CONCLUSIONS

Abnormal patterns of metabolism could be detected, in decreasing order, in schizophrenia, mania and depression. Some of these abnormalities are likely to be due to medication, but others will be associated with structural or functional abnormalities of the frontolimbic system in the diagnostic groups.

Regional cerebral blood flow in patients with schizophrenia: relevance to symptom structures

Regional cerebral blood flow (rCBF) was measured with technetium-99m hexamethylpropyleneamine oxime single photon emission computed tomography in 38 neuroleptic-treated schizophrenic patients. To improve the validity of the evaluation of symptomatology, we applied findings previously derived in a principal component analysis (PCA) of the Positive and Negative Syndrome Scale. The PCA had disclosed five orthogonal independent symptom structures (i.e., negative, hostile/excited, thought disordered, delusional/hallucinatory, and depressive components), and obtained factor scores for 70 schizophrenic subjects, including the present sample. Stepwise regression analysis elucidated some of the cortical regions in which relative rCBF predicted the severity of symptoms--namely, lateral and orbital prefrontal, lateral temporal, inferior parietal, and medial temporal regions. Findings suggested that symptom structures derived from PCA could prove helpful in elucidating the pathophysiology of neural mechanisms.

Exploring 'theory of mind' in people with schizophrenia

Mentalizing ability was studied in 46 symptomatic schizophrenic patients and 44 non-symptomatic controls. Subjects heard six stories and simultaneously were shown simple cartoon pictures depicting the action sequencing occurring in the stories. All the stories involved false belief or deception, so that it was necessary to infer the mental states of the characters in order to understand their behaviour. After each story, subjects were asked one memory/reality question (concerning an event in the story) and one question that depended on the ability to infer the mental state of one of the characters. Patients with paranoid delusions were impaired on the questions concerning mental states. Patients with behavioural signs (i.e. negative features or incoherence) were also impaired on the mental state questions, but this difficulty was associated with memory impairments. Patients with symptoms of passivity (e.g. delusions of control) and patients in remission did not differ from normal controls. These results are consistent with the hypothesis that certain of the positive symptoms of schizophrenia reflect an impairment in the ability to infer the mental states of others.

Schizophrenic auditory hallucinations are associated with increased regional cerebral blood flow during verbal memory activation in a study using single photon emission computed tomography

Single photon emission tomography with split-dose technetium-99m-d, l-hexamethyl-propylene amine oxime was used to measure regional cerebral blood flow (rCBF) during a memory-activation paradigm in a group of 18 medicated DSM-III-R schizophrenic patients. The relationship between clinical features of schizophrenia and rCBF patterns was examined. Increased blood flow to the left basal ganglia was revealed during activation in patients reporting hallucinations in the previous month, a finding that was not influenced by medication dose or other confounding variables. This result adds to previous functional imaging studies that have related basal ganglia abnormalities to hallucinatory phenomena and suggests that left basal ganglia hyperactivity may be relevant to an internal monitoring deficit responsible for the appearance of those symptoms in schizophrenia.

Regional cerebral blood flow in first break and chronic schizophrenic patients and normal controls

Dynamic 133Xe Single Photon Emission Computed Tomography (SPECT) was used to measure the resting regional cerebral blood flow (rCBF) in 16 neuroleptic free schizophrenic and schizophreniform male patients and 13 age-matched male normal controls. A subgroup consisting of 'first break' patients who had never been exposed to neuroleptic treatment were age-matched to a subgroup of young chronic patients most of whom had been previously exposed to neuroleptics. The age-adjusted rCBF values were compared among first breaks, young chronics, normal controls, and a subgroup of older, more chronic patients. In first break patients, we found significantly lower absolute global cerebral blood flow and significantly lower superior frontal, middle frontal, and middle temporal absolute rCBF compared to normals. We also found significantly lower relative superior frontal rCBF in first breaks vs. normals, and higher relative superior frontal and relative middle frontal rCBF in older chronics vs. the other groups. For relative posterior temporal rCBF there was greater asymmetry (right side > left) in first breaks and young chronics compared to normals and older chronics.

Brain single-photon emission tomography with technetium-99m hexamethylpropylene amine oxime in adolescents with initial-stage schizophrenia

The objective of this study was to search for regional cerebral blood flow (rCBF) abnormalities in adolescents with initial-stage schizophrenia by means of brain single-photon emission tomography (SPET) using technetium-99m hexamethylpropylene amine oxime (HMPAO). SPET studies were performed on a homogeneous sample of 15 carefully selected adolescents with a recent diagnosis of schizophrenia, and without previous electroconvulsive or antipsychotic drug treatment. Computed tomography (CT) and electro-encephalographic (EEG) studies were performed in all patients. Qualitative and semiquantitative analysis of 99mTc-HMPAO SPET studies showed an impaired rCBF in 12 patients (80%). The most common pattern was a decreased uptake of 99mTc-HMPAO in the frontal lobes, usually in the left hemisphere. Conventional and quantitative EEG was positive in 12 (80%) and 15 (100%) patients, respectively. CT findings were positive in two patients (13%). There was a high level of concordance between SPET and EEG results and between SPET and clinical features (P>0.05). This study suggests that previously untreated patients in the first stages of schizophrenia present functional abnormalities that are revealed by brain SPET.

Schizophrenia--a brain disease? A critical review of structural and functional cerebral abnormality in the disorder

BACKGROUND

With genetic and neurochemical findings pointing to a biological aetiology, considerable effort has been devoted to finding direct evidence of brain abnormality in schizophrenia.

METHOD

CT, MRI, post-mortem and functional imaging studies are reviewed to assess which structural and/or functional brain abnormalities have been consistently demonstrated.

RESULTS

The only well-established structural abnormality in schizophrenia is lateral ventricular enlargement; this is modest and there is a large overlap with the normal population. There is no consensus on the presence of any localised structural abnormality from MRI and post-mortem studies, but the most promising findings concern temporal lobe limbic structures. Hypofrontality is not a well-replicated finding in schizophrenia under resting conditions, but the evidence is stronger for a selective association with negative symptoms. A number of studies have found hypofrontality under conditions of neuropsychological task activation. However, findings in these studies are divided and a recent methodologically sophisticated study has failed to confirm it, although this study suggested a decoupling of prefrontal and temporal function.

CONCLUSION

Schizophrenia is characterised by minor structural abnormality which, in the case of lateral ventricular enlargement, may be better understood as a risk factor than a causative lesion. The functional imaging findings are not transparent but suggest that, as a disorder, schizophrenia shows complex alterations in regional patterns of activity rather than any simple deficit in prefrontal function.

Hypofrontality revisited: a high resolution single photon emission computed tomography study in schizophrenia

Hypofrontality or reduced activity in the prefrontal cortex, measured as reduced frontal perfusion or glucose uptake, has gained the status of an established finding in the medical literature on schizophrenia. Many relevant studies, however, have potential sources of bias, such as small subject numbers, or unreliable performance of activation tasks by the patients during the scanning procedure. Seventy patients with non-affective and non-organic psychoses were recruited--most qualifying for DSM III-R schizophrenia or schizophreniform psychosis (n = 60)--together with 20 healthy volunteers. They underwent single photon emission computed tomography with 99mTc-exametazime, carried out at rest. Tracer uptake was normalised to the occipital cortex. Group differences in tracer uptake were predicted in anterior regions of interest (prefrontal cortex and mesial frontal/cingulate cortex). Actively psychotic (including schizophrenic) patients not taking any drugs showed increased uptake in the prefrontal cortex. Reduced tracer uptake occurred in the mesial frontal cortex of schizophrenic patients, particularly if they were taking drugs. Relatively increased prefrontal tracer uptake associated with relatively decreased mesial frontal uptake characterised the patients in comparison with the controls. Generalised hypofrontality is, therefore, not a feature of schizophrenic patients at rest whether taking drugs or not.

Brain imaging in schizophrenia

Neuroimaging provides an unprecedented means by which to study psychiatric disorders. Structural imaging methods, i.e. computerized tomography (CT) and magnetic resonance imaging (MRI), have revealed subtle differences in the brains of schizophrenic patients that appear to be present before symptom onset. Radionuclide functional methods such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) have led to hypotheses about dysfunction in specific neuronal networks in schizophrenia. New advances in MRI allow functional data to be obtained noninvasively in a single individual using conventional MRI scanners. This chapter discusses the parallels between the historical technical developments in neuroimaging and the deepening understanding of the etiology and manifestations of schizophrenia.

Inner connections within domain of dementia praecox: role of supervisory mental processes in schizophrenia

Kraepelin's conclusion that there were underlying common features justifying the amalgamation of catatonia, hebephrenia and paranoia hallucinatoria to form a single illness is confirmed by factor analytic studies delineating the various dimensions of schizophrenic psychopathology. Neuropsychological studies reveal that the three cardinal dimensions reflect disorder of the supervisory mental processes responsible for initiation, selection and monitoring of self-generated mental activity. Brain-imaging studies indicate that the underlying neuropathology entails disordered functional connectivity within the neural networks in multimodal association cortex that are the substrate of the supervisory mental processes, consistent with Kraepelin's own speculation about the essential nature of the condition.

PASAT performance and the pattern of uptake of 99mTc-exametazime in brain estimated with single photon emission tomography

The effect of the paced auditory serial addition test (PASAT) on the regional uptake of 99mTc-exametazime was determined by single photon emission computed tomography. Twenty insulin-treated diabetic outpatients were scanned at rest and during the performance of the PASAT task using split-dose injection of tracer. When resting and activation scans were compared there were significant decreases in tracer uptake in the right anterior cingulate and left posterior cingulate areas during PASAT activation. The findings are compared with previous studies which had implicated the anterior cingulate area in the mechanisms of attention in humans and other animals. The potentially confounding role of anxiety during attentional tasks is discussed.

Correlation of regional cerebral blood flow equivalents measured by single photon emission computerized tomography with P300 latency and eye movement abnormality in schizophrenia

Single photon emission tomography with the intravenous blood flow marker 99mTc-exametazime was carried out in 14 acutely ill drug-free schizophrenic patients from whom P300 event-related potential, smooth eye pursuit eye tracking and verbal fluency were measured within a few days of scanning. Smooth pursuit eye movement abnormality correlated significantly with abnormal tracer uptake in superior pre-frontal cortex on the right and left and inferior pre-frontal cortex on the left. Abnormal eye movement was also associated with higher tracer uptake in left anterior cingulate and left posterior cingulate. P300 latency was significantly correlated with higher tracer uptake in left superior pre-frontal and left parietal regions. Verbal fluency performance was negatively correlated with tracer uptake in left frontal region. Eye tracking abnormality in schizophrenia is associated with bilateral frontal lobe disturbance and P300 latency increase with left-sided frontal and temporoparietal dysfunction. There was, however, a significant inverse relation between eye tracking abnormalities and abnormal perfusion in the left anterior cingulate region.