A lack of cerebral lateralization in schizophrenia is within the normal variation in brain maturation but indicates late, slow maturation

Significant gender-specific difference in brain lateralization of schizophrenia patients assessed by new combined foot dominance scale

Objective

Reduced hemispheric asymmetry has been identified as a potential risk factor for schizophrenia, characterized by diminished brain lateralization and a lack of dominance in the left hemisphere. Moreover, there is growing evidence of disrupted connectivity between various cortical regions. This study aimed to investigate gender differences in left-footedness as a potential biological marker for neuronal dysontogenesis in individuals with schizophrenia and control subjects.

Materials and methods

A New Combined Foot Dominance Scale (14 foot tests), comprising a Modified Chapman & Chapman Subscale (10 foot tests) and a Complex Tasks Subscale (four foot tests) was administered as performance tasks in 180 subjects [98 schizophrenia patients with mean age 34.45 years (SD = 15.67, range 23-79) for men and 42.20 years (SD = 11.38, range 21-63) for women and 82 controls with a mean age 34.70 years (SD = 16,82, range 18-79) for men and 44.50 years (SD = 10.73, range 23-67)]. As our data are not continuous and lacks normal distribution, the non-parametric Mann-Whitney test was used for comparing categorical data.

Results

The mean left-footedness, as assessed by the New Combined Foot Dominance Scale, is significantly higher in individuals with schizophrenia compared to control subjects. Our findings from inter-gender comparisons reveal that female schizophrenia patients exhibit a significantly greater average left-footedness than female control subjects, while in males no such a statistical significant difference is detected.

Conclusion

Left foot dominance is higher in patients with schizophrenia than in control subjects and women contribute significantly more to this difference.

Covarying structural alterations in laterality of the temporal lobe in schizophrenia: A case for source-based laterality

The human brain is asymmetrically lateralized for certain functions (such as language processing) to regions in one hemisphere relative to the other. Asymmetries are measured with a laterality index (LI). However, traditional LI measures are limited by a lack of consensus on metrics used for its calculation. To address this limitation, source-based laterality (SBL) leverages an independent component analysis for the identification of laterality-specific alterations, identifying covarying components between hemispheres across subjects. SBL is successfully implemented with simulated data with inherent differences in laterality. SBL is then compared with a voxel-wise analysis utilizing structural data from a sample of patients with schizophrenia and controls without schizophrenia. SBL group comparisons identified three distinct temporal regions and one cerebellar region with significantly altered laterality in patients with schizophrenia relative to controls. Previous work highlights reductions in laterality (ie, reduced left gray matter volume) in patients with schizophrenia compared with controls without schizophrenia. Results from this pilot SBL project are the first, to our knowledge, to identify covarying laterality differences within discrete temporal brain regions. The authors argue SBL provides a unique focus to detect covarying laterality differences in patients with schizophrenia, facilitating the discovery of laterality aspects undetected in previous work.

Dermatoglyphic Pattern Types in Subjects with Nonsyndromic Cleft Lip with or without Cleft Palate (CL/P) and Their Unaffected Relatives in the Philippines

Objective

To investigate dermatoglyphic patterns in 95 nonsyndromic Filipino subjects with nonsyndromic cleft lip with or without cleft palate (CL/P) and 90 of their unaffected relatives.

Design

Retrospective study of dermatoglyphic pattern types.

Setting

Negros Occidental and Cavite in the Philippines.

Participants

Nonsyndromic subjects with CL/P and their unaffected relatives.

Methods

Dermatoglyphic patterns were categorized as arch, ulnar loop, radial loop, whorl, or other by three independent raters. Pattern data from the subjects, the unaffected relatives, and an unaffected control population (from the literature) were compared using chi-square tests. As a measure of asymmetry, dissimilarity between pattern types on homologous fingers was quantified and compared using Student's t tests.

Results

The frequency of arches (p = .016) and ulnar loops (p = .04) were significantly increased, and whorls decreased in the affected group (p = .0015), compared with the unaffected group. Affected female subjects had significantly more ulnar loops and arches (p = .009 and p = .023, respectively) and fewer whorls (p < .0001) than the unaffected female subjects. There were no significant differences between affected and unaffected male subjects. Dissimilarity scores were significantly different between male and female subjects and between subjects with CL/P and unaffected relatives. Additionally, pattern type frequencies for the relatives fell in between the frequencies for the CL/P group and the controls.

Conclusions

In this Filipino population, differences in frequency of dermatoglyphic pattern types and pattern dissimilarity exist between individuals with orofacial clefts and their unaffected relatives and between both groups and controls, with the major effect seen in female subjects.

Functional MRI of sentence-level language comprehension in schizophrenia: a coordinate-based analysis

Numerous authors have hypothesised that abnormal pathways for language play a key role in the pathophysiology of schizophrenia, a notion that is supported by structural imaging and post-mortem findings especially in patients with thought disorder and auditory verbal hallucinations. Recently, an increasing number of functional magnetic resonance imaging (fMRI) investigations addressed language comprehension schizophrenia. We present a systematic review of the fMRI-studies on sentence- and text-level language comprehension in schizophrenia. 13 studies met the inclusion criteria. Additional studies specifically addressed language lateralization. Coordinates for differential contrasts for healthy controls>patients reported in these studies indicate that the left fronto-temporal language network is altered in schizophrenia. 33 out of the 51 reported coordinates are located in the left hemisphere. Overactivation in schizophrenia extends into premotor areas and is about equally divided among the left and right hemispheres. Several negative studies indicate heterogeneity within schizophrenia, which could possibly be related to the severity of thought disorder or auditory verbal hallucinations of patients. Activation changes related to thought disorder within schizophrenia (n=4 studies) include the inferior frontal and superior temporal gyri and are moderately lateralized to the left hemisphere. Although current fMRI literature is still insufficient to draw decisive conclusions, results point towards functionally altered pathways for language in schizophrenia. This notion is also plausible from the viewpoint of psychopathology especially since hallmark symptoms of the disease, thought disorder, auditory verbal hallucinations and alogia, are expressed in terms of language or represent abnormalities of language function.

The evolutionary paradox and the missing heritability of schizophrenia

Schizophrenia is one of the most detrimental common psychiatric disorders, occurring at a prevalence of approximately 1%, and characterized by increased mortality and reduced reproduction, especially in men. The heritability has been estimated around 70% and the genome-wide association meta-analyses conducted by the Psychiatric Genomics Consortium have been successful at identifying an increasing number of risk loci. Various theories have been proposed to explain why genetic variants that predispose to schizophrenia persist in the population, despite the fitness reduction in affected individuals, a question known as the evolutionary paradox. In this review, we consider evolutionary perspectives of schizophrenia and of the empirical evidence that may support these perspectives. Proposed evolutionary explanations include balancing selection, fitness trade-offs, fluctuating environments, sexual selection, mutation-selection balance and genomic conflicts. We address the expectations about the genetic architecture of schizophrenia that are predicted by different evolutionary scenarios and discuss the implications for genetic studies. Several potential sources of "missing" heritability, including gene-environment interactions, epigenetic variation, and rare genetic variation are examined from an evolutionary perspective. A better understanding of evolutionary history may provide valuable clues to the genetic architecture of schizophrenia and other psychiatric disorders, which is highly relevant to genetic studies that aim to detect genetic risk variants.

Laterality patterns of brain functional connectivity: gender effects

Lateralization of brain connectivity may be essential for normal brain function and may be sexually dimorphic. Here, we study the laterality patterns of short-range (implicated in functional specialization) and long-range (implicated in functional integration) connectivity and the gender effects on these laterality patterns. Parallel computing was used to quantify short- and long-range functional connectivity densities in 913 healthy subjects. Short-range connectivity was rightward lateralized and most asymmetrical in areas around the lateral sulcus, whereas long-range connectivity was rightward lateralized in lateral sulcus and leftward lateralizated in inferior prefrontal cortex and angular gyrus. The posterior inferior occipital cortex was leftward lateralized (short- and long-range connectivity). Males had greater rightward lateralization of brain connectivity in superior temporal (short- and long-range), inferior frontal, and inferior occipital cortices (short-range), whereas females had greater leftward lateralization of long-range connectivity in the inferior frontal cortex. The greater lateralization of the male's brain (rightward and predominantly short-range) may underlie their greater vulnerability to disorders with disrupted brain asymmetries (schizophrenia, autism).

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.

Development of DSM-V and ICD-11: tendencies and potential of new classifications in psychiatry at the current state of knowledge

A reason for the necessity to revise ICD-10 and DSM-IV is the increase of knowledge in the past 20 years, especially neurobiological knowledge. But is this increase of knowledge, for example in the field of neurogenetics, of such magnitude that a revision of the psychiatric classification is necessary and promises to be fruitful? The current plans for DSM-V or ICD-11, respectively, focus on different improvements. In this context also the introduction of a purely syndromatic/dimensional approach without including etiopathogenetic hypotheses, is discussed. A switch to such a dimensional approach, which was discussed among others in the DSM-V task force Deconstructing Psychosis, would be the most radical development. It could avoid many theoretical pre-assumptions about causal hypotheses, which are still associated with ICD-10 and DSM-IV. This would indeed increase the validity of psychiatric classification, but it would also reduce the information as compared to traditional diagnostic categories with all the current implications concerning etiopathogenesis, therapy and prognosis. Such a dimensional approach would also mean that the syndromes would have to be assessed in a standardized way for each person seeking help from the psychiatric service system or for each person undergoing psychiatric research. This would have to be a multi-dimensional assessment covering all syndromes existing within different psychiatric disorders. Based on the different aspects that must be considered in this context, a careful revision seems more advisable than a radical change of classification.

The forthcoming revision of the diagnostic and classificatory system: perspectives based on the European psychiatric tradition

Europe has a rich tradition in psychopathology and psychiatric classification. This could be helpful developing new classification systems like ICD-11 and DSM-V. Some examples of this are described and further discussed, such as the categorical vs. the syndromatological approach, the relevance of hierarchical rules for the delineation of nosological entities, the antagonistic tradition of unitarian vs. splitting approaches and the relevance of a differentiated psychopathological description. Finally, the conclusion is that a too radical change of the classificatory system, e.g. in the direction of a purely symptomatical/dimensional systematic, or a totally new classification based on modern new biological findings, might be problematic and premature.

Dysfunction of the attentional brain network in children with Developmental Coordination Disorder: a fMRI study

Children with Developmental Coordination Disorder (DCD) present impaired motor skills, frequently associated with impaired attentional and executive functions. The objective of this study was to assess the impact of DCD on effective connectivity applied to a putative model of inhibition. fMRI was performed in 9 children with DCD and 10 control children (8-13 years old) performing a go-nogo task. As previously reported, children with DCD obtained a similar score for correct inhibitions as controls, but responses were slower and more variable than in controls. Compared to controls, Structural Equation Modeling indicated that: (1) path coefficients from both middle frontal cortex (MFC) and anterior cingulate cortex (ACC) to inferior parietal cortex (IPC) increased in children with DCD particularly in the left hemisphere; (2) path coefficients between striatum and parietal cortex decreased in children with DCD in the right hemisphere. Results suggest that DCD could be characterized by abnormal brain hemispheric specialization during development. Furthermore, connectivity in the MFC-ACC-IPC network could indicate that children with DCD are less able than healthy children to easily and/or promptly switch between go and nogo motor responses. However, children with DCD seem to compensate for this poor efficiency by more actively engaging the ACC to prevent commissions allowing maintenance of a good level of inhibition.

Psychosis and autism as diametrical disorders of the social brain

Autistic-spectrum conditions and psychotic-spectrum conditions (mainly schizophrenia, bipolar disorder, and major depression) represent two major suites of disorders of human cognition, affect, and behavior that involve altered development and function of the social brain. We describe evidence that a large set of phenotypic traits exhibit diametrically opposite phenotypes in autistic-spectrum versus psychotic-spectrum conditions, with a focus on schizophrenia. This suite of traits is inter-correlated, in that autism involves a general pattern of constrained overgrowth, whereas schizophrenia involves undergrowth. These disorders also exhibit diametric patterns for traits related to social brain development, including aspects of gaze, agency, social cognition, local versus global processing, language, and behavior. Social cognition is thus underdeveloped in autistic-spectrum conditions and hyper-developed on the psychotic spectrum.;>We propose and evaluate a novel hypothesis that may help to explain these diametric phenotypes: that the development of these two sets of conditions is mediated in part by alterations of genomic imprinting. Evidence regarding the genetic, physiological, neurological, and psychological underpinnings of psychotic-spectrum conditions supports the hypothesis that the etiologies of these conditions involve biases towards increased relative effects from imprinted genes with maternal expression, which engender a general pattern of undergrowth. By contrast, autistic-spectrum conditions appear to involve increased relative bias towards effects of paternally expressed genes, which mediate overgrowth. This hypothesis provides a simple yet comprehensive theory, grounded in evolutionary biology and genetics, for understanding the causes and phenotypes of autistic-spectrum and psychotic-spectrum conditions.

Systematic of psychiatric disorders between categorical and dimensional approaches: Kraepelin's dichotomy and beyond

This paper describes basic principles of systematics for psychiatric disorders such as the categorical and dimensional approach. It summarises validity aspects of the traditional psychiatric nosology and syndromatology. The importance and limitations of the dichotomy of schizophrenia and affective disorders, first suggested by Kraepelin, is reviewed in the light of results from modern research in the field of classification, follow-up and neurobiological studies, especially neurochemical, neurogenetic and neuroimaging studies. Current developments towards DSM-V and ICD-11 are critically reflected. The conclusion is reached that there might be insufficient data to establish a new systematics of psychoses. Therefore it might be premature to leave the Kraepelinian dichotomy totally although it has to be modified in the light of new research.

Infantile autism: a chronic psychosis since infancy due to synaptic pruning of the supplementary motor area

The rise in Infantile Autism, learning problems, cognitive decline with age, Alzheimer's, Parkinson's Diseases and the SIDS epidemic, has a common cause in the rising dietary deficit in Omega-3 brain-food. This paper suggests that aside from the wider concept of Autism Spectrum Disorders (ASD) and Pervasive Developmental Disorders (PDD), the rise in Infantile Autism (IA) in the last decade is the effect of deficient brain-food (Omega-3). The consequent delay of development prolongs the 2nd regressive event in infancy to pruning of the centre in the Medial Frontal Lobe System that connects Hippocampus and Cingulum. With a consequently defective Supplementary Motor Area (SMA), the Delayed Response Function is affected leading to persistent psychosis. Post-Pubertal Episodic Psychoses are associated with acute reduction of excitation, a risk of breakdown of circuitry, insufficient fill-in mechanisms, and silent spots. An acute psychosis occurs if the silent spots comprise of SMA. Only two brain areas have continuous neurogenesis, indicating their important functions: the Hippocampus and Olfactory Bulb that belongs to the Lateral Frontal Lobe System essential to survival. Concerned with necessity of action in response to the environment, it relies upon short-term memory and Acute Feedback Mechanisms influenced by emotion and motivation from the external world. In contrast, the Medial Frontal Lobe network is controlled by Feed-Forward Predictive Mechanisms related to storage of information. The Delayed Response Function is mastered at 7 months, when 2nd event occurs with pruning of axons and dendrites. An abolished or defective Delayed Response Function seriously incapacitates an individual: A defective "Social Brain" with an inability for conscious action and to communicate, predominates in IA. There is a near lack of speech, despite normal vision and hearing in the minority without marked adversity in pregnancy, at delivery or in infancy. I propose that the recent rise in IA despite no rise in adversity signifies a rising deficiency in brain-food. That this is so is suggested by a changing clinical picture: no Mental Retardation in an IA majority. Deficit in Olfaction is pathognomonic in schizophrenia since 30 yrs and distinguishes the Asperger Syndrome. If brain-food deficiency alone sufficiently prolongs pruning to cause absent activity in SMA in infancy, less mentally retarded IA from other causes might be observed. Deficit in brain-food was evident in the Sudden Infant Death Syndrome: birthweight averaged 200-300 g lower than sibs, Omega-3 levels in brainstem were lower than controls. Only 20 % SIDS died in first hypoxic episode, suggesting such episodes are more frequent than we imagined. Children with learning-behaviour problems have similarly depressed birthweight. A general deficiency in Omega-3 contributes to the lacking reduction in Schizophrenia, despite early puberty predominates. Olfactory Bulb is first affected in the Alzheimer's and Parkinson's Disease. Cognitive decline with age, Hippocampal dysfunctions rise markedly irrespective of disease, but the major mental illnesses and Infantile Autism in particular, benefit from "brain-food" that might also prevent a development of these disorders. To secure optimal brain function in the coming generations, there is a need to change the diet now from its emphasis on protein for body growth to food for the brain. This means there is a need to increase fish and sea food consumption.

Increased prefrontal gyrification in a large high-risk cohort characterizes those who develop schizophrenia and reflects abnormal prefrontal development

BACKGROUND

In our cohort considered at high risk (HR) of developing schizophrenia, we previously found a significant difference in extent of right prefrontal cortical folding between those who subsequently developed schizophrenia and a matched group who remained well. This study aimed to determine if this preexisting difference distinguished 17 individuals who developed schizophrenia from the 128 HR individuals in the cohort who remained well and to explore possible underlying differences in cortical composition.

METHODS

Prefrontal cortical folding was measured by an automated version of the Gyrification Index (A-GI), a ratio reflecting extent of folding. Multivariate logistic regression assessed the probability that prefrontal A-GI predicts diagnostic outcome and subsequently assessed the effect on A-GI of regional cerebrospinal fluid and gray and white matter.

RESULTS

High-risk individuals who subsequently developed schizophrenia were distinguished from the remaining cohort by increased right prefrontal cortex (PFC) A-GI. Mean right PFC gray matter volume also differed between groups, but white matter volume did not. Correlations of age with gray and white matter further distinguished groups and a linear regression analysis showed a significant interaction between age and diagnosis on mean volume of right PFC white matter.

CONCLUSIONS

Increased A-GI appears to indicate abnormal right prefrontal development in those who develop schizophrenia.

Cerebral asymmetry and behavioral lateralization in rats chronically lacking n-3 polyunsaturated fatty acids

BACKGROUND

Anatomic and functional brain lateralization underlies hemisphere specialization for cognitive and motor control, and deviations from the normal patterns of asymmetry appear to be related to behavioral deficits. Studies on n-3 polyunsaturated fatty acid (PUFA) deficiency and behavioral impairments led us to postulate that a chronic lack of n-3 PUFA can lead to changes in lateralized behavior by affecting structural or neurochemical patterns of asymmetry in motor-related brain structures.

METHODS

We compared the effects of a chronic n-3 PUFA deficient diet with a balanced diet on membrane phospholipid fatty acids composition and immunolabeling of choline acetyltransferase (ChAt), as a marker of cholinergic neurons, in left and right striatum of rats. Lateral motor behavior was assessed by rotation and paw preference.

RESULTS

Control rats had an asymmetric PUFA distribution with a right behavioral preference, whereas ChAt density was symmetrical. In deficient rats, the cholinergic neuron density was 30% lower on the right side, associated with a loss of PUFA asymmetry and behavior laterality. They present higher rotation behavior, and significantly more of them failed the handedness test.

CONCLUSION

These results indicate that a lack of n-3 PUFA is linked with a lateral behavior deficit, possibly leading to cognitive disturbances.

A "new-old" way of thinking about brain disorder, cerebral excitability--the fundamental property of nervous tissue

Cerebral excitability is normally distributed, and pubertal age is a distinguishing factor. The final developmental event in CNS comprising selective pruning of excitatory synapses coincides with puberty. With early puberty, excess excitation and synaptic density, we have photic susceptibility, paroxysmal EEGs, disturbed circadian rhythms, paroxysmal disorders treated with drugs lowering excitation. Manic-depressive psychosis accords with this. Migraine with paroxysmal EEG, photophobia, hemianopsia, scintillating scotomas, excess excitation in the visual system, benefits from lowering excitation. With late puberty, attenuated CNS, we have disorders in need of raising excitation to avoid breakdown of circuitry, insufficient fill-in mechanism, silent spots, subjectively experienced only--objectively verifiable psychosis: i.e., schizophrenia treated with convulsant neuroleptics. By affecting pubertal age, we affect the distribution of excitation and of post-pubertal brain disorders in accordance with their level of excitation. Excitation is equally important in chronic disorders: l'dopa adversity in Parkinsonism could be due to further lowering of excitation in patients with a deficiency, a schizophrenia-like psychosis develops. Given unavoidable adversity of anti-psychotics, and a marked rise in suicide in schizophrenic and manic-depressive since their introduction, we want to prevent the occurrence of disorders at the extremes, whether very early or late puberty. DHA normalises excitability at all levels of excitation. An adequate daily intake of DHA, before puberty as well as after, might probably reduce or eliminate a development of psychopathology. Lithium is a robust neurotropic agent, and lithiation of the drinking water could be a way of reducing suicide, homicide, violent behaviour, and drug abuse.

From superior adaptation and function to brain dysfunction--the neglect of epigenetic factors

With optimal pregnancy conditions (natural, enriched diet which includes fish) African (Digo) infants are 3-4 weeks ahead of European/American infants in sensorimotor terms at birth, and during the first year. Infants of semi-aquatic sea-gypsies swim before they walk, and have superior visual acuity compared with us. With adverse pregnancy behaviour (fear of fat, a trend to dieting), neglecting the need for brain fat to secure normal brain development and function, we run a risk of dysfunction--death. Sudden Infant Death Syndrome victims have depressed birth weight, lower levels of marine fat in brainstem than controls, and >80 suffer multiple hypoxic episodes prior to death. Depressed birth weight (more than 10% below mean) is seen in learning and behaviour disorders, and a trend towards weights of less than 3kg is increasing, which supports a rise in antenatal sub optimality. Given marine fat deficiency in pregnancy and infancy, neurons starved for fuel could delay myelination and maturation in the latest developed Frontal Lobes. The phylogenetic oldest Lateral Frontal Lobe System (feed-back mechanism etc.) derived from olfactory bulb-amygdala, which crosses in Anterior Commisure is probably spared, while the Medial Frontal Lobe System derived from Hippocampus-Cingulum and crosses in Corpus Callosum (delayed response task) is most likely affected. The rise in infantile autism (intact vision and hearing) with deficit in delayed response task only, could suggest a deficit in the Medial Frontal Lobe System. The human species is unique; 70% of total energy to the foetus goes to development of the brain, which mainly consists of marine fat. It undergoes pervasive regressive events, before birth, in infancy and at puberty. Minimal retraction of neuronal arborisation is advantageous. Attributable to adverse pregnancy childrearing practice, excessive retraction is likely prenatally and in infancy. Pubertal age affects the fundamental property of nervous tissue, excitability: excessive excitatory drive is seen in early, and a deficiency in late puberty. It is postulated that with adequate marine fat, there is probably no risk of psychopathology at the extremes, whereas a deficiency could lead to paroxysmal (subcortical) dysfunction in early puberty, and breakdown of cortical circuitry and cognitive dysfunctions in late puberty. The post-pubertal psychoses, schizophrenia and manic-depressive psychosis at the extremes of the pubertal age continuum, with contrasting excitability and biological treatment, are probably the result of continuous dietary deficiency, which has inactivated the expression of genes for myelin development and oligodendrocyte-related genes in their production of myelin. The beneficial effect of marine fat in both disorders, in other CNS disorders as well as in developmental dyslexia (DD) and ADHD among others, supports our usual diet is persistently deficient. We have neglected the similarity of our great brain to other mammals, and our marine heritage. Given the amount of marine fat needed to secure normal brain development and function is not known, nor the present dietary level, it seems unduly conjectural to postulate that a dietary deficiency in marine fat is causing brain dysfunction and death. However, all observations point in the same direction: our diet focusing on protein mainly, is deficient, the deficiency is most pronounced in maternal nutrition and in infancy.

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.

Functional lateralization of the sensorimotor cortex in patients with schizophrenia: effects of treatment with olanzapine

BACKGROUND

Earlier cross-sectional studies with functional magnetic resonance imaging (fMRI) in treated patients with schizophrenia have reported abnormalities of cortical motor processing, including reduced lateralization of primary sensory motor cortex. The objective of the present longitudinal study was to evaluate whether such cortical abnormalities represent state or trait phenomena of the disorder.

METHODS

Seventeen acutely ill, previously untreated patients were studied after 4 weeks and after 8 weeks of olanzapine therapy. Seventeen matched healthy subjects served as control subjects. All subjects underwent two fMRI scans 4 weeks apart during a visually paced motor task using a simple periodic block design. Functional magnetic resonance imaging data were analyzed in Statistical Parametric Mapping (SPM99). Region of interest analyses were used to determine a laterality quotient (an index of lateralization) of motor cortical regions.

RESULTS

The fMRI data indicated that patients had reduced activation of the primary sensory motor cortex at 4 weeks but not at 8 weeks; however, the laterality quotient in the primary sensory motor cortex was reduced in patients at both time points.

CONCLUSIONS

These results suggest that some cortical abnormalities during motor processing represent state phenomena, whereas reduced functional lateralization of the primary sensory motor cortex represents an enduring trait of schizophrenia.

Learning problems, delayed development, and puberty

Language-based learning disorders such as dyslexia affect millions of people, but there is little agreement as to their cause. New evidence from behavioral measures of the ability to hear tones in the presence of background noise indicates that the brains of affected individuals develop more slowly than those of their unaffected counterparts. In addition, it seems that brain changes occurring at approximately 10 years of age, presumably associated with puberty, may prematurely halt this slower-than-normal development when improvements would normally continue into adolescence. The combination of these ideas can account for a wide range of previous results, suggesting that delayed brain development, and its interaction with puberty, may be key factors contributing to learning problems.

Schizophrenia—an evolutionary enigma?

The term 'schizophrenia' refers to a group of disorders that have been described in every human culture. Two apparently well established findings have corroborated the need for an evolutionary explanation of these disorders: (1) cross-culturally stable incidence rates and (2) decreased fecundity of the affected individuals. The rationale behind this relates to the evolutionary paradox that susceptibility genes for schizophrenia are obviously preserved in the human genepool, despite fundamental reproductive disadvantages associated with the disorders. Some researchers have therefore proposed that a compensatory advantage must exist in people who are carriers of these genes or in their first-degree relatives. Such advantages were hypothesised to be outside the brain (e.g. greater resistance against toxins or infectious diseases), or within the social domain (e.g. schizotypal shamans, creativity). More specifically, T.J. Crow has suggested an evolutionary theory of schizophrenia that relates the disorders to an extreme of variation of hemispheric specialisation and the evolution of language due to a single gene mutation located on homologous regions of the sex chromosomes. None of the evolutionary scenarios does, however, fully account for the diversity of the symptomatology, nor does any one hypothesis acknowledge the objection that the mere prevalence of a disorder must not be confused with adaptation. In the present article, I therefore discuss the evolutionary hypotheses of schizophrenia, arguing that a symptom-based approach to psychotic disorders in evolutionary perspective may improve upon the existing models of schizophrenia.

Evolutionary perspectives on schizophrenia

The theory of evolution may be relevant to psychiatric disorders. Evolution reflects changes in genes throughout time. Thus, evolutionary forces can shape any phenotype that is genetically rooted and that possesses a long history. Schizophrenia is likely an ancient condition with a substantial genetic component. Since the 1960s, several researchers have applied evolutionary principles to the study of schizophrenia. In general, schizophrenia is either viewed as an evolutionary advantageous condition or as a disadvantageous byproduct of normal brain evolution. This paper reviews major evolutionary explanations--historical and current--that speculate on the possible origins of schizophrenia.

Our neglect of the normal variation is linked to a reluctance to accept multifactorial inheritance and the role of environment

One of the most surprising evolutionary discoveries is that wild species similar to human contain a vast reservoir of variability. Why are we persistently reluctant to discuss normal variation in brain structure and function and label any deviation pathological? Despite the failure of Mendelian Genetics to solve the genetic puzzle in psychiatry, we refuse to discuss multifactorial inheritance and the role of environmental factors. Rising living conditions (high protein diet) accelerate maturation, lower pubertal age, shift body-built toward more weight for height and cerebral excitability toward higher levels. Another environmental factor which has to be provided by diet is marine fat which our brain consists of. It normalizes brain function at all levels of excitability and possibly prevents psychotic episodes if adequately supplied. As part of Human Variation in Growth and Maturation, Schizophrenia and Manic-depressive psychosis are multifactorially inherited and share susceptibility loci. They are localized at the extremes of variation. Excitability, body-built, clinical picture and CNS finding accord with this, their phenotypic characteristics might prove valuable in a hunt for genes not common to both disorders.

Lateralized perceptual organization deficits on the global-local task in schizotypal personality disorder

Right and left hemisphere contributions to perceptual organization functions were examined using a divided-attention version of the global-local task in a sample of 21 unmedicated participants diagnosed with schizotypal personality disorder (SPD) and 20 controls. The SPD participants showed an abnormal global processing advantage. When the visual angle of the hierarchical stimuli was increased from 3 degrees to 9 degrees, the controls showed an increasing local processing advantage, but the SPD participants continued to show an abnormal global processing advantage. These findings suggest a local processing deficit on divided-attention versions of the global-local task in schizophrenia spectrum disorders. Female SPD participants, who had less severe interpersonal deficit symptoms, showed a more abnormal global processing advantage. Hemispheric and processing resource mechanisms that might explain these findings are discussed.

Manic depressive psychosis and schizophrenia are neurological disorders at the extremes of CNS maturation and nutritional disorders associated with a deficit in marine fat

The maturational theory of brain development comprises manic depressive psychosis and schizophrenia. It holds that the disorders are part of human diversity in growth and maturation, which explains their ubiquity, shared susceptibility genes and multifactorial inheritance. Rate of maturation and age at puberty are the genotype; the disorders are localized at the extremes with normality in between. This is based on the association between onset of puberty and the final regressive event, with pruning of 40% of excitatory synapses leaving the inhibitory ones fairly unchanged. This makes excitability, a fundamental property of nervous tissue, a distinguishing factor: the earlier puberty, the greater excitability--the later puberty, the greater deficit. Biological treatment supports deviation from the norm: neuroleptics are convulsant; antidepressives are anti-epiletogenic. There is an association between onset of puberty and body-build: early maturers are pyknic broad-built, late ones linearly leptosomic. This discrepancy is similar to that in the two disorders, supporting the theory that body-build is the phenotype. Standard of living is the environmental factor, which affects pubertal age and shifts the panorama of mental illness accordingly. Unnatural death has increased with antipsychotics. Other treatment is needed. PUFA deficit has been observed in RBC in both disorders and striking improvements with addition of minor amounts of PUFA. This supports that dietary deficit might cause psychotic development and that prevention is possible. Other neurological disorders also profit from PUFA, underlining a general deficit in the diet.

Recent advances in infant cognition: implications for long-chain polyunsaturated fatty acid supplementation studies

The assessment of cognitive function in early life has recently become an issue for consideration in long-chain polyunsaturated fatty acid (LC-PUFA) supplementation studies. This article reviews the various means by which such assessment has been done in past LC-PUFA supplementation studies and provides some background on recent advances in the measurement of infant cognition that may need to be considered when planning or designing future supplementation studies. These include (i) consideration of the specificity of LC-PUFA effects on cognition, (ii) inclusion of multiple tasks or levels of measurement as outcome measures, and (iii) a stronger emphasis on developmental processes in the design of such studies.

Imprinted genes, cognition and behaviour

The idea that genes can influence behavioural predispositions and their underlying psychological determinants is becoming increasingly tractable. In this article, recent findings are reviewed on a special type of inheritance, related to the transmission of traits via what have been termed 'imprinted' genes. In imprinted genes one allele is silenced according to its parental origin. This results in the inheritance of traits down the maternal or paternal line, in contrast to the more frequent mode of inheritance that is indifferent to the parental origin of the allele. Drawing on the advances made possible by combining the approaches of cognitive neuropsychology, behavioural neuroscience and contemporary molecular genetics, the detailed evidence for imprinted effects on behavioural and cognitive phenotypes is considered, focusing on findings from mental disorders, Turner's syndrome and experimental work in animal models. As prevailing evolutionary theories stress an essential antagonistic role of imprinted effects, these data might link such apparently diverse issues as neurodevelopment and the vulnerability to mental disease with the 'battle of the sexes', as joined at the level of cognitive and behavioural functioning.

Commentary on Annett, Yeo et al., Klar, Saugstad and Orr: cerebral asymmetry, language and psychosis--the case for a Homo sapiens-specific sex-linked gene for brain growth

Annett, Yeo et al. and Klar have each proposed theories that relate the genetics of cerebral lateralization to predisposition to psychosis. These theories are considered in relation to the central paradox that psychosis is associated with a substantial biological disadvantage. Annett's heterozygote advantage hypothesis critically identified lateralization as a major determinant of ability, but it appears that what is inherited is degrees (as suggested by Yeo et al.) rather than (or as well as) direction of lateralization. Relative hand skill has been shown (Crow, T.J., Crow, L.R., Done, D.J., Leask, S.J., 1998. Relative hand skill predicts academic ability: global deficits at the point of hemispheric indecision. Neuropsychologia 36, 1275-1282.) to be a powerful predictor (interacting with sex) of academic ability but the greatest region of vulnerability (that includes reading disability and predisposition to psychosis) is close to the point of equal hand skill ('hemispheric indecision'). In contrast with Annett's single locus, Yeo's polygenic and Klar's strand-segregation hypotheses, each of which postulates an autosomal locus or loci, the hypothesis of a single gene for asymmetry located in a sex-specific region of homology on both X and Y chromosomes can account for sex differences, as observed in age of onset, and premorbid precursors of psychosis, as well as differences in the general population in relation to degrees of hand skill, verbal ability and cerebral asymmetry. The evolutionarily recent transposition to, and subsequent paracentric inversion in, the Y chromosome short arm of a 4-Mb block from Xq21.3 (the proximal long arm of the X) are candidates for speciation events in the lineage that led to Homo sapiens. A gene associated with a range of variation (that may be due to a high mutation site, or perhaps to epigenetic modification) on the Y that overlaps with, but differs quantitatively from, that on the X may explain the sex differences associated with psychosis, and may be relevant to its persistence. Such a gene could be the principal determinant in Man of the rate of brain growth, as suggested by Saugstad and by the findings of a recent study of adolescent onset psychosis (James, A., Crow, T.J., Renowden, S., Wardell, M., Smith, D.M., Anslow, P., in press. Is the course of brain development in schizophrenia delayed? Evidence from onsets in adolescence. Schizophr. Res.).