Persecutory delusions and the determination of self-relevance: an fMRI investigation

BACKGROUND

People with persecutory delusions regard ambiguous data in the social domain as self-relevant and selectively attend to threatening information. This study aimed to characterize these social cognitive biases in functional neuroanatomical terms.

METHOD

Eight schizophrenic patients with active persecutory delusions and eight matched normal controls underwent functional magnetic resonance imaging while determining the self-relevance of ambiguous self-relevant or unambiguous other-relevant neutral and threatening statements.

RESULTS

In determining self-relevance, the deluded subjects showed a marked absence of rostral-ventral anterior cingulate activation together with increased posterior cingulate gyrus activation in comparison to the normal subjects. The influence of threat on self-relevance determination did not yield statistically significant differences between deluded and normal subjects.

CONCLUSIONS

Abnormalities of cingulate gyrus activation while determining self-relevance suggest impaired self-reflection in the persecutory deluded state. This may contribute to persecutory belief formation and maintenance.

Lateralisation of language function in young adults born very preterm

OBJECTIVE

To explore, using functional magnetic resonance imaging (MRI), the functional organisation of phonological processing in young adults born very preterm.

SUBJECTS

Six right handed male subjects with radiological evidence of thinning of the corpus callosum were selected from a cohort of very preterm subjects. Six normal right handed male volunteers acted as controls.

METHOD

Blood oxygenation level dependent contrast echoplanar images were acquired over five minutes at 1.5 T while subjects performed the tasks. During the ON condition, subjects were visually presented with pairs of non-words and asked to press a key when a pair of words rhymed (phonological processing). This task alternated with the OFF condition, which required subjects to make letter case judgments of visually presented pairs of consonant letter strings (orthographic processing). Generic brain activation maps were constructed from individual images by sinusoidal regression and non-parametric testing. Between group differences in the mean power of experimental response were identified on a voxel wise basis by analysis of variance.

RESULTS

Compared with controls, the subjects with thinning of the corpus callosum showed significantly reduced power of response in the left hemisphere, including the peristriate cortex and the cerebellum, as well as in the right parietal association area. Significantly increased power of response was observed in the right precentral gyrus and the right supplementary motor area.

CONCLUSIONS

The data show evidence of increased frontal and decreased occipital activation in male subjects with neurodevelopmental thinning of the corpus callosum, which may be due to the operation of developmental compensatory mechanisms.

Self-responsibility and the self-serving bias: an fMRI investigation of causal attributions

We use causal attributions to infer the most likely cause of events in the social world. Internal attributions imply self-responsibility for events. The self-serving bias describes the tendency of normal subjects to attribute the causation of positive events internally ("I am responsible em leader ") and negative events externally ("Other people or situational factors are responsible em leader "). The self-serving bias has been assumed to serve a positive motivational function by enhancing self-esteem. Abnormalities of attributional style have been implicated in both depression and psychosis. We examined the neural basis of both self-responsibility and the self-serving bias using functional magnetic resonance imaging during the performance of attributional decision tasks. We found that the determination of self-responsibility recruits areas previously implicated in action simulation (bilateral premotor cortex and cerebellum), suggesting that such higher order social cognition is related to simpler internal models of goal-directed action. The dorsal striatum, previously implicated in motivated behavior, mediates the self-serving bias.

Prevalence of autism and parentally reported triggers in a north east London population

BACKGROUND

The recorded prevalence of autistic spectrum disorders has risen over recent decades. Measles, mumps and rubella (MMR) vaccine has been blamed, by causing a "new variant" form of "regressive autism" associated with "autistic enterocolitis".

AIMS

To estimate the prevalence of autism and to assess any changes in parental perception regarding the onset or causes of autism.

METHODS AND RESULTS

A total of 567 children with autistic spectrum disorder in five districts in north east London were identified, born 1979-98. Reported autism, excluding the 94 cases of Asperger's syndrome, increased by year of birth until 1992, since when prevalence has plateaued. This flattening off persisted after allowing for expected delay in diagnosis in more recent birth cohorts. The age at diagnosis of autistic spectrum disorder was estimated to have decreased per five year period since 1983, by 8.7% for childhood autism and by 11.0% for atypical autism. There was some evidence that MMR was more likely to be mentioned as a trigger after August 1997 than before.

CONCLUSIONS

The prevalence of autism, which was apparently rising from 1979 to 1992, reached a plateau from 1992 to 1996 at a rate of some 2.6 per 1000 live births. This levelling off, together with the reducing age at diagnosis, suggests that the earlier recorded rise in prevalence was not a real increase but was likely due to factors such as increased recognition, a greater willingness on the part of educationalists and families to accept the diagnostic label, and better recording systems. The proportion of parents attributing their child's autism to MMR appears to have increased since August 1997.

Recall bias, MMR, and autism

Parents of autistic children with regressive symptoms who were diagnosed after the publicity alleging a link with measles, mumps, and rubella (MMR) vaccine tended to recall the onset as shortly after MMR more often than parents of similar children who were diagnosed prior to the publicity. This is consistent with the recall bias expected under such circumstances.

Sensitivity of the Procleix HIV-1/HCV assay for detection of human immunodeficiency virus type 1 and hepatitis C virus RNA in a high-risk population

The Procleix HIV-1/HCV Assay is a high-throughput nucleic acid test for the simultaneous detection of human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) RNA during blood donor screening. This study evaluated the clinical sensitivity of the Procleix assay and assessed the assay's ability to identify HIV-1- and HCV-infected individuals undetected by standard serologic tests. Plasma samples were obtained prospectively from 539 individuals at high risk for HIV-1 and HCV infection at seven clinics affiliated with Johns Hopkins University. Samples were tested in the Procleix HIV-1/HCV Assay and, if reactive, were then tested in the Procleix HIV-1 and HCV discriminatory assays to differentiate the source of viral RNA positivity. Of these 539 subjects, 287 (53.2%) tested reactive in the Procleix HIV-1/HCV Assay. In discriminatory assay testing, 12 of 287 subjects (4.2%) were reactive for HIV-1 RNA only, 260 (90.6%) were reactive for HCV RNA only, and 11 (3.8%) were coinfected with HIV-1 and HCV. The clinical sensitivity for samples tested neat was 100% for HIV-1 and 99.3% for HCV. Three subjects with Procleix HCV reactive/seronegative results seroconverted upon follow-up and were confirmed as Procleix HCV yield cases. The Procleix HIV-1/HCV Assay is a highly sensitive test that detects ongoing and early HIV-1 and HCV infection in a significant number of subjects at high risk for these diseases. Confirmation of Procleix yield cases upon follow-up demonstrated the ability of the Procleix HIV-1/HCV Assay to detect the presence of HIV-1 and HCV in blood earlier than standard serologic tests.

The neural correlates of intentional and incidental self processing

The neuroscientific study of the 'Self' is just beginning to emerge. We used functional Magnetic Resonance Imaging (fMRI) to investigate cerebral activation while subjects processed words describing personality traits and physical features, in two experiments with contrasting designs: incidental and intentional. In the first experiment (intentional self processing), subjects were presented with personality trait adjectives and made judgements as to their self descriptiveness (versus non self descriptiveness). In the second experiment (incidental self processing), subjects categorised words according to whether they described physical versus psychological attributes, while unaware that the words had been arranged in blocks according to self descriptiveness. The subjects had previously rated all words for self descriptiveness 6 weeks prior to the scanning session. A reaction time advantage was present in both experiments for self descriptive trait words, suggesting a facilitation effect. Common areas of activation for the two experiments included the left superior parietal lobe, with adjacent regions of the lateral prefrontal cortex also active in both experiments. Differential signal changes were present in the left precuneus for the intentional and the right middle temporal gyrus for the incidental experiment. The results suggest that self processing involves distinct processes and can occur on more than one cognitive level with corresponding functional neuroanatomic correlates in areas previously implicated in the awareness of one's own state.

Apolipoprotein E epsilon4 allele affects the relationship between stress and depression in caregivers of patients with Alzheimer's disease

We examined the effect of the apolipoprotein E (apo E) epsilon4 allele on the relationship between self-reported stress and mood in caregivers of patients with Alzheimer's disease. Eighty-six female subjects between the ages of 28 and 82 years who were community-dwelling AD patient caregivers participated in the study. A cross-sectional analysis of stress and mood was performed using the Revised Memory and Behavior Problem Checklist and the Geriatric Depression Scale. All subjects were evaluated for normal cognitive function (Mini-Mental Status Examination) and apo E genotype. The results indicated that increased levels of stress were associated with increased levels of depressive symptoms in nondemented caregivers with the epsilon4 allele. This relationship was not observed in caregivers without the epsilon4 allele. These results suggest that carriers of the epsilon4 allele may respond differently to psychological stress than do individuals without the epsilon4 allele.

Effects of estrogen replacement therapy on human brain aging: an in vivo 1H MRS study

Estrogen replacement therapy (ERT) may preserve cognitive function in postmenopausal women, but the mechanism is unknown. Thus, the authors studied aging of parietal lobe and hippocampus using proton MR spectroscopy. ERT naïve postmenopausal women had a significant increase in choline-containing compounds (Cho) compared to long-term ERT users and young women. Cho reflects increased neuronal/glial membrane turnover. Thus, ERT's "neuroprotective" effect may include modulating the effects of age on neural integrity in brain regions involved in cognitive function.

Neuroimaging correlates of negative priming

Many theoretical accounts of selective attention and memory retrieval include reference to active inhibitory processes, such as those argued to underlie the negative priming effect. fMRI was used in order to investigate the areas of cortical activation associated with Stroop interference, Stroop facilitation and Stroop negative priming tasks. The most significant activation within the negative priming task was within the inferior parietal lobule, left temporal lobe and frontal lobes. Areas of cortical activation are discussed with reference to theoretical accounts of the negative priming effect.

Volumetric analysis reveals corticospinal tract degeneration and extramotor involvement in ALS

BACKGROUND

Pathologic changes in the motor cortex and corticospinal tracts in ALS may be reflected by abnormal signal intensities on conventional MRI. The sensitivity of these changes in detecting underlying pathology remains unclear.

METHOD

The authors used automated image analysis to quantify volumes of cerebral gray and white matter in 16 patients with ALS (eight limb onset, eight bulbar onset) and eight normal controls. Previously they had demonstrated a reduction in N-acetyl aspartate/creatine + phosphocreatine (NAA/[Cr + PCr]) measured by (1)H-MRS in the subcortical white matter in the motor cortex region in the patients with bulbar-onset ALS. To determine whether this resulted from axonal degeneration, they also compared gray and white matter volumes in the patients with limb- and bulbar-onset ALS.

RESULTS

There were no differences in the total brain volumes of gray or white matter for the three subject groups (p > 0.23). Comparison of the total ALS group and controls revealed localized deficits in gray matter volume centered on Brodmann areas 8, 9, and 10 bilaterally. Comparison of the patients with limb- and bulbar-onset ALS revealed deficits in the white matter volume in the bulbar-onset group, extending bilaterally from the precentral gyrus into the internal capsule and brainstem, consistent with the course of the corticospinal tract. There was no loss in gray matter volume in the precentral gyri.

CONCLUSIONS

The loss of gray matter in the frontal regions (total ALS group) provides further support that ALS is a multisystem disorder. In addition, there is in vivo evidence of axonal degeneration in the subcortical white matter in the motor region in patients with bulbar-onset ALS. This is consistent with a "dying back" process affecting cortical motoneurons in bulbar-onset ALS.

Distributed grey and white matter deficits in hyperkinetic disorder: MRI evidence for anatomical abnormality in an attentional network

BACKGROUND

Previous neuroimaging studies of children with attention deficit hyperactivity disorder (ADHD) have demonstrated anatomic and functional abnormalities predominantly in frontal and striatal grey matter. Here we report the use of novel image analysis methods, which do not require prior selection of regions of interest, to characterize distributed morphological deficits of both grey and white matter associated with ADHD.

METHODS

Eighteen children with a refined phenotype of ADHD, who also met ICD-10 criteria for hyperkinetic disorder (mean age 10.4 years), and 16 normal children (mean age 10.3 years) were compared using magnetic resonance imaging. The groups were matched for handedness, sex, height, weight and head circumference. Morphological differences between groups were estimated by fitting a linear model at each voxel in standard space, applying a threshold to the resulting voxel statistic maps to generate clusters of spatially contiguous suprathreshold voxels, and testing cluster 'mass', or the sum of suprathreshold voxel statistics in each 2D cluster, by repeated random resampling of the data.

RESULTS

The hyperkinetic children had significant grey matter deficits in right superior frontal gyrus (Brodmann area (BA) 8/9), right posterior cingulate gyrus (BA 30) and the basal ganglia bilaterally (especially right globus pallidus and putamen). They also demonstrated significant central white matter deficits in the left hemisphere anterior to the pyramidal tracts and superior to the basal ganglia.

CONCLUSIONS

This pattern of spatially distributed grey matter deficit in the right hemisphere is compatible with the hypothesis that ADHD is associated with disruption of a large scale neurocognitive network for attention. The left hemispheric white matter deficits may be due to dysmyelination.

Herpesvirus and multiple sclerosis

Evidence suggests that multiple sclerosis (MS) is caused by host genetic factors in association with one or more environmental agents. The clinical and pathological features of MS implicate viral infections as either cofactors in its aetiology or triggers of relapses, although no specific environmental factors have been identified. In particular, several herpesviruses have attracted interest because their ability to cause latent infections that periodically reactivate has some familiarity with the relapsing-remitting course of MS. Further, most human herpesviruses can be readily found within the central nervous system and several are known to be capable of inducing demyelination, both in humans and in experimentally infected animals. This brief review takes a systematic look at reported associations between herpesviruses and MS and suggests some criteria that must be met in further studies. One of the greatest challenges in confirming or refuting a role for herpesviruses in chronic diseases is their ubiquitous nature. It is stated from the outset that the associations described here remain controversial.

MRI based diffusion and perfusion predictive model to estimate stroke evolution

In this study we present a novel automated strategy for predicting infarct evolution, based on MR diffusion and perfusion images acquired in the acute stage of stroke. The validity of this methodology was tested on novel patient data including data acquired from an independent stroke clinic. Regions-of-interest (ROIs) defining the initial diffusion lesion and tissue with abnormal hemodynamic function as defined by the mean transit time (MTT) abnormality were automatically extracted from DWI/PI maps. Quantitative measures of cerebral blood flow (CBF) and volume (CBV) along with ratio measures defined relative to the contralateral hemisphere (r(a)CBF and r(a)CBV) were calculated for the MTT ROIs. A parametric normal classifier algorithm incorporating these measures was used to predict infarct growth. The mean r(a)CBF and r(a)CBV values for eventually infarcted MTT tissue were 0.70 +/- 0.19 and 1.20 +/- 0.36. For recovered tissue the mean values were 0.99 +/- 0.25 and 1.87 +/- 0.71, respectively. There was a significant difference between these two regions for both measures (p < 0.003 and p < 0.001, respectively). Mean absolute measures of CBF (ml/100g/min) and CBV (ml/100g) for the total infarcted territory were 33.9 +/- 9.7 and 4.2 +/- 1.9. For recovered MTT tissue, the mean values were 41.5 +/- 7.2 and 5.3 +/- 1.2, respectively. A significant difference was also found for these regions (p < 0.009 and p < 0.036, respectively). The mean measures of sensitivity, specificity, positive and negative predictive values for modeling infarct evolution for the validation patient data were 0.72 +/- 0.05, 0.97 +/- 0.02, 0.68 +/- 0.07 and 0.97 +/- 0.02. We propose that this automated strategy may allow possible guided therapeutic intervention to stroke patients and evaluation of efficacy of novel stroke compounds in clinical drug trials.

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

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

SPAMM, cine phase contrast imaging and fast spin-echo T2-weighted imaging in the study of intracranial cerebrospinal fluid (CSF) flow

AIM

To compare the qualitative assessment of cerebrospinal fluid (CSF) flow using a SPAMM (spatial modulation of magnetization) technique with cine phase contrast images (cine PC) and fast spin echo (FSE) T2-weighted images.

MATERIALS AND METHODS

SPAMM, PC and T2-weighted sequences were performed on 22 occasions in 19 patients. Eleven of the studies were performed following a neuroendoscopic third ventriculostomy (NTV), and in these cases, the success of the NTV was determined by clinical follow-up. Two observers used consensus to grade the presence of CSF flow at nine different sites for each study.

RESULTS

At 14 of the 178 matched sites, which could be assessed by both SPAMM and cine PC, SPAMM CSF flow grade was higher than that of cine PC. At a further 14/178 matched sites, the cine PC grade was higher than that of SPAMM. There was definite CSF flow at 113/182 (62%) of all the cine PC sites assessed, and 110/181 (61%) of all SPAMM sites assessed whilst 108/198 (54%) of FSE T2-weighted image sites demonstrated flow voids. Cine PC grades were higher than SPAMM at the cerebral aqueduct (P < 0.05, Wilcoxon sign rank test). Definite CSF flow within the anterior third ventricle was present in 4/5 (SPAMM) and 3/5 (cine PC) successful NTVs, 0/2 (SPAMM and cine PC) unsuccessful NTVs and 1/10 (SPAMM and cine PC) patients without NTV.

CONCLUSION

SPAMM provides a comparable assessment of intracranial CSF flow to that of cine phase contrast imaging at all CSF sites except the cerebral aqueduct.

Superior temporal gyrus abnormalities in early-onset schizophrenia: similarities and differences with adult-onset schizophrenia

OBJECTIVE

The superior temporal gyrus is associated with developmental mechanisms of brain lateralization and the pathogenesis of language-related schizophrenic symptoms. It therefore lends itself to investigation of developmental deviance in the early onset of schizophrenia.

METHOD

Using stereological methods, the authors obtained bilateral measurements of the superior temporal gyrus (total, gray matter, and white matter volumes) from 40 adolescents with recent-onset schizophrenia and an equal number of matched healthy volunteers. Symptoms were rated by using the Positive and Negative Syndrome Scale.

RESULTS

The total and gray matter volume of the right superior temporal gyrus was significantly lower in patients with early-onset schizophrenia than in the healthy volunteers, even after differences in whole brain volume were controlled. Bilateral superior temporal gyrus volumes were positively correlated with the age at onset of psychosis, while severity of thought disorder and hallucinations were inversely related to right superior temporal gyrus volume.

CONCLUSIONS

In patients with early-onset schizophrenia, the predominantly right-sided volumetric abnormalities found in the superior temporal gyrus may reflect a particularly early neurodevelopmental disruption. The relationship between language-related symptoms and superior temporal gyrus volume is similar to that seen in adult-onset cases but not as lateralized.

The effect of acute hypoglycemia on brain function and activation: a functional magnetic resonance imaging study

The authors' aim was to examine the regional anatomy of brain activation by cognitive tasks commonly used in hypoglycemia research and to assess the effect of acute hypoglycemia on these in healthy volunteers. Eight right-handed volunteers performed a set of cognitive tasks-finger tapping (FT), simple reaction time (SRT), and four-choice reaction time (4CRT)-twice during blood oxygen level-dependent (BOLD) functional magnetic resonance imaging of the brain on two occasions. In study 1 (n = 6), plasma glucose was maintained at euglycemia (5 mmol/l) throughout. In study 2 (n = 6), plasma glucose was reduced to 2.5 mmol/l for the second set. Performance of the tasks resulted in specific group brain activation maps. During hypoglycemia, FT slowed (P = 0.026), with decreased BOLD activation in right premotor cortex and supplementary motor area and left hippocampus and with increased BOLD activation in left cerebellum and right frontal pole. Although there was no significant change in SRT, BOLD activation was reduced in right cerebellum and visual cortex. The 4CRT deteriorated (P = 0.020), with reduction in BOLD activation in motor and visual systems but increased BOLD signal in a large area of the left parietal association cortex, a region involved in planning. Hypoglycemia impairs simple brain functions and is associated with task-specific localized reductions in brain activation. For a task with greater cognitive load, the increased BOLD signal in planning areas is compatible with recruitment of brain regions in an attempt to limit dysfunction. Further investigation of these mechanisms may help devise rational treatment strategies to limit cortical dysfunction during acute iatrogenic hypoglycemia.

Magnetic resonance markers of ischaemia: their correlation with vasodilatory reserve in patients with carotid artery stenosis and occlusion

OBJECTIVES

Better methods of identifying patients with asymptomatic carotid artery stenosis who are at high risk of stroke are required. It has been suggested that proton magnetic resonance spectroscopy (MRS) may allow the identification of ongoing ischaemia in this patient group by the detection of a potentially reversible reduction of N-acetyl aspartate (NAA), a presumed marker of neuronal integrity, and the presence of lactate, a marker of anaerobic metabolism. Previous studies have reported metabolite ratios rather than absolute concentrations. This study was performed to determine if NAA was reduced ipsilateral to carotid stenosis or occlusion, and if its concentration was related to carbon dioxide reactivity, a marker of cerebrovascular reserve.

METHODS

Twenty one patients with unilateral carotid stenosis (>70%) or occlusion were studied. Single voxel proton MRS was performed in the ipsilateral and contralateral hemispheres, with the voxel positioned in the arterial borderzone region between the middle and anterior cerebral artery territories. Absolute quantification of metabolite concentrations was performed. Cerebrovascular reactivity to 6% carbon dioxide was determined in both middle cerebral artery territories using transcranial Doppler ultrasonography.

RESULTS

Mean (SD) cerebrovascular reactivity was significantly lower in the stenosed compared with the contralateral hemisphere (13.3 (7.7) v 19.2 (8.2)%/kPa, p=0.002). There were no significant differences in the absolute concentrations of NAA, choline, or creatine between the ipsilateral and contralateral hemispheres (for example, NAA 10.1 (1.1) v 10.5 (1.1) mmol/l, p=0.1). No lactate peak was seen in any spectra. For each metabolite measured, there was no correlation between the absolute concentration and cerebrovascular reactivity for either hemisphere.

CONCLUSIONS

In patients with carotid stenosis and occlusion we found no evidence that chronic hypoperfusion is associated with a reduction in NAA or the presence of lactate. Magnetic resonance spectroscopy is unlikely to help in the selection of patients with asymptomatic carotid stenosis for endarterectomy.

Nef triggers a transcriptional program in T cells imitating single-signal T cell activation and inducing HIV virulence mediators

Gene expression profiling was used to explore the role of Nef in HIV. Nef induces a transcriptional program in T cells that is 97% identical to that of anti-CD3 T cell activation. This program is inhibited in the presence of cyclosporin. A requirement for TCR zeta and ZAP-70 is demonstrated for formation of the complete profile. Among eight factors particular to the anti-CD3 activation profile are IL16 and YY1, negative regulators of HIV transcription. In contrast, Nef exclusively upregulates factors positively regulating HIV, including Tat-SF1, U1 SNRNP, and IRF-2. New genes associated with Nef include CDK9, the induction of which enhances Tat function. Thus, Nef acts as a master switch early in the viral life cycle, forcing an environment conducive to dynamic viral production.

Corpus callosum area and functioning in schizophrenic patients with auditory--verbal hallucinations

Auditory--verbal hallucinations (AVH) are a characteristic feature of schizophrenia. Patients with AVHs have been found to differ from non-hallucinating patients in volumes of certain asymmetrical brain structures on MRI, and on certain neuropsychological measures. There is also evidence of corpus callosum (CC) abnormalities in schizophrenia, and it has been proposed that abnormalities of inter-hemispheric transmission may underlie hallucinations and other symptoms. The aim of this study was to examine whether patients with AVHs have smaller corpora callosa than those without AVH, and whether CC size is related to performance on neuropsychological tests of functional cerebral asymmetry. Seventy-one DSM-IV male schizophrenics were recruited on the basis of their hallucination history plus 33 matched normal controls. Twenty-nine patients had no history of AVH, and 42 had a strong history of AVH. The mid-sagittal surface area and longitudinal length of the CC were measured from T(1)-weighted spin echo images. Callosal area was divided into four sections. There were no significant differences in any of the measurements between the two patient groups, or between patients with schizophrenia and controls. There was no association between CC measures and handedness, or performance on dichotic listening or finger tapping tasks. The results of this study do not lend support for there being a major morphological abnormality of the corpus callosum in schizophrenic patients, or for a specific relationship to AVH. However, a significant association between CC area and overall grey and white matter volumes was noted in the hallucinating patients and, to a lesser extent, in the non-hallucinators, which may point to differing influences on brain development or degeneration in such patients compared with normal controls.