Magnetic resonance imaging in schizophrenia: altered brain morphology associated with P300 abnormalities and eye tracking dysfunction

Magnetic resonance imaging in schizophrenia: Luxury or necessity? (Review)

Schizophrenia, one of the most common psychiatric disorders, with a worldwide annual incidence rate of approximately 0.3-0.7%, known to affect the population below 25 years of age, is persistent throughout lifetime and includes people from all layers of society. With recent technological progress that allows better imaging techniques, such as the ones provided by computed tomography and particularly magnetic resonance imaging (MRI), research on schizophrenia imaging has grown considerably. The purpose of this review is to establish the importance of using imaging techniques in the early detection of brain abnormalities in patients diagnosed with schizophrenia. We reviewed all articles which reported on MRI imaging in schizophrenia. In order to do this, we used the PubMed database, using as search words ‘MRI’ and ‘schizophrenia’. MRI studies of first episode patients and chronic patients, suggest reduction of the whole brain volume. Enlargement of lateral ventricles was described as positive in 15 studies out of 19 and was similar to findings in chronic patients. Moreover, for the first episode patients, all data collected point to important changes in medial temporal lobe structures, diminished hippocampal volume, the whole frontal lobe, asymmetry in prefrontal cortex, diminished volume in cingulate, corpus callosum, and cavum septum pellucidum reported abnormalities. MRI is recommended as an important tool in the follow-up process of patients with schizophrenia. Yet, it is still under debate whether the abnormalities described in this condition are able to be used as diagnostic biomarkers.

Constructing the rodent stereotaxic brain atlas: a survey

The stereotaxic brain atlas is a fundamental reference tool commonly used in the field of neuroscience. Here we provide a brief history of brain atlas development and clarify three key conceptual elements of stereotaxic brain atlasing: brain image, atlas, and stereotaxis. We also refine four technical indices for evaluating the construction of atlases: the quality of staining and labeling, the granularity of delineation, spatial resolution, and the precision of spatial location and orientation. Additionally, we discuss state-of-the-art technologies and their trends in the fields of image acquisition, stereotaxic coordinate construction, image processing, anatomical structure recognition, and publishing: the procedures of brain atlas illustration. We believe that the use of single-cell resolution and micron-level location precision will become a future trend in the study of the stereotaxic brain atlas, which will greatly benefit the development of neuroscience.

[Evoked potentials N200/P300 disorders and clinical phenotype in Cuban families with paranoid schizophrenia: a family-based association study]

INTRODUCTION

N200 and P300 event-related evoked potentials provide sensitive measurements of sensory and cognitive function and have been used to study information processing in patients with schizophrenia and their unaffected first-degree relatives. Reduced amplitude and increased latency of N200 and P300 potentials have been consistently reported in schizophrenia. Thus, event-related evoked potentials abnormalities are promising possible biological markers for genetic vulnerability to schizophrenia.

OBJECTIVE

To assess the association of changes in latency, amplitude and topographic distribution of potentials N200 and P300 of patients with paranoid schizophrenia and their healthy first-degree relatives, in families with schizophrenia multiplex.

METHODOLOGY

We measured latency and amplitude of the N200 and P300 component of evoked potentials using an auditory odd-ball paradigm in 25 schizophrenic patients (probands) from 60 families multiply affected with paranoid schizophrenia, 23 of their non-schizophrenic first-degree relatives and 25 unrelated healthy controls, through a study of family association.

RESULTS

Schizophrenic patients and their relatives showed significant latency prolongation and amplitude reduction of the N200 and P300 waves compared to controls. Left-temporal as compared to right-temporal N200 and P300 were significantly smaller in schizophrenic patients and their non-schizophrenic first-degree relatives than in controls. Our results suggest that event-related evoked potentials abnormalities may serve as markers of genetic vulnerability in schizophrenia.

CONCLUSIONS

Confirming results of other researchers, this present study suggests that latency prolongation and amplitude reduction of the N200 and P300 waves and an altered topography at temporal sites may be a trait “marker” of paranoid schizophrenia.

Eye movements and neurocognitive function in treatment resistant schizophrenia: a pilot study

Objectives: It is increasingly important to develop predictors of treatment response and outcome in schizophrenia. Neuropsychological impairments, particularly those reflecting frontal lobe function, appear to predict poor outcome. Eye movement abnormalities probably also reflect frontal lobe deficits. We wished to see if these two aspects of schizophrenia were correlated and whether they could distinguish a treatment resistant from a treatment responsive group.

Methods: Ten treatment resistant schizophrenic patients were compared with ten treatment responsive patients on three eye movement paradigms (reflexive saccades, antisaccades and smooth pursuit), clinical psychopathology (BPRS, SANS and CGI) and a neuropsychological test battery designed to detect frontal lobe dysfunction. Ten aged-matched controls also carried out the eye movement tasks.

Results: Both treatment responsive (p = 0.038) and treatment resistant (p = 0.007) patients differed significantly from controls on the antisaccade task. The treatment resistant group had a higher error rate than the treatment responsive group, but the difference was not statistically significant. Similar poor neuropsychological test performance was found in both groups.

Conclusions: To demonstrate the biological differences characteristic of treatment resistance, larger sample sizes and wider differences in outcome between the two groups are necessary.

Alterations in brain structures underlying language function in young adults at high familial risk for schizophrenia

INTRODUCTION

Neuroanatomical and cognitive alterations typical of schizophrenia (SZ) patients are observed to a lesser extent in their adolescent and adult first-degree relatives, likely reflecting neurodevelopmental abnormalities associated with genetic risk for the illness. The anatomical pathways for language are hypothesized to be abnormal and to underlie the positive symptoms of schizophrenia. Examining non-psychotic relatives at high familial risk (FHR) for schizophrenia may clarify if these deficits represent trait markers associated with genetic vulnerability, rather than specific markers resulting from the pathological process underlying schizophrenia.

METHODS

T1 MRI scans from a 3T Siemens scanner of young adult FHR subjects (N=46) and controls with no family history of illness (i.e. at low genetic risk LRC; N=31) were processed using FreeSurfer 5.0. We explored volumetric and lateralization alterations in regions associated with language processing. An extensive neuropsychological battery of language measures was administered.

RESULTS

No significant differences were observed between groups on any language measures. Controlling intracranial volume, significantly smaller left pars triangularis (PT) (p<0.01) and right pars orbitalis (PO) (p<0.01) volumes and reversal of the L>R pars orbitalis (p<0.001) lateralization were observed in FHR subjects. In addition, the L pars triangularis and R pars orbitalis correlated with performance on tests of linguistic function in the FHR group.

CONCLUSIONS

Reduced volume and reversed structural asymmetry in language-related regions hypothesized to be altered in SZ are also found in first degree relatives at FHR, despite normal language performance. To clarify if these findings are endophenotypes for Sz, future studies would need to be performed of ill and well family members no longer within the age range of risk for illness to show these deficits segregate with schizophrenia within families. Moreover, measures of complex language need to be studied to determine if FHR individuals manifest impairments in some aspects of language function.

Movement sequencing abilities and basal ganglia morphology in first-episode schizophrenia

INTRODUCTION

Studies of brain morphology suggest a link between movement sequencing ability and basal ganglia dysfunction. Unfortunately, relevant studies have provided inconsistent data, which may be the result of differences in the methods of brain morphology assessment, statistical analysis or heterogeneity of the populations studied.

AIM

To test the hypothesis of a link between the dysfunction of movement sequencing and basal ganglia morphology in a homogenous sample of first-episode schizophrenia patients.

METHOD

Thirty-seven first-episode schizophrenia patients underwent an assessment of movement sequencing abilities using the NES scale and basal ganglia morphology from MR images. The data were compared with a group of 19 age- and sex-matched healthy controls.

RESULTS

The group of first-episode patients had a higher concentration of gray matter than healthy controls in the putamen and pallidum in both hemispheres. Patients with abnormal sequencing of movements had lower gray matter concentration than patients without such abnormalities in the left putamen, and no differences were found between the symptomatic group and healthy controls.

SUMMARY AND CONCLUSION

Our study suggests the involvement of the left putamen in the movement sequencing abnormalities in schizophrenia. Because of the potential confounding effect of medication, the lack of support from external evidence and the low power to perform the whole-brain analysis the results should be considered as preliminary. Further studies, especially with antipsychotic-naive first-episode schizophrenia patients are needed to solve these issues.

Verbal fluency deficits and altered lateralization of language brain areas in individuals genetically predisposed to schizophrenia

Alterations of verbal fluency may correlate with deficits of gray matter volume and hemispheric lateralization of language brain regions like the pars triangularis (PT) in schizophrenia. Examining non-psychotic individuals at high genetic risk (HR) for schizophrenia may clarify if these deficits represent heritable trait markers or state dependent phenomena. We assessed adolescent and young adult HR subjects (N=60) and healthy controls (HC; N=42) using verbal fluency tests and Freesurfer to process T1-MRI scans. We hypothesized volumetric and lateralization alterations of the PT and their correlation with verbal fluency deficits. HR subjects had letter verbal fluency deficits (controlling for IQ), left PT deficits (p=.00), (controlling ICV) and reversal of the L>R PT asymmetry noted in HC. Right Heschl's (p=.00), left supramarginal (p=.00) and right angular gyrii (p=.02) were also reduced in HR subjects. The L>R asymmetry of the Heschl's gyrus seen in HC was exaggerated and asymmetries of L>R of supramarginal and R>L of angular gyri, seen in HC were attenuated in HR subjects. L>R asymmetry of the PT predicted better verbal fluency across the pooled HR and HC groups. Young relatives of schizophrenia patients have verbal fluency deficits, gray matter volume deficits and reversed asymmetry of the pars triangularis. A reversed structural asymmetry of the PT in HR subjects may impair expressive language abilities leading to verbal fluency deficits. Volumetric deficits and altered asymmetry in inferior parietal and Heschl's gyrii may accompany genetic liability to schizophrenia.

The Wisconsin Card Sort Test and P300 responses to novel auditory stimuli in schizophrenic patients

The authors studied the relationship between performance on the Wisconsin Card Sort Test (WCST) and P300 activity in schizophrenics and normal controls. Fourteen male predominantly medicated schizophrenics and matched non-ill controls were administered the WCST and tests of temporal lobe (delayed verbal and spatial memory) and general intellectual functioning (Shipley). Patients were rated with negative and positive symptom scales extracted from the Brief Psychiatric Rating Scale. Subjects performed a tone discrimination task requiring identification of rare targets in both a standard oddball paradigm and a three-stimulus paradigm that included rare novel sounds. Reference independent data from 16 scalp electrodes yielded Global Field Power (GFP), from which P300 latency was determined. P300 amplitude measures included amplitude at this identified latency as well as amplitude integrated over a 100 ms time window centered over it. These amplitude measures were examined at six selected electrode locations. Schizophrenics produced smaller P300 responses that tended to be slower, but there were no group differences in the relationships between neuropsychological performance and P300 responses. Across diagnostic groups percent perseverative errors predicted lower integrated and peak P300 amplitude during the novel but not the standard oddball paradigm. The effect on integrated P300 amplitude was localized to anterior leads after novel stimuli. Negative symptoms predicted lower WCST performance, lower integrated P300 amplitude, and smaller GFP after novel stimuli. Positive symptoms predicted reduced overall GFP and specific but inconsistent reductions in parietal P300 amplitude. The results suggest relationships between dorsolateral prefrontal competence, P300 activity in response to stimulus novelty, and negative symptoms in schizophrenic patients, paralleling findings obtained from blood flow and other measures of brain activity.

Antisaccade and smooth pursuit performance in positive- and negative-symptom schizotypy

Schizophrenic patients have well-documented abnormalities in smooth pursuit eye movements and antisaccade performance. In populations at risk for schizophrenia, smooth pursuit abnormalities are also well documented. Antisaccade deficits have been replicated in high-risk populations as well, but the findings are more variable and the reasons for the variability are not clear. Some evidence suggests that antisaccade deficits increase in high-risk populations in relation to the presence of positive symptoms. Whether antisaccade deficits increase in relation to negative symptoms in high-risk populations is relatively uninvestigated. We evaluated antisaccade and pursuit performance in "psychometric schizotypes" who had elevated scores on either the Perceptual Aberration Scale (PerAb; i.e., positive symptoms) or the Physical Anhedonia Scale (PhysAnh; i.e., negative symptoms) but not both, and in normal controls. We used the standard version of the antisaccade task, for which results in positive-symptom schizotypes have previously been reported, and investigated performance on a gap and overlap version. We replicated the finding that a significantly larger percentage of positive-symptom schizotypes than controls have elevated antisaccade error rates on the standard antisaccade task (P=0.03); the percentage of negative-symptom schizotypes with elevated antisaccade error rates did not differ from that of control subjects. Neither schizotypal group was impaired on the gap or overlap versions of the task. On the pursuit task, a higher percentage of positive- and negative-symptom schizotypes were classified as having deviant performance than control subjects (both Ps<0.04). These findings suggest that antisaccade deficits may be better at identifying high-risk subjects with positive symptoms. Pursuit deficits identified both positive- and negative-symptom schizotypes, but was better at identifying the latter.

Structural neural networks subserving oculomotor function in first-episode schizophrenia

BACKGROUND

Smooth pursuit and antisaccade abnormalities are well documented in schizophrenia, but their neuropathological correlates remain unclear.

METHODS

In this study, we used statistical parametric mapping to investigate the relationship between oculomotor abnormalities and brain structure in a sample of first-episode schizophrenia patients (n = 27). In addition to conventional volumetric magnetic resonance imaging, we also used magnetization transfer ratio, a technique that allows more precise tissue characterization.

RESULTS

We found that smooth pursuit abnormalities were associated with reduced magnetization transfer ratio in several regions, predominantly in the right prefrontal cortex. Antisaccade errors correlated with gray matter volume in the right medial superior frontal cortex as measured by conventional magnetic resonance imaging but not with magnetization transfer ratio.

CONCLUSIONS

These preliminary results demonstrate that specific structural abnormalities are associated with abnormal eye movements in schizophrenia.

Aberrant localization of synchronous hemodynamic activity in auditory cortex reliably characterizes schizophrenia

BACKGROUND

Among the most prominent features of schizophrenic brains are abnormalities in auditory cortex structure and function, particularly in the superior temporal gyrus (STG). In this study, we attempted to examine auditory cortex function using an intrinsic, task-uncorrelated measure.

METHODS

Using functional magnetic resonance imaging data, we calculated synchronous hemodynamic independent maps (SHIMs) of auditory cortex in patients with schizophrenia and matched healthy control subjects while they performed an auditory oddball task.

RESULTS

Patient SHIMs revealed greater synchrony in ventral and medial STG regions (including auditory association Brodmann area [BA] 42); control SHIMs had greater synchrony in dorsal and lateral STG regions (which did not include BA 42). A within-participant subtractive comparison of these two sets of regions differentiated schizophrenic from healthy control subjects with 97% accuracy initially (further validated by a retest of the healthy control subjects) and performed with 94% accuracy in a confirmatory study of new subjects scanned at a different site.

CONCLUSIONS

These results shed new light on STG functional differences in schizophrenia, suggest that aberrant patterns of coherence in temporal lobe cortical regions are a cardinal abnormality in schizophrenia, and have the potential to provide a powerful, quantitative clinical tool for the assessment of schizophrenia.

Nongenetic pathologic developments of brain-wave patterns in monozygotic twins discordant and concordant for schizophrenia

Evidence from previous studies has suggested that the inter-individual differences in human brain-wave patterns (EEG) are predominantly determined by genetic factors. In particular, the within-pair EEG concordance of monozygotic (mz) twins was found to be typically as high as r = 0.81 across channels and frequency bands, thus being comparable to that between repeated assessments on the same individual with typically r = 0.83. Yet our investigations into mz twins discordant and concordant for schizophrenia yielded a significantly reduced within-pair EEG concordance for both, the pairs discordant for schizophrenia and the pairs concordant for schizophrenia (with concordance for schizophrenia assessed through a syndrome-oriented approach). A multivariate discriminant function of EEG parameters distinguished in a reproducible way between affected and unaffected subjects at an overall performance of >75% correctly classified subjects, while the severity of illness, as derived from EEG-differences between affected and unaffected subjects, was closely related to the severity of illness as provided by psychopathology syndrome scores. Consequently, EEG anomalies associated with schizophrenia and manifested differently in the mz co-twins concordant for schizophrenia are likely the effect of nongenetic, pathologic processes that evolved independently in the co-twins' genetically identical brains once the illness began to progress. The existence of such nongenetic processes would suggest a modification of the standard phenotype-to-genotype search strategies of molecular-genetic studies that aim to link the schizophrenia phenotype to genetic vulnerability factors.

Meta-analysis of P300 and schizophrenia: patients, paradigms, and practical implications

The goal of the present meta-analysis was to identify factors that contribute to P300 event-related brain potential (ERP) differences in patients with schizophrenia compared to unaffected controls in an attempt to characterize the clinically relevant dimensions underlying P300 deficits in patients with schizophrenia. P300 effect size (d) was smaller in amplitude and longer in latency in schizophrenic patients compared to normal controls, with the strongest effects obtained from the auditory oddball. Paranoid subtype demonstrated larger P300 amplitude effect sizes than other disease subtypes, and P300 latency effect size decreased with disease duration. Psychopathology severity and antipsychotic medications were unrelated to P300 amplitude effect size. Gender proportion, educational level, and stimulus and task variables also affected P300 amplitude and latency effect sizes. The findings are used to formulate a theoretical account of the empirical data and provide suggestions for maximizing the utility of the P300 component in the assessment of schizophrenia.

Amygdala volume in schizophrenia: post-mortem study and review of magnetic resonance imaging findings

BACKGROUND

Claims that schizophrenia is a disease of the limbic system have been strengthened by meta-analyses of magnetic resonance imaging (MRI) studies finding reduced hippocampus and amygdala volumes. Some post-mortem studies do not find these abnormalities.

AIMS

To assess the volume of the amygdala in a series of brains post-mortem.

METHOD

Amygdala volume was estimated using point-counting in both hemispheres of the brains of 10 male and 8 female patients with schizophrenia, and a comparison group of 9 males and 9 females.

RESULTS

No significant reduction of amygdala volume was found.

CONCLUSIONS

Significant volume reduction of the amygdala is not a consistent feature of schizophrenia; findings from early MRI studies using coarse delineation methods may introduce bias to subsequent meta-analyses.

Prefrontal cortex, negative symptoms, and schizophrenia: an MRI study

The present study measured prefrontal cortical gray and white matter volume in chronic, male schizophrenic subjects who were characterized by a higher proportion of mixed or negative symptoms than previous patients that we have evaluated. Seventeen chronic male schizophrenic subjects and 17 male control subjects were matched on age and handedness. Regions of interest (ROI) were measured using high-resolution magnetic resonance (MR) acquisitions consisting of contiguous 1.5-mm slices of the entire brain. No significant differences were found between schizophrenic and control subjects in mean values for prefrontal gray matter volume in either hemisphere. However, right prefrontal white matter was significantly reduced in the schizophrenic group. In addition, right prefrontal gray matter volume was significantly correlated with right hippocampal volume in the schizophrenic, but not in the control group. Furthermore, an analysis in which the current data were combined with those from a previous study showed that schizophrenic subjects with high negative symptom scores had significantly smaller bilateral white matter volumes than those with low negative symptom scores. White matter was significantly reduced in the right hemisphere in this group of schizophrenic subjects. Prefrontal volumes were also associated with negative symptom severity and with volumes of medial-temporal lobe regions - two results that were also found previously in schizophrenic subjects with mostly positive symptoms. These results underscore the importance of temporal-prefrontal pathways in the symptomatology of schizophrenia, and they suggest an association between prefrontal abnormalities and negative symptoms.

A review of MRI findings in schizophrenia

After more than 100 years of research, the neuropathology of schizophrenia remains unknown and this is despite the fact that both Kraepelin (1919/1971: Kraepelin, E., 1919/1971. Dementia praecox. Churchill Livingston Inc., New York) and Bleuler (1911/1950: Bleuler, E., 1911/1950. Dementia praecox or the group of schizophrenias. International Universities Press, New York), who first described 'dementia praecox' and the 'schizophrenias', were convinced that schizophrenia would ultimately be linked to an organic brain disorder. Alzheimer (1897: Alzheimer, A., 1897. Beitrage zur pathologischen anatomie der hirnrinde und zur anatomischen grundlage einiger psychosen. Monatsschrift fur Psychiarie und Neurologie. 2, 82-120) was the first to investigate the neuropathology of schizophrenia, though he went on to study more tractable brain diseases. The results of subsequent neuropathological studies were disappointing because of conflicting findings. Research interest thus waned and did not flourish again until 1976, following the pivotal computer assisted tomography (CT) finding of lateral ventricular enlargement in schizophrenia by Johnstone and colleagues. Since that time significant progress has been made in brain imaging, particularly with the advent of magnetic resonance imaging (MRI), beginning with the first MRI study of schizophrenia by Smith and coworkers in 1984 (Smith, R.C., Calderon, M., Ravichandran, G.K., et al. (1984). Nuclear magnetic resonance in schizophrenia: A preliminary study. Psychiatry Res. 12, 137-147). MR in vivo imaging of the brain now confirms brain abnormalities in schizophrenia. The 193 peer reviewed MRI studies reported in the current review span the period from 1988 to August, 2000. This 12 year period has witnessed a burgeoning of MRI studies and has led to more definitive findings of brain abnormalities in schizophrenia than any other time period in the history of schizophrenia research. Such progress in defining the neuropathology of schizophrenia is largely due to advances in in vivo MRI techniques. These advances have now led to the identification of a number of brain abnormalities in schizophrenia. Some of these abnormalities confirm earlier post-mortem findings, and most are small and subtle, rather than large, thus necessitating more advanced and accurate measurement tools. These findings include ventricular enlargement (80% of studies reviewed) and third ventricle enlargement (73% of studies reviewed). There is also preferential involvement of medial temporal lobe structures (74% of studies reviewed), which include the amygdala, hippocampus, and parahippocampal gyrus, and neocortical temporal lobe regions (superior temporal gyrus) (100% of studies reviewed). When gray and white matter of superior temporal gyrus was combined, 67% of studies reported abnormalities. There was also moderate evidence for frontal lobe abnormalities (59% of studies reviewed), particularly prefrontal gray matter and orbitofrontal regions. Similarly, there was moderate evidence for parietal lobe abnormalities (60% of studies reviewed), particularly of the inferior parietal lobule which includes both supramarginal and angular gyri. Additionally, there was strong to moderate evidence for subcortical abnormalities (i.e. cavum septi pellucidi-92% of studies reviewed, basal ganglia-68% of studies reviewed, corpus callosum-63% of studies reviewed, and thalamus-42% of studies reviewed), but more equivocal evidence for cerebellar abnormalities (31% of studies reviewed). The timing of such abnormalities has not yet been determined, although many are evident when a patient first becomes symptomatic. There is, however, also evidence that a subset of brain abnormalities may change over the course of the illness. The most parsimonious explanation is that some brain abnormalities are neurodevelopmental in origin but unfold later in development, thus setting the stage for the development of the symptoms of schizophrenia. Or there may be additional factors, such as stress or neurotoxicity, that occur during adolescence or early adulthood and are necessary for the development of schizophrenia, and may be associated with neurodegenerative changes. Importantly, as several different brain regions are involved in the neuropathology of schizophrenia, new models need to be developed and tested that explain neural circuitry abnormalities effecting brain regions not necessarily structurally proximal to each other but nonetheless functionally interrelated. (ABSTRACT TRUNCATED)

Saccadic and smooth-pursuit eye movements in deficit and non-deficit schizophrenia

We have analyzed eye movement performances in schizophrenics showing primary negative or deficit symptoms (n=16) and non-deficit schizophrenics (n=55), and compared them with those of controls (n=34) in order to study the relationships between negative symptoms and eye movement abnormalities. Patients were subtyped into deficit and non-deficit subgroups using the Schedule for the Deficit Syndrome. Three oculomotor paradigms were used: smooth pursuit, a reflexive saccade paradigm and an antisaccadic task. The smooth pursuit gain was significantly decreased (and the rate of catch-up saccades increased) in schizophrenics as compared with controls, but no difference was observed between patient groups. In the reflexive saccade paradigm, no difference was found between controls and patients, except for latency in deficit patients. In the antisaccade paradigm, the number of errors and the latency of successful antisaccades were significantly increased in schizophrenics as compared with controls. The latency of successful antisaccades in both directions was significantly increased in deficit patients as compared with non-deficit patients. The latency of rightward successful antisaccades was significantly increased as compared with the latency of leftward antisaccades in deficit patients only. However, when patients were classified into negative and non-negative groups using the PANSS, no difference was found in the antisaccade paradigm. Smooth pursuit impairment does not seem to depend on the primary enduring negative symptoms.In deficit schizophrenics, the abnormalities observed in the antisaccadic task are consistent with prefrontal dysfunction, and may suggest parietal lobe dysfunction as well.

[The p300 cognitive event-related potential. II. Individual variability and clinical application in psychopathology]

The P300 wave is one of the cognitive components of the event-related potential (ERP) that is used to investigate the cognitive processes, and which can be used to study patient populations with a variety of psychiatric disorders. Its clinical utility has been increased by the identification of factors that contribute to the variability in its amplitude and latency. However, its value as a diagnostic index has not been entirely established. It can provide a useful recording of patients' information processing, and indicate the severity of the clinical state and its possible evolution. It can also assist in determining what therapeutic approach to adopt. In the present review, the findings in the literature concerning interindividual variation in the P300 wave are first described; several variables significantly influence the amplitude and latency of this wave, such as age, gender, intelligence and personality. Following this, the relevance of the data in the literature on the clinical applications of P300 in psychopathology is examined, including the studies undertaken to obtain an objective diagnostic index for mental disorders and also those carried out to assess the problems concerning the interpretation of information connected with the mental pathologies examined. P300-associated findings on dementia, schizophrenia, depression, alcoholism, drug addiction, anxiety disorders (panic disorder, obsessive-compulsive disorder, and post-traumatic stress syndrome) and on personality disorders (schizoid, antisocial or borderline personality disorder) have been examined in detail.

Altered cerebral perfusion measured by SPECT in relatives of patients with schizophrenia. Correlations with memory and P300

BACKGROUND

Genetic studies in schizophrenia are hampered by the complex heterogeneous clinical phenotype. Biological variables identified as trait markers of risk could clarify the mode of inheritance, define clinical subgroups and provide clues about aetiology.

AIMS

To use single photon emission computed tomography (SPECT) to compare brain perfusion maps in patients with schizophrenia (n = 19), their asymptomatic 'high-risk' relatives (n = 36) and control subjects (n = 34) and to examine the relationships between imaging, memory and P300 event-related potential.

METHOD

SPECT, memory tests and P300 recording were carried out.

RESULTS

In the patients with schizophrenia and their relatives, perfusion was reduced in left inferior prefrontal and anterior cingulate cortex and increased bilaterally in a subcortical region. Perfusion significantly correlated with verbal memory and P300 amplitude in left inferior prefrontal cortex and with P300 latency in anterior cingulate cortex.

CONCLUSIONS

Medication- and symptom-free relatives had altered regional perfusion intermediate between subjects with schizophrenia and controls. Impaired perfusion, verbal memory and P300 appear to be related traits associated with an increased risk of illness.

MRI anatomy of schizophrenia

Structural magnetic resonance imaging (MRI) data have provided much evidence in support of our current view that schizophrenia is a brain disorder with altered brain structure, and consequently involving more than a simple disturbance in neurotransmission. This review surveys 118 peer-reviewed studies with control group from 1987 to May 1998. Most studies (81%) do not find abnormalities of whole brain/intracranial contents, while lateral ventricle enlargement is reported in 77%, and third ventricle enlargement in 67%. The temporal lobe was the brain parenchymal region with the most consistently documented abnormalities. Volume decreases were found in 62% of 37 studies of whole temporal lobe, and in 81% of 16 studies of the superior temporal gyrus (and in 100% with gray matter separately evaluated). Fully 77% of the 30 studies of the medial temporal lobe reported volume reduction in one or more of its constituent structures (hippocampus, amygdala, parahippocampal gyrus). Despite evidence for frontal lobe functional abnormalities, structural MRI investigations less consistently found abnormalities, with 55% describing volume reduction. It may be that frontal lobe volume changes are small, and near the threshold for MRI detection. The parietal and occipital lobes were much less studied; about half of the studies showed positive findings. Most studies of cortical gray matter (86%) found volume reductions were not diffuse, but more pronounced in certain areas. About two thirds of the studies of subcortical structures of thalamus, corpus callosum and basal ganglia (which tend to increase volume with typical neuroleptics), show positive findings, as do almost all (91%) studies of cavum septi pellucidi (CSP). Most data were consistent with a developmental model, but growing evidence was compatible also with progressive, neurodegenerative features, suggesting a "two-hit" model of schizophrenia, for which a cellular hypothesis is discussed. The relationship of clinical symptoms to MRI findings is reviewed, as is the growing evidence suggesting structural abnormalities differ in affective (bipolar) psychosis and schizophrenia.

Reduced auditory P300 amplitude, medial temporal volume reduction and psychopathology in schizophrenia

Twenty-five schizophrenic patients diagnosed by DSM-III-R underwent event-related potentials and magnetic resonance imaging scans. Latency and amplitude of P300 waveform were measured using an auditory odd-ball paradigm. Anterior and posterior volumes of the superior temporal gyrus and medial temporal structure were measured from contiguous coronal images using the level of the mammillary body as an anatomical landmark. Principal component analysis of P300 latency and amplitude disclosed two orthogonal independent factors each: overall latency and residual, and amplitudes from posterior and anterior recordings, respectively. Structural volumes consisted of four orthogonally independent factors: left superior temporal volume, anterior medial temporal volume, right superior temporal volume, and posterior medial temporal volume. The factor score of the P300 amplitude from posterior recordings correlated with the factor score of volumetric changes in the anterior medial temporal structures. The present study failed to replicate a previously reported association between auditory P300 amplitude and superior temporal volume. Furthermore, the factor score of the P300 amplitude was correlated with the severity of clinical ratings of attentional impairments and positive thought disorder. These findings demonstrate that the information processing dysfunction of schizophrenia indicated by reduced P300 amplitude is associated with structural abnormality in the medial temporal lobe.

Clinical symptoms of schizophrenia affect reference-independent measures of task-induced EEG alpha asymmetry

Differential patterns of EEG alpha asymmetry during verbal and spatial cognitive activity are commonly described and are thought to reflect predominance of left- vs. right-sided cortical activation. Although these patterns have been difficult to elicit reliably in schizophrenics, the authors have previously suggested that clinical status may have confounded results. Therefore, EEG data from 17 additional schizophrenic patients, 16 mood disorder patient controls, and 17 normal controls were used to examine the relationship between severity of schizophrenic symptoms and task induced alpha asymmetry. Subjects performed verbal and spatial tasks during recording of 16-channel EEG. After transformation to the average reference, log alpha power from central and temporal leads was analyzed by MANOVA and MANCOVA. The expected task-side interaction (P < 0.02) was present for the total sample and for each control group when analyzed alone. However, it was only present in schizophrenics when the BPRS score was entered as a covariable. Patterns of correlations between BPRS scores, left temporal alpha power, right/left temporal alpha ratios, and task differences in ratios suggested that higher symptom levels were associated with excessive left-sided activation during spatial activity. This is consistent with other evidence of left hemisphere overactivity in schizophrenics.

Enlarged frontal P300 to stimulus change in panic disorder

This study investigated event-related potential (ERP) indices of information processing in sufferers of panic disorder (PD). ERPs were recorded from 14 PD patients and 15 controls during an auditory target detection task. The task required subjects to discriminate infrequent target tones (p = .14; 2000 Hz) from frequent (p = .72; 1000 Hz) and infrequent (p = .14; 500 Hz) distractor tones. A frontal P300 (P3a) identified in the PD group was characteristic of activity that would be expected to novel, task-irrelevant stimuli and is consistent with junctional pathology involving the prefrontal-limbic pathways. This study provides psychophysiological evidence of an abnormality in PD of the brain's processing of physical changes in the stimulus field that occurs even under conditions of low stimulus load. It may assist in helping to understand the breakdown in information processing that occurs in PD under high load conditions such as crowds and supermarkets.

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.

"Schizoid" personality in childhood: auditory P300 and eye tracking responses at follow-up in adult life

The auditory P300 response and smooth pursuit eye tracking were recorded from a group of 23 male adult subjects who had been diagnosed in childhood as having schizoid personality. No differences were found in these physiological measures between the study group, their matched controls of other child psychiatric patients, and a group of population controls. The essentially negative findings are discussed in the light of abnormalities of these psychophysiological responses previously found in schizophrenic patients, in some of their biological relatives, and in other groups of psychiatric patients, including autistic children and adults with a diagnosis of borderline and schizotypal personality disorder. Results suggest that "schizoid" children, despite their high scores on a measure of schizotypy, do not have schizophrenia spectrum disorder or that schizotypy is a heterogeneous condition.

On the origin of the P3 event-related potential component

Human findings indicate that the most important brain regions in the electrogenesis of the P3 event-related potential component are the junction of the parieto-temporal lobes, parts of the limbic system and some parts of the thalamus. Data collected in animal experiments support the results of the human studies emphasizing the role of the association cortical areas, that of limbic structures and possibly of some thalamic nuclei. It is not clear as yet how the activity of these hypothesized generators are integrated and to what extent, and how they contribute to the scalp-recorded P3.

Ventricle size and P300 in schizophrenia

Both ventricular enlargement and reduced P3 amplitudes are consistent findings in schizophrenic patients, suggesting that the two measures reflect a common underlying pathophysiological process in schizophrenia. Investigating 14 stabilized schizophrenic outpatients, a relationship between the size of the lateral ventricles as well as of the third ventricle on CT scans and the auditory event-related P3 amplitude was, however, not found. This negative result suggests that ventricular enlargement and reduced P3 amplitudes in schizophrenics reflect different pathophysiological processes. It is assumed that the P3 amplitude is related rather to abnormalities in the temporal lobe of schizophrenic patients.

Neuropsychological and P300 abnormalities in schizophrenics and their relatives

Schizophrenic subjects (N = 30) performed less well than controls (N = 30) on neuropsychological tests sensitive to frontal and temporal lobe impairment and showed prolonged latency of the P300 event-related potential. Relatives of schizophrenic probands were also tested. Relatives with an abnormal P300 had a similar range of neuropsychological deficits as were found in the schizophrenic group and relatives with a normal P300 response performed as well as the normal control group. The results suggest that neurophysiological and neuropsychological testing of relatives may help to clarify the mode of inheritance of schizophrenia in some families.

Normal eye tracking is associated with abnormal morphology of medial temporal lobe structures in schizophrenia

Eye tracking and brain morphology assessed by magnetic resonance imaging were examined in 48 patients in their first episode of schizophrenia and in 15 normal controls. Schizophrenic patients showed higher rates of eye tracking dysfunction and more abnormal brain morphology involving the lateral ventricles, medial temporal lobe (MTL) structures and the frontal-parietal cortex than controls. Enlargement of the lateral ventricles and global rating of abnormal brain morphology were significantly more prevalent in male schizophrenics than female schizophrenics. These findings indicate that abnormalities in a variety of brain regions are present in some schizophrenics during the period shortly after the first hospitalization and could not be a function of treatment or chronic illness. We found no relation between abnormal eye tracking and any single feature of abnormal brain morphology. However, normal eye tracking was significantly associated with MTL abnormalities in schizophrenics, reflecting an inverse association between quality of eye tracking and degree of abnormality in MTL structures. These results suggest that abnormal eye tracking is not mediated by the same processes that lead to structural brain anomalies in schizophrenia.