Gender differences in the left inferior frontal gyrus in normal children

Univariate and multivariate sex differences and similarities in gray matter volume within essential language-processing areas

BACKGROUND

Sex differences in language-related abilities have been reported. It is generally assumed that these differences stem from a different organization of language in the brains of females and males. However, research in this area has been relatively scarce, methodologically heterogeneous and has yielded conflicting results.

METHODS

Univariate and multivariate sex differences and similarities in gray matter volume (GMVOL) within 18 essential language-processing brain areas were assessed in a sex-balanced sample (N = 588) of right-handed young adults. Univariate analyses involved location, spread, and shape comparisons of the females' and males' distributions and were conducted with several robust statistical methods able to quantify the size of sex differences and similarities in a complementary way. Multivariate sex differences and similarities were estimated by the same methods in the continuous scores provided by two distinct multivariate procedures (logistic regression and a multivariate analog of the Wilcoxon-Mann-Whitney test). Additional analyses were addressed to compare the outcomes of these two multivariate analytical strategies and described their structure (that is, the relative contribution of each brain area to the multivariate effects).

RESULTS

When not adjusted for total intracranial volume (TIV) variation, "large" univariate sex differences (males > females) were found in all 18 brain areas considered. In contrast, "small" differences (females > males) in just two of these brain areas were found when controlling for TIV. The two multivariate methods tested provided very similar results. Multivariate sex differences surpassed univariate differences, yielding "large" differences indicative of larger volumes in males when calculated from raw GMVOL estimates. Conversely, when calculated from TIV-adjusted GMVOL, multivariate differences were "medium" and indicative of larger volumes in females. Despite their distinct size and direction, multivariate sex differences in raw and TIV-adjusted GMVOL shared a similar structure and allowed us to identify the components of the SENT_CORE network which more likely contribute to the observed effects.

CONCLUSIONS

Our results confirm and extend previous findings about univariate sex differences in language-processing areas, offering unprecedented evidence at the multivariate level. We also observed that the size and direction of these differences vary quite substantially depending on whether they are estimated from raw or TIV-adjusted GMVOL measurements.

Structural networking of the developing brain: from maturation to neurosurgical implications

Modern neuroscience agrees that neurological processing emerges from the multimodal interaction among multiple cortical and subcortical neuronal hubs, connected at short and long distance by white matter, to form a largely integrated and dynamic network, called the brain "connectome." The final architecture of these circuits results from a complex, continuous, and highly protracted development process of several axonal pathways that constitute the anatomical substrate of neuronal interactions. Awareness of the network organization of the central nervous system is crucial not only to understand the basis of children's neurological development, but also it may be of special interest to improve the quality of neurosurgical treatments of many pediatric diseases. Although there are a flourishing number of neuroimaging studies of the connectome, a comprehensive vision linking this research to neurosurgical practice is still lacking in the current pediatric literature. The goal of this review is to contribute to bridging this gap. In the first part, we summarize the main current knowledge concerning brain network maturation and its involvement in different aspects of normal neurocognitive development as well as in the pathophysiology of specific diseases. The final section is devoted to identifying possible implications of this knowledge in the neurosurgical field, especially in epilepsy and tumor surgery, and to discuss promising perspectives for future investigations.

Sex differences in neural processing of speech in neonates

The large majority of studies shows that girls develop their language skills faster than boys in the first few years of life. Are girls born with this advantage in language development? The present study used fNIRS in neonates to investigate sex differences in neural processing of speech within the first days of life. We found that speech stimuli elicited significantly more brain activity than non-speech stimuli in both groups of male and female neonates. However, whereas girls showed significant HbO changes to speech stimuli only within the left hemisphere, boys exhibited simultaneous neural activations in both hemispheres, with a larger and more significant fronto-temporal cluster in the right hemisphere. Furthermore, in boys, the variation in time-to-peak latencies was considerably greater than in girls. These findings suggest an earlier maturation of language-related brain areas in girls and highlight the importance of sex-specific investigations of neural language networks in infants.

The beauty of diversity in cognitive neuroscience: The case of sex-related effects in language production networks

Over the past few decades, several studies have focused on potential sex-related differences in the trajectories of language development and functioning. From a behavioral point of view, the available literature shows controversial results: differences between males and females in language production tasks may not always be detectable and, even when they are, are potentially biased by sociological and educational confounding factors. The problem regarding potential sex-related differences in language production has also been investigated at the neural level, again with controversial results. The current minireview focuses on studies assessing sex-related differences in the neural networks of language production. After providing a theoretical framework of language production, it is shown that the few available investigations have provided mixed results. The major reasons for discrepant findings are discussed with theoretical and methodological implications for future studies.

Sex differences in the intrinsic reading neural networks of Chinese children

Sex differences in reading performance have been considered a relatively stable phenomenon. However, there is no general agreement about their neural basis, which might be due to that sex differences are largely influenced by age. This paper focuses on the sex differences in the reading-related neural network of Chinese children and its interaction with age. We also attempt to predict reading abilities based on neural network. Fifty-three boys and 56 girls (8.2–14.6 years of age) were recruited. We collected their resting-state fMRI and behavioural data. Restricted sex differences were found in the resting-state reading neural network compared to extensive age by sex interaction effect. Specifically, the interactions between sex and age indicated that with increasing age, girls showed greater connectivity strength between visual orthographic areas and other brain areas within the reading network, while boys showed an opposite trend. After controlling age, the prediction models of reading performance for the girls mainly included interhemispheric connections, while the intrahemispheric connections (particularly the phonological route) mainly contributed to predicting the reading ability for boys. Taken together, these findings suggest that sex differences in reading neural networks are modulated by age. Partialling out age, boys and girls also show the stable sex differences in relationship between reading neural circuit and reading behaviour.

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Sex differences in reading neural networks are modulated by age.

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Girls’ RSFCs within reading neural networks increase with age, contrary to boys.

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Intra- and interhemispheric RSFCs predict the reading ability of boys and girls, respectively.

Forgiveness Mediates the Relationship Between Middle Frontal Gyrus Volume and Clinical Symptoms in Adolescents

Dispositional forgiveness is positively associated with many facets of wellbeing and has protective implications against depression and anxiety in adolescents. However, little work has been done to examine neurobiological aspects of forgiveness as they relate to clinical symptoms. In order to better understand the neural mechanisms supporting the protective role of forgiveness in adolescents, the current study examined the middle frontal gyrus (MFG), which comprises the majority of the dorsolateral prefrontal cortex (DLPFC) and is associated with cognitive regulation, and its relationship to forgiveness and clinical symptoms in a sample of healthy adolescents. In this cross-sectional study (n = 64), larger MFG volume was significantly associated with higher self-reported dispositional forgiveness scores and lower levels of depressive and anxiety symptoms. Forgiveness mediated the relationship between MFG volume and both depressive and anxiety symptom levels. The mediating role of forgiveness in the relationship between MFG volume and clinical symptoms suggests that one way that cognitive regulation strategies supported by this brain region may improve adolescent mental health is via increasing a capacity for forgiveness. The present study highlights the relevance of forgiveness to neurobiology and their relevance to emotional health in adolescents. Future longitudinal studies should focus on the predictive quality of the relationship between forgiveness, brain volume and clinical symptoms and the effects of forgiveness interventions on these relationships.

Sex differences in the effects on the brain of early cognitive stimulation

A study by Farah and colleagues (2021) of the effects on the adult brain of a cognitively intense early childhood experience revealed large effects, but primarily in the brains of male subjects, while causing equally large increases of childhood IQ in males and females. The present analysis advances and tests a conjecture about one reason for the sex difference. Among the control subjects, the summed volume of four small regions of the cortex, associated with language and cognitive processes, is proportionally larger in females. Based on these four regions, a new brain measure, the "cognitive ratio", is defined. The cognitive ratio is found to be strongly and negatively correlated with variations in the effect of the early experience on brain volume among the males, and explains a large proportion of the difference between males and females, as well as the greater sensitivity of the male brains to that experience.

Cerebral White Matter Myelination and Relations to Age, Gender, and Cognition: A Selective Review

White matter makes up about fifty percent of the human brain. Maturation of white matter accompanies biological development and undergoes the most dramatic changes during childhood and adolescence. Despite the advances in neuroimaging techniques, controversy concerning spatial, and temporal patterns of myelination, as well as the degree to which the microstructural characteristics of white matter can vary in a healthy brain as a function of age, gender and cognitive abilities still exists. In a selective review we describe methods of assessing myelination and evaluate effects of age and gender in nine major fiber tracts, highlighting their role in higher-order cognitive functions. Our findings suggests that myelination indices vary by age, fiber tract, and hemisphere. Effects of gender were also identified, although some attribute differences to methodological factors or social and learning opportunities. Findings point to further directions of research that will improve our understanding of the complex myelination-behavior relation across development that may have implications for educational and clinical practice.

Investigating Sexual Dimorphism of Human White Matter in a Harmonized, Multisite Diffusion Magnetic Resonance Imaging Study

Axonal myelination and repair, critical processes for brain development, maturation, and aging, remain controlled by sexual hormones. Whether this influence is reflected in structural brain differences between sexes, and whether it can be quantified by neuroimaging, remains controversial. Diffusion-weighted magnetic resonance imaging (dMRI) is an in vivo method that can track myelination changes throughout the lifespan. We utilize a large, multisite sample of harmonized dMRI data (n = 551, age = 9-65 years, 46% females/54% males) to investigate the influence of sex on white matter (WM) structure. We model lifespan trajectories of WM using the most common dMRI measure fractional anisotropy (FA). Next, we examine the influence of both age and sex on FA variability. We estimate the overlap between male and female FA and test whether it is possible to label individual brains as male or female. Our results demonstrate regionally and spatially specific effects of sex. Sex differences are limited to limbic structures and young ages. Additionally, not only do sex differences diminish with age, but tracts within each subject become more similar to one another. Last, we show the high overlap in FA between sexes, which implies that determining sex based on WM remains open.

Influence of the hypothalamus-pituitary-gonadal axis reactivation and corresponding surging sex hormones on the amplitude of low-frequency oscillations in early pubertal girls: A resting state fMRI study

BACKGROUND

There has been a myriad of neuroimaging studies that have suggested that pubertal stages and sex steroid fluctuations contribute to pubertal brain maturation. Investigations on the influence of hypothalamus-pituitary-gonadal (HPG) axis reactivation and the correlated elevated sex hormones on brain maturation have not unraveled these interactions to date. Here, we aimed to explore the impact of the reactivated HPG axis on spontaneous brain activity changes, by analyzing the amplitude of low-frequency fluctuation (ALFF) in developing girls aged 8-11 years old.

METHODS

The gonadotropin-releasing hormone (GnRH) stimulation test was used to determine the HPG axis status and categorize subjects into two groups (HPG+ or HPG- group). Intelligence quotient (IQ) and the parent-rated Child Behavior Checklist (CBCL) were used to evaluate cognitive and behavioral performance. Two-sample t-tests were used to compare intergroup differences, the relations between brain areas' activities, age and hormonal levels were conducted by Pearson or Spearman correlation analyses.

RESULTS

Compared with the HPG- group, the HPG+ group showed decreased ALFF values in the left superior temporal gyrus (STG) but increased ALFF values in the right superior frontal gyrus (SFG). In addition, in the HPG+ group, prolactin (PRL) levels were positively correlated with ALFF values in the right SFG, and there was significant negative correlation between ALFF values in the left STG and CBCL activities scores.

LIMITATIONS

Due to the cross-sectional design of the present study, further study is needed to determine the relationships between age, reawakening of the HPG axis and related sex hormones and spontaneous brain activity change.

CONCLUSIONS

These findings suggested that the reactivated HPG axis and elevated PRL level could affect changes in brain activity and this effect may be the neuroendocrine basis of mood, cognition, and social behavior changes in early pubertal girls.

Sex differences in early communication development: behavioral and neurobiological indicators of more vulnerable communication system development in boys

Perhaps due to different roles they have had in social groups during evolution, men and women differ in their verbal abilities. These differences are also (if not even more) present in children, both in the course of typical and pathological development. Beside the fact that girls have a well-documented advantage in early language development, almost all developmental disorders primarily affecting communication, speech, and language skills are more frequent in boys. The sex-related difference in the prevalence of these disorders is especially pronounced in autism spectrum disorder (1 girl for each 4-5 boys is affected). The aim of this review is to present the sex differences in typical communication and language development and in the prevalence of communication-related neurodevelopmental disorders. Also, a special focus is put on data from the field of neuroscience that might provide insight into the neurobiological mechanisms that can add to the understanding of this phenomenon. We argue that the functional organization of the female brain gives women an inherent advantage in the acquisition of communication and language system over men.

Sex differences in early communication development: behavioral and neurobiological indicators of more vulnerable communication system development in boys

Perhaps due to different roles they have had in social groups during evolution, men and women differ in their verbal abilities. These differences are also (if not even more) present in children, both in the course of typical and pathological development. Beside the fact that girls have a well-documented advantage in early language development, almost all developmental disorders primarily affecting communication, speech, and language skills are more frequent in boys. The sex-related difference in the prevalence of these disorders is especially pronounced in autism spectrum disorder (1 girl for each 4-5 boys is affected). The aim of this review is to present the sex differences in typical communication and language development and in the prevalence of communication-related neurodevelopmental disorders. Also, a special focus is put on data from the field of neuroscience that might provide insight into the neurobiological mechanisms that can add to the understanding of this phenomenon. We argue that the functional organization of the female brain gives women an inherent advantage in the acquisition of communication and language system over men.

Atypical PT anatomy in children with autism spectrum disorder with expressive language deficits

Deficits in communication are a core feature of autism spectrum disorder (ASD), however, structural language abilities are highly variable, ranging from minimally verbal to superior linguistic skills. Differences in the anatomy of cortical language regions, including anterior and posterior areas, have been found in ASD. It remains unclear, however, if anatomical differences distinguish individuals with impaired expressive language from those without such deficits. In addition, anatomical differences have not been explored in children with extremely low expressive language. This study included 34 boys with ASD, 7-11 years old, including an expressive language impaired group (n = 17) and an average-high language group (n = 17). The language impaired group was subdivided into a low (n = 9) and extremely low (n = 8) language subgroup for exploratory analyses to determine whether children with ASD with extremely low expressive language abilities exhibit distinct anatomy. Gray matter volume of the pars triangularis, pars opercularis, and planum temporale (PT) were measured on MRIs. PT volume was smaller in the ASD group with expressive language impairment relative to those without language deficits. The right PT volume was also positively correlated with language scores. The exploratory analyses revealed differences in the left PT, with smaller volume in the extremely low language subgroup, relative to the average and moderately low language groups. Results suggest that smaller PT volumes in both hemispheres are associated with severe language impairments in ASD. The PT may therefore, be a biomarker of language outcome in young children with ASD, with more studies of PT anatomy necessary.

Exploring folding patterns of infant cerebral cortex based on multi-view curvature features: Methods and applications

The highly convoluted cortical folding of the human brain is intriguingly complex and variable across individuals. Exploring the underlying representative patterns of cortical folding is of great importance for many neuroimaging studies. At term birth, all major cortical folds are established and are minimally affected by the complicated postnatal environments; hence, neonates are the ideal candidates for exploring early postnatal cortical folding patterns, which yet remain largely unexplored. In this paper, we propose a novel method for exploring the representative regional folding patterns of infant brains. Specifically, first, multi-view curvature features are constructed to comprehensively characterize the complex characteristics of cortical folding. Second, for each view of curvature features, a similarity matrix is computed to measure the similarity of cortical folding in a specific region between any pair of subjects. Next, a similarity network fusion method is adopted to nonlinearly and adaptively fuse all the similarity matrices into a single one for retaining both shared and complementary similarity information of the multiple characteristics of cortical folding. Finally, based on the fused similarity matrix and a hierarchical affinity propagation clustering approach, all subjects are automatically grouped into several clusters to obtain the representative folding patterns. To show the applications, we have applied the proposed method to a large-scale dataset with 595 normal neonates and discovered representative folding patterns in several cortical regions, i.e., the superior temporal gyrus (STG), inferior frontal gyrus (IFG), precuneus, and cingulate cortex. Meanwhile, we have revealed sex difference in STG, IFG, and cingulate cortex, as well as hemispheric asymmetries in STG and cingulate cortex in terms of cortical folding patterns. Moreover, we have also validated the proposed method on a public adult dataset, i.e., the Human Connectome Project (HCP), and revealed that certain major cortical folding patterns of adults are largely established at term birth.

What has sex got to do with it? The role of hormones in the transgender brain

Sex differences and hormonal effects in presumed cisgender individuals have been well-studied and support the concept of a mosaic of both male and female "characteristics" in any given brain. Gonadal steroid increases and fluctuations during peri-puberty and across the reproductive lifespan influence the brain structure and function programmed by testosterone and estradiol exposures in utero. While it is becoming increasingly common for transgender and gender non-binary individuals to block their transition to puberty and/or use gender-affirming hormone therapy (GAHT) to obtain their desired gender phenotype, little is known about the impact of these manipulations on brain structure and function. Using sex differences and the effects of reproductive hormones in cisgender individuals as the backdrop, we summarize here the existing nascent neuroimaging and behavioral literature focusing on potential brain and cognitive differences in transgender individuals at baseline and after GAHT. Research in this area has the potential to inform our understanding of the developmental origins of gender identity and sex difference in response to gonadal steroid manipulations, but care is needed in our research questions and methods to not further stigmatize sex and gender minorities.

A systematic literature review of sex differences in childhood language and brain development

The extent of sex differences in childhood language development is unclear. We conducted a systematic literature review synthesizing results from studies examining sex differences in brain structure and function relevant to language development during childhood. We searched PubMed and Scopus databases, and this returned a total of 46 published studies meeting criteria for inclusion that directly examined sex differences in brain development relevant to language function in children. The results indicate that: (a) sex differences in brain structure or function do not necessarily lead to differences in language task performance; (b) evidence for sex differences in brain and language development are limited; (c) when present, sex differences often interact with a variety of factors such as age and task. Overall, the magnitude of sexual dimorphism of brain developmental trajectories associated with language is not as significant as previously thought. Sex differences were found, however, in studies employing tighter age ranges. This suggests that sex differences may be more prominent during certain developmental stages but are negligible in other stages, likely due to different rates of maturation between the sexes. More research is needed to improve our understanding of how sex differences may arise due to the influence of sex hormones and developmental stages, and how these differences may lead to differences in various language task performance. These studies are expected to provide normative information that may be used in studies examining neurodevelopmental disorders that frequently affect more males than females, and also often affect language development.

Transient sex differences during adolescence on auditory perceptual tasks

Many perceptual abilities differ between the sexes. Because these sex differences have been documented almost exclusively in adults, they have been attributed to sex-specific neural circuitry that emerges during development and is maintained in the mature perceptual system. To investigate whether behavioral sex differences in perception can also have other origins, we compared performance between males and females ranging in age from 8 to 30 years on auditory temporal-interval discrimination and tone-in-noise detection tasks on which there are no sex differences in adults. If sex differences in perception arise only from the establishment and subsequent maintenance of sex-specific neural circuitry, there should be no sex differences during development on these tasks. In contrast, sex differences emerged in adolescence but resolved by adulthood on two of the six conditions, with signs of a similar pattern on a third condition. In each case, males reached mature performance earlier than females, resulting in a sex difference in the interim. These results suggest that sex differences in perception may arise from differences in the maturational timing of common circuitry used by both sexes. They also imply that sex differences in perceptual abilities may be more prevalent than previously thought based on adult data alone.

Methods on Skull Stripping of MRI Head Scan Images-a Review

The high resolution magnetic resonance (MR) brain images contain some non-brain tissues such as skin, fat, muscle, neck, and eye balls compared to the functional images namely positron emission tomography (PET), single photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI) which usually contain relatively less non-brain tissues. The presence of these non-brain tissues is considered as a major obstacle for automatic brain image segmentation and analysis techniques. Therefore, quantitative morphometric studies of MR brain images often require a preliminary processing to isolate the brain from extra-cranial or non-brain tissues, commonly referred to as skull stripping. This paper describes the available methods on skull stripping and an exploratory review of recent literature on the existing skull stripping methods.

Can age at sexual maturity act as a predictive biomarker for prodromal negative symptoms?

BACKGROUND

Puberty and reproductive hormones have been identified as having a potential role in schizophrenia. Earlier reports have suggested associations between later age at puberty and schizophrenia in males. Similarly, associations have been reported between testosterone levels and psychotic symptoms. In this report, we examined the association between age at puberty and prodromal symptoms of psychosis.

METHODS

58 child or adolescent family members of individuals with schizophrenia were interviewed using the Scale of Prodromal Symptoms and the Tanner Maturational Scale. Age at Tanner pubertal stage was determined and regression analyses were used to explore associations between prodromal symptoms and age at puberty.

RESULTS

Among males, delayed age at puberty was associated with greater severity of prodromal symptoms; the association between negative prodromal symptoms and delayed age was significant (p=0.001). In females, the association was not statistically significant.

CONCLUSIONS

Our results suggest that delayed age at puberty may be associated with negative prodromal symptoms of schizophrenia in males. Our findings suggest that delayed age at puberty could potentially be a predictive biomarker for psychopathology in males at risk for schizophrenia.

Glutamatergic neurometabolites during early abstinence from chronic methamphetamine abuse

BACKGROUND

The acute phase of abstinence from methamphetamine abuse is critical for rehabilitation success. Proton magnetic resonance spectroscopy has detected below-normal levels of glutamate+glutamine in anterior middle cingulate of chronic methamphetamine abusers during early abstinence, attributed to abstinence-induced downregulation of the glutamatergic systems in the brain. This study further explored this phenomenon.

METHODS

We measured glutamate+glutamine in additional cortical regions (midline posterior cingulate, midline precuneus, and bilateral inferior frontal cortex) putatively affected by methamphetamine. We examined the relationship between glutamate+glutamine in each region with duration of methamphetamine abuse as well as the depressive symptoms of early abstinence. Magnetic resonance spectroscopic imaging was acquired at 1.5 T from a methamphetamine group of 44 adults who had chronically abused methamphetamine and a control group of 23 age-, sex-, and tobacco smoking-matched healthy volunteers. Participants in the methamphetamine group were studied as inpatients during the first week of abstinence from the drug and were not receiving treatment.

RESULTS

In the methamphetamine group, small but significant (5-15%, P<.05) decrements (vs control) in glutamate+glutamine were observed in posterior cingulate, precuneus, and right inferior frontal cortex; glutamate+glutamine in posterior cingulate was negatively correlated (P<.05) with years of methamphetamine abuse. The Beck Depression Inventory score was negatively correlated (P<.005) with glutamate+glutamine in right inferior frontal cortex.

CONCLUSIONS

Our findings support the idea that glutamatergic metabolism is downregulated in early abstinence in multiple cortical regions. The extent of downregulation may vary with length of abuse and may be associated with severity of depressive symptoms emergent in early recovery.

A meta-analysis of sex differences in human brain structure

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This is the first meta-analysis of sex differences in the typical human brain.

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Regional sex differences overlap with areas implicated in psychiatric conditions.

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The amygdala, hippocampus, planum temporale and insula display sex differences.

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On average, males have larger brain volumes than females.

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Most articles providing sex differences in volume are in the ‘mature’ category.

The prevalence, age of onset, and symptomatology of many neuropsychiatric conditions differ between males and females. To understand the causes and consequences of sex differences it is important to establish where they occur in the human brain. We report the first meta-analysis of typical sex differences on global brain volume, a descriptive account of the breakdown of studies of each compartmental volume by six age categories, and whole-brain voxel-wise meta-analyses on brain volume and density. Gaussian-process regression coordinate-based meta-analysis was used to examine sex differences in voxel-based regional volume and density. On average, males have larger total brain volumes than females. Examination of the breakdown of studies providing total volumes by age categories indicated a bias towards the 18–59 year-old category. Regional sex differences in volume and tissue density include the amygdala, hippocampus and insula, areas known to be implicated in sex-biased neuropsychiatric conditions. Together, these results suggest candidate regions for investigating the asymmetric effect that sex has on the developing brain, and for understanding sex-biased neurological and psychiatric conditions.

1H MRSI of middle frontal gyrus in pediatric ADHD

Neuroimaging studies in multiple modalities have implicated the left or right dorsolateral prefrontal cortex (here, middle frontal gyrus) in attentional functions, in ADHD, and in dopamine agonist treatment of ADHD. The far lateral location of this cortex in the brain, however, has made it difficult to study with magnetic resonance spectroscopy (MRS). We used the smaller voxel sizes of the magnetic resonance spectroscopic imaging (MRSI) variant of MRS, acquired at a steep coronal-oblique angle to sample bilateral middle frontal gyrus in 13 children and adolescents with ADHD and 13 age- and sex-matched healthy controls. Within a subsample of the ADHD patients, aspects of attention were also assessed with the Trail Making Task. In right middle frontal gyrus only, mean levels of N-acetyl-aspartate + N-acetyl-aspartyl-glutamate (tNAA), creatine + phosphocreatine (Cr), choline-compounds (Cho), and myo-inositol (mI) were significantly lower in the ADHD than in the control sample. In the ADHD patients, lower right middle frontal Cr was associated with worse performance on Trails A and B (focused attention, concentration, set-shifting), while the opposite relationship held true for the control group on Trails B. These findings add to evidence implicating right middle frontal cortex in ADHD. Lower levels of these multiple species may reflect osmotic adjustment to elevated prefrontal cortical perfusion in ADHD and/or a previously hypothesized defect in astrocytic production of lactate in ADHD resulting in decelerated energetic metabolism (Cr), membrane synthesis (Cho, mI), and acetyl-CoA substrate for NAA synthesis. Lower Cr levels may indicate attentional or executive impairments.

Volumetric analysis of medial temporal lobe structures in brain development from childhood to adolescence

Puberty is an important stage of development as a child's sexual and physical characteristics mature because of hormonal changes. To better understand puberty-related effects on brain development, we investigated the magnetic resonance imaging (MRI) data of 306 subjects from 4 to 18 years of age. Subjects were grouped into before and during puberty groups according to their sexual maturity levels measured by the puberty scores. An appearance model-based automatic segmentation method with patch-based local refinement was employed to segment the MRI data and extract the volumes of medial temporal lobe (MTL) structures including the amygdala (AG), the hippocampus (HC), the entorhinal/perirhinal cortex (EPC), and the parahippocampal cortex (PHC). Our analysis showed age-related volumetric changes for the AG, HC, right EPC, and left PHC but only before puberty. After onset of puberty, these volumetric changes then correlate more with sexual maturity level, as measured by the puberty score. When normalized for brain volume, the volumes of the right HC decrease for boys; the volumes of the left HC increase for girls; and the volumes of the left and right PHC decrease for boys. These findings suggest that the rising levels of testosterone in boys and estrogen in girls might have opposite effects, especially for the HC and the PHC. Our findings on sex-specific and sexual maturity-related volumes may be useful in better understanding the MTL developmental differences and related learning, memory, and emotion differences between boys and girls during puberty.

Hippocampal asymmetry: differences in structures and functions

The structural asymmetry of bilateral hippocampus in mammals has been well recognized. Recent findings highlighted the accompanying functional asymmetries, as well as the molecular differences of the hippocampus. The present paper summarized these recent advances in understanding the hippocampal asymmetries at molecular, circuit and functional levels. Additionally, the addition of new neurons to the hippocampal circuit during adulthood is asymmetrical. We conclude that these differences in molecules and structures of bilateral hippocampus determined the variances in functionality between the two sides.

Sex differences in brain maturation as measured using event-related potentials

Little is known about how sex influences functional brain maturation. The current study investigated sex differences in the maturation of event-related potential (ERP) amplitudes during an auditory oddball task (N = 170; age = 6-17 years). Performance improved with age. N200 amplitude declined with age: parietal sites showed earlier development than temporal and frontal locations. Girls showed greater bilateral frontal P300 amplitude development, approaching the higher values observed in boys during childhood. After controlling for age, right frontal P300 amplitude was associated with reaction time in girls. The findings demonstrate sex differences in ERP maturation in line with behavioral and neuroimaging studies.

Nucleus Accumbens Volume Is Associated with Frequency of Alcohol Use among Juvenile Justice-Involved Adolescents

Differential neural development of structures associated with reward and control systems may underlie risky behavior in adolescence. The nucleus accumbens and orbitofrontal cortex (OFC) have been implicated in substance use behavior, although structural studies have yet to explore specific relationships between nucleus accumbens and OFC volumes and alcohol use in adolescence. High resolution structural MRI scans and assessments of recent alcohol use and lifetime substance use were collected in a sample of 168 juvenile justice-involved adolescents to explore whether gray matter volumes were associated with past 3-month quantity and frequency of alcohol use. Gray matter volumes were not associated with average quantity of alcohol use. Accumbens volume was positively associated with past 3-month frequency of drinking, and OFC volume was negatively associated with drinking frequency. Results may suggest that structural differences in regions related to reward and control processing may contribute to risk behavior in adolescence.

Proton magnetic resonance spectroscopy and thought disorder in childhood schizophrenia

OBJECTIVE

Although magnetic resonance spectroscopy has identified metabolic abnormalities in adult and childhood schizophrenia, no prior studies have investigated the relationship between neurometabolites and thought disorder. This study examined this association in language-related brain regions using proton magnetic resonance spectroscopic imaging ((1)H MRSI).

METHOD

MRSI was acquired bilaterally from 28 youth with childhood-onset schizophrenia and 34 healthy control subjects in inferior frontal, middle frontal, and superior temporal gyri at 1.5T and short echo time (TR/TE = 1500/30 ms). CSF-corrected "total NAA" (tNAA; N-acetyl-aspartate + N-acetyl-aspartyl-glutamate), glutamate + glutamine (Glx), creatine + phosphocreatine (Cr + PCr), choline compounds (Cho), and myo-inositol (mI) were assayed in manually drawn regions-of-interest partitioned into gray matter, white matter, and CSF and then coregistered with MRSI. Speech samples of all subjects were coded for thought disorder.

RESULTS

In the schizophrenia group, the severity of formal thought disorder correlated significantly with tNAA in the left inferior frontal and superior temporal gyri and with Cr + PCr in left superior temporal gyrus.

CONCLUSIONS

Neurometabolite concentrations in language-related brain regions are associated with thought disorder in childhood-onset schizophrenia.

Functional development of fronto-striato-parietal networks associated with time perception

Compared to our understanding of the functional maturation of executive functions, little is known about the neurofunctional development of perceptive functions. Time perception develops during late adolescence, underpinning many functions including motor and verbal processing, as well as late maturing higher order cognitive skills such as forward planning and future-related decision making. Nothing, however, is known about the neurofunctional changes associated with time perception from childhood to adulthood. Using functional magnetic resonance imaging we explored the effects of age on the brain activation and functional connectivity of 32 male participants from 10 to 53 years of age during a time discrimination task that required the discrimination of temporal intervals of seconds differing by several hundred milliseconds. Increasing development was associated with progressive activation increases within left lateralized dorsolateral and inferior fronto-parieto-striato-thalamic brain regions. Furthermore, despite comparable task performance, adults showed increased functional connectivity between inferior/dorsolateral interhemispheric fronto-frontal activation as well as between inferior fronto-parietal regions compared with adolescents. Activation in caudate, specifically, was associated with both increasing age and better temporal discrimination. Progressive decreases in activation with age were observed in ventromedial prefrontal cortex, limbic regions, and cerebellum. The findings demonstrate age-dependent developmentally dissociated neural networks for time discrimination. With increasing age there is progressive recruitment of later maturing left hemispheric and lateralized fronto-parieto-striato-thalamic networks, known to mediate time discrimination in adults, while earlier developing brain regions such as ventromedial prefrontal cortex, limbic and paralimbic areas, and cerebellum subserve fine-temporal processing functions in children and adolescents.

10-year cognition in preterms after random assignment to fatty acid supplementation in infancy

OBJECTIVE

To test the hypothesis that long-chain polyunsaturated fatty acid (LCPUFA) supplementation in infancy would improve cognition into later childhood (after 9 years) at both general and specific levels.

METHODS

A comprehensive cognitive battery was completed by 107 formerly preterm infants (mean age: 128 months). As infants, they had been assigned randomly to receive LCPUFA-supplemented (N = 50) or control (N = 57) formula, between birth and 9 months; the docosahexaenoic acid level (DHA) in the supplemented formulas was 0.5%. In addition to randomized comparisons, we planned supplementary analyses to examine the effects of both gender and feeding group (those receiving some maternal breast milk versus those receiving none).

RESULTS

There were no significant differences between randomized diet groups on any cognitive measure. There was significant interaction between gender and supplementation; girls only showed beneficial effects of LCPUFAs on literacy. Significant interaction also occurred between feeding group and supplementation; increases of 0.7 SD in verbal IQ, full-scale IQ, and memory scores were found for the LCPUFA group, but only for infants who received only formula and no maternal breast milk.

CONCLUSIONS

The results of this post-9-year cognitive follow-up study in a randomized trial of LCPUFA-supplemented formula for preterm infants suggest no overall group effects but indicate that gender-specific and diet-specific effects may exist. The data provide some evidence that LCPUFAs are a key factor in the cognitive benefits of breast milk. Caution is advised in data interpretation because of the small groups used.

Gender differences in language and motor-related fibers in a population of healthy preterm neonates at term-equivalent age: a diffusion tensor and probabilistic tractography study

BACKGROUND AND PURPOSE

Sex differences in white matter structure are controversial. In this MR imaging study, we aimed to investigate possible sex differences in language and motor-related tracts in healthy preterm neonates by using DTI and probabilistic tractography.

MATERIALS AND METHODS

Thirty-eight preterm neonates (19 boys and 19 girls, age-matched), healthy at term-equivalent age and at 12 months were included. TBV was measured individually. Probabilistic tractography provided tract volumes, relative tract volumes (volume normalized to TBV), FA, MD, and λ(⊥) in the SLF, in the TRs, and in the CSTs. Data were compared by using independent t tests, and Bonferroni corrections were performed to adjust for multiple comparisons.

RESULTS

We showed that healthy preterm boys had larger TBV than girls. However, girls had statistically significantly larger relative tract volumes than boys bilaterally in the parieto-temporal SLF, and in the left CST. Moreover, in the left parieto-temporal SLF, a trend toward lower MD and λ(⊥) was observed in females.

CONCLUSIONS

Structural sex differences were found in preterm neonates at term-equivalent age in both sides of the parieto-temporal SLF and in the left CST. Further studies are necessary to investigate whether these structural differences are related to later sex differences in language skills and handedness or to the effect of prematurity.

Normative development of white matter tracts: similarities and differences in relation to age, gender, and intelligence

The white matter of the brain undergoes a range of structural changes throughout development; from conception to birth, in infancy, and onwards through childhood and adolescence. Several studies have used diffusion magnetic resonance imaging (dMRI) to investigate these changes, but a consensus has not yet emerged on which white matter tracts undergo changes in the later stages of development or what the most important driving factors are behind these changes. In this study of typically developing 8- to 16-year-old children, we use a comprehensive data-driven approach based on principal components analysis to identify effects of age, gender, and brain volume on dMRI parameters, as well as their relative importance. We also show that secondary components of these parameters predict full-scale IQ, independently of the age- and gender-related effects. This overarching assessment of the common factors and gender differences in normal white matter tract development will help to advance understanding of this process in late childhood and adolescence.

Developmental trajectories during adolescence in males and females: a cross-species understanding of underlying brain changes

Adolescence is a transitional period between childhood and adulthood that encompasses vast changes within brain systems that parallel some, but not all, behavioral changes. Elevations in emotional reactivity and reward processing follow an inverted U shape in terms of onset and remission, with the peak occurring during adolescence. However, cognitive processing follows a more linear course of development. This review will focus on changes within key structures and will highlight the relationships between brain changes and behavior, with evidence spanning from functional magnetic resonance imaging (fMRI) in humans to molecular studies of receptor and signaling factors in animals. Adolescent changes in neuronal substrates will be used to understand how typical and atypical behaviors arise during adolescence. We draw upon clinical and preclinical studies to provide a neural framework for defining adolescence and its role in the transition to adulthood.

1H MRSI and social communication deficits in pediatric complex partial seizures

PURPOSE

To investigate relationships between regional brain metabolites, social communication deficits, and seizure frequency in children and adolescents with cryptogenic epilepsy with complex partial seizures (CPS).

METHODS

In 12 children and adolescents with CPS and 23 age- and gender-matched healthy controls, we acquired proton magnetic resonance spectroscopic imaging (MRSI) at 1.5 T and 30 ms echo-time from bilateral inferior frontal and superior temporal gyri, regions associated with social communication deficits. Videotaped speech samples of all the subjects were coded for social communication deficits and parents provided information on seizure frequency.

KEY FINDINGS

Four MRSI findings emerged in right inferior frontal gyrus. N-acetyl-aspartate (NAA) plus N-acetyl-aspartyl-glutamate (NAAG)--together called "tNAA"--was 11.4% lower in patients with CPS than in controls. Choline-compounds (Cho) were 15.4% lower in CPS than in controls. Within CPS, higher tNAA was associated with more frequent seizures and abnormal social communication.

SIGNIFICANCE

Localization of findings to right inferior frontal cortex supports the involvement of this area in social communication deficits and may be related to atypical lateralization of expressive language in pediatric epilepsy. Lower levels of tNAA and Cho may indicate local neuronal or glial damage or underpopulation due to excitotoxicity or other causes. The sensitivity of tNAA to seizure frequency suggests effects of ongoing CPS on neuronal and glial function in this brain region.

Sex differences in orbitofrontal gray as a partial explanation for sex differences in antisocial personality

Attention is increasingly being given to understanding sex difference in psychopathology to better understand the etiology of disorders. This study tests the hypothesis that sex differences in ventral and middle frontal gray volume contribute to sex differences in antisocial personality disorder (APD) and crime. Participants were recruited from temporary employment agencies, consisting of normal controls, substance/alcohol-dependent controls, axis I/II psychiatric controls and individuals with APD. An independent sample of female volunteers was also recruited. Magnetic resonance imaging volumes of superior frontal, middle frontal, inferior frontal, orbital frontal and rectal gyral frontal gray matter, and dimensional scores of APD and criminal behavior were assessed. APD males when compared with male controls showed an 8.7% reduction in orbitofrontal gray volume, a 17.3% reduction in middle frontal gray and a 16.1% reduction in right rectal gray. Reduced middle and orbitofrontal volumes were significantly associated with increased APD symptoms and criminal offending in both males and females. Males as a whole had reduced orbitofrontal and middle frontal gray volume when compared with females, and controlling for these brain differences reduced the gender difference in the antisocial personality/behavior by 77.3%. Findings were not a function of psychiatric comorbidity, psychosocial risk factors, head injury or trauma exposure. Findings implicate structural differences in the ventral and middle frontal gray as both a risk factor for APD and as a partial explanation for sex differences in APD.

Sex differences in adolescent white matter architecture

BACKGROUND

Sex-specific trajectories in white matter development during adolescence may help explain cognitive and behavioral divergences between males and females. Knowledge of sex differences in typically developing adolescents can provide a basis for interpreting sexual dimorphisms in abilities and actions.

METHOD

We examined 58 healthy adolescents (12-14years of age) with diffusion tensor imaging (DTI). Diffusion parameters fractional anisotropy (FA), and mean (MD), radial (RD), and axial diffusivities (AD) were subjected to whole-brain voxel-wise group comparisons using tract-based spatial statistics. Sex differences in white matter microstructure were examined in relation to pubertal development.

RESULTS

Early adolescent females (n=29) evidenced higher FA in the right superior corona radiata, higher FA and AD in bilateral corticospinal tracts (≥164μl, p<.01), and lower MD in the right inferior longitudinal fasciculus (ILF) and left forceps major (≥164μl, p<.01) than age-matched males (n=29). Males did not show any areas of higher FA or lower MD than females, but had higher AD in the right superior longitudinal fasciculus, ILF, and forceps minor (≥ 164μl, p<.01). Pubertal stage did not account for sex disparities.

CONCLUSION

In early adolescence, females' motor tracts may reflect widespread changes, while males may undergo relatively more microstructural change in projection and association fibers.

Age, sex, and pubertal phase influence mentalizing about emotions and actions in adolescents

This study examined (1) emotional versus cognitive developmental trajectories and (2) the influence of age-extrinsic factors (i.e., sex and puberty). Using a cross-sectional design, adolescents (N = 252) divided into four age-groups (ages 13, 15, 17, 19) performed two versions of a mentalizing task, about emotions and actions, as well as the Tower task. First, performance on all tasks improved linearly into late adolescence (age 19). Thus no differential trajectories were found for emotional versus cognitive development. Second, girls outperformed boys in mentalizing speed regarding both emotions and actions. In boys, a later pubertal phase was associated with increased mentalizing speed after controlling for age-group.

Adolescent brain development and the risk for alcohol and other drug problems

Dynamic changes in neurochemistry, fiber architecture, and tissue composition occur in the adolescent brain. The course of these maturational processes is being charted with greater specificity, owing to advances in neuroimaging and indicate grey matter volume reductions and protracted development of white matter in regions known to support complex cognition and behavior. Though fronto-subcortical circuitry development is notable during adolescence, asynchronous maturation of prefrontal and limbic systems may render youth more vulnerable to risky behaviors such as substance use. Indeed, binge-pattern alcohol consumption and comorbid marijuana use are common among adolescents, and are associated with neural consequences. This review summarizes the unique characteristics of adolescent brain development, particularly aspects that predispose individuals to reward seeking and risky choices during this phase of life, and discusses the influence of substance use on neuromaturation. Together, findings in this arena underscore the importance of refined research and programming efforts in adolescent health and interventional needs.

Atlasing location, asymmetry and inter-subject variability of white matter tracts in the human brain with MR diffusion tractography

The purpose of this study is to create a white matter atlas of the human brain using diffusion tensor imaging (DTI) tractography and to describe the constant and variable features of the major pathways. DTI was acquired from 40 healthy right-handed adults and reconstructed tracts mapped within a common reference space (MNI). Group effect maps of each tract defined constant anatomical features while overlap maps were generated to study inter-subject variability and to compare DTI derived anatomy with a histological atlas. Two patients were studied to assess the localizing validity of the atlas. The DTI-derived maps are overall consistent with a previously published histological atlas. A statistically significant leftward asymmetry was found for the volume and number of streamlines of the cortico-spinal tract and the direct connections between Broca's and Wernicke's territories (long segment). A statistically significant rightward asymmetry was found for the inferior fronto-occipital fasciculus and the fronto-parietal connections (anterior segment) of the arcuate fasciculus. Furthermore, males showed a left lateralization of the fronto-temporal segment of the arcuate fasciculus (long segment), while females had a more bilateral distribution. In two patients with brain lesions, DTI was acquired and tractography used to show that the tracts affected by the lesions were correctly identified by the atlas. This study suggests that DTI-derived maps can be used together with a previous histological atlas to establish the relationship of focal lesions with nearby tracts and improve clinico-anatomical correlation.

Unbiased average age-appropriate atlases for pediatric studies

Spatial normalization, registration, and segmentation techniques for Magnetic Resonance Imaging (MRI) often use a target or template volume to facilitate processing, take advantage of prior information, and define a common coordinate system for analysis. In the neuroimaging literature, the MNI305 Talairach-like coordinate system is often used as a standard template. However, when studying pediatric populations, variation from the adult brain makes the MNI305 suboptimal for processing brain images of children. Morphological changes occurring during development render the use of age-appropriate templates desirable to reduce potential errors and minimize bias during processing of pediatric data. This paper presents the methods used to create unbiased, age-appropriate MRI atlas templates for pediatric studies that represent the average anatomy for the age range of 4.5-18.5 years, while maintaining a high level of anatomical detail and contrast. The creation of anatomical T1-weighted, T2-weighted, and proton density-weighted templates for specific developmentally important age-ranges, used data derived from the largest epidemiological, representative (healthy and normal) sample of the U.S. population, where each subject was carefully screened for medical and psychiatric factors and characterized using established neuropsychological and behavioral assessments. Use of these age-specific templates was evaluated by computing average tissue maps for gray matter, white matter, and cerebrospinal fluid for each specific age range, and by conducting an exemplar voxel-wise deformation-based morphometry study using 66 young (4.5-6.9 years) participants to demonstrate the benefits of using the age-appropriate templates. The public availability of these atlases/templates will facilitate analysis of pediatric MRI data and enable comparison of results between studies in a common standardized space specific to pediatric research.

Impact of breast milk on intelligence quotient, brain size, and white matter development

Although observational findings linking breast milk to higher scores on cognitive tests may be confounded by factors associated with mothers' choice to breastfeed, it has been suggested that one or more constituents of breast milk facilitate cognitive development, particularly in preterms. Because cognitive scores are related to head size, we hypothesized that breast milk mediates cognitive effects by affecting brain growth. We used detailed data from a randomized feeding trial to calculate percentage of expressed maternal breast milk (%EBM) in the infant diet of 50 adolescents. MRI scans were obtained (mean age=15 y 9 mo), allowing volumes of total brain (TBV) and white and gray matter (WMV, GMV) to be calculated. In the total group, %EBM correlated significantly with verbal intelligence quotient (VIQ); in boys, with all IQ scores, TBV and WMV. VIQ was, in turn, correlated with WMV and, in boys only, additionally with TBV. No significant relationships were seen in girls or with gray matter. These data support the hypothesis that breast milk promotes brain development, particularly white matter growth. The selective effect in males accords with animal and human evidence regarding gender effects of early diet. Our data have important neurobiological and public health implications and identify areas for future mechanistic study.

Cortical morphometric subclassification of frontotemporal lobar degeneration

BACKGROUND AND PURPOSE

Frontotemporal lobar degeneration (FTLD) is a primary neurodegenerative disease comprising 3 clinical subtypes: frontotemporal dementia (FTD), semantic dementia (SD), and progressive nonfluent aphasia (PNFA). The subdivision is primarily based on the characteristic clinical symptoms displayed by each subtype. We hypothesized that these symptoms would be correlated to characteristic patterns of brain atrophy, which could be indentified and used for subclassification of subjects with FTLD.

MATERIALS AND METHODS

Volumes of 9 cortical regions were manually parcellated and measured on both hemispheres on 27 controls, 12 patients with FTD, 9 patients with PNFA, and 13 patients with SD. The volumetric data were analyzed by traditional t tests and by a multivariate discriminant analysis (partial least squares discriminant analysis).

RESULTS

The ensemble or pattern of atrophy was a good discriminator in pair-wise comparison between the subtypes: FTD compared with SD (sensitivity 100% [12/12], specificity 100% [13/13]); FTD compared with PNFA (sensitivity 92% [11/12], specificity 89% [8/9]); and SD compared with PNFA (sensitivity 86% [11/13], specificity 100% [9/9]). Temporal-versus-frontal atrophy was the most important pattern for discriminating SD from the other 2 subtypes. Right-sided versus left-sided atrophy was the most important pattern for discriminating between subjects with FTD and PNFA.

CONCLUSIONS

FTLD subtypes generally display a characteristic pattern of atrophy, which may be considered in diagnosing patients with FTLD.

Broca's area: nomenclature, anatomy, typology and asymmetry

In this review, we (i) describe the nomenclature of Broca's area and show how the circumscribed definition of Broca's area is disassociated from Broca's aphasia, (ii) describe in detail how the gross anatomy of Broca's area varies between people, and how the definitions vary between studies, (iii) attempt to reconcile the findings of structural asymmetry of Broca's area with the differences in methodological approaches, (iv) consider the functional significance of cytoarchitectonic definitions of Broca's area, and (v) critically elucidate the significance of circumscribed regions of cortex for language lateralisation and language development. Contrary to what has previously been reported in the literature, asymmetry of Broca's area has not been reproducibly demonstrated, particularly on a gross morphological level. This may be due to major inconsistencies in methodology (including different anatomical boundaries, measurement techniques and samples studied) or that the sulcal contours defining Broca's area are so naturally variable between people making a standard definition difficult. Cytoarchitectonic analyses more often than not report leftward asymmetry of some component of area 44 and/or area 45. If a structural asymmetry of Broca's area does exist, it is variable, which differs from that of the functional asymmetry of language, which is more consistent. One reason for this might be that the link between cellular architecture, connectivity and language function still remains to be elucidated. There is currently no convincing explanation to associate asymmetry of Broca's area with the lateralisation of language.

DEVELOPMENTAL SEX DIFFERENCES IN THE RELATION OF NEUROANATOMICAL CONNECTIVITY TO INTELLIGENCE

Recent neuroimaging research has shown sex-related differences in the relationship between brain structure and cognitive function. Anatomical studies have shown a greater reliance for cognitive function on white matter structure in adult females, and a greater reliance on gray matter structure in adult males. Functional neuroimaging studies have also shown a greater correlation between brain connectivity and cognitive function in females. However, this relationship is not present in young childhood (5 years old) but appears during the developmental period. Here sex differences in structure-function relationships and their developmental trajectory are investigated using diffusion tensor imaging (DTI) on a large cohort of over 100 normal children ages 5-18. Significant sex-X-IQ interactions on fractional anisotropy (FA), a marker for white matter organization, were seen in the left frontal lobe, in fronto-parietal areas bilaterally, and in the arcuate fasciculus bilaterally, with girls showing positive correlations of FA with IQ, and boys showing a negative correlation. Significant sex-X-IQ-X-age interactions on FA were also seen in the left frontal lobe and in fronto-parietal areas bilaterally, showing a developmental effect. These results strongly corroborate previous findings regarding sex differences in structure-function relationships regarding intelligence. Results also indicate that a naïve interpretation of "more is better" with respect to FA may not be accurate, especially in adult males.

Thought disorder and frontotemporal volumes in pediatric epilepsy

The aim of this study was to determine if volumes of frontotemporal regions associated with language were related to thought disorder in 42 children, aged 5-16 years, with cryptogenic epilepsy, all of whom had complex partial seizures (CPS). The children with CPS and 41 age- and gender-matched healthy children underwent brain MRI scans at 1.5 T. Tissue was segmented, and total brain, frontal lobe, and temporal lobe volumes were computed. Thought disorder measures, IQ, and seizure information were collected for each patient. The subjects with CPS had more thought disorder, smaller total gray matter and orbital frontal gray matter volumes, as well as larger temporal lobe white matter volumes than the control group. In the CPS group, thought disorder was significantly related to smaller orbital frontal and inferior frontal gray matter volumes, increased Heschl's gyrus gray matter volumes, and smaller superior temporal gyrus white matter volumes. However, significantly larger orbital frontal gyrus, superior temporal gyrus, and temporal lobe gray matter volumes and decreased Heschl's gyrus white matter volumes were associated with thought disorder in the control group. These findings suggest that thought disorder might represent a developmental disability involving frontotemporal regions associated with language in pediatric CPS.

Developmental differences in white matter architecture between boys and girls

Previous studies have found developmental differences between males and females in brain structure. During childhood and adolescence, relative white matter volume increases faster in boys than in girls. Sex differences in the development of white matter microstructure were investigated in a cohort of normal children ages 5-18 in a cross-sectional diffusion tensor imaging (DTI) study. Greater fractional anisotropy (FA) in boys was shown in associative white matter regions (including the frontal lobes), while greater FA in girls was shown in the splenium of the corpus callosum. Greater mean diffusivity (MD) in boys was shown in the corticospinal tract and in frontal white matter in the right hemisphere; greater MD in girls was shown in occipito-parietal regions and the most superior aspect of the corticospinal tract in the right hemisphere. Significant sex-age interactions on FA and MD were also shown. Girls displayed a greater rate of fiber density increase with age when compared with boys in associative regions (reflected in MD values). However, girls displayed a trend toward increased organization with age (reflected in FA values) only in the right hemisphere, while boys displayed this trend only in the left hemisphere. These results indicate differing developmental trajectories in white matter for boys and girls and the importance of taking sex into account in developmental DTI studies. The results also may have implications for the study of the relationship of brain architecture with intelligence.

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.