The temporal lobes, reversed asymmetry and the genetics of schizophrenia

Altered language network activity in young people at familial high-risk for schizophrenia

BACKGROUND

Abnormalities in language and language neural circuitry are observed in schizophrenia (SZ). Similar, but less pronounced language deficits are also seen in young first-degree relatives of people with SZ, who are at higher familial risk (FHR) for the disorder than the general population. The neural underpinnings of these deficits in people with FHR are unclear.

METHODS

Participants were 43 people with FHR and 32 comparable controls. fMRI scans were collected while participants viewed associated and unrelated word pairs, and performed a lexical decision task. fMRI analyses conducted in SPM8 examined group differences in the modulation of hemodynamic activity by semantic association.

RESULTS

There were no group differences in demographics, IQ or behavioral semantic priming, but FHR participants had more schizotypal traits than controls. Controls exhibited the expected suppression of hemodynamic activity to associated versus unrelated word pairs. Compared to controls, FHR participants showed an opposite pattern of hemodynamic modulation to associated versus unrelated word pairs, in the left inferior frontal gyrus (IFG), right superior and middle temporal gyrus (STG) and the left cerebellum. Group differences in activation were significant, FWE-corrected for multiple comparisons (p<0.05). Activity within the IFG during the unrelated condition predicted schizotypal symptoms in FHR participants.

CONCLUSIONS

FHR for SZ is associated with abnormally increased neural activity to semantic associates within an inferior frontal/temporal network. This might increase the risk of developing unusual ideas, perceptions and disorganized language that characterize schizotypal traits, potentially predicting which individuals are at greater risk to develop a psychotic disorder.

Reduced laterality as a trait marker of schizophrenia--evidence from structural and functional neuroimaging

Laterality is a characteristic principle of the organization of the brain systems for language, and reduced hemispheric asymmetry has been considered a risk factor for schizophrenia. Here we sought support for the risk factor hypothesis by investigating whether reduced asymmetry of temporal lobe structure and function is also present in unaffected relatives. Sixteen schizophrenia patients, 16 age-matched first-degree relatives, and 15 healthy controls underwent high-resolution three-dimensional anatomical imaging and functional magnetic resonance imaging during auditory stimulation. Both the overall auditory cortex and planum temporale volumes and the lateralization to the left hemisphere were markedly reduced in patients. The decrease of lateralization correlated with increased severity of symptoms. In addition, both the overall functional activation in response to auditory stimulation and its asymmetry were reduced in the patients. Relatives had intermediate values between patients and controls on both structural and functional measures. This study provides added support for the idea that reduced hemispheric asymmetry is a biological risk factor for schizophrenia.

Stability of functional language lateralization over time in schizophrenia patients

BACKGROUND

Cross-sectional functional imaging studies have shown a reduced leftward language lateralization in schizophrenic patients. An unanswered question is whether this reduced leftward lateralization is stable over time or is modified over the course of the illness.

METHODS

Ten right-handed (RH) patients (DSM-IV) and 10 RH controls were matched one-to-one for sex, age, and level of education. The subjects underwent two separate fMRI sessions while engaged in a story listening task, 21 months apart. After each session, story comprehension (task performance) was assessed through a 12-item questionnaire. The stability of the decreased asymmetry indices in the semantic region of interest (LANG) was investigated with an ANOVA to compare groups and sessions. In order to test the evolution of functional asymmetry indices at an individual level, a linear correlation between both fMRI session asymmetry indices was calculated in all subjects. Correlations between asymmetry indices and the severity of psychotic symptoms or task performances were computed.

RESULTS

The asymmetry indices of the LANG were significantly reduced in patients as compared to controls and strongly correlated between sessions. Values of asymmetry indices were unrelated to either psychotic symptoms or task performances.

CONCLUSIONS

This reduced leftward lateralization for language did not vary over time and was not influenced by the psychosis severity or the task performances. This result reinforces the hypothesis that schizophrenia is characterized by a particular organization of language.

Shape changes in prefrontal, but not parieto-occipital regions: brains of schizophrenic patients come closer to a circle in coronal and sagittal view

There is some evidence for prefrontal (PF) lobe changes in schizophrenia while the parieto-occipital (PO) region seems to be unaffected. This magnetic resonance imaging (MRI) study was performed to examine shape differences as part of the spectrum of structural abnormalities in schizophrenia. The measurements were done on families affected with schizophrenia to identify the influence of genetic and environmental factors on these changes. The sample under study consisted of 164 subjects including 45 family members (FM) suffering from schizophrenia, 27 FM with other psychiatric disorders and 51 FM without psychiatric disorders based on ICD-10 criteria. In addition, 41 nonpsychiatric control subjects were included in the study. On defined planes at the corpus callosum boundary of the PF and the PO, brain width, height and length were measured on coronal slices. Ratios of these linear measurements were also calculated based on the idea that a plane can be approximated by a circle if the concerning ratio comes close to 1. It was hypothesized that these relative brain shape parameters, especially the PF ratio width/height, would show differences between schizophrenic patients and control subjects. For all members from families with schizophrenia compared with control subjects, there were significant differences in the PF, but not in the PO region. PF height was increased. PF ratios of width/height and height/(2 x length) were closer to 1 in affected families than in control subjects. The results can be interpreted as an indication for PF brain shape changes in subjects with a disposition for schizophrenia. On coronal and sagittal planes situated at the corpus callosum, their PF could be approximated by a circle better than in control subjects. As the frontal lobe takes shape late in brain development, underlying genetic mechanisms may be dysregulated in schizophrenic patients and subjects at risk to develop the disorder.

Resting neural activity distinguishes subgroups of schizophrenia patients

BACKGROUND

Schizophrenia is etiologically heterogeneous. It is anticipated, but unproven, that subgroups will differ in neuropathology and that neuroimaging may reveal these differences. The optimal imaging condition may be at rest, where greater variability is observed than during cognitive tasks, which more consistently reveal hypofrontality. We previously demonstrated symptom and physiologic differences between familial and sporadic schizophrenia patients and hypothesized that the groups would show different resting regional cerebral blood flow (rCBF) patterns.

METHODS

Ten familial and sixteen sporadic schizophrenia patients and nine comparison subjects had single photon emission computed tomography imaging during passive visual fixation. Images were spatially normalized into Talairach coordinates and analyzed for group rCBF differences using SPM with a Z value threshold of 2.80, p < .001.

RESULTS

The subgroups had similar age, gender, illness duration, and medication treatment. Sporadic patients had hypofrontality (anterior cingulate, paracingulate cortices, left dorsolateral and inferior-orbitofrontal), whereas familial patients had left temporoparietal hypoperfusion; all of these regions show resting activity in healthy subjects. Both groups hyperperfused the cerebellum/pons and parahippocampal gyrus; additional hyperperfusion for sporadic patients was observed in the fusiform; familial patients also hyperperfused the hippocampus, dentate, uncus, amygdala, thalamus, and putamen.

CONCLUSIONS

Familial and sporadic schizophrenia patients had different resting rCBF profiles, supporting the hypothesis that certain subgroups have distinct neural underpinnings. Different neuropathologic processes among subgroups of schizophrenia patients may account for the prior contradictory results of resting imaging studies.

Investigation of unirhinal olfactory identification in antipsychotic-free patients experiencing a first-episode schizophrenia

Although olfactory deficits have been reported in patients with schizophrenia, few studies have examined whether these deficits are lateralized or investigated their possible clinical correlates. In this study, we administered the University of Pennsylvania Smell Identification Test (UPSIT) unirhinally (one nostril at a time) to 15 patients experiencing a first-episode of schizophrenia and 17 healthy comparison subjects. Clinical and olfactory assessments were conducted on the same day in patients while they were antipsychotic drug-free. Patients performed more poorly compared to healthy volunteers in their ability to identify odors across both nostrils, but there were no group differences in right and left nostril impairment. Among patients, greater deficits in grooming and hygiene correlated significantly and more strongly with poorer ability in identifying odors presented to the left compared to the right nostril. Our findings suggest that deficits in grooming and hygiene, including poor body odor, observed in patients experiencing a first-episode of schizophrenia are associated with an impairment in left nostril, and possibly left hemisphere, olfactory processing.

Sex-dependent effects of schizophrenia: an MRI study of gyral folding, and cortical and white matter volume

Alterations, sometimes sex-dependent, in volumes and gyral structure of areas of cerebral cortex have been reported in schizophrenia. Such changes imply an anomaly of connectivity. The gyrification, percentage of tissue volume attributed to white matter, cortical volume and white matter volume were measured from magnetic resonance images in males and females with (n = 61) and without (n = 42) schizophrenia. The frontal, temporal and an amalgam of occipital and parietal lobes were examined in both hemispheres. There was no effect of schizophrenia on the gyrification of the brain. For the volume of occipito-parietal white matter, females with schizophrenia had bilaterally lower volumes, while males with schizophrenia had greater volumes than controls. It is concluded that the changes in connectivity underlying the pathogenesis of schizophrenia are sex-specific and expressed in occipito-parietal white matter.

Hemispheric laterality and dimensional complexity in schizophrenia under sound and light stimulation

The aim of the present study is to investigate the relationship between linear and non-linear activities in human electroencephalograms (EEGs) by examining the linear lateral asymmetry index and the correlation dimension as a non-linear measure of complexity and to typify the characteristics of EEGs between schizophrenic patients and normal controls. We recorded the EEG from 16 electrodes in 10 schizophrenics (6 males and 4 females) and 10 age-matched normal controls (10 males), and calculated their asymmetry indices. The asymmetry index shows which hemispheric activity is dominant through examination of interhemispheric pairs in the frequency domain with EEGs between two regions. We also estimated correlation dimension. Remarkably, lower dimensional complexities appeared on the brain regions, which had significantly lower brain activity, as determined by a lateral asymmetry analysis, in schizophrenics before sound and light (SL) stimulation. We may suggest the possibility of co-varying of both linear and non-linear properties. This co-varying phenomenon maintained after the SL stimulation. Furthermore, schizophrenic patients revealed opposite asymmetric patterns compared to normal controls, as well as reversal phenomena and abnormalities in the left frontal region when SL stimuli were applied.

Computed tomography of the brain morphology of patients with first-episode schizophrenic psychosis

OBJECTIVE

To report computed tomographic (CT) scan ratings of various aspects of brain morphology of a large representative sample of patients with a first episode of schizophrenic psychosis and to compare these ratings with those from a previously reported sample of patients with chronic schizophrenia.

METHODS

A brain CT scan was performed on 114 patients with a diagnosis of first episode of schizophrenia or schizophreniform psychosis. Ratings on sulcal and ventricular enlargement and sylvian fissure were obtained using the Computed Tomographic Rating Scale for Schizophrenia. The influence of age, sex, age of onset, duration of illness and clinical psychopathology on CT ratings was assessed using bivariate correlations and multiple regression analyses. The CT ratings were also compared with those from a sample of patients with chronic schizophrenia.

RESULTS

First-episode patients showed a modest enlargement of sulci and ventricles and a reversed asymmetry of the sylvian fissure. Age was the only independent predictor of these regional changes. Clinical symptoms, sex or duration of untreated psychosis showed no relation to CT ratings. A comparison of first-episode patients with chronically ill patients, with the effect of age covaried, revealed the sylvian fissure was significantly larger (right and left sides) in the chronically ill patients.

CONCLUSIONS

Patients with a first episode of schizophrenic psychosis showed evidence of morphological changes generally associated with chronic schizophrenia. Such changes are not likely related to sex, clinical symptoms or duration of untreated psychosis, but are influenced by age. Changes in the ventricles and sulcal size are unlikely to be progressive, suggesting a neurodevelopmental origin, whereas changes in the area of the sylvian fissure may be of a more degenerative nature.

The temporal lobe in schizophrenia from uni- and multiply affected families

To investigate the effect of genetic loading on brain structure in schizophrenia, we hypothesized that separating families into uniaffected and multiply affected would reveal effects of schizophrenia and family type. Volumes and asymmetries of the amygdala-hippocampus-complex (AHC) and sylvian fissure (SF) were determined using magnetic resonance imaging of subjects with schizophrenia from 12 uniaffected and 14 multiply affected families, and ten healthy controls. AHC volume was reduced in schizophrenia, particularly on the right side in subjects from uniaffected families. AHC asymmetry was disturbed, too. Enlargement of the right SF and disturbed SF asymmetry was demonstrated in subjects from uniaffected families as well. Comparing subjects from uni- and multiply affected families may be a useful strategy to reduce variability for future studies of environmental interactions with genetic risk for schizophrenia.

Amygdala-hippocampal volume and verbal memory in first-degree relatives of schizophrenic patients

Verbal memory deficits have been related to reduced volume of medial temporal structures in several neurological and psychiatric populations, including schizophrenic patients. Impairments in verbal memory have been proposed to be a marker of risk for schizophrenia. Recently, relatives of schizophrenic patients have been reported to have reduced volume of the amygdala-hippocampal complex. In this study, we evaluate the possibility that amygdala-hippocampal volume reductions may constitute one neural substrate of verbal memory deficits in first-degree relatives. Subjects were 20 healthy first-degree relatives of schizophrenic patients and 14 demographically similar controls. Verbal memory was assessed with the Logical Memory Test. Subjects were scanned with high-resolution MRI and the images were transformed into Talairach space. Volumes of interest were amygdala-anterior hippocampus and posterior hippocampus. Relatives of schizophrenic patients had intact immediate verbal memory but significantly poorer delayed verbal memory than controls. Relatives also had significantly reduced amygdala-anterior hippocampus volumes. Across all subjects, delayed verbal memory was significantly correlated with amygdala-anterior hippocampus volume. The magnitude of the correlation did not differ between the groups. These data provide an empirical link between memory performance and volumetric abnormalities in the amygdala-hippocampal complex in the relatives of schizophrenic patients.

Hippocampal volume reduction in schizophrenia: effects of genetic risk and pregnancy and birth complications

BACKGROUND

Hippocampal volume reduction has been repeatedly demonstrated in schizophrenia. The relative contribution of genetic and environmental factors to this is unclear.

METHODS

To address this question, we compared volumetric measurements of the left and right hippocampus, obtained using stereological methods from brain MRI scans, from two groups of patients with schizophrenia as well as healthy controls (n = 26). Patients (n = 27) in the first group, had no family history of schizophrenia and had experienced severe pregnancy and birth complications (PBCs). The second group comprised of patients (n = 21) without a history of severe PBCs from families multiply affected with schizophrenia.

RESULTS

Reduction of the left hippocampal volume was associated with the diagnosis of schizophrenia but was present only in patients with a history of severe PBCs; in this group the smaller hippocampal volume, the earlier the onset of psychosis.

CONCLUSIONS

Our findings suggest that environmental factors, in this case severe PBCs, make a significant contribution to hippocampal abnormalities in schizophrenia.

Neurological signs and psychomotor performance in patients with schizophrenia, their relatives and healthy controls

Schizophrenic patients (DSM-III-R) were consecutively recruited and 39 were included. Twenty-one were first-episode and 18 were chronic schizophrenic patients. Thirty of the patients were on neuroleptic medication. Thirty-three parents were included, of whom nine were classified as 'family history positive' and 22 as 'family history negative' of a disposition to psychosis. Fifty-five healthy controls volunteered. The subjects were investigated according to a protocol divided into neurological signs and psychomotor performance (finger-tapping rate, Purdue pegboard test, pronation-supination test, gait and hand-grasp strength). Seventy-eight percent of the patients and 7% of the controls were classified as globally aberrant in signs. The patients and their parents, classified as 'family history positive', exhibited a similar laterality pattern in a finger-tapping test improving performance with the preferred hand, significantly different from the performance of the 'family history negative' parents and normal subjects. Duration of illness, neuroleptic medication and negative symptoms were not related to the occurrence of neurological signs and psychomotor performance. These findings indicate that neurological aberrations are present at the onset of illness and that hereditary factors are associated with motor laterality.

The planum temporale: a systematic, quantitative review of its structural, functional and clinical significance

The planum temporale (PT) is a triangular area situated on the superior temporal gyrus (STG), which has enjoyed a resurgence of interest across several disciplines, including neurology, psychiatry and psychology. Traditionally, the planum is thought to be larger on the left side of the brain in the majority of normal subjects [N. Geschwind, W. Levitsky, Human brain: left-right asymmetries in temporal speech regions, Science 161 (1968) 186-87.]. It coincides with part of Wernicke's area and it is believed to consist cytoarchitectonically of secondary auditory cortex. Consequently, it has long been thought to be intimately involved in language function. The PT is, therefore, of relevance to disorders where language function is impaired, such as schizophrenia and dyslexia. The gross anatomical boundaries remain in dispute, and only recently has its cytoarchitecture begun to be studied again after 60 years silence, and finally its functional significance is only now being explored. In the first part of this review the structural aspects and anatomical boundaries of the PT in the normal brain from post mortem and magnetic resonance imaging (MRI) and methods of measurement are discussed. In the second part, studies of the functional significance of the PT in the normal brain are reviewed critically. Finally a meta-analysis of MRI measurements of the distribution of planum anatomy in normal subjects is presented. Comparison is made with clinical populations, including schizophrenia and dyslexia, and the influence of handedness and gender on such measurements is quantified. Although there are many ways of defining and measuring the PT with a wide variety of results, overall there is a significant leftward asymmetry in normals, which is reduced in left handers and females. The leftward asymmetry is much reduced in patients with schizophrenia due to a relatively larger right PT than normal controls. The review is intended to guide future researchers in this area.