Molecular approaches to brain asymmetry and handedness

Asymmetries in event-related potentials part 1: A systematic review of face processing studies

The human brain shows distinct lateralized activation patterns for a range of cognitive processes. One such function, which is thought to be lateralized to the right hemisphere (RH), is human face processing. Its importance for social communication and interaction has led to a plethora of studies investigating face processing in health and disease. Temporally highly resolved methods, like event-related potentials (ERPs), allow for a detailed characterization of different processing stages and their specific lateralization patterns. This systematic review aimed at disentangling some of the contradictory findings regarding the RH specialization in face processing focusing on ERP research in healthy participants. Two databases were searched for studies that investigated left and right electrodes while participants viewed (mostly neutral) facial stimuli. The included studies used a variety of different tasks, which ranged from passive viewing to memorizing faces. The final data selection highlights, that strongest lateralization to the RH was found for the N170, especially for right-handed young male participants. Left-handed, female, and older participants showed less consistent lateralization patterns. Other ERP components like the P1, P2, N2, P3, and the N400 were overall less clearly lateralized. The current review highlights that many of the assumed lateralization patterns are less clear than previously thought and that the variety of stimuli, tasks, and EEG setups used, might contribute to the ambiguous findings.

Motor network dynamic resting state fMRI connectivity of neurotypical children in regions affected by cerebral palsy

Background

Normative childhood motor network resting-state fMRI effective connectivity is undefined, yet necessary for translatable dynamic resting-state-network-informed evaluation in pediatric cerebral palsy.

Methods

Cross-spectral dynamic causal modeling of resting-state-fMRI was investigated in 50 neurotypically developing 5- to 13-year-old children. Fully connected six-node network models per hemisphere included primary motor cortex, striatum, subthalamic nucleus, globus pallidus internus, thalamus, and contralateral cerebellum. Parametric Empirical Bayes with exhaustive Bayesian model reduction and Bayesian modeling averaging informed the model; Purdue Pegboard Test scores of hand motor behavior were the covariate at the group level to determine the effective-connectivity-functional behavior relationship.

Results

Although both hemispheres exhibited similar effective connectivity of motor cortico-basal ganglia-cerebellar networks, magnitudes were slightly greater on the right, except for left-sided connections of the striatum which were more numerous and of opposite polarity. Inter-nodal motor network effective connectivity remained consistent and robust across subjects. Age had a greater impact on connections to the contralateral cerebellum, bilaterally. Motor behavior, however, affected different connections in each hemisphere, exerting a more prominent effect on the left modulatory connections to the subthalamic nucleus, contralateral cerebellum, primary motor cortex, and thalamus.

Discussion

This study revealed a consistent pattern of directed resting-state effective connectivity in healthy children aged 5-13 years within the motor network, encompassing cortical, subcortical, and cerebellar regions, correlated with motor skill proficiency. Both hemispheres exhibited similar effective connectivity within motor cortico-basal ganglia-cerebellar networks reflecting inter-nodal signal direction predicted by other modalities, mainly differing from task-dependent studies due to network differences at rest. Notably, age-related changes were more pronounced in connections to the contralateral cerebellum. Conversely, motor behavior distinctly impacted connections in each hemisphere, emphasizing its role in modulating left sided connections to the subthalamic nucleus, contralateral cerebellum, primary motor cortex, and thalamus. Motor network effective connectivity was correlated with motor behavior, validating its physiological significance. This study is the first to evaluate a normative effective connectivity model for the pediatric motor network using resting-state functional MRI correlating with behavior and serves as a foundation for identifying abnormal findings and optimizing targeted interventions like deep brain stimulation, potentially influencing future therapeutic approaches for children with movement disorders.

Lateralisation of nasal cycle is not reflected in the olfactory bulb volumes and cerebral activations

Nasal cycle (NC) is a rhythmic change of lateralised nasal airflow mediated by the autonomous nervous system. Previous studies reported the dependence of NC dominance or more patent side on handedness and hemispheric cerebral activity. We aimed to investigate firstly the possible lateralised effect of NC on olfactory bulb volume and secondly the association of NC with the lateralised cerebral dominance in terms of olfactory processing. Thirty-five subjects (22 women and 13 men, mean age 26 ± 3 years) participated in the study. NC was ascertained using a portable rhino-flowmeter. Structural and functional brain measurements were assessed using a 3T MR scanner. Vanillin odorant was presented during functional scans using a computer-controlled olfactometer. NC was found to be independent of the olfactory bulb volumes. Also, cerebral activations were found independent of the NC during odorant perception. NC potency is not associated with lateralised structural or functional differences in the cerebral olfactory system.

Strength of spatial correlation between gray matter connectivity and patterns of proto-oncogene and neural network construction gene expression is associated with diffuse glioma survival

Introduction

Like other forms of neuropathology, gliomas appear to spread along neural pathways. Accordingly, our group and others have previously shown that brain network connectivity is highly predictive of glioma survival. In this study, we aimed to examine the molecular mechanisms of this relationship via imaging transcriptomics.

Methods

We retrospectively obtained presurgical, T1-weighted MRI datasets from 669 adult patients, newly diagnosed with diffuse glioma. We measured brain connectivity using gray matter networks and coregistered these data with a transcriptomic brain atlas to determine the spatial co-localization between brain connectivity and expression patterns for 14 proto-oncogenes and 3 neural network construction genes.

Results

We found that all 17 genes were significantly co-localized with brain connectivity (p < 0.03, corrected). The strength of co-localization was highly predictive of overall survival in a cross-validated Cox Proportional Hazards model (mean area under the curve, AUC = 0.68 +/- 0.01) and significantly (p < 0.001) more so for a random forest survival model (mean AUC = 0.97 +/- 0.06). Bayesian network analysis demonstrated direct and indirect causal relationships among gene-brain co-localizations and survival. Gene ontology analysis showed that metabolic processes were overexpressed when spatial co-localization between brain connectivity and gene transcription was highest (p < 0.001). Drug-gene interaction analysis identified 84 potential candidate therapies based on our findings.

Discussion

Our findings provide novel insights regarding how gene-brain connectivity interactions may affect glioma survival.

Associations between handedness and brain functional connectivity patterns in children

Handedness develops early in life, but the structural and functional brain connectivity patterns associated with it remains unknown. Here we investigate associations between handedness and the asymmetry of brain connectivity in 9- to 10-years old children from the Adolescent Brain Cognitive Development (ABCD) study. Compared to right-handers, left-handers had increased global functional connectivity density in the left-hand motor area and decreased it in the right-hand motor area. A connectivity-based index of handedness provided a sharper differentiation between right- and left-handers. The laterality of hand-motor connectivity varied as a function of handedness in unimodal sensorimotor cortices, heteromodal areas, and cerebellum (P < 0.001) and reproduced across all regions of interest in Discovery and Replication subsamples. Here we show a strong association between handedness and the laterality of the functional connectivity patterns in the absence of differences in structural connectivity, brain morphometrics, and cortical myelin between left, right, and mixed handed children.

Assessing mental demand in consecutive interpreting: Insights from an fNIRS study

Consecutive interpreting involves a demanding language task where mental workload (MWL) is crucial for assessing interpreters' performance. An elevated cognitive load in interpreters may lead to the interpretation failures. The widely used NASA-TLX questionnaire effectively measures MWL. However, a global score was employed in previous interpretation studies, overlooking the distinct contributions of MWL components to the interpreters' performance. Accordingly, we recruited twenty novice interpreters who were postgraduate students specializing in interpreting to complete the consecutive interpreting task. Throughout the process, we used functional near-infrared spectroscopy (fNIRS) to monitor the hemodynamic response in participants' brains. The NASA-TLX was used to measure the MWL during interpreting with six components, including mental demand, physical demand, temporal demand, performance, effort, and frustration. Five interpretation experts were invited to assess the interpretation quality. The Bayes factor approach was employed to explore the components that contributes the most to the interpretation quality. It indicated that mental demand strongly contributed to the interpretation quality. Moreover, the mediation analysis revealed a positive correlation between mental demand and brain activation in three brain areas, which, in turn, was negatively correlated with interpretation quality, indicating the predictive role of mental demand in interpretation quality through the mediating of brain activation. The functions of the mediating brain areas, including the inferior frontal gyrus, middle temporal gyrus, and inferior temporal gyrus, aligned with the three efforts proposed by Gile's effort model, which emphasizes the significance of three fundamental efforts in achieving successful interpreting. These findings have implications for interpreter learning and training.

Brain asymmetries from mid- to late life and hemispheric brain age

The human brain demonstrates structural and functional asymmetries which have implications for ageing and mental and neurological disease development. We used a set of magnetic resonance imaging (MRI) metrics derived from structural and diffusion MRI data in N=48,040 UK Biobank participants to evaluate age-related differences in brain asymmetry. Most regional grey and white matter metrics presented asymmetry, which were higher later in life. Informed by these results, we conducted hemispheric brain age (HBA) predictions from left/right multimodal MRI metrics. HBA was concordant to conventional brain age predictions, using metrics from both hemispheres, but offers a supplemental general marker of brain asymmetry when setting left/right HBA into relationship with each other. In contrast to WM brain asymmetries, left/right discrepancies in HBA are lower at higher ages. Our findings outline various sex-specific differences, particularly important for brain age estimates, and the value of further investigating the role of brain asymmetries in brain ageing and disease development.

Abnormal hemispheric specialization and inter-hemispheric functional cooperation in generalized anxiety disorder

Abnormal hemispheric specialization and inter-hemispheric interactions may contribute to the pathogenesis of general anxiety disorder (GAD). The current study investigated these abnormalities in GAD patients based on the two analytic approaches and examined whether such abnormalities are correlated with anxiety symptom severity. Seventy-three patients with GAD and 60 matched healthy controls were recruited. All participants completed anxiety symptoms assessment and resting-state functional magnetic resonance imaging (rs-fMRI). The autonomy index (AI) and Connectivity between Functionally Homotopic voxels (CFH) were applied to measure and compared between groups. Compared to controls, patients showed stronger AI in the right middle temporal gyrus (MTG). Seed-based analysis revealed stronger functional connectivity (FC) of the right MTG with both right precuneus and right dorsolateral prefrontal cortex (dlPFC) in patients. Patients also exhibited greater CFH in right anterior cingulate cortex (ACC) but decreased CFH in bilateral postcentral gyrus (PCG) and superior occipital gyrus (SOG). Further there were significant correlations between these regional CFH and anxiety symptoms severity. GAD patients demonstrate right hemispheric specialization and aberrant inter-hemispheric functional cooperation, and abnormal inter-hemispheric coordination is associated with anxiety symptom severity. These findings provide a clue to understanding the neuropathological mechanisms of GAD.

Carving the Biodevelopment of Same-Sex Sexual Orientation at Its Joints

Sexual orientation is a core aspect of human experience and understanding its development is fundamental to psychology as a scientific discipline. Biological perspectives have played an important role in uncovering the processes that contribute to sexual orientation development. Research in this field has relied on a variety of populations, including community, clinical, and cross-cultural samples, and has commonly focused on female gynephilia (i.e., female sexual attraction to adult females) and male androphilia (i.e., male sexual attraction to adult males). Genetic, hormonal, and immunological processes all appear to influence sexual orientation. Consistent with biological perspectives, there are sexual orientation differences in brain development and evidence indicates that similar biological influences apply across cultures. An outstanding question in the field is whether the hypothesized biological influences are all part of the same process or represent different developmental pathways leading to same-sex sexual orientation. Some studies indicate that same-sex sexually oriented people can be divided into subgroups who likely experienced different biological influences. Consideration of gender expression in addition to sexual orientation might help delineate such subgroups. Thus, future research on the possible existence of such subgroups could prove to be valuable for uncovering the biological development of sexual orientation. Recommendations for such future research are discussed.

Language network lateralization is reflected throughout the macroscale functional organization of cortex

Hemispheric specialization is a fundamental feature of human brain organization. However, it is not yet clear to what extent the lateralization of specific cognitive processes may be evident throughout the broad functional architecture of cortex. While the majority of people exhibit left-hemispheric language dominance, a substantial minority of the population shows reverse lateralization. Using twin and family data from the Human Connectome Project, we provide evidence that atypical language dominance is associated with global shifts in cortical organization. Individuals with atypical language organization exhibit corresponding hemispheric differences in the macroscale functional gradients that situate discrete large-scale networks along a continuous spectrum, extending from unimodal through association territories. Analyses reveal that both language lateralization and gradient asymmetries are, in part, driven by genetic factors. These findings pave the way for a deeper understanding of the origins and relationships linking population-level variability in hemispheric specialization and global properties of cortical organization.

Gestational age-related changes in relaxation times of neonatal brain by quantitative synthetic magnetic resonance imaging

OBJECTIVE

This study aimed to explore the correlation between T1 and T2 relaxation times of synthetic MRI (SyMRI) and gestational age (GA) in each hemisphere of preterm and term newborns at the initial 28 days of birth.

METHODS

Seventy preterm and full-term infants were prospectively included in this study. All subjects completed 3.0 T routine MRI and SyMRI (MAGiC) one-stop scanning within 28 days of birth (aged 34-42 W at examination). The SyMRI postprocessing software (v8.0.4) was used to measure the T1 and T2 relaxation values of each brain region. The linear regression equations of quantitative relaxation values with GA were established to compare the variation speed in each brain region.

RESULTS

A significant linear and negative correlation was found between relaxation times and GA in the neonate cerebral cortex and subcortical gray and white matter regions (All p<.05). The relaxation time of the left centrum semiovale decreased with maximum variance with increasing GA among all white matter regions (T1: b = -51.45, β = -0.65, p < .0001; T2: b = -8.77, β = -0.71, p < .0001), whereas the right posterior limb of internal capsule showed minimal variance (T1: b = -27.94, β = -0.60, p < .0001; T2: b = -3.25, β = -0.68, p < .0001). Among all gray matter regions, the right globus pallidus and thalamus indicated the most significant decreasing degree of T1 and T2 relaxation values with GA (right globus pallidus T1: b = -33.14, β = -0.64, p < .0001; right thalamus T2: b = -3.94, β = -0.81, p < .0001), and the right and left occipital lobes indicated the least significant decreasing degree of T1 and T2 relaxation values with GA, respectively (right occipital lobes T1: b = -11.18, β = -0.26, p = .028; left occipital lobes T2: b = -1.22, β = -0.27, p = .024).

CONCLUSIONS

SyMRI could quantitatively evaluate the linear changes of T1 and T2 relaxation values with GA in brain gray and white matter of preterm and term neonates.

Gyral peaks and patterns in human brains

Cortical folding patterns are related to brain function, cognition, and behavior. Since the relationship has not been fully explained on a coarse scale, many efforts have been devoted to the identification of finer grained cortical landmarks, such as sulcal pits and gyral peaks, which were found to remain invariant across subjects and ages and the invariance may be related to gene mediated proto-map. However, gyral peaks were only investigated on macaque monkey brains, but not on human brains where the investigation is challenged due to high inter-individual variabilities. To this end, in this work, we successfully identified 96 gyral peaks both on the left and right hemispheres of human brains, respectively. These peaks are spatially consistent across individuals. Higher or sharper peaks are more consistent across subjects. Both structural and functional graph metrics of peaks are significantly different from other cortical regions, and more importantly, these nodal graph metrics are anti-correlated with the spatial consistency metrics within peaks. In addition, the distribution of peaks and various cortical anatomical, structural/functional connective features show hemispheric symmetry. These findings provide new clues to understanding the cortical landmarks, as well as their relationship with brain functions, cognition, behavior in both healthy and aberrant brains.

Brain functional specialization in obsessive-compulsive disorder associated with neurotransmitter profiles

BACKGROUND

Cerebral specialization is an important functional architecture of the human brain. Abnormal cerebral specialization may be the underlying pathogenesis of obsessive-compulsive disorder (OCD). Resting-state functional magnetic resonance imaging (rs-fMRI) was used to show that the specialization pattern of OCD was of great significance for early warning and precise intervention of the disease.

METHOD

The autonomy index (AI) based on the rs-fMRI was calculated to compare brain specializations between 80 OCD patients and 81 matched healthy controls (HCs). In addition, we also correlated the AI alteration patterns with neurotransmitter receptor/transporter densities.

RESULTS

OCD patients showed increased AI in the right insula and right superior temporal gyrus when compared with HCs. In addition, AI differences were associated with serotonin receptors (5-HT_1AR and 5HT₄R), dopamine D2 receptors, norepinephrine transporters, and metabotropic glutamate receptor densities.

LIMITATIONS

Drug effect; cross-sectional study design; the selection of positron emission tomography template.

CONCLUSIONS

This study showed abnormal specialization patterns in OCD patients, which may lead to the elucidation of the underlying pathological mechanism of the disease.

Morphological development of the human fetal striatum during the second trimester

The morphological development of the fetal striatum during the second trimester has remained poorly described. We manually segmented the striatum using 7.0-T MR images of the fetal specimens ranging from 14 to 22 gestational weeks. The global development of the striatum was evaluated by volume measurement. The absolute volume (Vabs) of the caudate nucleus (CN) increased linearly with gestational age, while the relative volume (Vrel) showed a quadratic growth. Both Vabs and Vrel of putamen increased linearly. Through shape analysis, the changes of local structure in developing striatum were specifically demonstrated. Except for the CN tail, the lateral and medial parts of the CN grew faster than the middle regions, with a clear rostral-caudal growth gradient as well as a distinct "outside-in" growth gradient. For putamen, the dorsal and ventral regions grew obviously faster than the other regions, with a dorsal-ventral bidirectional developmental pattern. The right CN was larger than the left, whereas there was no significant hemispheric asymmetry in the putamen. By establishing the developmental trajectories, spatial heterochrony, and hemispheric dimorphism of human fetal striatum, these data bring new insight into the fetal striatum development and provide detailed anatomical references for future striatal studies.

Lateralization of short-term memory in the frontal cortex

Despite essentially symmetric structures in mammalian brains, the left and right hemispheres do not contribute equally to certain cognitive functions. How both hemispheres interact to cause this asymmetry remains unclear. Here, we study this question in the anterior lateral motor cortex (ALM) of mice performing five versions of a tactile-based decision-making task with a short-term memory (STM) component. Unilateral inhibition of ALM produces variable behavioral deficits across tasks, with the left, right, or both ALMs playing critical roles in STM. Neural activity and its encoding capability are similar across hemispheres, despite that only one hemisphere dominates in behavior. Inhibition of the dominant ALM disrupts encoding capability in the non-dominant ALM, but not vice versa. Variable behavioral deficits are predicted by the influence on contralateral activity across sessions, mice, and tasks. Together, these results reveal that the left and right ALM interact asymmetrically, leading to their differential contributions to STM.

Patient-Specific Characteristics Associated with Favorable Response to Vagus Nerve Stimulation

OBJECTIVE

The expansion in treatments for medically refractory epilepsy heightens the importance of identifying patients who are likely to benefit from vagus nerve stimulation (VNS). Here, we identify predictors with a positive VNS response.

METHODS

We present a retrospective analysis of 158 patients with medically refractory epilepsy. Patients were categorized as VNS responders or nonresponders. Baseline characteristics and time to VNS response were recorded. Univariate and multivariate Cox regression were used to identify predictors of response. Recursive partitioning analysis was used to identify likely VNS responders.

RESULTS

Eighty-nine (56.3%) patients achieved ≥50% seizure frequency reduction. Left-hand dominance (hazard ratio [HR] 1.703, P = 0.038), age at epilepsy onset ≥15 years (HR 2.029, P = 0.005), duration of epilepsy ≥8 years (HR 1.968, P = 0.007) and age at implantation ≥35 years (HR 1.809, P = 0.020), and baseline seizure frequency <5/month (HR 1.569, P = 0.044) were significant univariate predictors of VNS response. Following multivariate Cox regression, left-hand dominance, age at epilepsy onset ≥15 years, and duration of epilepsy ≥8 years remained significant. With recursive partitioning analysis, patients with either age at epilepsy onset ≥15 years, left-hand dominance, or baseline seizure frequency <5/month were stratified into Group A and had a 73.9% responder rate; the remaining patients stratified into Group B had a 43.8% responder rate.

CONCLUSIONS

Patients with age at epilepsy onset ≥15 years, left-hand dominance, or baseline seizure frequency <5/month are ideal candidates for VNS.

Neuropathological fingerprints of survival, atrophy and language in primary progressive aphasia

Primary progressive aphasia is a neurodegenerative disease that selectively impairs language without equivalent impairment of speech, memory or comportment. In 118 consecutive autopsies on patients with primary progressive aphasia, primary diagnosis was Alzheimer's disease neuropathological changes (ADNC) in 42%, corticobasal degeneration or progressive supranuclear palsy neuropathology in 24%, Pick's disease neuropathology in 10%, transactive response DNA binding proteinopathy type A [TDP(A)] in 10%, TDP(C) in 11% and infrequent entities in 3%. Survival was longest in TDP(C) (13.2 ± 2.6 years) and shortest in TDP(A) (7.1 ± 2.4 years). A subset of 68 right-handed participants entered longitudinal investigations. They were classified as logopenic, agrammatic/non-fluent or semantic by quantitative algorithms. Each variant had a preferred but not invariant neuropathological correlate. Seventy-seven per cent of logopenics had ADNC, 56% of agrammatics had corticobasal degeneration/progressive supranuclear palsy or Pick's disease and 89% of semantics had TDP(C). Word comprehension impairments had strong predictive power for determining underlying neuropathology positively for TDP(C) and negatively for ADNC. Cortical atrophy was smallest in corticobasal degeneration/progressive supranuclear palsy and largest in TDP(A). Atrophy encompassed posterior frontal but not temporoparietal cortex in corticobasal degeneration/progressive supranuclear palsy, anterior temporal but not frontoparietal cortex in TDP(C), temporofrontal but not parietal cortex in Pick's disease and all three lobes with ADNC or TDP(A). There were individual deviations from these group patterns, accounting for less frequent clinicopathologic associations. The one common denominator was progressive asymmetric atrophy overwhelmingly favouring the left hemisphere language network. Comparisons of ADNC in typical amnestic versus atypical aphasic dementia and of TDP in type A versus type C revealed fundamental biological and clinical differences, suggesting that members of each pair may constitute distinct clinicopathologic entities despite identical downstream proteinopathies. Individual TDP(C) participants with unilateral left temporal atrophy displayed word comprehension impairments without additional object recognition deficits, helping to dissociate semantic primary progressive aphasia from semantic dementia. When common and uncommon associations were considered in the set of 68 participants, one neuropathology was found to cause multiple clinical subtypes, and one subtype of primary progressive aphasia to be caused by multiple neuropathologies, but with different probabilities. Occasionally, expected clinical manifestations of atrophy sites were absent, probably reflecting individual peculiarities of language organization. The hemispheric asymmetry of neurodegeneration and resultant language impairment in primary progressive aphasia reflect complex interactions among the cellular affinities of the degenerative disease, the constitutive biology of language cortex, familial or developmental vulnerabilities of this network and potential idiosyncrasies of functional anatomy in the affected individual.

Acute Effects of Various Movement Noise in Differential Learning of Rope Skipping on Brain and Heart Recovery Analyzed by Means of Multiscale Fuzzy Measure Entropy

In search of more detailed explanations for body-mind interactions in physical activity, neural and physiological effects, especially regarding more strenuous sports activities, increasingly attract interest. Little is known about the underlying manifold (neuro-)physiological impacts induced by different motor learning approaches. The various influences on brain or cardiac function are usually studied separately and modeled linearly. Limitations of these models have recently led to a rapidly growing application of nonlinear models. This study aimed to investigate the acute effects of various sequences of rope skipping on irregularity of the electrocardiography (ECG) and electroencephalography (EEG) signals as well as their interaction and whether these depend on different levels of active movement noise, within the framework of differential learning theory. Thirty-two males were randomly and equally distributed to one of four rope skipping conditions with similar cardiovascular but varying coordinative demand. ECG and EEG were measured simultaneously at rest before and immediately after rope skipping for 25 mins. Signal irregularity of ECG and EEG was calculated via the multiscale fuzzy measure entropy (MSFME). Statistically significant ECG and EEG brain area specific changes in MSFME were found with different pace of occurrence depending on the level of active movement noise of the particular rope skipping condition. Interaction analysis of ECG and EEG MSFME specifically revealed an involvement of the frontal, central, and parietal lobe in the interplay with the heart. In addition, the number of interaction effects indicated an inverted U-shaped trend presenting the interaction level of ECG and EEG MSFME dependent on the level of active movement noise. In summary, conducting rope skipping with varying degrees of movement variation appears to affect the irregularity of cardiac and brain signals and their interaction during the recovery phase differently. These findings provide enough incentives to foster further constructive nonlinear research in exercise-recovery relationship and to reconsider the philosophy of classical endurance training.

Common principles in the lateralisation of auditory cortex structure and function for vocal communication in primates and rodents

This review summarises recent findings on the lateralisation of communicative sound processing in the auditory cortex (AC) of humans, non-human primates, and rodents. Functional imaging in humans has demonstrated a left hemispheric preference for some acoustic features of speech, but it is unclear to which degree this is caused by bottom-up acoustic feature selectivity or top-down modulation from language areas. Although non-human primates show a less pronounced functional lateralisation in AC, the properties of AC fields and behavioral asymmetries are qualitatively similar. Rodent studies demonstrate microstructural circuits that might underlie bottom-up acoustic feature selectivity in both hemispheres. Functionally, the left AC in the mouse appears to be specifically tuned to communication calls, whereas the right AC may have a more 'generalist' role. Rodents also show anatomical AC lateralisation, such as differences in size and connectivity. Several of these functional and anatomical characteristics are also lateralized in human AC. Thus, complex vocal communication processing shares common features among rodents and primates. We argue that a synthesis of results from humans, non-human primates, and rodents is necessary to identify the neural circuitry of vocal communication processing. However, data from different species and methods are often difficult to compare. Recent advances may enable better integration of methods across species. Efforts to standardise data formats and analysis tools would benefit comparative research and enable synergies between psychological and biological research in the area of vocal communication processing.

Deciphering the Interregional and Interhemisphere Proteome of the Human Brain in the Context of the Human Proteome Project

This study, which performs an extensive mass spectrometry-based analysis of 19 brain regions from both left and right hemispheres, presents the first draft of the human brain interhemispheric proteome. This high-resolution proteomics data provides comprehensive coverage of 3300 experimentally measured (nonhypothetical) proteins across multiple regions, allowing the characterization of protein-centric interhemispheric differences and synapse biology, and portrays the regional mapping of specific regions for brain disorder biomarkers. In the context of the Human Proteome Project (HPP), the interhemispheric proteome data reveal specific markers like chimerin 2 (CHN2) in the cerebellar vermis, olfactory marker protein (OMP) in the olfactory bulb, and ankyrin repeat domain 63 (ANKRD63) in basal ganglia, in line with regional brain transcriptomes mapped in the Human Protein Atlas (HPA). In addition, an in silico analysis pipeline was used to predict the structure and function of the uncharacterized uPE1 protein ANKRD63, and parallel reaction monitoring (PRM) was applied to validate its region-specific expression. Finally, we have built the Interhemispheric Brain Proteome Map (IBPM) Portal (www.brainprot.org) to stimulate the scientific community's interest in the brain molecular landscape and accelerate and support research in neuroproteomics. Data are available via ProteomeXchange with identifier PXD019936.

How does hemispheric specialization contribute to human-defining cognition?

Uniquely human cognitive faculties arise from flexible interplay between specific local neural modules, with hemispheric asymmetries in functional specialization. Here, we discuss how these computational design principles provide a scaffold that enables some of the most advanced cognitive operations, such as semantic understanding of world structure, logical reasoning, and communication via language. We draw parallels to dual-processing theories of cognition by placing a focus on Kahneman's System 1 and System 2. We propose integration of these ideas with the global workspace theory to explain dynamic relay of information products between both systems. Deepening the current understanding of how neurocognitive asymmetry makes humans special can ignite the next wave of neuroscience-inspired artificial intelligence.

Atypical Brain Asymmetry in Human Situs Inversus: Gut Feeling or Real Evidence?

The alignment of visceral and brain asymmetry observed in some vertebrate species raises the question of whether this association also exists in humans. While the visceral and brain systems may have developed asymmetry for different reasons, basic visceral left–right differentiation mechanisms could have been duplicated to establish brain asymmetry. We describe the main phenotypical anomalies and the general mechanism of left–right differentiation of vertebrate visceral and brain laterality. Next, we systematically review the available human studies that explored the prevalence of atypical behavioral and brain asymmetry in visceral situs anomalies, which almost exclusively involved participants with the mirrored visceral organization (situs inversus). The data show no direct link between human visceral and brain functional laterality as most participants with situs inversus show the typical population bias for handedness and brain functional asymmetry, although an increased prevalence of functional crowding may be present. At the same time, several independent studies present evidence for a possible relation between situs inversus and the gross morphological asymmetry of the brain torque with potential differences between subtypes of situs inversus with ciliary and non-ciliary etiologies.

Sexual Dimorphisms and Asymmetries of the Thalamo-Cortical Pathways and Subcortical Grey Matter of Term Born Healthy Neonates: An Investigation with Diffusion Tensor MRI

Diffusion-tensor-MRI was performed on 28 term born neonates. For each hemisphere, we quantified separately the axial and the radial diffusion (AD, RD), the apparent diffusion coefficient (ADC) and the fractional anisotropy (FA) of the thalamo-cortical pathway (THC) and four structures: thalamus (TH), putamen (PT), caudate nucleus (CN) and globus-pallidus (GP). There was no significant difference between boys and girls in either the left or in the right hemispheric THC, TH, GP, CN and PT. In the combined group (boys + girls) significant left greater than right symmetry was observed in the THC (AD, RD and ADC), and TH (AD, ADC). Within the same group, we reported left greater than right asymmetry in the PT (FA), CN (RD and ADC). Different findings were recorded when we split the group of neonates by gender. Girls exhibited right > left AD, RD and ADC in the THC and left > right FA in the PT. In the group of boys, we observed right > left RD and ADC. We also reported left > right FA in the PT and left > right RD in the CN. These results provide insights into normal asymmetric development of sensory-motor networks within boys and girls.

A probabilistic atlas of the human ventral tegmental area (VTA) based on 7 Tesla MRI data

Functional magnetic resonance imaging (fMRI) BOLD signal is commonly localized by using neuroanatomical atlases, which can also serve for region of interest analyses. Yet, the available MRI atlases have serious limitations when it comes to imaging subcortical structures: only 7% of the 455 subcortical nuclei are captured by current atlases. This highlights the general difficulty in mapping smaller nuclei deep in the brain, which can be addressed using ultra-high field 7 Tesla (T) MRI. The ventral tegmental area (VTA) is a subcortical structure that plays a pivotal role in reward processing, learning and memory. Despite the significant interest in this nucleus in cognitive neuroscience, there are currently no available, anatomically precise VTA atlases derived from 7 T MRI data that cover the full region of the VTA. Here, we first provide a protocol for multimodal VTA imaging and delineation. We then provide a data description of a probabilistic VTA atlas based on in vivo 7 T MRI data.

The effects of hand preference and sex on right-left asymmetry in dorsal digit lengths among adults and children

BACKGROUND

Right-hand preference is related to stronger right-directional asymmetry in the length of proximal upper-limb bones, although the relationships of hand preference with directional asymmetry in phalangeal bone lengths are not known. Furthermore, dorsal digit length is an easy-to-measure, faithful proxy of X-rayed phalangeal bone length (which is costly and difficult to measure).

AIM

To study the effects of hand preference, sex, and age on right-left (R-L) asymmetry in dorsal digit lengths.

METHODS

We measured all dorsal digit lengths (except the thumb) in comparable numbers of left-handers and right-handers in samples of adults (N = 151, age: M = 22.6 years, SD = 3.3) and children (N = 65, age: M = 5.0 years, SD = 1.0).

RESULTS

Right-handers and adults had stronger right-directional asymmetry in digit lengths than left-handers and children. A Bayesian analysis yielded an 'extremely strong likelihood' of no sex differences in the R-L asymmetry of dorsal digit lengths 2 and 4.

CONCLUSIONS

The effects of hand preference, sex, and age on R-L asymmetry appear to be similar for phalangeal bone length and other (proximal) upper-limb bone lengths. Two distinct biologic mechanisms (i.e., a general right-directional asymmetry mechanism and a handedness-related directional asymmetry mechanism) may contribute to observed R-L asymmetry in limbs. Fingertip fat and bone digit length do not seem to contribute to sex differences in the R-L asymmetry (Dr-l) of the widely studied second-to-fourth digit ratio (2D:4D).

GABAergic motor neurons bias locomotor decision-making in C. elegans

Proper threat-reward decision-making is critical to animal survival. Emerging evidence indicates that the motor system may participate in decision-making but the neural circuit and molecular bases for these functions are little known. We found in C. elegans that GABAergic motor neurons (D-MNs) bias toward the reward behavior in threat-reward decision-making by retrogradely inhibiting a pair of premotor command interneurons, AVA, that control cholinergic motor neurons in the avoidance neural circuit. This function of D-MNs is mediated by a specific ionotropic GABA receptor (UNC-49) in AVA, and depends on electrical coupling between the two AVA interneurons. Our results suggest that AVA are hub neurons where sensory inputs from threat and reward sensory modalities and motor information from D-MNs are integrated. This study demonstrates at single-neuron resolution how motor neurons may help shape threat-reward choice behaviors through interacting with other neurons.

Handedness and Birth Order Among Heterosexual Men, Gay Men, and Sao Praphet Song in Northern Thailand

Previous research has examined handedness and birth order to inform sexual orientation and gender identity/role expression development; however, sexual orientation and gender identity/role expression have rarely been disentangled to provide a more nuanced perspective. In Thailand, we investigated sexual orientation and gender identity simultaneously via comparison of 282 heterosexual men, 201 gay men, and 178 sao praphet song-i.e., androphilic, markedly feminine males recognized as a "third" gender. Handedness was examined as: extremely left-handed, moderately left-handed, ambidextrous, moderately right-handed, or extremely right-handed. Birth order was examined as numbers of older and younger brothers and sisters, by using Berglin's, fraternal, and sororal indices, and by examining the older brother odds ratio and sibling sex ratio. Compared with heterosexual men, gay men and sao praphet song were more likely to be extremely right-handed. Sao praphet song were also more likely to be extremely left-handed than heterosexual and gay men. Heterosexual men and sao praphet song had later sororal birth order compared with the expected Thai population value, suggesting stopping rules influenced when probands' mothers ceased having children. These findings provide new insights and replicate previous findings in a non-Western sample. Regarding handedness, in males, mechanisms related to extreme right-handedness likely influence the development of androphilia, whereas mechanisms related to both extreme right- and extreme left-handedness likely explain the combination of androphilia and feminine gender identity/role expression. Regarding birth order, similar to the conclusions of some prior research, stopping rules pose a challenge for testing the fraternal birth order effect.

Paw preference is associated with behavioural despair and spatial reference memory in male rats

Paw preference, one of the well-studied behavioural markers of asymmetry, has been associated with affective states and pathologies such as behavioural despair, a rodent model of clinical depression. However, a consistent differential effect of paw preference has not been observed for cognitive functions. In order to investigate the affective properties of paw preference together with its potential cognitive effects, we grouped male Wistar rats as left- or right-pawed, and tested them in the forced swim test and Morris water maze for behavioural despair and spatial memory performance, respectively. We found that left-pawed rats were significantly more susceptible to behavioural despair, while spatial learning performance of the two groups were not different over a five-day Morris water maze task. Left-pawed rats, however, displayed a better reference memory than the right-pawed ones on the subsequent probe trial when the hidden platform of the maze was removed. These findings indicate paw preference as a vulnerability factor for behavioural despair and reveal a previously unknown association between left-paw preference and reference memory performance as assessed in the probe trial of the Morris water maze.

Reproducibility of leftward planum temporale asymmetries in two genetically isolated populations of chimpanzees (Pan troglodytes)

Once considered a hallmark of human uniqueness, brain asymmetry has emerged as a feature shared with several other species, including chimpanzees, one of our closest living relatives. Most notable has been the discovery of asymmetries in homologues of cortical language areas in apes, particularly in the planum temporale (PT), considered a central node of the human language network. Several lines of evidence indicate a role for genetic mechanisms in the emergence of PT asymmetry; however, the genetic determinants of cerebral asymmetries have remained elusive. Studies in humans suggest that there is heritability of brain asymmetries of the PT, but this has not been explored to any extent in chimpanzees. Furthermore, the potential influence of non-genetic factors has raised questions about the reproducibility of earlier observations of PT asymmetry reported in chimpanzees. As such, the present study was aimed at examining both the heritability of phenotypic asymmetries in PT morphology, as well as their reproducibility. Using magnetic resonance imaging, we evaluated morphological asymmetries of PT surface area (mm2) and mean depth (mm) in captive chimpanzees (n = 291) derived from two genetically isolated populations. Our results confirm that chimpanzees exhibit a significant population-level leftward asymmetry for PT surface area, as well as significant heritability in the surface area and mean depth of the PT. These results conclusively demonstrate the existence of a leftward bias in PT asymmetry in chimpanzees and suggest that genetic mechanisms play a key role in the emergence of anatomical asymmetry in this region.

Differential expression of microRNAs in the human fetal left and right cerebral cortex

Human brain is anatomically and functionally asymmetric. How brain asymmetry is initiated and established during fetal development is poorly understood. Accumulating evidence has shown that microRNAs (miRNAs) play crucial roles in brain development and function. In this study, we investigate miRNA expression profiles in left and right hemispheres of human fetal brains at 12 weeks post conception (PC), and identify 42 miRNAs showing differential expression between two hemispheres using Affymetrix microarray analyses. Target genes for left- and right-biased miRNAs are largely involved in developmental and functional regulations in the cortex such as axon guidance, GABAergic synapse and dopaminergic synapse pathways. Moreover, we find that predicted targets associated with canonical and non-canonical WNT signaling pathway show variations and differential expression between two hemispheres in response to left- and right-biased miRNAs. Our results highlight a potential role of miRNAs in regulating asymmetric development of human fetal brains.

Possible Physical Basis of Mirror Symmetry Effect in Racemic Mixtures of Enantiomers: From Wallach’s Rule, Nonlinear Effects, B–Z DNA Transition, and Similar Phenomena to Mirror Symmetry Effects of Chiral Objects

Effects associated with mirror symmetry may be underlying for a number of phenomena in chemistry and physics. Increase in the density and melting point of the 50%L/50%D collection of enantiomers of a different sign (Wallach’s rule) is probably based on a physical effect of the mirror image. The catalytic activity of metal complexes with racemic ligands differs from the corresponding complexes with enantiomers as well (nonlinear effect). A similar difference in the physical properties of enantiomers and racemate underlies L/D inversion points of linear helical macromolecules, helical nanocrystals of magnetite and boron nitride etc., B–Z DNA transition and phenomenon of mirror neurons may have a similar nature. Here we propose an explanation of the Wallach effect along with some similar chemical, physical, and biological phenomena related to mirror image.

Is Handedness Associated with the Depth of the Olfactory Sulcus?

BACKGROUND

Structural and functional asymmetry is frequent in biological systems. The aim of the present study was to examine whether there is a relation between handedness and the depth of the olfactory sulcus (OS) and reinvestigate whether there is a lateralization of OS depth.

METHODS

Forty-two healthy volunteers (mean age 24.1 years; 23 right-handed and 19 left-handed) participated. The subjects' brains were scanned using magnetic resonance imaging to assess OS depth. Normal olfactory function was ascertained using the Sniffin' Sticks odor identification test.

RESULTS

There was no significant difference in OS depth between right- and left-handed participants (right-handed mean: right OS depth = 11.3 mm, left OS = 10.6 mm; left-handed mean: right OS = 11.3 mm, left OS = 11.0 mm). Across all subjects, OS depth was significantly larger on the right side compared to the left.

CONCLUSION

Handedness has no major influence on OS depth. The present study confirmed that the right OS is deeper compared to the left OS, possibly indicating a right-sided lateralization of the olfactory system.

IMPLICATIONS

The depth of the right OS is larger than that of the left OS. No major effect of handedness was observed.

Frontal cerebral oxygenation asymmetry: intersubject variability and dependence on systemic physiology, season, and time of day

Significance: Our study reveals that frontal cerebral oxygenation asymmetry (FCOA), i.e. a difference in the oxygenation between the right and left prefrontal cortex (PFC), is a real phenomenon in healthy human subjects at rest. Aim: To investigate FCOA, we performed a study with 134 healthy right-handed subjects with the systemic physiology augmented functional near infrared spectroscopy (SPA-fNIRS) approach. Approach: Subjects were measured 2 to 4 times on different days resulting in an unprecedented number of 518 single measurements of the absolute values of tissue oxygen saturation (StO 2 ) and total hemoglobin concentration ([tHb]) of the right and left PFC. Measurements were performed with frequency-domain functional near-infrared spectroscopy. In addition, the cardiorespiratory parameters were measured simultaneously. Results: We found that (i) subjects showed an FCOA (higherStO 2 on the right PFC), but not for tHb; (ii) intrasubject variability was excellent for bothStO 2 and tHb, and fair for FCOA; (iii) StO 2 correlated significantly with bloodCO 2 concentration, [tHb] with heart rate, respiration rate (RR), and the pulse-respiration quotient (PRQ), and FCOA with RR and PRQ; (iv) FCOA andStO 2 were dependent on season and time of day, respectively; (v) FCOA was negatively correlated with the room temperature; and (vi) StO 2 and tHb were not correlated with the subjects mood but with their chronotype, whereas FCOA was not dependent on the chronotype. Conclusion: Our study demonstrates that FCOA is real, and it provides unique insights into this remarkable phenomenon.

Cerebral asymmetry during development using linear measures from MRI

Asymmetry of the human brain is a well-known phenomenon, but the nature and extent of these differences throughout postnatal development have not been examined. Accordingly, linear measurements of the brains of 121 infants, children, and adolescents were determined to ascertain cerebral hemispheric asymmetries. Using multiple statistical methods, the results showed that: 1) the frontal lobe is wider on the right, while the occipital lobe is wider on the left; 2) there are no side to side differences in cerebral hemispheric length or height; and 3) there are no major sex differences. Especially notable is the lack of any correlation between side to side differences in length, width, or height and increasing age, which was also the case for cerebral hemispheric area or volume with increasing age. Regarding petalias: 1) the right frontal petalia occurs in 61%, the left occipital in 60%, and both petalias in 36% of the cohort; 2) the right frontal and left occipital petalias are of similar lengths; 3) the distances of both petalias increase with advancing age but not when scaled to either cerebral hemispheric area or volume, indicating that petalias are equally prominent early in postnatal life compared to later development; and 4) there are no major sex differences in the frequency or magnitude of either petalia. These findings provide comprehensive new information regarding age and sex related cerebral hemispheric asymmetries during development.

Behavioural laterality in foraging bottlenose dolphins (Tursiops truncatus)

Lateralized behaviour is found in humans and a wide variety of other species. At a population level, lateralization of behaviour suggests hemispheric specialization may underlie this behaviour. As in other cetaceans, dolphins exhibit a strong right-side bias in foraging behaviour. Common bottlenose dolphins in The Bahamas use a foraging technique termed 'crater feeding', in which they swim slowly along the ocean floor, scanning the substrate using echolocation, and then bury their rostrums into the sand to obtain prey. The bottlenose dolphins off Bimini, The Bahamas, frequently execute a sharp turn before burying their rostrums in the sand. Based on data collected from 2012 to 2018, we report a significant right-side (left turn) bias in these dolphins. Out of 709 turns recorded from at least 27 different individuals, 99.44% (n = 705) were to the left (right side and right eye down) [z = 3.275, p = 0.001]. Only one individual turned right (left side and left eye down, 4/4 turns). We hypothesize that this right-side bias may be due in part to the possible laterization of echolocation production mechanisms, the dolphins' use of the right set of phonic lips to produce echolocation clicks, and a right eye (left hemisphere) advantage in visual discrimination and visuospatial processing.

The molecular genetics of hand preference revisited

Hand preference is a prominent behavioural trait linked to human brain asymmetry. A handful of genetic variants have been reported to associate with hand preference or quantitative measures related to it. Most of these reports were on the basis of limited sample sizes, by current standards for genetic analysis of complex traits. Here we performed a genome-wide association analysis of hand preference in the large, population-based UK Biobank cohort (N = 331,037). We used gene-set enrichment analysis to investigate whether genes involved in visceral asymmetry are particularly relevant to hand preference, following one previous report. We found no evidence supporting any of the previously suggested variants or genes, nor that genes involved in visceral laterality have a role in hand preference. It remains possible that some of the previously reported genes or pathways are relevant to hand preference as assessed in other ways, or else are relevant within specific disorder populations. However, some or all of the earlier findings are likely to be false positives, and none of them appear relevant to hand preference as defined categorically in the general population. Our analysis did produce a small number of novel, significant associations, including one implicating the microtubule-associated gene MAP2 in handedness.

High-Spatial-Resolution Diffusion MRI in Parkinson Disease: Lateral Asymmetry of the Substantia Nigra

Background Motor symptoms in Parkinson disease (PD) have exhibited lateral asymmetry, suggesting asymmetric neuronal loss in the substantia nigra (SN). Diffusion MRI may be able to help confirm tissue microstructural alterations in the substantia nigra to probe for the presence of asymmetry. Purpose To investigate lateral asymmetry in the SN of patients with PD by using diffusion MRI with both Gaussian and non-Gaussian models. Materials and Methods In this cross-sectional study conducted from March 2015 to March 2017, 27 participants with PD and 27 age-matched healthy control (HC) participants, all right handed, underwent MRI at 3.0 T. High-spatial-resolution diffusion images were acquired with a reduced field of view by using seven b values up to 3000 sec/mm². A continuous-time random-walk (CTRW) non-Gaussian diffusion model was used to produce anomalous diffusion coefficient (D_m) and temporal (α) and spatial (β) diffusion heterogeneity indexes followed by a Gaussian diffusion model to yield an apparent diffusion coefficient (ADC). Individual or linear combinations of diffusion parameters in the SN were unilaterally and bilaterally compared between the PD and HC groups. Results In the bilateral comparison between the PD and HC groups, differences were observed in β (0.67 ± 0.06 [standard deviation] vs 0.64 ± 0.04, respectively; P = .016), ADC (0.48 μm²/msec ± 0.08 vs 0.53 μm²/msec ± 0.06, respectively; P = .03), and the combination of CTRW parameters (P = .02). In the unilateral comparison, differences were observed in all diffusion parameters on the left SN (P < .03), but not on the right (P > .20). In a receiver operating characteristic (ROC) analysis to delineate left SN abnormality in PD, the combination of D_m, α, and β produced the best sensitivity (sensitivity, 0.78); the combination of D_m and β produced the best specificity (specificity, 0.85); and the combination of α and β produced the largest area under the ROC curve (area under the ROC curve, 0.73). Conclusion These results suggest that quantitative diffusion MRI is sensitive to brain tissue changes in participants with Parkinson disease and provide evidence of substantia nigra lateral asymmetry in this disease. © RSNA, 2019 Online supplemental material is available for this article.

Gray matter volumetric study of major depression and suicidal behavior

Structural brain deficits are linked to risk for suicidal behavior. However, there is disagreement about the nature of these deficits, probably due to the heterogeneity of suicidal behavior in terms of the suicidal act's lethality. We hypothesized that individuals with major depressive disorder (MDD) and history of more lethal suicide attempts would have lower gray matter volume (GMV) of the prefrontal regions and insula compared with MDD lower-lethality attempters and MDD non-attempters. We collected structural MRI scans on 91 individuals with MDD; 11 with history of higher-lethality suicide attempts, 14 with lower-lethality attempts, and 66 were non-attempters. Differences in GMV between these three groups were examined using both regions-of-interest (ROI) and brain-wide voxel-based morphometry (VBM) analyses. Both ROI and VBM analyses showed that higher-lethality suicide attempters have greater GMV of the prefrontal cortical regions and insula, compared with the other two groups. Although this contrasts with our hypothesis, the observed larger prefrontal cortex GMV in higher-lethality suicide attempters may underlie the set of attributes observed previously in this suicidal subgroup, including enhanced suicide attempt planning, greater response inhibition, and delayed reward capabilities. Future studies should further examine the role of these brain regions in relation to suicidal intent and planning.

Chiral Neuronal Motility: The Missing Link between Molecular Chirality and Brain Asymmetry

Left–right brain asymmetry is a fundamental property observed across phyla from invertebrates to humans, but the mechanisms underlying its formation are still largely unknown. Rapid progress in our knowledge of the formation of body asymmetry suggests that brain asymmetry might be controlled by the same mechanisms. However, most of the functional brain laterality, including language processing and handedness, does not share common mechanisms with visceral asymmetry. Accumulating evidence indicates that asymmetry is manifested as chirality at the single cellular level. In neurons, the growth cone filopodia at the tips of neurites exhibit a myosin V-dependent, left-helical, and right-screw rotation, which drives the clockwise circular growth of neurites on adhesive substrates. Here, I propose an alternative model for the formation of brain asymmetry that is based on chiral neuronal motility. According to this chiral neuron model, the molecular chirality of actin filaments and myosin motors is converted into chiral neuronal motility, which is in turn transformed into the left–right asymmetry of neural circuits and lateralized brain functions. I also introduce automated, numerical, and quantitative methods to analyze the chirality and the left–right asymmetry that would enable the efficient testing of the model and to accelerate future investigations in this field.

Acute Effects of Instructed and Self-Created Variable Rope Skipping on EEG Brain Activity and Heart Rate Variability

The influence of physical activity on brain and heart activity dependent on type and intensity of exercise is meanwhile widely accepted. Mainly cyclic exercises with longer duration formed the basis for showing the influence on either central nervous system or on heart metabolism. Effects of the variability of movement sequences on brain and heart have been studied only sparsely so far. This study investigated effects of three different motor learning approaches combined with a single bout of rope skipping exercises on the spontaneous electroencephalographic (EEG) brain activity, heart rate variability (HRV) and the rate of perceived exertion (RPE). Participants performed repetitive learning (RL) and two extremely variable rope skipping schedules according to the differential learning approach. Thereby one bout was characterized by instructed variable learning (DLi) and the other by self-created variable learning (DLc) in randomized order each on three consecutive days. The results show higher RPE after DLi and DLc than after RL. HRV analysis demonstrates significant changes in pre-post exercise comparison in all training approaches. No statistically significant differences between training schedules were identified. Slightly greater changes in HRV parameters were observed in both DL approaches indicating a higher activation of the sympathetic nervous system. EEG data reveals higher parietal alpha1 and temporal alpha2 power in RL compared to both DL schedules immediately post exercise. During the recovery of up to 30 min, RL shows higher temporal and occipital theta, temporal, parietal and occipital alpha, temporal and occipital beta and frontal beta3 power. In conclusion, already a single bout of 3 min of rope skipping can lead to brain states that are associated with being advantageous for cognitive learning. Combined with additional, cognitively demanding tasks in form of the DL approach, it seems to lead to an overload of the mental capacity, at least on the short term. Further research should fathom the reciprocal influence of cardiac and central-nervous strain in greater detail.

Single cell transcriptome profiling of retinal ganglion cells identifies cellular subtypes

Retinal ganglion cells (RGCs) convey the major output of information collected from the eye to the brain. Thirty subtypes of RGCs have been identified to date. Here, we analyze 6225 RGCs (average of 5000 genes per cell) from right and left eyes by single-cell RNA-seq and classify them into 40 subtypes using clustering algorithms. We identify additional subtypes and markers, as well as transcription factors predicted to cooperate in specifying RGC subtypes. Zic1, a marker of the right eye-enriched subtype, is validated by immunostaining in situ. Runx1 and Fst, the markers of other subtypes, are validated in purified RGCs by fluorescent in situ hybridization (FISH) and immunostaining. We show the extent of gene expression variability needed for subtype segregation, and we show a hierarchy in diversification from a cell-type population to subtypes. Finally, we present a website for comparing the gene expression of RGC subtypes.

Deregulation of polycomb repressor complex 1 modifier AUTS2 in T-cell leukemia

Recently, we identified deregulated expression of the B-cell specific transcription factor MEF2C in T-cell acute lymphoid leukemia (T-ALL). Here, we performed sequence analysis of a regulatory upstream section of MEF2C in T-ALL cell lines which, however, proved devoid of mutations. Unexpectedly, we found strong conservation between the regulatory upstream region of MEF2C (located at chromosomal band 5q14) and an intergenic stretch at 7q11 located between STAG3L4 and AUTS2, covering nearly 20 kb. While the non-coding gene STAG3L4 was inconspicuously expressed, AUTS2 was aberrantly upregulated in 6% of T-ALL patients (public dataset GSE42038) and in 3/24 T-ALL cell lines, two of which represented very immature differentiation stages. AUTS2 expression was higher in normal B-cells than in T-cells, indicating lineage-specific activity in lymphopoiesis. While excluding chromosomal aberrations, examinations of AUTS2 transcriptional regulation in T-ALL cells revealed activation by IL7-IL7R-STAT5-signalling and MEF2C. AUTS2 protein has been shown to interact with polycomb repressor complex 1 subtype 5 (PRC1.5), transforming this particular complex into an activator. Accordingly, expression profiling and functional analyses demonstrated that AUTS2 activated while PCGF5 repressed transcription of NKL homeobox gene MSX1 in T-ALL cells. Forced expression and pharmacological inhibition of EZH2 in addition to H3K27me3 analysis indicated that PRC2 repressed MSX1 as well. Taken together, we found that AUTS2 and MEF2C, despite lying on different chromosomes, share strikingly similar regulatory upstream regions and aberrant expression in T-ALL subsets. Our data implicate chromatin complexes PRC1/AUTS2 and PRC2 in a gene network in T-ALL regulating early lymphoid differentiation.

Brain Lateralization in Mice Is Associated with Zinc Signaling and Altered in Prenatal Zinc Deficient Mice That Display Features of Autism Spectrum Disorder

A number of studies have reported changes in the hemispheric dominance in autism spectrum disorder (ASD) patients on functional, biochemical, and morphological level. Since asymmetry of the brain is also found in many vertebrates, we analyzed whether prenatal zinc deficient (PZD) mice, a mouse model with ASD like behavior, show alterations regarding brain lateralization on molecular and behavioral level. Our results show that hemisphere-specific expression of marker genes is abolished in PZD mice on mRNA and protein level. Using magnetic resonance imaging, we found an increased striatal volume in PZD mice with no change in total brain volume. Moreover, behavioral patterns associated with striatal lateralization are altered and the lateralized expression of dopamine receptor 1 (DR1) in the striatum of PZD mice was changed. We conclude that zinc signaling during brain development has a critical role in the establishment of brain lateralization in mice.