Psychological, topographic EEG, and CT scan correlates of frontal lobe function in schizophrenia

EEG in psychiatric practice: to do or not to do?

Electroencephalography (EEG) is a non-invasive investigation that can aid the diagnosis of psychiatric and neuropsychiatric disorders. A good predictor of an abnormal EEG recording is the presence of an organic factor identified during the clinical assessment. The non-invasiveness and low cost of the procedure and its ability to measure spontaneous brain activity appear to attract clinicians to utilise this investigative tool. However, studies have reported that EEGs arising from psychiatric referrals have the lowest abnormality detection rate. The focus of this article is to improve this by highlighting the current pitfalls and providing recommendations for appropriate utilisation of EEG. We describe specific EEG changes associated with major psychiatric disorders. We conclude by offering pragmatic considerations when referring a patient for EEG, emphasising the fact that the information provided to the neurophysiologist plays a crucial role in interpreting the EEG recording in a diagnostically meaningful way.

Electrophysiological aberrations associated with negative symptoms in schizophrenia

Clinical heterogeneity is a confound common to all of schizophrenia research. Deficit schizophrenia has been proposed as a homogeneous disease entity within the schizophrenia syndrome. The use of the Schedule for the Deficit Syndrome (SDS) has allowed the definition of a subgroup dominated by persistent and primary negative symptoms. While a number of studies have appeared over the years examining the electrophysiological correlates of the cluster of negative symptoms in schizophrenia, only a few studies have actually focused on the Deficit Syndrome (DS). In this chapter, electrophysiological investigations utilizing EEG, Evoked Potentials (EPs), polysomnography (PSG), or magnetoencephalography (MEG) to probe "negative symptoms," or "Deficit Syndrome" are reviewed. While this line of research is evidently in its infancy, two significant trends emerge. First, spectral EEG studies link increased slow wave activity during wakefulness to the prevalence of negative symptoms. Second, sleep studies point to an association between decrease in slow wave sleep and prevalence of negative symptoms. Several studies also indicate a relationship of negative symptoms with reduced alpha activity. A host of other abnormalities including sensory gating and P300 attenuation are less consistently reported. Three studies specifically addressed electrophysiology of the DS. Two of the three studies provided evidence suggesting that the DS may be a separate disease entity and not simply a severe form of schizophrenia.

Age and diffusion tensor anisotropy in adolescent and adult patients with schizophrenia

Findings of white matter pathology as indicated by diffusion tensor anisotropy values in schizophrenia are well established, but the differences in this measure between the onset of the disease and the chronic state are not well known. To investigate the differences between these states in the progression of the disease of schizophrenia we acquired 1.5 T diffusion tensor anisotropy images on 35 adult patients with schizophrenia and schizoaffective disorder, 23 adolescents having their first psychotic episode, and age and sex matched controls (33 adults and 15 adolescents). Regions of interest in major cortical white matter tracts chosen as salient to the prefrontal executive deficit in schizophrenia were assessed using stereotaxic coordinates from the Talairach and Tournoux atlas. Regions of each tract along anterior-posterior and/or inferior-superior directions in both hemispheres were evaluated in multiway ANOVA. Tracts between the frontal lobe and other brain regions, but not temporal, occipital and interhemispheric tracts, showed a differential aging pattern in normals and patients indicating that the white matter pathology in these regions is not stable between the onset and the chronic state in schizophrenia. This suggests that tracts involved in the connectivity of the temporal lobe white matter deficits were already well in place in adolescent patients, while frontal lobe pathology continues to develop from adolescence to adulthood.

The Wisconsin Card Sorting impairment in schizophrenia is evident in the first four trials

BACKGROUND

Schizophrenia (SZ) patients' low scores on the Wisconsin Card Sorting Test (WCST) are often attributed to frequent perseverative errors, a pattern typically interpreted as a failure to shift from previously rewarded behavior in response to negative feedback. In this study we tested the hypothesis that SZ patients, due to dysregulated error-processing mechanisms, are more fundamentally impaired in their on-line, trial-to-trial use of feedback to guide behavior.

METHODS

Analysis of archival WCST data from 145 adults with schizophrenia and 80 healthy comparison subjects.

RESULTS

Schizophrenia patients' impaired use of negative feedback was evident on the first four WCST cards, where they were significantly less accurate than comparison subjects. Performance on these early cards significantly predicted overall task success as indexed by categories completed and proportion of perseverative errors.

CONCLUSIONS

Patients' poor performance on pre-shift WCST trials likely reflects a fundamental impairment in the ability to use feedback to guide behavior. Recent data from both humans and primates suggest that reward-based learning processes like those employed in the WCST are driven by phasic changes in midbrain dopamine activity. It might, therefore, be possible to interpret higher order executive dysfunction in schizophrenia as a manifestation of altered DA signaling.

Correlation of symptom clusters of schizophrenia with absolute powers of main frequency bands in quantitative EEG

Background

Research of QEEG activity power spectra has shown intriguing results in patients with schizophrenia. Different symptom clusters have been correlated to QEEG frequency bands. The findings have been to some extent inconsistent. Replication of the findings of previous research is thus an important task. In the current study we investigated the correlations between the absolute powers of delta, theta, alpha, and beta frequency bands over the fronto-central scalp area (FC) with the PANSS subscales and the Liddle's factors in 16 patients with schizophrenia.

The authors hypothesised a priori the correlations reported by Harris et al (1999) of PANSS negative subscale with delta power, Liddle's psychomotor poverty with delta and beta powers, disorganisation with delta power and reality distortion with alpha power on the midline FC.

Methods

The sample consisted of 16 patients with chronic schizophrenia considered as having insufficient clinical response to conventional antipsychotic treatment and evidencing a relapse. The correlations between quantitative electroencephalography (QEEG) absolute powers of delta (1.5–3.0 Hz), theta (3.0–7.5 Hz), alpha (7.5–12.5 Hz), and beta (12.5–20.0 Hz) frequency bands over the fronto-central scalp area (FC) with PANSS subscales and Liddle's factors (reality distortion, disorganisation, psychomotor poverty) were investigated.

Results

Significant positive correlations were found between the beta and psychomotor poverty (p < 0.05). Trends towards positive correlations (p < 0.1) were observed between delta and PANSS negative subscale and psychomotor poverty. Alpha did not correlate with reality distortion and delta did not correlate with disorganisation.

Post hoc analysis revealed correlations of the same magnitude between beta and psychopathology generally over FC.

Conclusion

The a priori hypothesis was partly supported by the correlation of the beta and psychomotor poverty. Liddle's factors showed correlations of the same magnitude with PANSS subscales. Supplementary analysis showed beta frequency correlating non-specifically over FC with a wide range of psychiatric symptomatology in patients with schizophrenia having a relapse.

Dynamic spectral analysis findings in first episode and chronic schizophrenia

The quantified analysis of the electroencephalogram (qEEG) has enabled the extraction of additional psychophysiological information from the raw EEG, but in turn has introduced a number of distortions. This study compared Dynamic Spectral Analysis (DSA), a novel and mathematically stringent technique for the evaluation of qEEG activity with conventional power spectral analysis in subjects with both first episode and chronic schizophrenia and matched controls. Advantages of the technique in the automated processing of data, rejection of artefact, avoidance of artefact introduced by the mathematical trans-formation of the data and the identification of irregular low frequency artefactual activity "pi" are discussed in detail. Using this method, the study has confirmed past observations of increased slow wave activity in schizophrenia, and identified a decrease in peak frequency in the alpha band in the subjects with chronic schizophrenia. The two clinical groups differed in mean peak frequency in the delta band with the first episode schizophrenia subjects having a raised mean peak frequency and the subjects with chronic schizophrenia having a lowered mean peak frequency. The results suggest continued change in the EEG with illness chronicity in schizophrenia. These changes were most evident in the frequency domain emphasizing the importance of routine measurement of mean band frequencies in qEEG studies.

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.

Executive function deficits associated with symptoms of schizotypy and obsessive-compulsive disorder

Research suggests that executive dysfunction is seen both in disorders of the schizophrenia constellation and in obsessive-compulsive disorder (OCD), but that the patterns of executive deficits may differ. While disorders of the schizophrenia spectrum reflect impairment of functions such as integration of cognitive activities, a tendency to perseverate, and a failure to notice details (e.g. impairment associated with the dorsolateral prefrontal cortex), OCD may involve problems of impulse control and regulation of behavior, and an inability to maintain cognitive set (e.g. impairment associated with the orbitofrontal cortex). The present study examined differences between high-scorers on a measure of schizotypy, high-scorers on a measure of OCD, high-scorers on both schizotypy and OCD and a control group in performance on executive function tests. As expected, the OCD group demonstrated relative deficits on measures thought to reflect orbitofrontal functioning. However, contrary to expectations, the schizotypal group did not demonstrate deficits on neuropsychological tests thought to reflect dorsolateral prefrontal cortex functioning, and the combined group showed no executive impairment.

Cognitive deficits and cognitive training in schizophrenic patients: a review

OBJECTIVE

The aim of this paper is to review the current status of knowledge of cognitive deficits and remediation in patients with schizophrenia.

METHOD

Relevant reports were identified by a literature survey. In addition, some outstanding researchers in these areas were asked to add to the identified list relevant literature that was not included.

RESULTS

Our review focuses on the cognitive deficits observed in the areas of attention, memory and executive functions. We attempt to classify dysfunctions as vulnerability- or symptom-linked factors, and we discuss the methodological question of a general performance deficit vs. a differential deficit. Furthermore, we briefly delineate how antipsychotics affect cognitive functions. Finally, controlled studies of cognitive training are discussed in more detail.

CONCLUSION

The most outstanding cognitive dysfunctions in patients with schizophrenia can be related to the areas of attention, memory and executive functions. Interest in cognitive remediation has to some extent been rekindled in the 1990s. However, few studies on the effects of cognitive training programs have been conducted.

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.

A neuropsychological study of prefrontal lobe function in the positive and negative subtypes of schizophrenia

The symptoms of schizophrenia are frequently divided into positive and negative subtypes. It has been suggested that the negative symptoms are similar to those seen with prefrontal lobe cortical dysfunction. Several neuropsychological investigations of that hypothesis have been carried out, but none have directly compared a negative symptom group with a positive symptom group on the same test battery. In the present study, the Positive and Negative Syndrome Scale (PANSS; Kay, Fiszbein, & Opler, 1987) was used to distinguish two groups of 20 patients with schizophrenia with predominant positive or negative symptoms. A battery of 7 neuropsychological tests considered capable of isolating prefrontal lobe dysfunction was administered. A significant group difference was noted on 6 of the tests; the negative symptom group performed much worse than the positive symptom group. The results of this study support the hypothesis that a relationship exists between the negative symptoms of schizophrenia and prefrontal lobe dysfunction.

Insight, neurocognitive function and symptom clusters in chronic schizophrenia

Only recently has there been interest in the systematic study of insight in schizophrenia. The present investigation was designed to evaluate the specific relationship between psychopathological symptoms, neurocognitive deficits and awareness of illness in chronic schizophrenia. Fifty-eight outpatients with the DSM-III-R diagnosis of schizophrenia were rated on David's Schedule for Assessing Insight, the Positive and Negative Syndrome Scale (PANSS), the Calgary Depression Scale and the Wisconsin Card Sorting Test (WCST). Results indicate that there is a significant association among these variables and that approximately 44% of the variance in the dependent variable could be explained by this combination of independent variables. Notably, however, negative symptoms were only moderately inversely correlated with awareness of illness, and they were not associated with scores on the WCST. Moreover, neither negative symptoms nor per cent perseverative errors contributed significantly to the prediction of insight in schizophrenia. These findings argue against the notion that unawareness of illness is the product of neuropsychological dysfunction in the frontal lobes. Instead, the most significant associations and predictors of insight were related to the positive symptoms of schizophrenia.

Non-selective impairment of Wisconsin Card Sorting Test performance in patients with schizophrenia

Sixty-two schizophrenic patients and 26 healthy volunteers were administered the Wisconsin Card Sorting Test (WCST) a task putatively specific for frontal functions and the Wechsler Adult Intelligence Scale (WAIS). The purpose of this study was to evaluate the presence of specific frontal lobe deficits in the course of schizophrenia and the capacity of these tasks to discriminate between patients and controls. Schizophrenic patients showed a poorer performance than control subjects in both tests. No evidence emerged to support a higher discriminant power for the WCST in identifying schizophrenic subjects from healthy controls compared with the WAIS. Our data suggest that the deficit in WCST performance is not selective, but rather part of a more generalized neuropsychological impairment in schizophrenic patients.

Negative symptoms and EEG alpha in schizophrenia: a replication

The authors previously reported that negative symptoms were associated with reduced EEG alpha power and coherence in medication-free schizophrenic inpatients. These post-hoc findings were based on resting EEG data in an eyes open condition. This report describes the replication of these results in a new sample of 17 male veterans (aged 38 +/- 8) recently hospitalized with DSM-III-R schizophrenia. All patients had been free of neuroleptic medication at least 12-14 days. The relationships between resting alpha (7.5-12.5 Hz) power and coherence and symptom ratings (as measured by subscales derived from the Brief Psychiatric Rating Scale) were examined with multivariate repeated measure analyses of covariance. Results were similar to those obtained earlier, with a main effect of negative symptoms (p = 0.05) on log alpha power, a localized effect on right frontal-parietal alpha coherence (p < 0.02), and a main effect (p < 0.03) on between-hemisphere alpha coherence. There was also a trend for an asymmetrical effect on power favoring the right side in parietal leads. Negative symptoms were associated with reduced alpha power and less alpha coherence between hemispheres and between right parietal and frontal regions. The authors discuss the implications of these results on neurodevelopmental, genetic, and attentional aspects of schizophrenia.

Cognitive function in schizophrenia: association with negative and positive symptoms

20 schizophrenic patients were classified as having either predominantly negative (n = 11) or predominantly positive symptoms (n = 9), utilizing the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms. Cognitive functioning was evaluated in these participants and 10 nonpatient controls using a word-fluency test and word-generation task. Finally, all participants were evaluated using the Coglab Card Sort Test, a computerized version of the Wisconsin Card Sort Test. The only reliable difference in performance among groups was on perseverative errors on the Coglab Card Sort Test. Schizophrenic participants made significantly more perseverative errors than controls and those classified as having primarily negative symptoms made more perseverative errors than those classified as having predominantly positive symptoms. These findings confirm previous reports with respect to cognitive functioning of schizophrenic patients and are consistent with the hypotheses regarding frontal lobe dysfunction in schizophrenia. These data encourage research with larger samples.

Computerized EEG and brain imaging studies in untreated schizophrenic patients: a report of seven cases

We undertook routine EEG, Z-map, CT and PET scans in seven acute untreated schizophrenics. Routine EEGs showed slower activity in only one case. However, the Z-map showed slower activity in all the cases. CT demonstrated brain atrophy in three of the cases, and PET revealed hypofrontality in two, right hypoparietality in four, and both conditions in one case. There was no relation between CT and PET or the Z-map. However, a significant increase in alpha 1 activity was demonstrated on the Z-map in cases who were found to be the parietal type on PET; this was not conspicuous in the frontal type on PET. Moreover, in three of the patients, the Z-map findings were similar to the lesion indicated on PET.

Cognitive functioning and anhedonia in subjects at risk for schizophrenia

This study investigated the performance of individuals with familiar loading of schizophrenia (healthy siblings of schizophrenic inpatients) on three neuropsychological tasks assumed to require frontal lobe functions: Trail Making Test (TMT), verbal fluency and Wisconsin Card Sorting Test (WCST). Healthy siblings of schizophrenics differed in performance from healthy controls not only on the WCST, but also on the Trail Making Test and the verbal fluency task. Furthermore, scores of physical anhedonia, assessed in a self-report rating scale (Chapman et al., 1976) were also significantly higher in the high risk group than in the control sample. However, healthy siblings of schizophrenics did not differ from controls with regard to experiences of perceptual aberrations, measured by the same method (Chapman et al., 1978). Neuropsychological performance and elevated anhedonia scores in the high risk group were interpreted under the conceptual framework of vulnerability markers: they were supposed to represent a trait shared by family members of schizophrenic probands. Amongst the neuropsychological tests, there were significant correlations between the physical anhedonia score and WCST and Trail Making test performance in the group of healthy siblings of schizophrenics, but not in the control group.

Spectral and topographic analysis of EEG in schizophrenic patients

The authors performed spectral analysis of electroencephalograms (EEG), recorded awake, with eyes closed, in 13 patients with schizophrenia and 9 age-matched individuals without psychiatric diagnosis. We tested several possible parameterizations of the data, and two data-reduction strategies; these yielded similar results. Comparison of the two groups revealed a relative increase in alpha frequency activity in the frontal regions in the patient group. The authors believe that this finding is consistent with data from neuropsychologic tests, metabolic imaging studies, and evoked potential studies that suggest impaired activation of frontal brain areas in patients with schizophrenia.

Computerized EEG topography findings in schizophrenic patients before and after haloperidol treatment

An increase of delta and fast beta activity in schizophrenic patients when compared with normal controls has been consistently reported. Topography of these abnormalities, in particular a possible frontal localization of delta, and their relationship to drug treatment and clinical status are still debated. In order to assess these issues, a multilead CEEG investigation was carried out in a group of 20 DSM-III-R schizophrenics, both before and after haloperidol treatment. All findings are described in terms of amplitude and relative power. Drug-free schizophrenics, when compared with a group of normal controls, showed a generalized increase of delta and fast beta, and a decrease of alpha 2 relative power. After acute treatment, patients showed a significant decrease of delta, and an increase of theta 2, beta 1, and beta 2. After 28 days of haloperidol treatment, similar changes were observed for delta, together with an increase of alpha 1, and a decrease of fast beta.

Influence of education on WCST performances in schizophrenic patients

Schizophrenic patients have been widely reported to fail in performing Wisconsin Card Sorting Test (WCST). These data have been mostly interpreted as cognitive difficulties and/or neurofunctional impairment inherent to schizophrenia. Nevertheless, checking sample characteristics, the importance of variables as education appears relevant. In our study we examined schizophrenic patients and controls with low and high educational levels respectively. ANOVA results show significant differences on WCST performances for the variable diagnosis (schizophrenics and controls) and for the variable educational level (low and high educational level). It therefore seems necessary call for caution in interpreting WCST results in schizophrenic patients when educational level is not considered.

Frontal and non-frontal lobe neuropsychological test performance and clinical symptomatology in schizophrenia

Schizophrenic subjects performed significantly worse on neuropsychological tests of frontal lobe function but not on tests of non-frontal lobe function when compared to a matched group of normal subjects. Correlations expected between frontal lobe neuropsychological test performance and negative symptoms were not found.

Wisconsin Card Sorting Test: an indicator of vulnerability to schizophrenia?

The Wisconsin Card Sorting Test (WCST) is a neuropsychological test, hypothesized to be an indicator of dorsolateral prefrontal cortex (DLPFC) functioning. The performance of schizophrenic patients in our sample (off medication) was worse than the performance of healthy controls in all variables of the WCST, including perseverative responses (PR) as well as non-perseverative responses (NPR). The rate of perseverative and non-perseverative responses was neither a function of the severity of the illness (measured by SANS/SAPS scales) nor the duration of the disease. Healthy siblings of schizophrenic probands revealed more perseverative responses than healthy controls, but did not show any difference with respect to the non-perseverative responses. This finding suggests that the difficulty to shift a cognitive set, reflected by the frequency of perseverative responses, is in favor of the WCST as a vulnerability marker for schizophrenia, whereas non-perseverative responses presumably indicate a state, but not a trait marker of the disease. However, the usefulness of this indicator may be limited by its association with age, which is worthy of being studied in closer detail.

Smooth pursuit eye movements and neuropsychological tests in schizophrenic patients: possible involvement of attentional components

The relationships among different components of frontal lobe dysfunction and voluntary attention were studied. Drug-free schizophrenic patients and matched normal controls were recruited and assessed for smooth pursuit eye movements, voluntary saccadic eye movements and by means of neuropsychological tests (Toluse-Pieron test and Wisconsin Card Sorting Test). No clear-cut relationship was found between eye movement performance and neuropsychological impairment.

Hypofrontality on topographic EEG in schizophrenia. Correlations with neuropsychological and psychopathological parameters

Topographic EEG was performed in 17 DSM-III-R schizophrenic patients and in 15 sex- and age-matched healthy controls. Eleven patients were first-onset (neuroleptic naive) schizophrenics. EEG band power was compared with psychopathology, neuropsychology and neurological soft signs. The EEG was recorded at 14 topographic locations monopolarly and movements of the eye and of the lid were monitored by two bipolar electro-oculogram (EOG) derivations, one vertical and one horizontal. A multivariate correction of EOG artefacts was performed based on regression analysis with respect to EOG channels. Schizophrenic patients showed higher mean and median power in most bands. These differences were marked in the delta band, in the fast alpha and beta bands, in particular at left frontal sites. Delta power at F7 was by far the best separating variable between schizophrenics and controls in a discriminant analysis. Significant positive correlations were found between the Brief Psychiatric Rating Scale scores "Anxiety-depression" and "Activation" and power in the fast bands and negative ones between "Anergia" and the beta bands. Positive significant correlations emerged between the total score in the Negative Symptoms Rating Scale and the amount of delta power, predominantly over the temporal region. Impairment in the Luria-Nebraska neuropsychological scores "Rhythm" and "Memory" correlated highly significantly with EEG band power. No correlations were found between neurological soft signs and EEG band power. Our results are in line with the hypothesis of a hypofrontality in schizophrenia. It is unlikely that these findings are an artefact of prior psychiatric treatment, as they were also observed in first-onset, neuroleptic naive schizophrenics.(ABSTRACT TRUNCATED AT 250 WORDS)

Coherence on electroencephalography and aberrant functional organisation of the brain in schizophrenic patients during activation tasks

Thirty schizophrenic patients (20 medicated, 10 off medication) were compared with 30 normal control subjects matched for age, sex, handedness, and intelligence. During the performance of left-hemisphere cognitive activation tasks, normal subjects had significantly increased EEG alpha coherence in areas related to left focal frontal sites, with decreases in temporal and posterior areas. Schizophrenic patients did not show the same degree of focal activation of left frontal areas. During the performance of right-hemisphere cognitive activation tasks, normal subjects and schizophrenic patients had similar patterns of right posterior increases in alpha coherence. Discriminant analyses were able to classify 81.4% of all subjects correctly. It is suggested that the findings indicate an aberrant functional organisation of the brain in schizophrenia, particularly affecting the left hemisphere.

Frontal and callosal neuropsychological performances in schizophrenia. Further evidence of possible attention and mnesic dysfunctions

Some level of frontal and callosal dysfunction has been reported in patients with schizophrenia. In the present study 68 normal controls and 117 schizophrenic patients were administered the Wisconsin Card Sorting Test (WCST), which involves the function of the frontal areas, and the Auditory Comprehension Test (ACT) which involves the corpus callosum and to a lesser degree attention and mnesic mechanisms. WCST correctly discriminated 69.8% of schizophrenics and 74.2% of controls, ACT 86.7% of schizophrenics and 90.2% of controls. Moreover, schizophrenics correctly classified by the WCST performed more poorly than schizophrenics incorrectly classified by the WCST on the related ACT indices for the attention and mnesic mechanisms. There were no differences in present age, age at onset, duration of the illness, diagnostic subtype and course of the disease between correctly and incorrectly classified schizophrenics by the WCST and the ACT. These data indicate a prevalent malfunctioning of attention and mnesic mechanisms in schizophrenia. Finally there seems to be no relationship between these neurofunctional abnormalities and demographic and clinical characteristics of the disease.

Subtype diagnosis in schizophrenia and its relation to neuropsychological and computerized tomography measures

We compared schizophrenic patients with a subtype diagnosis of paranoia (n = 14) to those with nonparanoid subtype diagnoses (n = 18) on the Wisconsin Card Sorting Test (WCST) and multiple computed tomography (CT) scan measures. The results showed that patients with nonparanoid diagnoses sorted fewer categories and made more perseverative errors on the WCST than did patients with the paranoid diagnosis. However, patients in the nonparanoid group could not be distinguished from those in the paranoid group on CT scan measures of brain structure. Additionally, a significant correlation was found between right frontal sulcal enlargement on CT scans and the number of perseverative errors made on the WCST.

Correlation of negative symptoms in schizophrenia with frontal lobe parameters on magnetic resonance imaging

Among 24 chronic schizophrenic patients, the 10 with high ratings for negative symptoms had significantly higher left-frontal: temporal-cortical T2 ratios. This finding was unrelated to age, dose of medication, length of illness or handedness. No T1 or T2 changes were found to be associated with positive symptoms or tardive dyskinesia in the regions examined.