Asymmetries of the skull and handedness: Phrenology revisited

Some of the asymmetries noted in cerebral computerized transaxial tomography (CTT) studies are reflected in the shape of the skull resulting most often in backward protrusion of the occipital bone on the left and a less striking forward protrusion of the right frontal bone. Asymmetries are less marked in left-handed individuals but the opposite features, i.e. forward protrusion of the left frontal bone and posterior protrusion of the right occipital bone, are more frequent in left handers than in right handers.     

Asymmetries in event-related potentials during rhyme-matching: confirmation of the null effects of handedness

Event-related potentials (ERPs) were recorded from 16 right- and 16 left-handed subjects during two variants of a sequential rhyme-judgement task. These variants manipulated the demands placed on short-term memory, by requiring subjects to match a word either with one or with three previously presented words. In both tasks, ERPs exhibited two lateral asymmetries: (i) during the interval prior to the final word, the CNV was more negative over the left hemisphere, and (ii) rhyme/non-rhyme differences in the amplitude of the N450 component of the ERPs to the final word were larger over the right than the left hemisphere. Neither of these asymmetries was smaller or more variable in left- than in right-handed subjects. It is suggested that these data may indicate that some aspects of language processing are, irrespective of handedness, relatively invariant in the direction and degree of their cerebral lateralization.     

Relationships among handedness, familial handedness, sex and ocular sighting-dominance

Fifty-four males and 71 females were tested on a measure of handedness and a measure of ocular sighting-dominance. Familial handedness was also ascertained via the handedness questionnaire. There were no sex or handedness differences in the incidence of familial sinistrality. Handedness, sex and familial handedness affected sighting-dominance in complex and unexpected ways. It is suggested that these variables, as well as others not tested here, will need to be considered in future studies of ocular laterality and its relationship to functional cerebral asymmetries.     

Remission status and cortical thickness in childhood-onset schizophrenia

ObjectiveFew studies have examined prediction of schizophrenia outcome in relation to brain magnetic resonance imaging measures. In this study, remission status at the time of discharge was examined in relation to admission cortical thickness for childhood-onset schizophrenia probands. We hypothesized that total, frontal, temporal, and parietal gray matter thickness would be greater in patients who subsequently remit.MethodThe relation between admission cortical brain thickness on magnetic resonance imaging and remission status at the time of discharge an average of 3 months later was examined for 56 individuals (32 males) ages 6 to 19 diagnosed with childhood-onset schizophrenia. Cortical thickness was measured across the cerebral hemispheres at admission. Discharge remission criteria were adapted from the 2005 Remission in Schizophrenia Working Group criteria.ResultsPatients remitted at discharge (n = 16 [29%]) had thicker regional cortex in left orbitofrontal, left superior, and middle temporal gyri and bilateral postcentral and angular gyri (p ≤ .008).ConclusionsOur results provide neuroanatomic correlates of clinical remission in schizophrenia and evidence that response to treatment may be mediated by these cortical brain regions. J. Am. Acad. Child Adolesc. Psychiatry, 2008;47(10):1133–1140.     

Cerebellar asymmetry,cortical asymmetry and handedness: Two independent networks

ABSTRACT

In 46 right-handers and 46 left-handers, we used functional magnetic resonance imaging to record activity in the frontal lobes while they generated words, the temporal lobe while they made synonym judgments, and the parietal lobe while they watched videos of manual actions. In each case we also recorded activity in the cerebellum. Laterality indices showed a significant left-hemispheric bias in each cortical lobe and a right-hemispheric bias in the cerebellum for the 2 language tasks, but not during action observation. Cerebellar asymmetry also correlated negatively with frontal and temporal asymmetry, reflecting contralateral connections, but not with parietal asymmetry. A factor analysis of the inter-correlations among laterality indices revealed 2 factors, implying independent lateralized networks, with cerebellar asymmetry strongly linked to a language network in frontal and temporal cortices, and handedness strongly linked to an action-observation network in the parietal lobe.     

Cerebral cortical thickness and a history of obstetric complications in schizophrenia

Introduction

Magnetic resonance imaging (MRI) studies have demonstrated that patients with schizophrenia have thinner brain cortices compared with healthy control subjects. Neurodevelopment is vulnerable to obstetric complications (OCs) such as hypoxia and birth trauma, factors that are also related to increased risk of developing schizophrenia. With the hypothesis that OCs might explain the thinner cortices found in schizophrenia, we studied patients with schizophrenia and healthy controls subjects for association between number and severity of OCs and variation in cortical thickness.

Methods

MRI scans of 54 adults with schizophrenia or schizoaffective disorder and 54 healthy controls were acquired at Karolinska Institutet, Stockholm, Sweden. Measures of brain cortical thickness were obtained using automated computer processing (FreeSurfer). OCs were assessed from obstetric records and scored blindly according to the McNeil–Sjöström scale. At numerous cortical locations, putative effects of OCs on cortical thickness variation were tested for each trimester, for labour, for composite OC scores, severe OC scores, and hypoxia scores among patients and controls separately.

Results

Number and severity of OCs varied among both patient and control subjects but were not associated with cortical thickness in either of the groups. Patients demonstrated thinner brain cortices but there were no significant differences in number and severity of OC scores across groups.

Conclusion

In the present study, number and severity of obstetric complications were not associated with brain cortical thickness, in patients with schizophrenia or in healthy control subjects. The thinner brain cortices found in patients with schizophrenia were not explained by a history of OCs.     

Effects of clozapine and olanzapine on cortical thickness in childhood-onset schizophrenia

BackgroundLittle is known about the effects of antipsychotic medications on gray matter (GM) in schizophrenia. Although clozapine remains the most effective antipsychotic medication in treatment-refractory cases, it is unknown whether it has a differential effect on GM development.MethodsIn an exploratory analysis, we used automated cortical thickness measurements and prospectively scanned childhood-onset schizophrenia (COS) patients who were maintained on one medication. Two atypical antipsychotic medications, clozapine (n = 12, 37 scans) and olanzapine (n = 12, 33 scans) were compared with respect to effects on cortical development, in contrast to GM trajectories of matched controls.ResultsThere were no significant differences in the trajectories of cortical thickness between the two treatment groups with the exception of a small circumscribed area in the right prefrontal cortex, where the olanzapine group showed thicker cortex. As expected, both groups showed thinner GM compared to matched controls.ConclusionsAlthough these analyses do not rule out effects of antipsychotic medications on GM development in schizophrenia, they show no differential effect between clozapine and olanzapine on GM trajectory.     

Possible dysregulation of cortical plasticity in auditory verbal hallucinations-A cortical thickness study in schizophrenia

IntroductionInvestigations of gray matter changes in relation with auditory verbal hallucinations (AVH) have reported conflicting results. Assuming that alterations in gray matter might be related to certain symptoms in schizophrenia this study aimed to investigate changes in cortical thickness specific to AVH. It was hypothesized that schizophrenia patients suffering from persistent AVH would show significant differences in cortical thickness in regions involved in language-production and perception when compared to schizophrenia patients which had never experienced any hallucinations.MethodsUsing cortical thickness analysis the present study investigated ten schizophrenic patients suffering from AVH, ten non-hallucinating schizophrenic patients, and ten healthy control subjects. Anatomical data were acquired on a 3 T MRI system, transformed into standard space and cortically aligned to investigate local differences in whole brain cortical thickness between the two patient groups. Based on this comparison, brain regions with alterations specific for the patients with AVH were identified and then used as regions of interest to compare both patient groups to the healthy subjects respectively.ResultsHallucinating patients showed gray matter reductions in the dominant hemisphere predominantly in sensory language areas relevant for speech processing. Increased cortical thickness was found in regions related to self-monitoring.ConclusionsGray matter reductions in chronic schizophrenic patients may be the sequel of synaptic derangement or disease-related deregulation of language circuits. In order to clarify the ambiguous information processing additional demands might be put on cortical structures responsible for self-monitoring processes leading to changes in cortical thickness in the sense of neural plasticity.     

Language dominance, handedness and sex: Recessive X-linkage theory and test

The possibility is investigated that cerebral dominance for language and handedness share a common X-linkage and that the relation between the two is therefore a function of sex. In particular, an X-linked recessive account is shown to predict an overall configuration of language dominance, handedness and sex within which there is a sex effect in the pattern of language dominance among right-handed but not left-handed people. The recent accurate determination of cerebral dominance among relatively large samples of the general population by means of functional transcranial Doppler ultrasonography makes it possible to test this new theory rigorously, and its parameter-free pattern of predictions is found to be supported.     

Episodic odor memory: influences of handedness, sex, and side of nose

It is not known whether, or to what degree, odor memory is influenced by lateralized brain processes. In this study, we administered a 12-item match-to-sample odor memory test separately to the left and right sides of the nose of 30 left- and 30 right-handed subjects of equivalent age, sex distribution, and overall general smell ability. For each test item, one of three delay intervals (10-, 30-, and 60-s) was interspersed between smelling the target stimulus and smelling the first of four response alternatives. Women, but not men, performed significantly better on the left than on the right side of the nose, conceivably reflecting greater reliance upon left-hemisphere semantic processes. Subjects who received the first test on the right side of the nose outperformed those who received the first test on the left side of the nose. As in previous work, an age-related decrement in odor memory test scores was present. These data contribute to the debate on the role of lateralized brain processes in episodic odor memory, and suggest that performance on a standardized match-to-sample odor memory task is influenced by a number of interacting factors.     

Ontogenesis of handedness and somatosensory cortical response

The development of handedness in human infants was studied in parallel with the development of the cortical somatosensory evoked response.     

Increases in regional subarachnoid CSF without apparent cortical gray matter deficits in schizophrenia: modulating effects of sex and age

OBJECTIVE: The authors investigated the modulating effects of biological sex and age on regional decreases in cortical gray matter and increases in subarachnoid CSF in 25 patients with chronic schizophrenia and 28 group-matched healthy comparison subjects. METHOD: Computational cortical pattern-matching methods were employed to measure the local proportions of gray matter and subarachnoid CSF at thousands of homologous cortical surface locations in each subject using high-resolution magnetic resonance images. Principal-component analysis reduced tissue proportion values obtained at each cortical surface point into component scores for each subject. Principal-component analysis scores were used as dependent variables in statistical analyses that included diagnosis, age, and sex as predictor variables. To reveal more regional changes in tissue proportions, statistical differences in gray matter and CSF were compared at each cortical surface location and mapped in three dimensions. RESULTS: Principal-component analyses revealed main effects of diagnosis, sex, and age for the CSF increases seen in the schizophrenia patients, in male subjects, and in association with age. Significant diagnosis-by-age, diagnosis-by-sex, and diagnosis-by-sex-by-age interactions were also observed, revealing CSF increases in male patients at younger ages. Statistical maps showed regional increases in subarachnoid CSF in association with the above effects. For cortical gray matter measurements, only main effects of age were observed. CONCLUSIONS: Regionally specific increases in sulcal and subarachnoid CSF occur during adulthood and appear prematurely in male schizophrenia patients. Cortical gray matter reductions show aging effects but are below the threshold of significance in schizophrenia.     

Spatial lateralization: The relationship among sex, handedness and familial sinistrality

Spatial lateralization was examined in 80 subjects by use of a strictly balanced design contrasting sex, handedness and familial sinistrality (absent and present). A modified version of Witelson's dichaptic stimulation task (verbal and nonverbal) was employed. The verbal task showed a significant main effect for the right-hand score. On the nonverbal task only two groups displayed a significant difference between hand scores: left-handed males with familial sinistrality and right-handed females with no familial sinistrality. Results are discussed in relation to previously reported data.     

Associations of cortical thickness and cognition in patients with schizophrenia and healthy controls

Previous studies have found varying relationships between cognitive functioning and brain volumes in patients with schizophrenia. However, cortical thickness may more closely reflect cytoarchitectural characteristics than gray matter density or volume estimates. Here, we aimed to compare associations between regional variation in cortical thickness and executive functions, memory, as well as verbal and spatial processing in patients with schizophrenia and healthy controls (HCs). We obtained magnetic resonance imaging and neuropsychological data for 131 patients and 138 matched controls. Automated cortical pattern matching methods allowed testing for associations with cortical thickness estimated as the shortest distance between the gray/white matter border and the pial surface at thousands of points across the entire cortical surface. Two independent measures of working memory showed robust associations with cortical thickness in lateral prefrontal cortex in HCs, whereas patients exhibited associations between working memory and cortical thickness in the right middle and superior temporal lobe. This study provides additional evidence for a disrupted structure-function relationship in schizophrenia. In line with the prefrontal inefficiency hypothesis, schizophrenia patients may engage a larger compensatory network of brain regions other than frontal cortex to recall and manipulate verbal material in working memory.     

A crossover interaction between sex, sexual orientation, and handedness

The distribution of handedness scores was analysed in 1414 heterosexual, bisexual, and homosexual men and women. Hand preference was assessed by a questionnaire that distinguishes consistently right-handed from partially or completely left-handed individuals, and sexual orientation was measured by the Kinsey scales. As expected from population-based studies, heterosexual men were, on average, more left-handed than heterosexual women. By contrast, gay men were more right-handed than lesbians or heterosexual men, and lesbians were more left-handed than gay men or heterosexual women. This crossover interaction suggests that a common variable influences sex, sexual orientation, and hand preference.