Hemispheric and gender-related differences in the gross morphology of the anterior cingulate/paracingulate cortex in normal volunteers: an MRI morphometric study

Group-based differences in anti-aging bias among medical students

Medical students (MS) may develop ageist attitudes early in their training that may predict their future avoidance of caring for the elderly. This study sought to determine MS' patterns of explicit and implicit anti-aging bias, intent to practice with older people and using the quad model, the role of gender, race, and motivation-based differences. One hundred and three MS completed an online survey that included explicit and implicit measures. Explicit measures revealed a moderately positive perception of older people. Female medical students and those high in internal motivation showed lower anti-aging bias, and both were more likely to intend to practice with older people. Although the implicit measure revealed more negativity toward the elderly than the explicit measures, there were no group differences. However, using the quad model the authors identified gender, race, and motivation-based differences in controlled and automatic processes involved in anti-aging bias.

Cingulum bundle diffusivity and delusions of reference in first episode and chronic schizophrenia

The goal of this study was to assess integrity of the cingulum bundle in patients diagnosed with first episode schizophrenia, chronic schizophrenia, and matched controls as well as to determine the relationship between diffusion measures of cingulum bundle integrity and severity of patients' delusions of reference. Participants, who comprised 18 first episode patients, 20 chronic patients, and two groups of matched controls (20 subjects in each), underwent 3 T MRI diffusion tensor imaging. Patients diagnosed with schizophrenia (chronic+first episode) showed decreased fractional anisotropy in the right cingulum bundle compared with controls. First episode patients exhibited higher trace bilaterally, compared with matched controls, and on the left compared with chronic patients. Axial diffusivity was increased in first episode patients, bilaterally, compared with matched controls and chronic patients. Radial diffusivity was also higher, bilaterally, in first episode patients compared with matched controls, and on the right compared with chronic patients. Trace diffusity and radial diffusivity in first episode patients were significantly correlated with increased severity of delusions of reference. Given that the abnormalities were present only in first episode patients and were not observed in chronic cases, it appears that they normalize over time. These abnormalities in first episode patients involved diffusivity measures in all directions (trace, radial and axial), suggesting a likely acute, partially reversible process in which there is an increase in brain water content, i.e., swelling, edema, or inflammation, that may reflect an early neuroinflammatory response in first episode patients.

Architecture and morphology of the human ventromedial prefrontal cortex

A previous report identified the location of comparable architectonic areas in the ventral frontal cortex of the human and macaque brains [S. Mackey & M. Petrides (2010) Eur. J. Neurosci., 32, 1940-1950]. The present article provides greater detail with regard to the definition of architectonic areas within the ventromedial part of the human ventral frontal cortex and describes their location: (i) in Montreal Neurological Institute proportional stereotactic space; and (ii) in relation to sulcal landmarks. Structural magnetic resonance scans of four brains were obtained before the preparation of the histological specimens, so that the architectonic parcellation could be reconstructed in its original three-dimensional volume. The areal density of individual cortical layers was sampled quantitatively in the ventromedial prefrontal cortex of eight brains (16 hemispheres). The agranular cortex along the ventral edge of the corpus callosum and posterior margin of the ventromedial surface is replaced by a graded series of increasingly granular and more complexly laminated areas that succeed one another in a posterior-to-anterior direction. In parallel, the width of the supragranular layers (i.e. layers II and III) increases as compared with the infragranular layers (i.e. layers V and VI) from posterior to anterior. A measure of how rapidly cortical features change at areal boundaries also showed that the rate of change in the granule and pyramidal cell densities of layers IV and V, respectively, was greater at the borders between posterior areas than between anterior areas. This article will facilitate the anatomical identification and comparison of experimental data involving the human vmPFC.

Folding of the anterior cingulate cortex partially explains inhibitory control during childhood: a longitudinal study

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Difficulties in cognitive control are related to several psychiatric conditions.

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Inhibitory control (IC) of children predicts academic and professional successes.

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ACC sulcal patterns at age 5 were related to IC efficiency at age 5 (Stroop scores).

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ACC sulcal patterns at age 5 explained IC efficiency at age 9 (Stroop scores).

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ACC sulcal patterns constrain IC efficiency during childhood.

Difficulties in cognitive control including inhibitory control (IC) are related to the pathophysiology of several psychiatric conditions. In healthy subjects, IC efficiency in childhood is a strong predictor of academic and professional successes later in life. The dorsal anterior cingulate cortex (ACC) is one of the core structures responsible for IC. Although quantitative structural characteristics of the ACC contribute to IC efficiency, the qualitative structural brain characteristics contributing to IC development are less-understood. Using anatomical magnetic resonance imaging, we investigated whether the ACC sulcal pattern at age 5, a stable qualitative characteristic of the brain determined in utero, explains IC at age 9. 18 children performed Stroop tasks at age 5 and age 9. Children with asymmetrical ACC sulcal patterns (n = 7) had better IC efficiency at age 5 and age 9 than children with symmetrical ACC sulcal patterns (n = 11). The ACC sulcal patterns appear to affect specifically IC efficiency given that the ACC sulcal patterns had no effect on verbal working memory. Our study provides the first evidence that the ACC sulcal pattern – a qualitative structural characteristic of the brain not affected by maturation and learning after birth – partially explains IC efficiency during childhood.

Diffusion properties of major white matter tracts in young, typically developing children

Brain development occurs rapidly during the first few years of life involving region-specific changes in both gray matter and white matter. Due to the inherent difficulties in acquiring magnetic resonance imaging data in young children, little is known about the properties of white matter in typically developing toddlers. In the context of an ongoing study of young children with autism spectrum disorder, we collected diffusion-weighted imaging data during natural nocturnal sleep in a sample of young (mean age=35months) typically developing male and female (n=41 and 25, respectively) children. Axial diffusivity, radial diffusivity, mean diffusivity and fractional anisotropy were measured at 99 points along the length of 18 major brain tracts. Influences of hemisphere, age, sex, and handedness were examined. We find that diffusion properties vary significantly along the length of the majority of tracks. We also identify hemispheric and sex differences in diffusion properties in several tracts. Finally, we find the relationship between age and diffusion parameters changes along the tract length illustrating variability in age-related white-matter development at the tract level.

Altered asymmetry of the anterior cingulate cortex in subjects at genetic high risk for psychosis

OBJECTIVE

Many studies have reported that patients with schizophrenia often have structural abnormalities of the anterior cingulate cortex (ACC) and that some of these seem to be of genetic origin, therefore predating the onset of illness. The present study aimed to investigate whether these alterations in the ACC are genetic in origin by comparing the morphological patterns of three groups: normal controls, subjects at genetic high risk (GHR) for psychosis, and patients with schizophrenia. The relationships between morphological variations and executive function were also investigated.

METHODS

This study examined the magnetic resonance images of cingulate sulcus/paracingulate sulcus (CS/PCS) folding patterns in 222 subjects (103 normal subjects, 30 individuals at GHR, and 89 patients with schizophrenia) and evaluated differences in the morphological and asymmetrical patterns of the ACC among groups. Neurocognitive tests were then performed and differences in cognitive performance were analyzed according to morphological variation.

RESULTS

Differences in PCS folding were detected; the control group was significantly more likely than were other groups to show a well-developed left PCS (p=0.009) and leftward asymmetry of the PCS (p<0.001). However, neither GHR subjects (p=0.346) nor patients (p=0.784) showed this leftward asymmetry. No statistically significant differences in CS continuity were observed. A more prominent left PCS (p=0.031) and leftward PCS asymmetry (p=0.030) were both associated with higher scores on the working memory task.

CONCLUSION

The results suggest that GHR subjects have distinct neurodevelopmental anomalies that resemble those of patients with schizophrenia even though they do not display any psychotic symptoms. Certain developmental alterations in the ACC, such as the loss of leftward sulcal asymmetry in patients with schizophrenia, might be related to genetic factors. Additionally, this morphological alteration might partly account for the impaired executive function in schizophrenia.

Behavioral laterality of the brain: support for the binary construct of hemisity

THREE TERMS DEFINE BRAIN BEHAVIORAL LATERALITY

hemispheric dominance identifies the cerebral hemisphere producing one's first language. Hemispheric asymmetry locates the brain side of non-language skills. A third term is needed to describe a person's binary thinking, learning, and behaving styles. Since the 1950s split-brain studies, evidence has accumulated that individuals with right or left brain behavioral orientations (RPs or LPs) exist. Originally, hemisphericity sought, but failed, to confirm the existence of such individual differences, due to its assertion that each individual lay somewhere on a gradient between competing left and right brain extremes. Recently, hemisity, a more accurate behavioral laterality context, has emerged. It posits that one's behavioral laterality is binary: i.e., inherently either right or left brain-oriented. This insight enabled the quantitative determination of right or left behavioral laterality of thousands of subjects. MRI scans of right and left brain-oriented groups revealed two neuroanatomical differences. The first was an asymmetry of an executive element in the anterior cingulate cortex (ACC). This provided hemisity both a rationale and a primary standard. RPs and LPs gave opposite answers to many behavioral preference "either-or," forced choice questions. This showed that several sex vs. hemisity traits are being conflated by society. Such was supported by the second neuroanatomical difference between the hemisity subtypes, that RPs of either sex had up to three times larger corpus callosi than LPs. Individuals of the same hemisity but opposite sex had more personality traits in common than those of the same sex but different hemisity. Although hemisity subtypes were equally represented in the general population, the process of higher education and career choice caused substantial hemisity sorting among the professions. Hemisity appears to be a valid and promising area for quantitative research of behavioral laterality.

Neural correlates of sexual arousal in heterosexual and homosexual women and men

Most men have a category-specific pattern of genital and subjective sexual arousal, responding much more strongly to erotic stimuli depicting their preferred sex than to erotic stimuli depicting their nonpreferred sex. In contrast, women tend to have a less specific arousal pattern. To better understand this sex difference, we used neuroimaging to explore its neural correlates. Heterosexual and homosexual women viewed erotic photographs of either men or women. Evoked neural activity was monitored via fMRI and compared with responses to the same stimuli in heterosexual and homosexual men. Overall, a network of limbic (as well as the anterior cingulate) and visual processing regions showed significantly less category-specific activity in women than men. This was primarily driven by weaker overall activations to preferred-sex stimuli in women, though there was also some evidence of stronger limbic activations to nonpreferred-sex stimuli in women. Primary results were similar for heterosexual and homosexual participants. Women did show some evidence of category-specific responses in the visual processing regions, although even in these regions they exhibited less differential activity than men. In the anterior cingulate, a region with high concentrations of sex-hormone receptors, subjective and neural category specificity measures correlated positively for women but negatively for men, suggesting a possible sex difference in the role of the anterior cingulate. Overall, results suggest that men tend to show more differentiated neural responses than do women to erotic photographs of one sex compared to the other sex, though women may not be entirely indifferent to which sex is depicted.

The morphology of midcingulate cortex predicts frontal-midline theta neurofeedback success

Humans differ in their ability to learn how to control their own brain activity by neurofeedback. However, neural mechanisms underlying these inter-individual differences, which may determine training success and associated cognitive enhancement, are not well-understood. Here, it is asked whether neurofeedback success of frontal-midline (fm) theta, an oscillation related to higher cognitive functions, could be predicted by the morphology of brain structures known to be critically involved in fm-theta generation. Nineteen young, right-handed participants underwent magnetic resonance imaging of T1-weighted brain images, and took part in an individualized, eight-session neurofeedback training in order to learn how to enhance activity in their fm-theta frequency band. Initial training success, measured at the second training session, was correlated with the final outcome measure. We found that the inferior, superior, and middle frontal cortices were not associated with training success. However, volume of the midcingulate cortex as well as volume and concentration of the underlying white matter structures act as predictor variables for the general responsiveness to training. These findings suggest a neuroanatomical foundation for the ability to learn to control one's own brain activity.

The shape of the ACC contributes to cognitive control efficiency in preschoolers

Cognitive success at school and later in life is supported by executive functions including cognitive control (CC). The pFC plays a major role in CC, particularly the dorsal part of ACC or midcingulate cortex. Genes, environment (including school curricula), and neuroplasticity affect CC. However, no study to date has investigated whether ACC sulcal pattern, a stable brain feature primarily determined in utero, influences CC efficiency in the early stages of cognitive and neural development. Using anatomical MRI and three-dimensional reconstruction of cortical folds, we investigated the effect that ACC sulcal pattern may have on the Stroop score, a classical behavioral index of CC efficiency, in 5-year-old preschoolers. We found higher CC efficiency, that is, lower Stroop interference scores for both RTs and error rates, in children with asymmetrical ACC sulcal pattern (i.e., different pattern in each hemisphere) compared with children with symmetrical pattern (i.e., same pattern in both hemispheres). Critically, ACC sulcal pattern had no effect on performance in the forward and backward digit span tasks suggesting that ACC sulcal pattern contributes to the executive ability to resolve conflicts but not to the ability to maintain and manipulate information in working memory. This finding provides the first evidence that preschoolers' CC efficiency is likely associated with ACC sulcal pattern, thereby suggesting that the brain shape could result in early constraints on human executive ability.

Women are more sensitive than men to prior trial events on the Stop-signal task

Sexual dimorphism in the brain and cognition is a topic of widespread interest. Many studies of sex differences have focused on visuospatial and verbal abilities, but few studies have investigated sex differences in executive functions. We examined two key components of executive function - response inhibition and response monitoring - in healthy men (n = 285) and women (n = 346) performing the Stop-signal task. In this task, participants are required to make a key press to a stimulus, unless a tone is presented at some delay following the initial stimulus presentation; on these infrequent trials, participants are instructed to inhibit their planned response. Response inhibition was assessed with an estimate of the latency needed to inhibit a response (stop-signal reaction time), and response monitoring was measured by calculating the degree to which participants adjusted their reaction times based on the immediately preceding trial (e.g., speeding following correct trials and slowing following errors). There were no sex differences in overall accuracy or response inhibition, but women showed greater sensitivity to trial history. Women sped up more than men following correct 'Go' trials, and slowed down more than men following errors. These small but statistically significant effects (Cohen's d = 0.25-0.3) suggest more flexible adjustments in speed-accuracy trade-offs in women and greater cognitive flexibility associated with the responsive control of action.

Initiation of joint attention is associated with morphometric variation in the anterior cingulate cortex of chimpanzees (Pan troglodytes)

In developing human children, joint attention (JA) is an important preverbal skill fundamental to the development of language. Poor JA skills have been described as a behavioral risk factor for some neurodevelopmental disorders, such as autism spectrum disorder. It has been hypothesized that the anterior cingulate cortex (ACC) plays an important role in the development of JA in human children. Here, we tested whether the morphometry and lateralization of the ACC differed between chimpanzees that were classified as either consistently or inconsistently engaging in JA with a human experimenter. Results showed that chimpanzees that performed poorly on the JA task had larger gray matter (GM) volumes in the ACC compared to apes that performed well on the task. In addition, both population-level asymmetries and sex differences in the volume of GM were found within the ACC. Specifically, females had relatively larger GM volumes in two of the three subregions of the ACC compared to males, and significant leftward asymmetries were found for two of the subregions whereas a rightward bias was observed in the third. Based on these findings, we suggest that the ACC plays an important role in mediating JA, not just in humans, but also chimpanzees. We further suggest that the differences found between groups may reflect inherent differences in the amount of white matter within the ACC, thereby suggesting reduced connectivity between the ACC and other cortical regions in chimpanzees with poor JA skills.

The cerebral cortex of Albert Einstein: a description and preliminary analysis of unpublished photographs

Upon his death in 1955, Albert Einstein's brain was removed, fixed and photographed from multiple angles. It was then sectioned into 240 blocks, and histological slides were prepared. At the time, a roadmap was drawn that illustrates the location within the brain of each block and its associated slides. Here we describe the external gross neuroanatomy of Einstein's entire cerebral cortex from 14 recently discovered photographs, most of which were taken from unconventional angles. Two of the photographs reveal sulcal patterns of the medial surfaces of the hemispheres, and another shows the neuroanatomy of the right (exposed) insula. Most of Einstein's sulci are identified, and sulcal patterns in various parts of the brain are compared with those of 85 human brains that have been described in the literature. To the extent currently possible, unusual features of Einstein's brain are tentatively interpreted in light of what is known about the evolution of higher cognitive processes in humans. As an aid to future investigators, these (and other) features are correlated with blocks on the roadmap (and therefore histological slides). Einstein's brain has an extraordinary prefrontal cortex, which may have contributed to the neurological substrates for some of his remarkable cognitive abilities. The primary somatosensory and motor cortices near the regions that typically represent face and tongue are greatly expanded in the left hemisphere. Einstein's parietal lobes are also unusual and may have provided some of the neurological underpinnings for his visuospatial and mathematical skills, as others have hypothesized. Einstein's brain has typical frontal and occipital shape asymmetries (petalias) and grossly asymmetrical inferior and superior parietal lobules. Contrary to the literature, Einstein's brain is not spherical, does not lack parietal opercula and has non-confluent Sylvian and inferior postcentral sulci.

Modulation of frontal-midline theta by neurofeedback

Cortical oscillations demonstrate a relationship with cognition. Moreover, they also exhibit associations with task performance and psychiatric mental disorders. This being the case, the modification of oscillations has become one of the key interests of neuroscientific approaches for cognitive enhancement. For such kind of alterations, neurofeedback (NF) of brain activity constitutes a promising tool. Concerning specific higher cognitive functions, frontal-midline theta (fm-theta) has been suggested as an important indicator of relevant brain processes. This paper presents a novel approach for an individualized, eight-session NF training to enhance fm-theta. An individual's dominant fm-theta frequency was determined based on experiments tapping executive functions. Effects of the actual NF training were compared to a pseudo-NF training. Participants of the pseudo-NF training experienced a comparable degree of motivation and commitment as the subjects of the actual NF training, but found the "training" slightly easier. In comparison to the pseudo-NF training, proper NF training significantly enhanced fm-theta amplitude in the actual training sessions, as well as during the whole course of training. However, unspecific changes in the alpha and beta frequency ranges found with both the actual NF and the pseudo-NF training groups emphasize the relevance of active control groups for neurofeedback studies.

Correcting power and p-value calculations for bias in diffusion tensor imaging

Diffusion tensor imaging (DTI) provides quantitative parametric maps sensitive to tissue microarchitecture (e.g., fractional anisotropy, FA). These maps are estimated through computational processes and subject to random distortions including variance and bias. Traditional statistical procedures commonly used for study planning (including power analyses and p-value/alpha-rate thresholds) specifically model variability, but neglect potential impacts of bias. Herein, we quantitatively investigate the impacts of bias in DTI on hypothesis test properties (power and alpha-rate) using a two-sided hypothesis testing framework. We present theoretical evaluation of bias on hypothesis test properties, evaluate the bias estimation technique SIMEX for DTI hypothesis testing using simulated data, and evaluate the impacts of bias on spatially varying power and alpha rates in an empirical study of 21 subjects. Bias is shown to inflame alpha rates, distort the power curve, and cause significant power loss even in empirical settings where the expected difference in bias between groups is zero. These adverse effects can be attenuated by properly accounting for bias in the calculation of power and p-values.

Morphometric differences in central stress-regulating structures between women with and without borderline personality disorder

BACKGROUND

Experiences of early life stress, increased psychological arousal and the body's physiologic stress response seem to play an important role in the pathogenesis and maintenance of borderline personality disorder (BPD). In the present study, we investigated alterations in grey matter of central stress-regulating structures in female patients with BPD.

METHODS

We examined T1-weighted structural magnetic resonance imaging scans of unmedicated, right-handed female patients with BPD (according to DSM-IV criteria) and healthy controls matched for age, intelligence and education using fully automated DARTEL voxel-based morphometry. Our regions of interest analyses included the hippocampus, amygdala, anterior cingulate cortex (ACC) and hypothalamus.

RESULTS

We enrolled 30 patients and 33 controls in our study. The grey matter of patients with BPD was reduced in the hippocampus, but increased in the hypothalamus compared with healthy participants. Hypothalamic volume correlated positively with the history of traumatization in patients with BPD. No significant alterations were found in the amygdala and ACC.

LIMITATIONS

This study is limited by the lack of measures of corticotropin-releasing hormone, adrenocorticotropic hormone and cortisol levels. Furthermore, moderate sample size and comorbid disorders need to be considered.

CONCLUSION

Our findings provide new evidence for grey matter alterations in the hypothalamus and replicate previously reported decrements in hippocampal volume in patients with BPD. Understanding the role of the hypothalamus and other central stress-regulating structures could help us to further understand the neurobiological underpinnings of this complex disorder.

Sex differences in structural brain asymmetry predict overt aggression in early adolescents

The devastating social, emotional and economic consequences of human aggression are laid bare nightly on newscasts around the world. Aggression is principally mediated by neural circuitry comprising multiple areas of the prefrontal cortex and limbic system, including the orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), amygdala and hippocampus. A striking characteristic of these regions is their structural asymmetry about the midline (i.e. left vs right hemisphere). Variations in these asymmetries have been linked to clinical disorders characterized by aggression and the rate of aggressive behavior in psychiatric patients. Here, we show for the first time that structural asymmetries in prefrontal cortical areas are also linked to aggression in a normal population of early adolescents. Our findings indicate a relationship between parent reports of aggressive behavior in adolescents and structural asymmetries in the limbic and paralimbic ACC and OFC, and moreover, that this relationship varies by sex. Furthermore, while there was no relationship between aggression and structural asymmetries in the amygdala or hippocampus, hippocampal volumes did predict aggression in females. Taken together, the results suggest that structural asymmetries in the prefrontal cortex may influence human aggression, and that the anatomical basis of aggression varies substantially by sex.

Gray matter volume in major depressive disorder: a meta-analysis of voxel-based morphometry studies

We designed this study to perform a meta-analysis of gray matter (GM) findings in major depressive disorder (MDD) by using the signed differential mapping (SDM) toolbox. The Pubmed, ScienceDirect and Scopus databases were searched, and only studies published or published online before November 2010 have been included. Twenty voxel-based morphometry (VBM) studies of adult MDD patients were entered in the meta-analysis by SDM toolbox with threshold criteria set as error probability less than 0.00005 and cluster more than 50 voxels. Onset age, numbers of patients and controls, gender ratio of both groups, ratio of medicated patients, depression rating scores, illness duration, co-morbidity and existence of corrected p value were also meta-regressed as covariates to exclude confounding biases. Voxel-wise meta-analytic results of these 20 VBM studies in MDD patients revealed that GM deficits were observed in the right anterior cingulate cortex and left anterior cingulate cortex when patients were compared with controls. The findings remained mostly unchanged in jackknife sensitivity analyses. The potential confounding factors had little impact on the results. This meta-analysis suggested GM deficits of the anterior cingulate cortex might be important in the etiology of MDD.

Automatic statistical shape analysis of cerebral asymmetry in 3D T1-weighted magnetic resonance images at vertex-level: application to neuroleptic-naïve schizophrenia

The study of the structural asymmetries in the human brain can assist the early diagnosis and progression of various neuropsychiatric disorders, and give insights into the biological bases of several cognitive deficits. The high inter-subject variability in cortical morphology complicates the detection of abnormal asymmetries especially if only small samples are available. This work introduces a novel automatic method for the local (vertex-level) statistical shape analysis of gross cerebral hemispheric surface asymmetries which is robust to the individual cortical variations. After segmentation of the cerebral hemispheric volumes from three-dimensional (3D) T1-weighted magnetic resonance images (MRI) and their spatial normalization to a common space, the right hemispheric masks were reflected to match with the left ones. Cerebral hemispheric surfaces were extracted using a deformable model-based algorithm which extracted the salient morphological features while establishing the point correspondence between the surfaces. The interhemispheric asymmetry, quantified by customized measures of asymmetry, was evaluated in a few thousands of corresponding surface vertices and tested for statistical significance. The developed method was tested on scans obtained from a small sample of healthy volunteers and first-episode neuroleptic-naïve schizophrenics. A significant main effect of the disease on the local interhemispheric asymmetry was observed, both in females and males, at the frontal and temporal lobes, the latter being often linked to the cognitive, auditory, and memory deficits in schizophrenia. The findings of this study, although need further testing in larger samples, partially replicate previous studies supporting the hypothesis of schizophrenia as a neurodevelopmental disorder.

Variations in midcingulate morphology are related to ERP indices of cognitive control

The midcingulate cortex (MCC; often somewhat imprecisely referred to as dorsal or cognitive part of the anterior cingulate cortex or dACC) is a core region contributing to cognitive control. Neuroanatomical deviations in the midcingulate region have been observed in a variety of mental disorders. Even in healthy subjects a high degree of morphological variability is seen, for example concerning the degree of anterior midcingulate fissurization. To investigate the relationship between anterior midcingulate morphology and function, individuals with a leftward midcingulate folding asymmetry (LEFT) were compared to individuals showing a lower degree of fissurization or a rightward asymmetric folding (REST). Data from two experiments, a masked Stroop paradigm and a combined go/no-go and stop-signal task, are reported. With the masked Stroop task, LEFT subjects revealed a better processing of incongruent Stroop stimuli when compared to REST subjects. This was reflected in both augmented N400 responses as well as significantly higher accuracy scores. In addition, similar effects were found with event-related potentials from the combined go/no-go and stop-signal task. Here, the N200 but not the P300, which have been associated with conflict-related and evaluative processing stages, respectively, was found to be significantly increased with LEFT subjects. The results of this study foster an association of midcingulate fissurization with differences in behavior and neurophysiological functioning related to cognitive control.

Orbitofrontal sulcogyral patterns are related to temperamental risk for psychopathology

There are marked individual differences in the pattern of cortical (sulcogyral) folding in the orbitofrontal cortex (OFC), and there is a growing literature suggesting that these individual differences are associated with risk for psychotic disorders. To date, however, no study has investigated whether OFC folding patterns are associated with broader risk factors relevant to a range of psychopathology. This study helps address this knowledge gap by examining whether OFC sulcogyral folding patterns are associated with putative risk factors, specifically affective temperament and psychiatric symptoms, in a large community sample (N = 152) of adolescents. Results showed that the most common pattern of folding ('Type I', marked by discontinuity of the medial orbital sulcus and continuity of the lateral orbital sulcus) was associated with low levels of Surgency, high levels of Negative Affectivity (in girls) and higher depressive symptoms. This pattern was also associated with reduced thickness of OFC gray matter. Overall, the findings, combined with previous work, suggest some specificity of neurodevelopmental risk for different types of psychopathology. Thus, these results have the potential to inform the early identification of at-risk individuals.

Serotonin receptor, SERT mRNA and correlations with symptoms in males with alcohol dependence and suicide

OBJECTIVE

This study tested the hypothesis that abnormalities in components of the serotonin (5HT) system in the prefrontal cortex are associated with suicide in alcohol-dependent subjects. Second, we assessed the relationship of lifetime impulsivity and mood symptoms with prefrontal cortex 5-HT measures.

METHOD

Tissue was obtained from Brodmann's areas (BA) 9 and 24 in postmortem samples of individuals who were alcohol dependent with suicide (n = 5), alcohol dependent without suicide (n = 9) and normal controls (n = 5). Serotonin receptor (5HT) and serotonin reuptake transporter (SERT) mRNA were measured. Interviews with next of kin estimated lifetime impulsivity and mood symptoms in the last week of life.

RESULTS

Serotonin receptor 1A (5HT1A) mRNA in BA 9 was elevated in the alcohol dependence without suicide group compared with controls. In the alcohol dependence with suicide group, anxiety symptoms were associated with decreased BA 24 SERT mRNA and depressive symptoms with BA 9 5HT1A mRNA expression. In the alcohol dependent only group impulsivity is correlated with increased BA 9, and BA 24 serotonin receptor 2A mRNA.

CONCLUSION

Our data suggest region-specific change, rather than global serotonin blunting is involved in alcohol dependence and suicide. It also suggests that symptoms are differentially influenced by prefrontal cortex serotonin receptor mRNA levels.

Anterior temporobasal sulcal morphology: development of a reliable rating protocol and normative data

The three anterior temporobasal (aTB) sulci, which are the collateral, rhinal, and occipitotemporal sulci, contribute to the morphology of memory-related structures and are important landmarks for neuroimaging. Prevalence of inter-connections among these sulci may distinguish healthy adults and individuals with memory-related disorders (Kim et al. Neurology 70:2159-2165, 2008; Zhan et al. Hum Brain Mapp 30:874-882, 2009). However, methods for quantifying the existence and nature of such connections are vague and varied, and normative frequencies are inconsistent across studies. Therefore, the goals of the current study are twofold: (1) to develop a reliable method of identifying aTB sulci and their interconnections based on surface renderings generated from serial magnetic resonance images (MRIs). This protocol includes training materials and a rating log (see supplementary materials) that can be disseminated and applied by other researchers. (2) To determine the prevalence of interconnections among the three aTB sulci in a large sample of healthy adults (200 undergraduate students), which can be used as normative data for future comparison with clinical samples. Notably, the resulting protocol, called the Sulcal Classification Rating Protocol for anterior Temporobasal sulci, distinguishes "clear" from "ambiguous" connections. When only clear connections are included, our prevalence rates are consistent with post-mortem findings of Ono et al. (Atlas of the Cerebral Sulci. Thieme Medical Publishers, Inc., New York, 1990); when both clear and ambiguous connections are counted as a connection, our results largely replicate MRI-based findings (e.g., Kim et al. Neurology 70:2159-2165, 2008). We propose that systematic variations in rater classification of ambiguous connections could explain discrepancies in the literature.

Effects of age on prefrontal subregions and hippocampal volumes in young and middle-aged healthy humans

There are limited data available regarding the effects of age and sex on discrete prefrontal gray and white matter volumes or posterior and anterior hippocampal volumes in healthy humans. Volumes of the superior frontal gyrus, anterior cingulate gyrus, and orbital frontal lobe were computed manually from contiguous magnetic resonance (MR) images in 83 (39M/44F) healthy humans (age range = 16-40) and segmented into gray and white matter. Volumes of the posterior and anterior hippocampal formation were also computed with reliable separation of the anterior hippocampal formation from the amygdala. There were significant age-by-tissue type interactions for the superior frontal gyrus and orbital frontal lobe such that gray matter within these regions correlated significantly and inversely with age. In contrast, no significant age effects were evident within regional white matter volumes. Analysis of hippocampal volumes indicated that men had larger volumes of the anterior, but not posterior hippocampal formation compared to women even following correction for total brain size. These data highlight age effects within discrete prefrontal cortical gray matter regions in young and middle aged healthy humans and suggest that the white matter comprising these regions may be more resistant to age effects. Furthermore, understanding the potential role of sex and age in mediating prefrontal cortical and hippocampal volumes may have strong relevance for psychiatric disorders such as schizophrenia that have implicated neurodevelopmental abnormalities within frontotemporal circuits in their pathogenesis.

Alexithymia in healthy young men: a voxel-based morphometric study

BACKGROUND

Alexithymia is a personality construct predominately associated with an impaired ability to identify and communicate emotions. Functional imaging studies showed that an altered function of the anterior cingulate cortex (ACC) may be relevant in alexithymia. In this study we investigated if the altered functional anatomy is related to structural changes (A) in the whole brain and (B) specifically in the ACC by applying a region-of-interest analysis.

METHODS

33 high- and 31 low-alexithymic right-handed young male subjects (selected by the 20-item Toronto Alexithymia Scale, TAS-20) were investigated using voxel-based morphometry (VBM) on high-resolution 3D magnetic resonance images. The group differences were analyzed by applying voxel-wise comparisons using two-sample t-tests. Moreover regression analyses with regard to the individual TAS-20 sum scores were calculated.

RESULTS

Neither the subtraction analyses nor the correlation analyses revealed significant differences between high- and low-alexithymic subjects. Thus, according to our results, the null hypothesis of no structural difference between the groups could not be rejected.

LIMITATIONS

The findings cannot be generalized to female subjects.

CONCLUSIONS

Our results did not reveal morphological differences between high- and low-alexithymic subjects. The functional differences known from imaging studies could not be attributed to underlying anatomical changes. Thus, the personality trait of alexithymia might be associated with fewer morphological abnormalities than previously assumed.

A specific brain structural basis for individual differences in reality monitoring

Much recent interest has centered on understanding the relationship between brain structure variability and individual differences in cognition, but there has been little progress in identifying specific neuroanatomical bases of such individual differences. One cognitive ability that exhibits considerable variability in the healthy population is reality monitoring; the cognitive processes used to introspectively judge whether a memory came from an internal or external source (e.g., whether an event was imagined or actually occurred). Neuroimaging research has implicated the medial anterior prefrontal cortex (PFC) in reality monitoring, and here we sought to determine whether morphological variability in a specific anteromedial PFC brain structure, the paracingulate sulcus (PCS), might underlie performance. Fifty-three healthy volunteers were selected on the basis of MRI scans and classified into four groups according to presence or absence of the PCS in their left or right hemisphere. The group with absence of the PCS in both hemispheres showed significantly reduced reality monitoring performance and ability to introspect metacognitively about their performance when compared with other participants. Consistent with the prediction that sulcal absence might mean greater volume in the surrounding frontal gyri, voxel-based morphometry revealed a significant negative correlation between anterior PFC gray matter and reality monitoring performance. The findings provide evidence that individual differences in introspective abilities like reality monitoring may be associated with specific structural variability in the PFC.

Cerebellar white-matter changes in cannabis users with and without schizophrenia

BACKGROUND

The cerebellum is rich in cannabinoid receptors and implicated in the neuropathology of schizophrenia. Long-term cannabis use is associated with functional and structural brain changes similar to those evident in schizophrenia, yet its impact on cerebellar structure has not been determined. We examined cerebellar grey and white matter in cannabis users with and without schizophrenia.

METHOD

Seventeen patients with schizophrenia and 31 healthy controls were recruited; 48% of the healthy group and 47% of the patients were long-term heavy cannabis users (mean 19.7 and 17.9 years near daily use respectively). Cerebellar measures were extracted from structural 3-T magnetic resonance imaging (MRI) scans using semi-automated methods, and examined using analysis of covariance (ANCOVA) and correlational analyses.

RESULTS

Cerebellar white-matter volume was reduced in cannabis users with and without schizophrenia compared to healthy non-users, by 29.7% and 23.9% respectively, and by 17.7% in patients without cannabis use. Healthy cannabis users did not differ in white-matter volume from either of the schizophrenia groups. There were no group differences in cerebellar grey matter or total volumes. Total cerebellar volume decreased as a function of duration of cannabis use in the healthy users. Psychotic symptoms and illness duration correlated with cerebellar measures differentially between patients with and without cannabis use.

CONCLUSIONS

Long-term heavy cannabis use in healthy individuals is associated with smaller cerebellar white-matter volume similar to that observed in schizophrenia. Reduced volumes were even more pronounced in patients with schizophrenia who use cannabis. Cannabis use may alter the course of brain maturational processes associated with schizophrenia.

Sexually dimorphic distribution of orbitofrontal sulcogyral pattern in schizophrenia

AIM

The sulcogyral pattern of the orbitofrontal cortex (OFC) is characterized by a remarkable inter-individual variability that likely reflects neurobehavioral traits and genetic aspects of neurodevelopment. The aim of the present study was to evaluate the OFC sulcogyral pattern of patients with schizophrenia (SZ) and healthy controls (HC) to determine group differences in OFC sulcogyral pattern as well as gender differences between groups.

METHODS

Forty-seven SZ patients (M/F, 23/24) and forty-seven HC (M/F, 17/30), matched on age and gender, were analyzed using magnetic resonance imaging. The sulcogyral pattern was classified into type I, II, or III based on the guidelines set by Chiavaras and Petrides in a previous paper. Chi-squared analysis was used to investigate group and gender differences in the sulcogyral pattern distribution, and categorical regression was used to explore clinical correlations.

RESULTS

The distribution of OFC sulcogyral pattern in HC replicated the results found in the previous study (left, χ(2) = 0.02, P = 0.989; right, χ(2) = 0.97, P = 0.616), in that there were no gender differences. Moreover, the distribution in SZ-M was in accordance with that in the previous study (left, χ(2) = 1.59, P = 0.451; right, χ(2) = 0.14, P = 0.933). Additionally, within SZ-M, patients with the type III pattern had a higher total positive and negative syndrome scale score (β = 0.902, F = 14.75, P = 0.001). In contrast, the distribution in the right hemisphere in the SZ-F group differed significantly from that observed in SZ-M (χ(2) = 6.017, P = 0.046), but did not differ from HC (χ(2) = 2.557, P = 0.110).

CONCLUSION

OFC sulcogyral pattern is altered in SZ-M but not in SZ-F, possibly reflecting gender differences in early neurodevelopment.

Emotion regulation and brain plasticity: expressive suppression use predicts anterior insula volume

Expressive suppression is an emotion regulation strategy that requires interoceptive and emotional awareness. These processes both recruit the anterior insula. It is not known, however, whether increased use of expressive suppression is associated with increased anterior insula volume. In the present study, high-resolution anatomical MRI images were used to calculate insula volumes in a set of 50 healthy female subjects (mean 21.9 years) using both region of interest (ROI) and voxel-based morphometry (VBM) approaches. Participants also completed trait measures of expressive suppression usage, cognitive reappraisal usage, and negative emotional reactivity (the latter two served as control measures). As predicted, both ROI and VBM methods found that expressive suppression usage, but not negative affect and cognitive reappraisal, was positively related to anterior insula volume. These findings are consistent with the idea that trait patterns of emotion processing are related to brain structure.

Anterior and posterior cingulate cortex volume in healthy adults: effects of aging and gender differences

The cingulate cortex frequently shows gray matter loss with age as well as gender differences in structure and function, but little is known about whether individual cingulate Brodmann areas show gender-specific patterns of age-related volume decline. This study examined age-related changes, gender differences, and the interaction of age and gender in the relative volume of cingulate gray matter in areas 25, 24, 31, 23, and 29, over seven decades of adulthood. Participants included healthy, age-matched men and women, aged 20-87 (n=70). Main findings were as follows: (1) The whole cingulate showed significant age-related volume declines (averaging 5.54% decline between decades, 20s-80s). Each of the five cingulate areas also showed a significant decline with age, and individual areas showed different patterns of decline across the decades: Smaller volume with age was most evident in area 31, followed by 25 and 24. (2) Women had relatively larger cingulate gray matter volume than men overall and in area 24. (3) Men and women showed different patterns of age-related volume decline in area 31, at midlife and late in life. By delineating normal gender differences and age-related morphometric changes in the cingulate cortex over seven decades of adulthood, this study improves the baseline for comparison with structural irregularities in the cingulate cortex associated with psychopathology. The Brodmann area-based approach also facilitates comparisons across studies that aim to draw inferences between age- and gender-related structural differences in the cingulate gyrus and corresponding differences in cingulate function.

Errors and conflict at the task level and the response level

In the last decade, research on error and conflict processing has become one of the most influential research areas in the domain of cognitive control. There is now converging evidence that a specific part of the posterior frontomedian cortex (pFMC), the rostral cingulate zone (RCZ), is crucially involved in the processing of errors and conflict. However, error-related research has focused primarily on a specific error type, namely, response errors. The aim of the present study was to investigate whether errors on the task level rely on the same neural and functional mechanisms. Here we report a dissociation of both error types in the pFMC: whereas response errors activate the RCZ, task errors activate the dorsal frontomedian cortex. Although this last region shows an overlap in activation for task and response errors on the group level, a closer inspection of the single-subject data is more in accordance with a functional anatomical dissociation. When investigating brain areas related to conflict on the task and response levels, a clear dissociation was perceived between areas associated with response conflict and with task conflict. Overall, our data support a dissociation between response and task levels of processing in the pFMC. In addition, we provide additional evidence for a dissociation between conflict and errors both at the response level and at the task level.

Anterior cingulate cortex volume and emotion regulation: is bigger better?

Emotion dysregulation is a key feature of mood and anxiety disorders. Many of these disorders also involve volumetric reductions in brain regions implicated in emotion regulation, including the dorsal anterior cingulate cortex (dACC). Investigating this relationship in healthy individuals may clarify the link between emotion regulation and volumetric reductions in this key brain region. High-resolution anatomical MRI images were used to calculate dACC volumes in 50 healthy female subjects. Trait measures of emotion regulation (cognitive reappraisal and expressive suppression) and negative affect were also obtained. As predicted, cognitive reappraisal was positively related to dACC volume, but not the volume of a control region, the ventral ACC. Expressive suppression, negative affect, and age were not related to dACC volume. These findings indicate that individual differences in cognitive reappraisal are related to individual differences in dACC volume in healthy participants.

Sex differences in cognitive control are associated with midcingulate and callosal morphology

Sex differences in the processing of cognitively demanding tasks have attracted much attention in recent years. While there seems to be some agreement on differences between males and females concerning spatial abilities and language skills, a consensus regarding executive functions or cognitive control has not been reached yet. In the present study, male and female subjects participated in a lateralized, tactile Stop-Signal task. Although the behavioral data did not show any differences between sexes, event-related potentials pointed to varieties in neurocognitive processing. As inferred from N200 amplitudes, differences between left- and right-hand stimulation suggested a strong degree of functional lateralization in males in accordance with a left-hemispheric dominance. Females, on the other hand, rather seemed to exhibit a functionally symmetric organization of relevant processes. The P300 did also show evidence of sex-related differences, reflecting disparities in the degree or quality of interhemispheric interaction. In addition, behavioral and electrophysiological parameters were correlated with individual metrics concerning the degree of midcingulate folding asymmetry and the morphology of the corpus callosum. Differential associations of these morphological characteristics with the N200 and P300, respectively, underscore the notion of relevant structure-function associations of the midcingulate cortex and the N200 on the one hand, and the corpus callosum and the P300 on the other hand. Obviously, these variations in neuroanatomy contribute to the observed behavioral and electrophysiological differences between women and men.

Paracingulate sulcus asymmetry; sex difference, correlation with semantic fluency and change over time in adolescent onset psychosis

The left paracingulate sulcus (PCS) is longer than the right and the adjacent cortex is activated by the generation of words. In adult patients with chronic schizophrenia the anatomical asymmetry is reduced. In 35 controls and 38 adolescents with schizophrenia or schizoaffective disorder (mean age = 16 years) we found that semantic verbal fluency correlated with leftward PCS asymmetry in controls but not in patients. At intake, PCS length did not differ between patients and controls, but at follow-up (13 controls, 10 patients, mean age = 18 years) PCS asymmetry (comprising both increasing left and decreasing right length) increased significantly, the increase was greater in males than in females, and there was a trend for a diagnosis * sex * side * time interaction such that in controls leftward PCS asymmetry increased, while in patients of both sexes there was convergence toward symmetry. Thus sulcal anatomy develops differentially in the two sexes during adolescence, and the pattern of asymmetric sex-dependent change over time may distinguish patients with psychosis from controls. Greater change in asymmetry during adolescence may explain earlier age of onset in males and greater deficits in verbal fluency.

Diffusion tensor imaging of the cingulum bundle in children after traumatic brain injury

Structural damage to the prefrontal-cingulate network has been implicated in cognitive and neurobehavioral deficits associated with traumatic brain injury (TBI). Forty-six children who had sustained moderate-to-severe TBI and 43 children with extracranial injury were imaged using diffusion tensor imaging (DTI). Decreased fractional anisotropy (FA) and increased apparent diffusion coefficient (ADC) values were found in the cingulum bundles bilaterally in the TBI group. Cingulum ADC was related to frontal lesion volume, injury severity, and injury mechanism. Finally, cingulum DTI parameters were related to cognitive control measures. DTI detects TBI-related injury to the cingulum, which may facilitate advances in assessment and treatment.

Attenuated asymmetry of functional connectivity in schizophrenia: a high-resolution EEG study

The interhemispheric asymmetries that originate from connectivity-related structuring of the cortex are compromised in schizophrenia (SZ). Under the assumption that such abnormalities affect functional connectivity, we analyzed its correlate-EEG synchronization-in SZ patients and matched controls. We applied multivariate synchronization measures based on Laplacian EEG and tuned to various spatial scales. Compared to the controls who had rightward asymmetry at a local level (EEG power), rightward anterior and leftward posterior asymmetries at an intraregional level (1st and 2nd order S-estimator), and rightward global asymmetry (hemispheric S-estimator), SZ patients showed generally attenuated asymmetry, the effect being strongest for intraregional synchronization in the alpha and beta bands. The abnormalities of asymmetry increased with the duration of the disease and correlated with the negative symptoms. We discuss the tentative links between these findings and gross anatomical asymmetries, including the cerebral torque and gyrification pattern, in normal subjects and SZ patients.

Neurobiological markers of illness onset in psychosis and schizophrenia: The search for a moving target

In this review, we describe neuropsychological and brain imaging findings in the early stages of psychosis and schizophrenia. We focus on recent clinical high-risk studies and consider whether the evidence supports these as 'endophenotypes' of a vulnerability to the illness or as 'biomarkers' of illness onset and transition. The findings suggest that there are a number of processes at psychosis onset that may represent biomarkers of incipient illness. These neurobiological indices particularly implicate the integrity of frontal and temporal cortices, which may or may not be related to the genetics of psychosis (i.e. potential 'endophenotypes'). However, these brain regions are dynamically changing during normal maturation, meaning that any putative neurobiological markers identified at the earliest stages of illness may be relatively unstable.We suggest that, while such measures maybe readily identified as potential neurobiological markers of established illness, they are inconsistent at (or around) the time of illness onset when assessed cross-sectionally. Instead,identification of more valid risk markers may require longitudinal assessment to ascertain normal or abnormal trajectories of neurodevelopment. Accordingly, we assert that the current conceptualisations of potential biomarkers and/or 'endophenotypes' for schizophrenia may need to be reconsidered in the context of normal and abnormal brain maturational processes at the time of onset of psychotic disorders.

Sex differences in brain anatomy

Over the past decades scientific studies have revealed a number of striking sex differences in the human brain. This chapter highlights some of the most important discoveries with particular emphasis on macro-anatomical observations based on magnetic resonance imaging (MRI) data. Cross-references to animal studies and to post mortem analyses, as well as an overview with respect to micro-anatomical findings, are provided. The chapter concludes with a discussion of possible determinants of sex differences in brain anatomy. The main goal of this chapter is to exemplify the variety of findings and to demonstrate how the presence, magnitude, and direction of observed sex differences strongly depend on a number of factors including (but not limited to) the following: the brain structure examined (cerebral cortex, corpus callosum, etc.), the specific brain feature assessed (cortical thickness, cortical convolution, etc.), the degree of regional specificity (global gray matter volume, voxel-wise gray matter volume, etc.), and whether measurements are adjusted for individual brain size or not.

Brain surface contraction mapped in first-episode schizophrenia: a longitudinal magnetic resonance imaging study

Schizophrenia is associated with structural brain abnormalities, but the timing of onset and course of these changes remains unclear. Longitudinal magnetic resonance imaging (MRI) studies have demonstrated progressive brain volume decreases in patients around and after the onset of illness, although considerable discrepancies exist regarding which brain regions are affected. The anatomical pattern of these progressive changes in schizophrenia is largely unknown. In this study, MRI scans were acquired repeatedly from 16 schizophrenia patients approximately 2 years apart following their first episode of illness, and also from 14 age-matched healthy subjects. Cortical Pattern Matching, in combination with Structural Image Evaluation, using Normalisation, of Atrophy, was applied to compare the rates of cortical surface contraction between patients and controls. Surface contraction in the dorsal surfaces of the frontal lobe was significantly greater in patients with first-episode schizophrenia (FESZ) compared with healthy controls. Overall, brain surface contraction in patients and healthy controls showed similar anatomical patterns, with that of the former group exaggerated in magnitude across the entire brain surface. That the pattern of structural change in the early course of schizophrenia corresponds so closely to that associated with normal development is consistent with the hypothesis that a schizophrenia-related factor interacts with normal adolescent brain developmental processes in the pathophysiology of schizophrenia. The exaggerated progressive changes seen in patients with schizophrenia may reflect an increased rate of synaptic pruning, resulting in excessive loss of neuronal connectivity, as predicted by the late neurodevelopmental hypothesis of the illness.

Topographic analysis of individual activation patterns in medial frontal cortex in schizophrenia

Individual variability in the location of neural activations poses a unique problem for neuroimaging studies employing group averaging techniques to investigate the neural bases of cognitive and emotional functions. This may be especially challenging for studies examining patient groups, which often have limited sample sizes and increased intersubject variability. In particular, medial frontal cortex (MFC) dysfunction is thought to underlie performance monitoring dysfunction among patients with schizophrenia, yet previous studies using group averaging to compare schizophrenic patients to controls have yielded conflicting results. To examine individual activations in MFC associated with two aspects of performance monitoring, interference and error processing, functional magnetic resonance imaging data were acquired while 17 patients with schizophrenia and 21 healthy controls (HCs) performed an event-related version of the multisource interference task. Comparisons of averaged data revealed few differences between the groups. By contrast, topographic analysis of individual activations for errors showed that control subjects exhibited activations spanning across both posterior and anterior regions of MFC while patients primarily activated posterior MFC, possibly reflecting an impaired emotional response to errors in schizophrenia. This discrepancy between topographic and group-averaged results may be due to the significant dispersion among individual activations, particularly in HCs, highlighting the importance of considering intersubject variability when interpreting the medial frontal response to error commission.

Anatomical abnormalities of the anterior cingulate cortex in schizophrenia: bridging the gap between neuroimaging and neuropathology

The anterior cingulate cortex (ACC) is a functionally heterogeneous region involved in diverse cognitive and emotional processes that support goal-directed behaviour. Structural magnetic resonance imaging (MRI) and neuropathological findings over the past two decades have converged to suggest abnormalities in the region may represent a neurobiological basis for many of the clinical manifestations of schizophrenia. However, while each approach offers complimentary information that can provide clues regarding underlying patholophysiological processes, the findings from these 2 fields are seldom integrated. In this article, we review structural neuroimaging and neuropathological studies of the ACC, focusing on the unique information they provide. The available imaging data suggest grey matter reductions in the ACC precede psychosis onset in some categories of high-risk individuals, show sub-regional specificity, and may progress with illness duration. The available post-mortem findings indicate these imaging-related changes are accompanied by reductions in neuronal, synaptic, and dendritic density, as well as increased afferent input, suggesting the grey matter differences observed with MRI arise from alterations in both neuronal and non-neuronal tissue compartments. We discuss the potential mechanisms that might facilitate integration of these findings and consider strategies for future research.

Structural brain abnormalities in major depressive disorder: a selective review of recent MRI studies

BACKGROUND

While there is evidence to suggest that major depressive disorder (MDD) is associated with structural brain abnormalities, the precise nature of these abnormalities remains unclear.

AIMS

To review recent structural magnetic resonance imaging (MRI) research findings in MDD while considering the potential influence of key clinical and demographic variables.

METHOD

A selective review of all T1-weighted structural MRI studies published between 2000 and 2007 in adult samples of MDD patients.

RESULTS

Volumetric reductions of the hippocampus, basal ganglia and OFC and SGPFC are consistently found in MDD patients, with more persistent forms of MDD (e.g., multiple episodes or repeated relapses, longer illness duration) being associated with greater impact on regional brain volumes. Gender, medication, stage of illness, and family history all affect the nature of the findings in a regionally specific manner.

LIMITATIONS

Overall, differences between the samples in factors such as illness severity, medication, gender and family history of mental illness makes difficult to identify their confounding effects on the observed neuroanatomical changes. Also, the tracing protocols used for particular brain regions were different amongst the reviewed studies, making difficult to compare their findings.

CONCLUSIONS

The data support the notion that MDD involves pathological alterations of limbic and cortical structures, and that they are generally more apparent in patients with more severe or persistent forms of the illness.

Paracingulate asymmetry in anterior and midcingulate cortex: sex differences and the effect of measurement technique

Many structural brain asymmetries accompany left hemisphere language dominance. For example, the cingulate sulcus is larger in the medial cortex of the right hemisphere, while the more dorsal paracingulate sulcus is larger on the left. The functional significance of these asymmetries is unknown because fMRI studies rarely attempt to localize activation to specific sulci, possibly due to difficulties in consistent sulcal identification. In medial cortex, for example, there are many regions of partial sulcal overlap where MRI images do not provide sufficient information to unambiguously distinguish a paracingulate sulcus from a displaced anterior cingulate segment. As large samples of postmortem material are rarely available for cytoarchitectural studies of sulcal variation, we have investigated the effect of variation in boundary and sulcal definition on paracingulate asymmetry in the MRI scans of 200 healthy adults (100 men, 100 women). Although women displayed a reliable asymmetry in the size of the paracingulate sulcus, regardless of boundary definition or technique, asymmetry was greatest when (1) the measurement was limited to the midcingulate region between the genu and the anterior commissure; and (2) the more dorsal of two overlapping sulci was always classified as a paracingulate sulcus (rather than as a displaced cingulate segment). The fact that paracingulate asymmetry is maximal in the midcingulate region suggests that this region may play a particular role in hemispheric specialization for language. Future work should investigate the structural and functional correlates of sulcal variation in this region.

Effects of anterior cingulate fissurization on cognitive control during stroop interference

The midcingulate cortex, as part of the more anteriorly located cingulate regions, is thought to play a major role in cognitive processes like conflict monitoring or response selection. Regarding midcingulate fissurization, the occurrence of a second or paracingulate sulcus is more common in the left than in the right hemisphere and has been shown to be associated with an advantageous performance on tests of executive functions. However, the cognitive mechanisms underlying such behavioral differences are completely unknown. The current study addressed this issue by comparing subjects with a low and a high degree of left hemispheric midcingulate fissurization while collecting behavioral as well as electrophysiological correlates of Stroop interference. A high degree of fissurization was associated with decreased behavioral Stroop interference accompanied by a stronger and prolonged frontal negative potential to incongruent trials starting around 320 ms. This increased frontal negativity is assumed to reflect an enhanced activity of a conflict monitoring system located in the midcingulate cortex. In contrast and starting around 400 ms, subjects with low fissurization revealed an increased positivity over parieto-occipital regions suggesting a compensatory need for enhanced effortful cognitive control in this group. These results contribute to the understanding of the neuronal implementation of individual differences regarding attentional mechanisms.