Laterality in functional brain imaging studies of schizophrenia

In memory of Professor Iain Wilkinson: cognitive and neuroimaging endophenotypes in a consanguineous schizophrenia multiplex family

BACKGROUND

Schizophrenia endophenotypes may help elucidate functional effects of genetic risk variants in multiply affected consanguineous families that segregate recessive risk alleles of large effect size. We studied the association between a schizophrenia risk locus involving a 6.1Mb homozygous region on chromosome 13q22-31 in a consanguineous multiplex family and cognitive functioning, haemodynamic response and white matter integrity using neuroimaging.

METHODS

We performed CANTAB neuropsychological testing on four affected family members (all homozygous for the risk locus), ten unaffected family members (seven homozygous and three heterozygous) and ten healthy volunteers, and tested neuronal responses on fMRI during an n-back working memory task, and white matter integrity on diffusion tensor imaging (DTI) on four affected and six unaffected family members (four homozygous and two heterozygous) and three healthy volunteers. For cognitive comparisons we used a linear mixed model (Kruskal-Wallis) test, followed by posthoc Dunn's pairwise tests with a Bonferroni adjustment. For fMRI analysis, we counted voxels exceeding the p < 0.05 corrected threshold. DTI analysis was observational.

RESULTS

Family members with schizophrenia and unaffected family members homozygous for the risk haplotype showed attention (p < 0.01) and working memory deficits (p < 0.01) compared with healthy controls; a neural activation laterality bias towards the right prefrontal cortex (voxels reaching p < 0.05, corrected) and observed lower fractional anisotropy in the anterior cingulate cortex and left dorsolateral prefrontal cortex.

CONCLUSIONS

In this family, homozygosity at the 13q risk locus was associated with impaired cognition, white matter integrity, and altered laterality of neural activation.

Omission mismatch negativity of speech sounds reveals a functionally impaired temporal window of integration in schizophrenia

OBJECTIVE

We hypothesized that sensory memory associated with the temporal window of integration (TWI) would be impaired in patients with schizophrenia, an issue that had not been evaluated using omission mismatch negativity (MMN) of complex speech sounds. We aimed to assess the functional changes in auditory sensory memory associated with the TWI in patients with schizophrenia by investigating the effect of omission of complex speech stimuli on the MMN.

METHODS

In total, 17 patients with schizophrenia and 15 control individuals participated in the study. The MMN in response to omission deviants of complex speech sounds was recorded, while the participants were instructed to ignore the series of speech sounds.

RESULTS

The MMN latency in patients with schizophrenia was significantly prolonged by deviant stimuli to omissions corresponding to the early and late parts of the temporal TWI. There were no significant group differences in the amplitude of the MMN to omissions at different time points across the TWI.

CONCLUSIONS

Our results suggested that sensory tracing function in patients with schizophrenia is impaired in the early and the later half of the TWI.

SIGNIFICANCE

We showed that certain MMN abnormalities in patients with schizophrenia may be caused by an impaired TWI.

Functional asymmetry of thalamocortical networks in subjects at ultra-high risk for psychosis and first-episode schizophrenia

Disrupted functional asymmetry has been implicated in schizophrenia. However, it remains unknown whether disrupted functional asymmetry originates from intra-hemispheric and/or inter-hemispheric functional connectivity (FC) in the patients, and whether it starts at very early stage of psychosis. Seventy-six patients with first-episode, drug-naive schizophrenia, 74 subjects at ultra-high risk for psychosis (UHR), and 71 healthy controls underwent resting-state functional magnetic resonance imaging. The 'Parameter of asymmetry' (PAS) metric was calculated and support vector machine (SVM) classification analysis was applied to analyze the data. Compared with healthy controls, patients exhibited decreased PAS in the left thalamus/pallidum, right hippocampus/parahippocampus, right inferior frontal gyrus/insula, right thalamus, and left inferior parietal lobule, and increased PAS in the left calcarine, right superior occipital gyrus/middle occipital gyrus, and right precentral gyrus/postcentral gyrus. By contrast, UHR subjects showed decreased PAS in the left thalamus relative to healthy controls. A negative correlation was observed between decreased PAS in the right hippocampus/parahippocampus and Brief Visuospatial Memory Test-Revised (BVMT-R) scores in the patients (r = -0.364, p = 0.002). Moreover, the PAS values in the left thalamus could discriminate the patients/UHR subjects from the controls with acceptable sensitivities (68.42%/81.08%). First-episode patients and UHR subjects shared decreased PAS in the left thalamus. This observed pattern of functional asymmetry highlights the involvement of the thalamus in the pathophysiology of psychosis and may also be applied as a very early marker for psychosis.

Functional brain lateralization in schizophrenia based on the variability of resting-state fMRI signal

Abnormal brain lateralization has been implicated in schizophrenia but few studies have focused on the variability of resting-state fMRI signal and its lateralization in schizophrenia. Here we utilized standard deviations (SD) to quantify the variability of resting-state fMRI signal and measured the lateralization index (LI), on the basis of SD of the resting-state fMRI signal in order to assess the difference of brain signal variability across the hemispheres. We recruited 180 patients with schizophrenia and 358 age- and sex-matched healthy volunteers. Between-group comparison revealed that in comparison to healthy volunteers, schizophrenia patients have significantly higher SD of resting-state fMRI activity in left inferior temporal, left fusiform, and right superior medial frontal cortex, and lower SD in right precuneus, posterior cingulum on both sides, right lingual, and left calcarine in the occipital region. Using region of interest approach, most brain regions showed increased leftward lateralization in patients with schizophrenia, as compared with healthy controls. SD and LI were also found to be correlated to age of onset or duration of illness. These results provide further evidence that abnormal variability and lateralization exist in schizophrenia patients, and abnormality in fusiform, lingual and inferior temporal could have potential help to identify the dysfunctional brain lateralization in schizophrenia.

Plasticity of prefrontal cortex connectivity in schizophrenia in response to antisaccade practice

People with schizophrenia exhibit difficulties in cognitive control that are often attributed to deficits in prefrontal cortex (PFC) circuitry. Practice paradigms have been used to improve these PFC-mediated deficits. The neural consequences of practice on task-based PFC activation have been addressed. Effects on task-based PFC connectivity, however, are largely unknown. We recruited people with schizophrenia and controls to practice antisaccades, a measure of PFC-mediated cognitive control that is disrupted in people with schizophrenia. Subjects performed antisaccades during functional magnetic resonance imaging (fMRI) before and after eight days of antisaccade practice. A group (schizophrenia, controls) × time (pre-, post-test) repeated measures ANOVA on the results of a psychophysiological interaction (PPI) analysis was used to evaluate changes in PFC connectivity; a similar model was used to evaluate changes in antisaccade behavior. After practice, antisaccade behavior improved and PFC connectivity with insular/temporal regions (involved in bottom-up orienting processes) increased in the schizophrenia group. The level of connectivity at post-test in the schizophrenia group was similar to that seen at pre-test in controls and positively correlated with antisaccade performance. Increases in connectivity between bottom-up and top-down regions may underlie behavioral improvements in people with schizophrenia after cognitive control practice.

Limited Evidence for Association of Genome-Wide Schizophrenia Risk Variants on Cortical Neuroimaging Phenotypes

BACKGROUND

There are now over 100 established genetic risk variants for schizophrenia; however, their influence on brain structure and circuitry across the human lifespan are not known.

METHODS

We examined healthy individuals 8-86 years of age, from the Centre for Addiction and Mental Health, the Zucker Hillside Hospital, and the Philadelphia Neurodevelopmental Cohort. Following thorough quality control procedures, we investigated associations of established genetic risk variants with heritable neuroimaging phenotypes relevant to schizophrenia, namely thickness of frontal and temporal cortical regions (n = 565) and frontotemporal and interhemispheric white matter tract fractional anisotropy (FA) (n = 530).

RESULTS

There was little evidence for association of risk variants with imaging phenotypes. No association with cortical thickness of any region was present. Only rs12148337, near a long noncoding RNA region, was associated with white matter FA (splenium of corpus callosum) following multiple comparison correction (corrected p = .012); this single nucleotide polymorphism was also associated with genu FA and superior longitudinal fasciculus FA at p <.005 (uncorrected). There was no association of polygenic risk score with white matter FA or cortical thickness.

CONCLUSIONS

In sum, our findings provide limited evidence for association of schizophrenia risk variants with cortical thickness or diffusion imaging white matter phenotypes. When taken with recent lack of association of these variants with subcortical brain volumes, our results either suggest that structural neuroimaging approaches at current resolution are not sufficiently sensitive to detect effects of these risk variants or that multiple comparison correction in correlated phenotypes is too stringent, potentially "eliminating" biologically important signals.

Associations between schizotypy and cerebral laterality

Atypical lateralization for language has been found in schizophrenia, suggesting that language and thought disorders on the schizophrenia spectrum may be due to left hemispheric dysfunction. However, research with those with non-clinical schizotypy has been inconsistent, with some studies finding reduced or reversed language laterality (particularly with positive schizotypal traits), and others finding typical left hemispheric specialization. The aim of the current study was to use both a behavioural (dual reading-finger tapping) task and an functional magnetic resonance imaging lexical decision task to investigate language laterality in a university sample of high- and low-schizotypal adults. Findings revealed no evidence for atypical lateralization in our sample for both overall schizotypy (measured by the Oxford-Liverpool Inventory of Feelings and Experiences) and positive schizotypy (measured by the Unusual Experiences subscale) groups. Our findings provide further evidence that non-clinical schizotypy is not associated with atypical language laterality.

Neural Reorganization and Compensation in Aging

According to prominent theories of aging, the brain may reorganize to compensate for neural deterioration and prevent or offset cognitive decline. A frequent and striking finding in functional imaging studies is that older adults recruit additional regions relative to young adults performing the same task. This is often interpreted as evidence for functional reorganization, suggesting that, as people age, different regions or networks may support the same cognitive functions. Associations between additional recruitment and better performance in older adults have led to the suggestion that the additional recruitment may contribute to preserved cognitive function in old age and may explain some of the variation among individuals in preservation of function. However, many alternative explanations are possible, and recent findings and methodological developments have highlighted the need for more systematic approaches to determine whether reorganization occurs with age and whether it benefits performance. We reevaluate current evidence for compensatory functional reorganization in the light of recent moves to address these challenges.

Abnormal asymmetry of brain connectivity in schizophrenia

Recently, a growing body of data has revealed that beyond a dysfunction of connectivity among different brain areas in schizophrenia patients (SCZ), there is also an abnormal asymmetry of functional connectivity compared with healthy subjects. The loss of the cerebral torque and the abnormalities of gyrification, with an increased or more complex cortical folding in the right hemisphere may provide an anatomical basis for such aberrant connectivity in SCZ. Furthermore, diffusion tensor imaging studies have shown a significant reduction of leftward asymmetry in some key white-matter tracts in SCZ. In this paper, we review the studies that investigated both structural brain asymmetry and asymmetry of functional connectivity in healthy subjects and SCZ. From an analysis of the existing literature on this topic, we can hypothesize an overall generally attenuated asymmetry of functional connectivity in SCZ compared to healthy controls. Such attenuated asymmetry increases with the duration of the disease and correlates with psychotic symptoms. Finally, we hypothesize that structural deficits across the corpus callosum may contribute to the abnormal asymmetry of intra-hemispheric connectivity in schizophrenia.

Basic visual dysfunction allows classification of patients with schizophrenia with exceptional accuracy

Basic visual dysfunctions are commonly reported in schizophrenia; however their value as diagnostic tools remains uncertain. This study reports a novel electrophysiological approach using checkerboard visual evoked potentials (VEP). Sources of spectral resolution VEP-components C1, P1 and N1 were estimated by LORETA, and the band-effects (BSE) on these estimated sources were explored in each subject. BSEs were Z-transformed for each component and relationships with clinical variables were assessed. Clinical effects were evaluated by ROC-curves and predictive values. Forty-eight patients with schizophrenia (SZ) and 55 healthy controls participated in the study. For each of the 48 patients, the three VEP components were localized to both dorsal and ventral brain areas and also deviated from a normal distribution. P1 and N1 deviations were independent of treatment, illness chronicity or gender. Results from LORETA also suggest that deficits in thalamus, posterior cingulum, precuneus, superior parietal and medial occipitotemporal areas were associated with symptom severity. While positive symptoms were more strongly related to sensory processing deficits (P1), negative symptoms were more strongly related to perceptual processing dysfunction (N1). Clinical validation revealed positive and negative predictive values for correctly classifying SZ of 100% and 77%, respectively. Classification in an additional independent sample of 30 SZ corroborated these results. In summary, this novel approach revealed basic visual dysfunctions in all patients with schizophrenia, suggesting these visual dysfunctions represent a promising candidate as a biomarker for schizophrenia.

Excessive contralateral motor overflow in schizophrenia measured by fMRI

Schizophrenia is characterized by significant problems in control of behavior; however, the disturbances in neural systems that control movement remain poorly characterized. We used functional magnetic resonance imaging (fMRI) to evaluate the origin of motor overflow in schizophrenia. Twenty-seven clinically stable medicated outpatients with Diagnostic and Statistical Manual, 4th edition, text revision (DSM-IV-TR)-defined schizophrenia (SZ), and 18 healthy control (HC) subjects, all right-handed, performed a dominant-handed, single-choice visual sensorimotor reaction time paradigm during fMRI. Voxel-wise analyses were conducted within sensorimotor cortical and striatal regions on general linear model (GLM)-derived measures of blood oxygen level-dependent (BOLD) signal change. The SZ group was not different from the HC group in reaction time, activation in somatosensory or motor cortices ipsilateral to the active (intended) descending corticospinal tract, nor visual cortex. However, in the right hemisphere (contralateral to the active M1), the SZ group showed significantly higher activation in primary motor cortex and adjacent premotor and somatosensory cortices (right Brodmann areas (BA) 1 through 4, and 6), and significantly lower activation in bilateral basal ganglia. Right BA 4 activation was strongly related to disorganization and poverty symptoms (and unrelated to medications) in the patient group. This study provides evidence in SZ of excessive neural activity in motor cortex contralateral to the intended primary motor cortex, which may form the basis for altered motor laterality and motor overflow previously observed, and disorganized behavior. This pathological motor overflow may be partly due to altered modulation of intended movement within the basal ganglia and premotor cortex.

Tract-specific analysis of white matter integrity disruption in schizophrenia

Several studies have suggested that white matter integrity is disrupted in some brain regions in patients with schizophrenia. The purpose of this study was to assess the white matter integrity of the cingulum, uncinate fasciculus, fornix, and corpus callosum using diffusion tensor imaging (DTI). Participants comprised 39 patients with schizophrenia (19 males and 20 females) and 40 age-matched normal controls (20 males and 20 females). We quantitatively assessed the fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of the anterior cingulum, body of the cingulum, uncinate fasciculus, fornix, and corpus callosum on a tract-specific basis using diffusion tensor tractography (DTT). Group differences in FA and ADC between the patients and normal controls were sought. Additional exploratory analyses of the relationship between the FA or ADC and four clinical parameters (i.e., illness duration, positive symptom scores, negative symptom scores, and medication dosage) were performed. Results were analyzed in gender-combined and gender-separated group comparisons. FA was significantly lower on both sides of the anterior cingulum, uncinate fasciculus, and fornix in the schizophrenia patients irrespective of gender group separation. In the gender-combined analyses, significantly higher ADC values were demonstrated in the schizophrenia patients in both sides of the anterior cingulum, body of the cingulum and uncinate fasciculus, the left fornix, and the corpus callosum, compared with those of the normal controls. In the gender-separated analyses, the male patients showed higher ADC in the left anterior cingulum, the bilateral cingulum bodies, and the bilateral uncinate fasciculi. The female patients showed higher ADC in the right anterior cingulum, the left fornix, and the bilateral uncinate fasciculus. In correlation analyses, a significant negative correlation was found between illness duration and ADC in the right anterior cingulum in the gender-combined analyses. The gender-separated analyses found that the male patients had a significant negative correlation between negative symptom scores and FA in the right fornix, a positive correlation between illness duration and FA in the right anterior cingulum, and a negative correlation between illness duration and FA in the left uncinate fasciculus. Our DTI study showed that the integrity of white matter is disrupted in patients with schizophrenia. The results of our sub-analyses suggest that changes in FA and ADC may be related to negative symptom scores or illness duration.

Decoding episodic memory in ageing: a Bayesian analysis of activity patterns predicting memory

Normal ageing is associated with a decline in episodic memory, and neuroimaging studies in older adults have shown reduced activity in prefrontal cortex and other regions critical for memory function in the young. However, older adults also activate additional regions, suggesting a degree of functional reorganisation that has been attributed variously to detrimental and adaptive changes. Evaluation of these competing hypotheses depends critically upon inferences about the relative location and distribution of activity that are not well supported by current univariate or multivariate analyses. Here, we employed a recently developed model-based multivariate 'decoding' approach (Friston et al., 2008) to re-analyse a rich episodic encoding dataset and examine directly how the patterns of activity change in ageing. We assessed which spatial activity patterns, within lateral prefrontal cortex, best predict successful memory formation. Bayesian model comparison showed that the older adults had more distributed and bilateral (fragmented) predictive patterns of activity in anterior inferior frontal gyrus and middle frontal gyrus. With this direct multivariate test for changes in patterns of activity, we replicate and extend earlier findings of reduced prefrontal lateralisation in ageing. These findings extend conclusions based on conventional analyses, and support the notion that ageing alters the spatial deployment of neuronal activity, to render it less spatially coherent and regionally specific. This greater distribution of activity in older adults was also linked to poorer individual memory performance, suggesting that it reflects neural ageing, rather than adaptive compensatory responses.

Hand preference and hand skill in families with schizophrenia

Direction and degree of handedness in humans are variable between individuals and thought to be in part inherited. Several studies have shown an increase in non-right handedness among patients with schizophrenia, and some have included unaffected relatives. The present study was designed to determine whether reduced right handedness is more frequent among individuals with schizophrenia as compared with their well relatives and whether it clusters within families having multiple ill members. A total of 259 families comprising 418 individuals diagnosed with schizophrenia or schizoaffective disorder, 54 individuals with other psychoses, 145 family members with depression and other minor diagnoses, and 288 unaffected individuals were included. Hand preference was assessed by the Annett Scale and right relative to left hand skill measured using the Tapley-Bryden test. For all assessments of hand preference and hand skill, females were significantly more lateralised towards the right than males. Those individuals with schizophrenia or schizoaffective disorder had significantly less right hand preference than their unaffected relatives when measured as a quantitative index of items from the Annett Scale (p = .019), but not categorically (right, left or mixed). In contrast, there was no difference in hand skill between diagnostic groups. Hand preference was significantly correlated among male-male affected sibling pairs (p = .01) and similar results were found for hand skill among the total group of affected pairs (p = .001). Although these results only partially support a relationship between handedness and schizophrenia, they nevertheless draw attention to sex differences in hand preference and the familial aspects of hand preference in this disorder. More direct approaches to the genetics of cerebral dominance and psychosis are required.

Bilateral functional asymmetry disparity in positive and negative schizophrenia revealed by resting-state fMRI

Brain functional asymmetry abnormalities have previously been reported in schizophrenia. In the present study, we hypothesized that the pattern of functional asymmetry in schizophrenia may differ between patients suffering from positive and negative symptoms. We examined the relationship between altered asymmetry of functional connectivity and symptom type (positive/negative) using resting-state functional magnetic resonance imaging. We selected the dorsolateral prefrontal cortex, superior temporal gyrus, middle temporal gyrus and hippocampus as regions of interest, and analyzed functional connectivity patterns between these and other brain regions. Furthermore, a voxel-based two-level asymmetry analysis was conducted to investigate differences in the asymmetry of functional connectivity patterns within and between groups. Our results showed that patients exhibiting positive symptoms had significantly increased leftward asymmetry of functional connectivity. The negative symptom group, in contrast, exhibited increased rightward asymmetry of functional connectivity. The strength of the asymmetry in these regions was found to be significantly correlated with symptom ratings obtained using the Positive and Negative Syndrome Scale. These results suggest that predominantly positive and predominantly negative schizophrenia may have different neural underpinnings, and that certain regions in the frontal and temporal lobes, as well as the cingulate gyrus and precuneus, play important roles in mediating the symptoms of this complex disease. Our study also provided further evidence for the hypothesis that schizophrenia is related to abnormalities in functional brain networks.

The functional neuroanatomy of symptom dimensions in schizophrenia: a qualitative and quantitative review of a persistent question

One of the fundamental goals in understanding schizophrenia is linking the observable symptoms to the underlying unobservable pathophysiology. Given recent advances in medical imaging, researchers are increasingly investigating brain-behavior relationships to better understand the neural substrates of negative, positive, and disorganization symptoms in schizophrenia. This review focused on 25 task-related functional magnetic resonance imaging studies and found meaningful small to moderate associations between specific symptom dimensions and regional brain activity. Negative symptoms were related to the functioning of the ventrolateral prefrontal cortex and ventral striatum. Positive symptoms, particularly persecutory ideation, were related to functioning of the medial prefrontal cortex, amygdala, and hippocampus/parahippocampal region. Disorganization symptoms, although less frequently evaluated, were related to functioning of the dorsolateral prefrontal cortex. Surprisingly, no symptom domain had a consistent relationship with the middle or superior temporal regions. While a number of adaptations in experimental design and reporting standards can facilitate this work, current neuroimaging approaches appear to provide a number of consistent links between the manifest symptoms of schizophrenia and brain dysfunction.

Autistic spectrum disorders as functional disconnection syndrome

We outline the basis of how functional disconnection with reduced activity and coherence in the right hemisphere would explain all of the symptoms of autistic spectrum disorder as well as the observed increases in sympathetic activation. If the problem of autistic spectrum disorder is primarily one of desynchronization and ineffective interhemispheric communication, then the best way to address the symptoms is to improve coordination between areas of the brain. To do that the best approach would include multimodal therapeusis that would include a combination of somatosensory, cognitive, behavioral, and biochemical interventions all directed at improving overall health, reducing inflammation and increasing right hemisphere activity to the level that it becomes temporally coherent with the left hemisphere. We hypothesize that the unilateral increased hemispheric stimulation has the effect of increasing the temporal oscillations within the thalamocortical pathways bringing it closer to the oscillation rate of the adequately functioning hemisphere. We propose that increasing the baseline oscillation speed of one entire hemisphere will enhance the coordination and coherence between the two hemispheres allowing for enhanced motor and cognitive binding.

Altered volume and hemispheric asymmetry of the superficial cortical layers in the schizophrenia planum temporale

In vivo structural MRI studies in schizophrenia auditory cerebral cortex have reported smaller volumes and, less consistently, have reported altered hemispheric asymmetry of volumes. We used autopsy brains from 19 schizophrenia and 18 nonpsychiatric male subjects to measure the volume asymmetry of the planum temporal (PT). We then used the most recently autopsied 11 schizophrenia and 10 nonpsychiatric brains to measure the widths and fractional volumes of the upper (I-III) and lower (IV-VI) layers. Measurements of whole PT gray matter volumes did not show significant changes in schizophrenia. Nevertheless, laminar volume measurements revealed that the upper layers of the PT comprise a smaller fraction of the total cortex in schizophrenia than in nonpsychiatric brains. Subdivision of the PT showed that this change was especially prominent caudally, beyond Heschl's gyrus, whereas similar but less pronounced changes were found in the rostral PT and Heschl's gyrus. Complementary measures of laminar widths showed that the altered fractional volume in the caudal left PT was due mainly to approximately 8% thinner upper layers. However, the caudal right PT had a different profile, with thicker lower layers and comparatively unchanged upper layers. Thus, in the present study, laminar measurements provided a more sensitive method for detecting changes than measurement of whole PT volumes. Besides findings in schizophrenia, our cortical width measurements revealed normal hemispheric asymmetries consistent with previous reports. In schizophrenia, the thinner upper layers of the caudal PT suggest disrupted corticocortical processing, possibly affecting the multisensory integration and phonetic processing of this region.

Schizotypal personality traits and atypical lateralization in motor and language functions

Atypical cerebral lateralization in motor and language functions in regard to schizotypal personality traits in healthy populations, as well as among schizophrenic patients, has attracted attention because these traits may represent a risk factor for schizophrenia. Although the relationship between handedness and schizotypal personality has been widely examined, few studies have adopted an experimental approach. This study consisted of three experiments focusing on motor and language functional lateralization in regard to schizotypal personality in the absence of mental illness: line-drawing, finger tapping, and a semantic go/no-go task. The results suggested that positive schizotypal personality might be related to functional non-lateralization in regard to at least some functions (e.g., spatial motor control and semantic processing in the present study). Subjects with high schizotypal personality traits performed equally with their right and left-hands in the line-drawing task and they reacted equally with their right and left-hands in a semantic go/no-go task involving semantic auditory stimuli presented in both ears. However, those low in schizotypal personality traits showed typical lateralization in response to these tasks. We discuss the implications of these findings for schizotypal atypical lateralization.

Word and letter string processing networks in schizophrenia: evidence for anomalies and compensation

Imaging studies show that in normal language correlated activity between anterior and posterior brain regions increases as the linguistic and semantic content (i.e., from false fonts, letter strings, pseudo words, to words) of stimuli increase. In schizophrenia however, disrupted functional connectivity between frontal and posterior brain regions has been frequently reported and these disruptions may change the nature of language organization. We characterized basic linguistic operations in word and letter string processing in a region-of-interest network using structural equation modeling (SEM). Healthy volunteers and volunteers with schizophrenia performed an fMRI one-back matching task with real words and consonant letter strings. We hypothesized that left hemisphere network dysfunction in schizophrenia would be present during processes dealing with linguistic/semantic content. The modeling results suggest aberrant left hemisphere function in schizophrenia, even in tasks requiring minimal access to language. Alternative mechanisms included increases in right hemisphere involvement and increased top-down influence from frontal to posterior regions.

White matter alterations in schizophrenic patients with pronounced negative symptomatology and with positive family history for schizophrenia

BACKGROUND

In recent years, in vivo and post-mortem studies detected structural brain changes in schizophrenia. The aim of our analysis was to investigate potential changes of white matter in schizophrenic patients compared to controls, and the relationship to clinical characteristics.

METHODS

Fifty male, right-handed schizophrenic patients who met DSM-IV criteria for schizophrenia were recruited. Fifty right-handed, age- and sex-matched subjects without a psychiatric disorder were enrolled as controls. Volumes of white matter in several brain regions were measured by 1.5 T MRI using a volumetry and segmentation software (BRAINS). Regions of interest including frontal, temporal, parietal, occipital and subcortical areas were determined using Talairach spaces.

RESULTS

No significant differences in white matter volumes of total brain tissue and regions of interest were detected between patients and controls. A significant reduction of white matter in parietal cortex of right hemisphere was found in a subgroup of patients with pronounced negative symptoms. Furthermore, patients with first-grade relatives suffering from schizophrenia showed a reduction of subcortical white matter in the right hemisphere.

CONCLUSIONS

Our results indicate that subgroups of schizophrenic patients show alterations of white matter in distinct brain regions, including the right parietal lobe.

Cerebral connectivity and psychotic personality traits. A diffusion tensor imaging study

This study aims to investigate the relationship between regional connectivity in the brain white matter and the presence of psychotic personality traits, in healthy subjects with psychotic traits. Thirteen healthy controls were administered the MMPI-2, to assess psychotic traits and, according to MMPI results, a dichotomization into a group of "high-psychotic" and "low-psychotic" was performed. Diffusion tensor imaging (DTI) was used as a non-invasive measure, in order to obtain information about the fractional anisotropy (FA), an intravoxel index of local connectivity and, by means of a voxelwise approach, the between-group differences of the FA values were calculated. The "high-psychotic" group showed higher FA in the left arcuate fasciculus. Subjects with low scores for psychotic traits had significantly higher FA in the corpus callosum, right arcuate fasciculus, and fronto-parietal fibers. In line with previous brain imaging studies of schizophrenia spectrum disorders, our results suggest that psychotic personality traits are related to altered connectivity and brain asymmetry.

Hemispheric asymmetry and callosal integration of visuospatial attention in schizophrenia: a tachistoscopic line bisection study

BACKGROUND

A hallmark of visuospatial neglect syndrome is that patients with lesions to right parietal cortex misbisect horizontal lines far rightward of veridical center. Neurologically normal subjects misbisect lines with a systematic leftward bias (pseudoneglect). Both phenomena, as well as neuroimaging studies, disclose a predominant right-hemisphere control of spatial attention. Numerous studies of patients with schizophrenia have implicated global deficits of either right or left hemisphere function, as well as compromised integrity of the corpus callosum.

METHODS

To better understand the functional implications of schizophrenia we utilized a forced-choice tachistoscopic line bisection task to probe the status of right-hemisphere control of spatial attention, and compared left- versus right-hand unimanual responses to index the degree of callosal transfer of visuospatial information in both patient and control groups.

RESULTS

In contrast to the significant leftward bisection errors of control subjects, patients exhibit no significant leftward error. Whereas control subjects evince a significant correlation between left- and right-hand bisection errors, patients lack a significant intermanual correlation.

CONCLUSIONS

The lack of significant leftward bisection error of patients implies a deficit of right-hemisphere function. The lack of a significant correlation between left- and right-hand bisection errors in patients implies a loss of callosal integrity.

Handedness and the brain: a review of brain-imaging techniques

The author reviewed brain-imaging studies on human handedness reported in major academic journals for the last 12 years, classified them as having anatomical or functional interest, and attempted to determine consensus on findings and limitations among the studies. Present reviews suggest that there have been fewer functional than anatomical examinations into handedness and that findings from those studies have not been necessarily consistent, that participants' degree of handedness has not been consistent between left-handed and right-handed people, and that much more brain-imaging study is anticipated to examine functional and anatomical differences of handedness based on genetic and environmental models.

Relative Suppression of Magical Thinking: A Transcranial Magnetic Stimulation Study

The tendency to perceive meaning in noise (apophenia) has been linked to "magical thinking" (MT), a distinctive form of thinking associated with a range of normal cognitive styles, anomalous perceptual experiences and frank psychosis. Important aspects of MT include the propensity to imbue meaning or causality to events that might otherwise be considered coincidental. Structures in the lateral temporal lobes have been hypothesised to be involved in both the clinical and nonclinical aspects of MT. Accordingly, in this study we used single-pulse transcranial magnetic stimulation (TMS) to stimulate either the left or right lateral temporal areas, or the vertex, of 12 healthy participants (balanced for similar levels of MT, delusional ideation and temporal lobe disturbance) while they were required to indicate if they had "detected" pictures, claimed to be present by the experimenters, in visual noise. Relative to the vertex, TMS inhibition of the left lateral temporal area produced significant reduced tendency to report meaningful information, suggesting that left lateral temporal activation may be more important in MT and therefore producing and supporting anomalous beliefs and experiences. The effect cannot simply be explained by TMS induced cognitive slowing as reaction times were not affected.

Asymmetries of cortical shape: Effects of handedness, sex and schizophrenia

Some evidence suggests that sex, handedness and disease processes associated with schizophrenia affect the magnitude and/or direction of structural brain asymmetries. There are mixed findings, however, on how these factors influence cerebral torque, when torque is assessed with linear or volumetric measurements. We obtained MRI data from 67 healthy (30 males, 10 non-dextrals) and 84 schizophrenia subjects (60 males; 16 non-dextrals) and applied cortical pattern matching to spatially relate and compare differences in the surface morphology of the two cerebral hemispheres at high spatial resolution. Asymmetry indices, computed at thousands of matched hemispheric locations, were used to examine effects of sex, handedness and schizophrenia on hemispheric shape asymmetries while controlling for age and the other factors. Highly significant and discriminative right-frontal and left parietal-occipital surface expansions and protrusions (petalias) were mapped within groups. Although hemispheric shape asymmetries appeared less pronounced within female non-dextrals, asymmetry indices were not shown to differ significantly across sex, hand preference or diagnosis, or to reveal interactions of handedness with sex or diagnosis. Our 3D maps of spatially detailed anterior and posterior hemispheric shape asymmetries reflect subtle geometric distortions in hemispheric surface morphology that cannot be characterized with 2D or volumetric methods. Inter-individual variations in hemispheric torque appear minimally influenced by sex, dextrality or disease status. Biological factors driving language dominance or other lateralized brain functions dissociable from handedness, may more closely relate to hemispheric shape asymmetries, while the lateralization of other discrete brain regions may be more influenced by sexually dimorphic factors or by schizophrenia pathophysiology.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Impaired hemispheric communication in schizophrenia: a study using the consonant-vowel-consonant task

The ability of the left and right hemispheres to interact and cooperate in the processing of information is important for normal brain functioning. Some investigators have suggested that this cooperation in functioning occurs through a process called "metacontrol." Because studies have suggested that patients with schizophrenia may have problems with interhemispheric interaction, we considered that it could be informative to study such patients from the viewpoint of interhemispheric cooperation, and more specifically that of metacontrol. To do this we utilized an assessment procedure called the consonant-vowel-consonant (CVC) task, in which nonsense three-letter combinations (trigrams) are presented vertically to the left, right and both visual fields. The pattern of errors can be used to determine the type of processing the hemispheres use under the different conditions of presentation. Previous studies have shown that when trigram information is presented to both hemispheres, the left hemisphere appears to switch into a mode that more resembles right hemisphere processing, and we wished to determine if evidence for this switch in the mode of processing also occurred in a sample of patients with schizophrenia. To determine the specificity of any findings to schizophrenia, we also studied a group of patients with bipolar disorder. For the control and bipolar groups, our results showed the typical finding of superior processing in the right visual field (left hemisphere) over the left visual field, with presentation to both visual fields demonstrating a qualitative error pattern resembling that of the left visual field (right hemisphere). Patients with schizophrenia, however, did not demonstrate this switching into a right hemisphere mode upon bilateral presentation of the trigrams and instead seemed to show no switching, or actually switching into more of a left hemisphere mode. Our results suggest that patients with schizophrenia (but not bipolar disorder) may have abnormalities in the cooperative processing of information when it is presented to both hemispheres, and that this disturbance may reflect problems with metacontrol of hemispheric processing.

Study of childhood onset schizophrenia (COS) using SPECT and neuropsychological assessment

BACKGROUND

In recent years, the development of positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging has enhanced our understanding of the physiological functioning of the intact brain.

AIM

To study cerebral cortical perfusion defects in patients with childhood onset schizophrenia (COS) and to assess their neuropsychological functioning.

METHODS

This cross-sectional study comprised 14 patients with COS with onset at or before 14 years of age, diagnosed as per ICD-10 DCR criteria, attending a tertiary care centre in North India. All the patients were assessed on sociodemographic, clinical profile sheet, Positive and Negative Symptom Scale (PANSS) and Edinburgh Handedness Inventory (EHI). The Wisconsin Card Sorting Test (WCST) was used to assess their neuropsychological functioning. All patients underwent SPECT. A control group of 10 healthy subjects was studied with SPECT for comparison.

RESULTS

Nine patients (64.3%) showed perfusion anomaly on SPECT scan specifically in the left temporal and frontal areas of the brain. On WCST score these 9 patients showed a higher percentage of total errors (64.49%+/-9.42%) as compared to the other 5 patients (48.54%+/-12.70%) who showed no abnormality on SPECT scan. All normal control subjects showed no abnormality on SPECT.

CONCLUSION

The results from WCST show that COS patients have difficulty in executive functioning. Also, patients had perfusion anomaly in the left temporal, frontal and parietal areas. Deficits found in COS are similar to those found in adult onset schizophrenia (AOS). In view of the findings, the nature of COS and its relationship with AOS are discussed.

Prenatal influences on brain dopamine and their relevance to the rising incidence of autism

The incidence of autism has risen 10-fold since the early 1980s, with most of this rise not explainable by changing diagnostic criteria. The rise in autism is paradoxical in that autism is considered to be one of the most genetically determined of the major neurodevelopmental disorders and should accordingly either be stable or even declining. Because a variety of epigenetic influences, particularly those occurring during the prenatal period, can override or masquerade as genetic influences, these should be considered as prime contributors to the recent increase of autism. Prenatal influences on dopamine activity are especially well-documented, including the effects of maternal psychosocial stress, maternal fever, maternal genetic and hormonal status, use of certain medications, urban birth, and fetal hypoxia. All of these factors have been implicated in the genesis of autism, which is characterized by a "hyperdopaminergic" state based on evidence from monkey and human behavioral studies, pharmacological studies in humans, and a left-hemispheric predominance of both dopamine and autistic-like symptoms. Chronically high maternal levels of dopamine caused by the pressures of increasingly urbanized societies and by changing maternal demographics such as increased workforce participation, educational achievement level, and age at first birth, may be especially significant epigenetic contributors to the recent autism rise.

Schizophrenia and rightward bias in line bisection

This study investigated line bisection in 10 males with schizophrenia and 15 controls. There was an overall leftward bias, consistent with slight right "pseudoneglect", but the schizophrenia group showed more variation with experimental conditions, suggesting impaired interhemispheric transfer. Specifically, the rightward bias was especially marked when the lines were positioned on the right side of the page, when the right hand was used, and when a right to left scan was adopted. The rightward bias was associated with the predominance of negative symptoms. Findings are discussed with reference to the role of the corpus callosum in the transfer of spatial attention.

The role of the extrapersonal brain systems in religious activity

The neuropsychology of religious activity in normal and selected clinical populations is reviewed. Religious activity includes beliefs, experiences, and practice. Neuropsychological and functional imaging findings, many of which have derived from studies of experienced meditators, point to a ventral cortical axis for religious behavior, involving primarily the ventromedial temporal and frontal regions. Neuropharmacological studies generally point to dopaminergic activation as the leading neurochemical feature associated with religious activity. The ventral dopaminergic pathways involved in religious behavior most closely align with the action-extrapersonal system in the model of 3-D perceptual-motor interactions proposed by . These pathways are biased toward distant (especially upper) space and also mediate related extrapersonally dominated brain functions such as dreaming and hallucinations. Hyperreligiosity is a major feature of mania, obsessive-compulsive disorder, schizophrenia, temporal-lobe epilepsy and related disorders, in which the ventromedial dopaminergic systems are highly activated and exaggerated attentional or goal-directed behavior toward extrapersonal space occurs. The evolution of religion is linked to an expansion of dopaminergic systems in humans, brought about by changes in diet and other physiological influences.

Lateralized cognitive dysfunction and psychotic symptoms in schizophrenia

Our understanding of hemispheric asymmetries in schizophrenia can be attributed to extensive neuropsychological and neuroimaging research on this topic; however, it has yet to be determined whether lateralized cognitive dysfunction represents a single core trait in schizophrenia or whether the lateralized impairments are domain specific. To test whether lateralized deficits are core features in schizophrenia we examined performance across a wide range of lateralized cognitive domains including attention, fluency, recognition memory, perception, and arousal. We also examined the relationship between lateralized impairments and psychotic and affective symptoms to determine whether abnormal hemispheric asymmetries were possibly state-related. The sample consisted of 43 subjects with schizophrenia and 66 normal healthy comparison subjects without psychiatric illness. Schizophrenia subjects exhibited abnormal right hemisphere performance on a test of recognition memory and abnormal left hemisphere performance on a measure of arousal. These findings suggest that lateralized cognitive disturbances in schizophrenia do not represent a single core lateralized deficit. Regarding the symptom analyses, severity of positive symptoms was related to right hemisphere cognitive impairment (including fluency and recognition memory), whereas severity of negative symptoms was related to left hemisphere cognitive impairment (including fluency). Overall, our findings suggest that lateralized dysfunction can occur in both hemispheres in schizophrenia, and that the positive psychotic symptoms may relate more to right hemisphere impairment, whereas negative psychotic symptoms may related more to left hemisphere impairment.

SPECT study of Chinese schizophrenic patients suggests that cerebral hypoperfusion and laterality exist in different ethnic groups

Hypofrontality is a common finding in schizophrenia in many countries. To date, there have been few studies on Chinese patients with schizophrenia. We thus wondered whether hypofrontality exists in Chinese patients with schizophrenia. We investigated 45 patients with schizophrenia and 21 healthy controls using brain perfusion single photon emission computed tomography (SPECT). Subjects were also administered the Brief Psychiatric Rating Scale (BPRS), Scale for the Assessment of Positive Symptoms (SAPS), Scale for the Assessment of Negative Symptoms (SANS), Halstead-Reitan Neuropsychological Battery (HRNB) and the Wechsler Memory Scale-Revised (WMS-R). Images were analyzed using a semi-quantitative reading and a quantified region of interest analysis. We found that schizophrenic patients showed hypoperfusion in the frontal and temporal lobes and hyperperfusion in the basal ganglia. Schizophrenic patients with both negative and positive symptoms showed asymmetric perfusion in the temporal lobe. Schizophrenic patients with prominent negative symptoms also showed asymmetric perfusion in the prefrontal lobes. Negative symptoms showed a significantly negative correlation with regional cerebral blood flow (rCBF) in the left frontal lobe. Improved memory quotient (MQ) was significantly correlated with increased rCBF in the left temporal lobe. These findings from Chinese patients confirm a similar regional neuroanatomic dysfunction as in Western patients with the disease.

Intact hemispheric specialization for spatial and shape working memory in schizophrenia

OBJECTIVE

Using functional MRI, we investigated whether, like healthy subjects, patients with schizophrenia show a relative hemispheric specialization in ventrolateral prefrontal cortex (PFC) for spatial and shape working memory (WM). We hypothesized that reduced specialization in schizophrenia would reflect a failure to adopt optimal domain-specific strategies and would contribute to WM deficits.

METHODS

Twelve healthy subjects and 16 schizophrenia patients performed spatial and shape WM tasks and a non-WM control task. Direct comparisons of the spatial and shape WM tasks assessed specialization.

RESULTS

Despite deficient WM performance, both patients and controls showed a relative hemispheric specialization in ventrolateral PFC for spatial (right) and shape (left) WM and did not differ in this regard.

CONCLUSIONS

The finding of intact hemispheric specialization in ventrolateral PFC suggests that patients employ the same domain-specific strategies as healthy subjects during spatial and shape WM. Rather than reflecting a failure to adopt the optimal strategy, we hypothesize that WM deficits in schizophrenia reflect impairments of executive processes that are required for WM performance regardless of domain. These processes are associated with activity in the dorsolateral PFC, a region that has been repeatedly implicated in studies of WM.

Right hemispheric dysfunction in schizophrenia

This study uses the Poffenberger (1912) paradigm, which compares the difference between "crossed" (stimuli and motor response areas are contralateral) and "uncrossed" (stimuli and motor response areas are ipsilateral) conditions to estimate interhemispheric transfer time. Simple reaction time (RT) was recorded to stimuli presented to the left visual field (LVF), right visual field (RVF), or bilaterally (BVF) in individuals with schizophrenia (n = 10) and controls (n = 14), who responded using either the left or right hand. While the results provide no evidence for differences between the groups in information transfer between the hemispheres, the schizophrenia group were significantly slower to respond to LVF stimuli, suggesting right hemisphere dysfunction.

Symmetry of callosal information transfer in schizophrenia: a preliminary study

OBJECTIVE

While there is much evidence to suggest left hemisphere dysfunction and interhemispheric transfer deficits in schizophrenia, the right hemisphere is rarely implicated. This study uses 128-channel EEG to assess whether asymmetry of interhemispheric transfer found in normal individuals is present in those with schizophrenia, and whether this might point to a right-hemisphere dysfunction.

METHODS

Simple reaction time (RT) was recorded to stimuli presented to the left visual field (LVF), right visual field (RVF) or bilaterally (BVF) in 13 males with schizophrenia and 13 controls. 128-Channel EEG was simultaneously recorded. Interhemispheric transfer time (IHTT) in each direction was calculated by comparing the latencies of N160 EP components in the hemispheres contralateral and ipsilateral to stimulation.

RESULTS

While controls showed faster information transfer from the right-to-left hemisphere, this asymmetry was not present in the schizophrenia group who also exhibited a concomitant decrease in the amplitude of the N160 in the right hemisphere.

CONCLUSIONS

Results are interpreted with reference to a loss of rapidly conducting myelinated axons in the right hemisphere in schizophrenia.

Lack of asymmetrical transfer for linguistic stimuli in schizophrenia: an ERP study

OBJECTIVE

To assess the mechanisms underlying lack of speeded information transfer asymmetry (faster right to left) for verbal information in schizophrenia.

METHODS

Interhemispheric transfer times (IHTT) between the hemispheres were assessed using a lateralized lexical-decision task in males with schizophrenia (N = 12) and matched controls (N = 12). Words were presented to the left visual field (LVF), right visual field (RVF), or bilaterally (BVF) while 128-channel EEG was recorded continuously. A direct measure of IHTT in each direction was obtained by comparing the latencies of the N160 evoked potential (EP) component in the hemispheres contralateral and ipsilateral to stimulation.

RESULTS

Controls showed faster information transfer from the right to left hemisphere (R-to-L) for linguistic stimuli. The two groups did not differ for IHTTs L-to-R. Lack of IHTT asymmetry in the schizophrenia groups was associated with an overall concomitant decrease in the amplitude of the N160 in the right hemisphere.

CONCLUSIONS

Differences in IHTT asymmetry may be attributed to lack of right hemisphere activation and not callosal dysfunction as has been previously suggested.

SIGNIFICANCE

It is suggested that a relative excess of myelinated axons in the right hemisphere speeds IHTT faster R-to-L, findings are discussed with reference to differences in right hemisphere white matter connectivity in schizophrenia.

The acetylcholine fiber density of the neocortex is altered by isolated rearing and early methamphetamine intoxication in rodents

Alterations in the cholinergic physiology of the brain were the first to be observed when research on environmental influences on postnatal brain development began 35 years ago. Since then, the effects of isolated rearing (IR) or early pharmacological insults have been shown not only on the physiology, but also the anatomy of a variety of transmitter systems. The cholinergic fiber density, however, still remained to be assessed. We therefore used a histochemical procedure to stain cholinergic fibers in the brains of young adult gerbils reared either in groups in enriched environments or isolated in standard makrolon cages. Half of the animals from each rearing condition had received a single high dose of methamphetamine on postnatal day 14. Fiber densities were measured by computerized image analysis in the medial and orbital prefrontal cortex (PFC), dysgranular and granular insular cortex, sensorimotor cortices, and the entorhinal cortex of both hemispheres. Isolation rearing increased the cholinergic fiber densities in the prefrontal cortices of the left hemisphere and in the entorhinal cortex of the right hemisphere by about 10%, with no effect in the respective contralateral side. The early methamphetamine intoxication showed no influence in prefrontal and entorhinal cortices, but diminished the acetylcholine (ACh) innervation of the forelimb area of cortex in both hemispheres in IR gerbils and of the left hemisphere in ER gerbils, and reduced the acetylcholine innervation in the hindlimb area in both sides in both rearing groups. These results demonstrate that (a) cholinergic fiber density is differentially regulated in different cortical areas and (b) the plasticity of the cholinergic system can only be understood in the interplay with other neuromodulatory innervations.

Abnormal gyral complexity in first-episode schizophrenia

BACKGROUND

Abnormalities in the patterns and frequency of cortical folding might help identify temporal and regionally specific disturbances in normal neurodevelopmental processes that occur in association with schizophrenia. Few studies, however, have investigated gyral complexity in schizophrenia.

METHODS

High-resolution magnetic resonance images were used to examine differences in gyral complexity, measured three-dimensionally in five separate hemispheric regions covering the entire cortical surface, in patients with first-episode schizophrenia (n = 50) compared with demographically matched healthy comparison subjects (n = 50). The modulating effects of gender and hemisphere were also examined.

RESULTS

Significant increases in cortical folding were observed in the right superior frontal cortex in male schizophrenic patients compared with male control subjects, but not between female diagnostic groups. Significant main effects of hemisphere were found in frontal, parietal, and occipital regions in directions complementary to cerebral torques.

CONCLUSIONS

Results support previous findings of right frontal hypergyria in male schizophrenic patients and suggest that these abnormalities predate illness onset and are of neurodevelopmental origin. Therefore, in schizophrenia, sexually dimorphic developmental processes and differences in hemispheric connectivity, which have been shown to influence the organization and/or frequency of cortical folding, seem to be disturbed during gyral formation in utero.

Prepulse facilitation and prepulse inhibition in schizophrenia patients and their unaffected siblings

BACKGROUND

Deficits in schizophrenia patients and their first-degree relatives have been reported in prepulse inhibition (PPI), a phenomenon that measures an early stage of information processing (sensorimotor gating). It is less clear whether these information processing deficits extend to prepulse facilitation (PPF), which measures a later stage of generalized alerting or orienting.

METHODS

This study examined three separate issues: first, whether schizophrenia patients have deficits in PPI and PPF; second, whether the siblings of patients show deficits in these processes; and third, whether prepulse duration influences the degree of the deficits. These issues were examined in 76 schizophrenia patients, 36 of their siblings, and 41 normal control subjects.

RESULTS

Patients and siblings did not differ from control subjects in PPI, perhaps due to the use of different procedural parameters compared with other laboratories that have consistently found PPI deficits in schizophrenia patients. Patients and their siblings produced significantly less PPF than control subjects. For both PPI and PPF, prepulse duration was not a significant factor.

CONCLUSIONS

These results imply that PPF deficits reveal a generalized alerting or orienting deficit that is present in both schizophrenia patients and their siblings, suggesting that this deficit may be tapping an endophenotypic vulnerability factor.

Cortical motor activation in akinetic schizophrenic patients: A pilot functional MRI study

Akinesia is associated with supplementary motor area (SMA) dysfunction in Parkinson's disease. We looked for a similar association in patients with schizophrenia. Using functional magnetic resonance imaging (fMRI), we compared motor activation in 6 akinetic neuroleptic-treated schizophrenic patients and 6 normal subjects. Schizophrenic patients had a defective activation in the SMA, left primary sensorimotor cortex, bilateral lateral premotor and inferior parietal cortices, whereas the right primary sensorimotor cortex and a mesial frontal area were hyperactive. SMA was hypoactive in akinetic schizophrenic patients, emphasizing the role of this area in motor slowness. Other abnormal signals likely reflect schizophrenia-related abnormal intracortical connections.

No hypofrontality, but absence of prefrontal lateralization comparing verbal and spatial working memory in schizophrenia

Hypofrontality and decreased lateralization have been two major, albeit controversial, results from functional neuroimaging studies of schizophrenia. We used fMRI to study cortical activation during a verbal and spatial working memory (WM) task (2-back) in 15 inpatients acutely ill with schizophrenia and 15 matched control subjects. We hypothesized (i) hypofrontality in patients in both tasks and (ii) decreased lateralization of prefrontal activation in patients under the assumption that, in controls, left prefrontal cortex (PFC) is engaged preferentially in the verbal task (verbal domain dominance) and the right prefrontal cortex is engaged preferentially in the spatial task (spatial domain dominance). Our results showed no significant differences in frontal activation between controls and patients, i.e. no hypofrontality in patients, even at a very liberal threshold (p<0.01). This may be explained by the fact that nearly all patients studied received atypical neuroleptics. Nonetheless, we found evidence for more subtle, domain-related prefrontal dysfunction. Whereas controls showed verbal WM domain dominance in left inferior frontal cortex and spatial WM domain dominance in right prefrontal cortex, these domain dominance effects were absent in the patient group, i.e. there were no lateralization effects. Finally, only patients showed an inverse correlation between performance and right prefrontal activation in verbal WM. We conclude that the finding of hypofrontality may depend on the medication of the patients and that there is prefrontal dysfunction even in the absence of hypofrontality.

Neuromagnetic correlates of impaired automatic categorical perception of speech sounds in schizophrenia

Schizophrenia is associated with dysfunction in language processing. At the earliest stage of language processing, dysfunction of categorical perception of speech sounds in schizophrenia has been demonstrated in a behavioral task. The aim of this study was to assess automatic categorical perception of speech sounds as reflected by event-related changes in magnetic field power in schizophrenia. Using a whole-head magnetoencephalographic recording, the magnetic counterpart of mismatch negativity (MMNm) elicited by a phonetic change was evaluated in 16 right-handed patients with chronic schizophrenia and in 19 age-, sex-, and parental socioeconomic status-matched normal control subjects. Three types of MMNm (MMNm in response to a duration decrement of pure-tone stimuli; a vowel within-category change [duration decrement of Japanese vowel /a/]; vowel across-category change [Japanese vowel /a/ versus /o/]) were recorded. While the schizophrenia group showed an overall reduction in magnetic field power of MMNm, a trend was found toward more distinct abnormalities under the condition of vowel across-category change than under that of duration decrement of a vowel or tone. The patient group did not show abnormal asymmetries of MMNm power under any of the conditions. This study provides physiological evidence for impaired categorical perception of speech sounds in the bilateral auditory cortex in schizophrenia. The language-related dysfunction in schizophrenic patients may be present at the early stage of auditory processing of relatively simple stimuli such as phonemes, and not just at stages involving higher order semantic processes.

Lateralized Lexical Decision in Schizophrenia: Hemispheric Specialization and Interhemispheric Lexicality Priming

Reports of left-hemisphere dysfunction and abnormal interhemispheric transfer in schizophrenia are mixed. The authors used a unified paradigm, the lateralized lexical decision task, to assess hemispheric specialization in word recognition, hemispheric error monitoring, and interhemispheric transfer in male, right-handed participants with schizophrenia (n=34) compared with controls (n=20). Overall, performance and error monitoring were worse in patients. However, patients like controls showed left-hemisphere superiority for lexical processing and right-hemisphere superiority for error monitoring. Only patients showed selective-interhemispheric lexicality priming for accuracy, in which performance improved when the lexical status of target and distractor stimuli presented to each hemifield was congruent. Results suggest that schizophrenia is associated with impaired monitoring and with increased interhemispheric automatic information transfer rather than with changed hemispheric specialization for language or error monitoring.

Reversed hemispheric asymmetry during simple visual perception in schizophrenia

Processing of sensory information in the human brain progresses from primary areas, dedicated to a single sensory feature, to multimodal areas, which integrate many features across sensory modalities. For some of these processes hemispheric dominance has developed. Here we report the results of a passive viewing task using positron emission tomography. Subjects were scanned twice while staring at a stationary visual noise pattern. Normal subjects showed a significant reduction of regional cerebral blood flow (rCBF) in a distributed right hemisphere network of brain regions during the second visual task. Schizophrenic subjects, however, showed significant increases of right hemisphere rCBF during the second visual task and showed significant decreases only in the left hemisphere. These results are consistent with the notion of reversed hemispheric asymmetry during the processing of sensory information in schizophrenia.