The von Economo neurons in the frontoinsular and anterior cingulate cortex

Herbert Major on the insula: An early depiction of von Economo neurones?

Herbert Major (1850-1921) undertook histopathological studies of human and non-human primate brains at the West Riding Lunatic Asylum in Wakefield, England, during the 1870s. Two of his papers specifically investigated the structure of the island of Reil, or insula, "with the view of ascertaining its exact structure". In addition to describing and illustrating its lamination as six-layered, Major also identified "spindle-shaped" cells in the lower layers of human brains, but not in non-human primates. His written description, including measurements of cell body size, and illustration are suggestive that these were the neurones later described in the frontoinsular and anterior cingulate cortex by Constantin von Economo and Georg N. Koskinas and which were subsequently given the eponym "von Economo neurones". von Economo noted that this special neuronal type had been previously seen by Betz (1881), Hammarberg (1895), and Ramón y Cajal (1899-1904), but he did not mention Major's works. Major also ascribed linguistic functions to the insula. Hence, with respect to both anatomical and physiological features, Major may have pre-empted the findings of later research on this structure.

Impact of repeated blast exposure on active-duty United States Special Operations Forces

United States (US) Special Operations Forces (SOF) are frequently exposed to explosive blasts in training and combat, but the effects of repeated blast exposure (RBE) on SOF brain health are incompletely understood. Furthermore, there is no diagnostic test to detect brain injury from RBE. As a result, SOF personnel may experience cognitive, physical, and psychological symptoms for which the cause is never identified, and they may return to training or combat during a period of brain vulnerability. In 30 active-duty US SOF, we assessed the relationship between cumulative blast exposure and cognitive performance, psychological health, physical symptoms, blood proteomics, and neuroimaging measures (Connectome structural and diffusion MRI, 7 Tesla functional MRI, [11C]PBR28 translocator protein [TSPO] positron emission tomography [PET]-MRI, and [18F]MK6240 tau PET-MRI), adjusting for age, combat exposure, and blunt head trauma. Higher blast exposure was associated with increased cortical thickness in the left rostral anterior cingulate cortex (rACC), a finding that remained significant after multiple comparison correction. In uncorrected analyses, higher blast exposure was associated with worse health-related quality of life, decreased functional connectivity in the executive control network, decreased TSPO signal in the right rACC, and increased cortical thickness in the right rACC, right insula, and right medial orbitofrontal cortex-nodes of the executive control, salience, and default mode networks. These observations suggest that the rACC may be susceptible to blast overpressure and that a multimodal, network-based diagnostic approach has the potential to detect brain injury associated with RBE in active-duty SOF.

Updating functional brain units: Insights far beyond Luria

This paper reviews Luria's model of the three functional units of the brain. To meet this objective, several issues were reviewed: the theory of functional systems and the contributions of phylogenesis and embryogenesis to the brain's functional organization. This review revealed several facts. In the first place, the relationship/integration of basic homeostatic needs with complex forms of behavior. Secondly, the multi-scale hierarchical and distributed organization of the brain and interactions between cells and systems. Thirdly, the phylogenetic role of exaptation, especially in basal ganglia and cerebellum expansion. Finally, the tripartite embryogenetic organization of the brain: rhinic, limbic/paralimbic, and supralimbic zones. Obviously, these principles of brain organization are in contradiction with attempts to establish separate functional brain units. The proposed new model is made up of two large integrated complexes: a primordial-limbic complex (Luria's Unit I) and a telencephalic-cortical complex (Luria's Units II and III). As a result, five functional units were delineated: Unit I. Primordial or preferential (brainstem), for life-support, behavioral modulation, and waking regulation; Unit II. Limbic and paralimbic systems, for emotions and hedonic evaluation (danger and relevance detection and contribution to reward/motivational processing) and the creation of cognitive maps (contextual memory, navigation, and generativity [imagination]); Unit III. Telencephalic-cortical, for sensorimotor and cognitive processing (gnosis, praxis, language, calculation, etc.), semantic and episodic (contextual) memory processing, and multimodal conscious agency; Unit IV. Basal ganglia systems, for behavior selection and reinforcement (reward-oriented behavior); Unit V. Cerebellar systems, for the prediction/anticipation (orthometric supervision) of the outcome of an action. The proposed brain units are nothing more than abstractions within the brain's simultaneous and distributed physiological processes. As function transcends anatomy, the model necessarily involves transition and overlap between structures. Beyond the classic approaches, this review includes information on recent systemic perspectives on functional brain organization. The limitations of this review are discussed.

The insula: Leveraging cellular and systems-level research to better understand its roles in health and schizophrenia

Schizophrenia is a highly heterogeneous disorder characterized by a multitude of complex and seemingly non-overlapping symptoms. The insular cortex has gained increasing attention in neuroscience and psychiatry due to its involvement in a diverse range of fundamental human experiences and behaviors. This review article provides an overview of the insula's cellular and anatomical organization, functional and structural connectivity, and functional significance. Focusing on specific insula subregions and using knowledge gained from humans and preclinical studies of insular tracings in non-human primates, we review the literature and discuss the functional roles of each subregion, including in somatosensation, interoception, salience processing, emotional processing, and social cognition. Building from this foundation, we then extend these findings to discuss reported abnormalities of these functions in individuals with schizophrenia, implicating insular involvement in schizophrenia pathology. This review underscores the insula's vast role in the human experience and how abnormal insula structure and function could result in the wide-ranging symptoms observed in schizophrenia.

Single-cell dissection of the human motor and prefrontal cortices in ALS and FTLD

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) share many clinical, pathological, and genetic features, but a detailed understanding of their associated transcriptional alterations across vulnerable cortical cell types is lacking. Here, we report a high-resolution, comparative single-cell molecular atlas of the human primary motor and dorsolateral prefrontal cortices and their transcriptional alterations in sporadic and familial ALS and FTLD. By integrating transcriptional and genetic information, we identify known and previously unidentified vulnerable populations in cortical layer 5 and show that ALS- and FTLD-implicated motor and spindle neurons possess a virtually indistinguishable molecular identity. We implicate potential disease mechanisms affecting these cell types as well as non-neuronal drivers of pathogenesis. Finally, we show that neuron loss in cortical layer 5 tracks more closely with transcriptional identity rather than cellular morphology and extends beyond previously reported vulnerable cell types.

Altered empathy processing in frontotemporal dementia A task-based fMRI study

A lack of empathy, and particularly its affective components, is a core symptom of behavioural variant frontotemporal dementia (bvFTD). Visual exposure to images of a needle pricking a hand (pain condition) and Q-tips touching a hand (control condition) is an established functional magnetic resonance imaging (fMRI) paradigm used to investigate empathy for pain (EFP; pain condition minus control condition). EFP has been associated with increased blood oxygen level dependent (BOLD) signal in regions known to become atrophic in the early stages in bvFTD, including the anterior insula and the anterior cingulate. We therefore hypothesized that patients with bvFTD would display altered empathy processing in the EFP paradigm. Here we examined empathy processing using the EFP paradigm in 28 patients with bvFTD and 28 sex and age matched controls. Participants underwent structural MRI, task-based and resting-state fMRI. The Interpersonal Reactivity Index (IRI) was used as a measure of different facets of empathic function outside the scanner. The EFP paradigm was analysed at a whole brain level and using two regions-of-interest approaches, one based on a metanalysis of affective perceptual empathy versus cognitive evaluative empathy and one based on the controĺs activation pattern. In controls, EFP was linked to an expected increase of BOLD signal that displayed an overlap with the pattern of atrophy in the bvFTD patients (insula and anterior cingulate). Additional regions with increased signal were the supramarginal gyrus and the occipital cortex. These latter regions were the only ones that displayed increased BOLD signal in bvFTD patients. BOLD signal increase under the affective perceptual empathy but not the cognitive evaluative empathy region of interest was significantly greater in controls than in bvFTD patients. The controĺs rating on their empathic concern subscale of the IRI was significantly correlated with the BOLD signal in the EFP paradigm, as were an informantś ratings of the patientś empathic concern subscale. This correlation was not observed on other subscales of the IRI or when using the patient's self-ratings. Finally, controls and patients showed different connectivity patterns in empathy related networks during resting-state fMRI, mainly in nodes overlapping the ventral attention network. Our results indicate that reduced neural activity in regions typically affected by pathology in bvFTD is associated with reduced empathy processing, and a predictor of patientś capacity to experience affective empathy.

The prefrontal cortex: from monkey to man

The prefrontal cortex is so important to human beings that, if deprived of it, our behaviour is reduced to action-reactions and automatisms, with no ability to make deliberate decisions. Why does the prefrontal cortex hold such importance in humans? In answer, this review draws on the proximity between humans and other primates, which enables us, through comparative anatomical-functional analysis, to understand the cognitive functions we have in common and specify those that distinguish humans from their closest cousins. First, a focus on the lateral region of the prefrontal cortex illustrates the existence of a continuum between rhesus monkeys (the most studied primates in neuroscience) and humans for most of the major cognitive functions in which this region of the brain plays a central role. This continuum involves the presence of elementary mental operations in the rhesus monkey (e.g. working memory or response inhibition) that are constitutive of 'macro-functions' such as planning, problem-solving and even language production. Second, the human prefrontal cortex has developed dramatically compared to that of other primates. This increase seems to concern the most anterior part (the frontopolar cortex). In humans, the development of the most anterior prefrontal cortex is associated with three major and interrelated cognitive changes: (i) a greater working memory capacity, allowing for greater integration of past experiences and prospective futures; (ii) a greater capacity to link discontinuous or distant data, whether temporal or semantic; and (iii) a greater capacity for abstraction, allowing humans to classify knowledge in different ways, to engage in analogical reasoning or to acquire abstract values that give rise to our beliefs and morals. Together, these new skills enable us, among other things, to develop highly sophisticated social interactions based on language, enabling us to conceive beliefs and moral judgements and to conceptualize, create and extend our vision of our environment beyond what we can physically grasp. Finally, a model of the transition of prefrontal functions between humans and non-human primates concludes this review.

Association between polymorphism rs6295 of HTR1A serotonin receptor gene and personality traits among athletes of combat sport

HTR1A (5-hydroxytryptamine receptor 1A) and its polymorphic variants are highly important for athletes in different aspects, allowing us to hypothesize their biological influences. Hence, to investigate at least part of the relationship mentioned in the case literature, it was decided to study the association of the selected HTR1A polymorphism with personality traits measured by the Temperament and Character Inventory (TCI). The participants consisted of 250 mixed martial arts (combat sport) athletes and 209 healthy male participants (control group). The personality traits were measured for the Revised Temperament and Character Inventory (TCI-R). Genetic material was isolated from whole blood collected from patients, and then all samples were genotyped using the real-time PCR method. Statistical analysis was performed using a 2 × 3 factorial ANOVA. The research revealed a statistically significant effect of a complex factor of rs6295 of the HTR1A serotonin receptor gene with combat sport/control and with Novelty Seeking (F2,453 = 6.126; p = 0.0024; η2 = 0.026) and Harm Avoidance (F2,453 = 3.709; p = 0.0252; η2 = 0.016). The presence of the HTR1A GG genotype (rs6295) was found to be associated with higher scores in self-management and lower scores in harm avoidance, indicating genetic predispositions in the strength group towards better results in combat sports.

FTLD targets brain regions expressing recently evolved genes

In frontotemporal lobar degeneration (FTLD), pathological protein aggregation is associated with a decline in human-specialized social-emotional and language functions. Most disease protein aggregates contain either TDP-43 (FTLD-TDP) or tau (FTLD-tau). Here, we explored whether FTLD targets brain regions that express genes containing human accelerated regions (HARs), conserved sequences that have undergone positive selection during recent human evolution. To this end, we used structural neuroimaging from patients with FTLD and normative human regional transcriptomic data to identify genes expressed in FTLD-targeted brain regions. We then integrated primate comparative genomic data to test our hypothesis that FTLD targets brain regions expressing recently evolved genes. In addition, we asked whether genes expressed in FTLD-targeted brain regions are enriched for genes that undergo cryptic splicing when TDP-43 function is impaired. We found that FTLD-TDP and FTLD-tau subtypes target brain regions that express overlapping and distinct genes, including many linked to neuromodulatory functions. Genes whose normative brain regional expression pattern correlated with FTLD cortical atrophy were strongly associated with HARs. Atrophy-correlated genes in FTLD-TDP showed greater overlap with TDP-43 cryptic splicing genes compared with atrophy-correlated genes in FTLD-tau. Cryptic splicing genes were enriched for HAR genes, and vice versa, but this effect was due to the confounding influence of gene length. Analyses performed at the individual-patient level revealed that the expression of HAR genes and cryptically spliced genes within putative regions of disease onset differed across FTLD-TDP subtypes. Overall, our findings suggest that FTLD targets brain regions that have undergone recent evolutionary specialization and provide intriguing potential leads regarding the transcriptomic basis for selective vulnerability in distinct FTLD molecular-anatomical subtypes.

The anatomy of the four streams of the prefrontal cortex. Preliminary evidence from a population based high definition tractography study

The model of the four streams of the prefrontal cortex proposes 4 streams of information: motor through Brodmann area (BA) 8, emotion through BA 9, memory through BA 10, and emotional-related sensory through BA 11. Although there is a surge of functional data supporting these 4 streams within the PFC, the structural connectivity underlying these neural networks has not been fully clarified. Here we perform population-based high-definition tractography using an averaged template generated from data of 1,065 human healthy subjects acquired from the Human Connectome Project to further elucidate the structural organization of these regions. We report the structural connectivity of BA 8 with BA 6, BA 9 with the insula, BA 10 with the hippocampus, BA 11 with the temporal pole, and BA 11 with the amygdala. The 4 streams of the prefrontal cortex are subserved by a structural neural network encompassing fibers of the anterior part of the superior longitudinal fasciculus-I and II, corona radiata, cingulum, frontal aslant tract, and uncinate fasciculus. The identified neural network of the four streams of the PFC will allow the comprehensive analysis of these networks in normal and pathological brain function.

Theoretical Neurobiology of Consciousness Applied to Human Cerebral Organoids

Organoids and specifically human cerebral organoids (HCOs) are one of the most relevant novelties in the field of biomedical research. Grown either from embryonic or induced pluripotent stem cells, HCOs can be used as in vitro three-dimensional models, mimicking the developmental process and organization of the developing human brain. Based on that, and despite their current limitations, it cannot be assumed that they will never at any stage of development manifest some rudimentary form of consciousness. In the absence of behavioral indicators of consciousness, the theoretical neurobiology of consciousness being applied to unresponsive brain-injured patients can be considered with respect to HCOs. In clinical neurology, it is difficult to discern a capacity for consciousness in unresponsive brain-injured patients who provide no behavioral indicators of consciousness. In such scenarios, a validated neurobiological theory of consciousness, which tells us what the neural mechanisms of consciousness are, could be used to identify a capacity for consciousness. Like the unresponsive patients that provide a diagnostic difficulty for neurologists, HCOs provide no behavioral indicators of consciousness. Therefore, this article discusses how three prominent neurobiological theories of consciousness apply to human cerebral organoids. From the perspective of the Temporal Circuit Hypothesis, the Global Neuronal Workspace Theory, and the Integrated Information Theory, we discuss what neuronal structures and functions might indicate that cerebral organoids have a neurobiological capacity to be conscious.

Spectroscopic abnormalities in the pregenual anterior cingulate cortex in obsessive-compulsive disorder using proton magnetic resonance spectroscopy: a controlled study

BACKGROUND

The main aim of the present study is to determine the role of metabolites observed using proton magnetic resonance spectroscopy (1H-MRS) in obsessive-compulsive disorder (OCD). As the literature describing biochemical changes in OCD yields conflicting results, we focused on accurate metabolite quantification of total N-acetyl aspartate (tNAA), total creatine (tCr), total choline-containing compounds (tCh), and myo-inositol (mI) in the anterior cingulate cortex (ACC) to capture the small metabolic changes between OCD patients and controls and between OCD patients with and without medication.

METHODS

In total 46 patients with OCD and 46 healthy controls (HC) matched for age and sex were included in the study. The severity of symptoms in the OCD was evaluated on the day of magnetic resonance imaging (MRI) using the Yale-Brown Obsessive-Compulsive Scale (YBOCS). Subjects underwent 1H-MRS from the pregenual ACC (pgACC) region to calculate concentrations of tNAA, tCr, tCho, and mI. Twenty-eight OCD and 28 HC subjects were included in the statistical analysis. We compared differences between groups for all selected metabolites and in OCD patients we analyzed the relationship between metabolite levels and symptom severity, medication status, age, and the duration of illness.

RESULTS

Significant decreases in tCr (U = 253.00, p = 0.022) and mI (U = 197.00, p = 0.001) in the pgACC were observed in the OCD group. No statistically significant differences were found in tNAA and tCho levels; however, tCho revealed a trend towards lower concentrations in OCD patients (U = 278.00, p = 0.062). Metabolic concentrations showed no significant correlations with the age and duration of illness. The correlation statistics found a significant negative correlation between tCr levels and YBOCS compulsions subscale (cor = -0.380, p = 0.046). tCho and YBOCS compulsions subscale showed a trend towards a negative correlation (cor = -0.351, p = 0.067). Analysis of subgroups with or without medication showed no differences.

CONCLUSIONS

Patients with OCD present metabolic disruption in the pgACC. The decrease in tCr shows an important relationship with OCD symptomatology. tCr as a marker of cerebral bioenergetics may also be considered as a biomarker of the severity of compulsions. The study failed to prove that metabolic changes correlate with the medication status or the duration of illness. It seems that a disruption in the balance between these metabolites and their transmission may play a role in the pathophysiology of OCD.

Glutamatergic abnormalities in the pregenual anterior cingulate cortex in obsessive-compulsive disorder using magnetic resonance spectroscopy: A controlled study

In this study, we utilized proton magnetic resonance spectroscopy (MRS) to understand the role of glutamate (Glu), glutamine (Gln), and gamma-aminobutyric acid (GABA) of OCD patients in the pregenual anterior cingulate cortex (pgACC). In total, 54 patients with OCD and 54 healthy controls (HC) matched for age and sex were included in the study. They underwent MRS in the pgACC region to calculate the concentrations of Glu, Gln, GABA, and Glu + Gln (Glx). After quality control of the MRS data, 21 OCD and 21 HC were statistically analyzed. The severity of symptoms were evaluated using the Yale-Brown Obsessive-Compulsive Scale (YBOCS). In the statistical analysis, we compared differences between groups for the metabolites; in the OCD we analyzed the correlations with symptom severity, medication status, age, and duration of illness. A significant decrease in Glx, in Glu, and in Gln in the pgACC were observed in the OCD compared to HC. The correlation statistics showed a significant positive correlation between Glu levels and the YBOCS compulsions subscale. The results indicate that patients with OCD present a disturbance in glutamatergic metabolism in the pgACC. The results also demonstrate that these changes correlate with the severity of compulsions.

An Update on Apathy in Alzheimer's Disease

Apathy is a complex multi-dimensional syndrome that affects up to 70% of individuals with Alzheimer's disease (AD). Whilst many frameworks to define apathy in AD exist, most include loss of motivation or goal-directed behaviour as the central feature. Apathy is associated with significant impact on persons living with AD and their caregivers and is also associated with accelerated cognitive decline across the AD spectrum. Neuroimaging studies have highlighted a key role of fronto-striatial circuitry including the anterior cingulate cortex (ACC), orbito-frontal cortex (OFC) and associated subcortical structures. Importantly, the presence and severity of apathy strongly correlates with AD stage and neuropathological biomarkers of amyloid and tau pathology. Following from neurochemistry studies demonstrating a central role of biogenic amine neurotransmission in apathy syndrome in AD, recent clinical trial data suggest that apathy symptoms may improve following treatment with agents such as methylphenidate-which may have an important role alongside emerging non-pharmacological treatment strategies. Here, we review the diagnostic criteria, rating scales, prevalence, and risk factors for apathy in AD. The underlying neurobiology, neuropsychology and associated neuroimaging findings are reviewed in detail. Finally, we discuss current treatment approaches and strategies aimed at targeting apathy syndrome in AD, highlighting areas for future research and clinical trials in patient cohorts.

Towards a Neurophenomenological Understanding of Self-Disorder in Schizophrenia Spectrum Disorders: A Systematic Review and Synthesis of Anatomical, Physiological, and Neurocognitive Findings

The concept of anomalous self-experience, also termed Self-Disorder, has attracted both clinical and research interest, as empirical studies suggest such experiences specifically aggregate in and are a core feature of schizophrenia spectrum disorders. A comprehensive neurophenomenological understanding of Self-Disorder may improve diagnostic and therapeutic practice. This systematic review aims to evaluate anatomical, physiological, and neurocognitive correlates of Self-Disorder (SD), considered a core feature of Schizophrenia Spectrum Disorders (SSDs), towards developing a neurophenomenological understanding. A search of the PubMed database retrieved 285 articles, which were evaluated for inclusion using PRISMA guidelines. Non-experimental studies, studies with no validated measure of Self-Disorder, or those with no physiological variable were excluded. In total, 21 articles were included in the review. Findings may be interpreted in the context of triple-network theory and support a core dysfunction of signal integration within two anatomical components of the Salience Network (SN), the anterior insula and dorsal anterior cingulate cortex, which may mediate connectivity across both the Default Mode Network (DMN) and Fronto-Parietal Network (FPN). We propose a theoretical Triple-Network Model of Self-Disorder characterized by increased connectivity between the Salience Network (SN) and the DMN, increased connectivity between the SN and FPN, decreased connectivity between the DMN and FPN, and increased connectivity within both the DMN and FPN. We go on to describe translational opportunities for clinical practice and provide suggestions for future research.

Connecting Circuits with Networks in Addiction Neuroscience: A Salience Network Perspective

Human neuroimaging has demonstrated the existence of large-scale functional networks in the cerebral cortex consisting of topographically distant brain regions with functionally correlated activity. The salience network (SN), which is involved in detecting salient stimuli and mediating inter-network communication, is a crucial functional network that is disrupted in addiction. Individuals with addiction display dysfunctional structural and functional connectivity of the SN. Furthermore, while there is a growing body of evidence regarding the SN, addiction, and the relationship between the two, there are still many unknowns, and there are fundamental limitations to human neuroimaging studies. At the same time, advances in molecular and systems neuroscience techniques allow researchers to manipulate neural circuits in nonhuman animals with increasing precision. Here, we describe attempts to translate human functional networks to nonhuman animals to uncover circuit-level mechanisms. To do this, we review the structural and functional connections of the salience network and its homology across species. We then describe the existing literature in which circuit-specific perturbation of the SN sheds light on how functional cortical networks operate, both within and outside the context of addiction. Finally, we highlight key outstanding opportunities for mechanistic studies of the SN.

Alteration of the Functional Connectivity of the Cortical Areas Characterized by the Presence of Von Economo Neurons in Schizophrenia, a Pilot Study

Von Economo neurons (VENs) are rod, stick, or corkscrew cells mostly located in layer V of the frontoinsular and anterior cingulate cortices. VENs are projection neurons related to human-like social cognitive abilities. Post-mortem histological studies found VEN alterations in several neuropsychiatric disorders, including schizophrenia (SZ). This pilot study aimed to evaluate the role of VEN-containing areas in shaping patterns of resting-state brain activation in patients with SZ (n = 20) compared to healthy controls (HCs; n = 20). We performed a functional connectivity analysis seeded in the cortical areas with the highest density of VENs followed by fuzzy clustering. The alterations found in the SZ group were correlated with psychopathological, cognitive, and functioning variables. We found a frontotemporal network that was shared by four clusters overlapping with the salience, superior-frontal, orbitofrontal, and central executive networks. Differences between the HC and SZ groups emerged only in the salience network. The functional connectivity of the right anterior insula and ventral tegmental area within this network were negatively correlated with experiential negative symptoms and positively correlated with functioning. This study provides some evidence to show that in vivo, VEN-enriched cortical areas are associated with an altered resting-state brain activity in people with SZ.

Morphological Features of Human Dendritic Spines

Dendritic spine features in human neurons follow the up-to-date knowledge presented in the previous chapters of this book. Human dendrites are notable for their heterogeneity in branching patterns and spatial distribution. These data relate to circuits and specialized functions. Spines enhance neuronal connectivity, modulate and integrate synaptic inputs, and provide additional plastic functions to microcircuits and large-scale networks. Spines present a continuum of shapes and sizes, whose number and distribution along the dendritic length are diverse in neurons and different areas. Indeed, human neurons vary from aspiny or "relatively aspiny" cells to neurons covered with a high density of intermingled pleomorphic spines on very long dendrites. In this chapter, we discuss the phylogenetic and ontogenetic development of human spines and describe the heterogeneous features of human spiny neurons along the spinal cord, brainstem, cerebellum, thalamus, basal ganglia, amygdala, hippocampal regions, and neocortical areas. Three-dimensional reconstructions of Golgi-impregnated dendritic spines and data from fluorescence microscopy are reviewed with ultrastructural findings to address the complex possibilities for synaptic processing and integration in humans. Pathological changes are also presented, for example, in Alzheimer's disease and schizophrenia. Basic morphological data can be linked to current techniques, and perspectives in this research field include the characterization of spines in human neurons with specific transcriptome features, molecular classification of cellular diversity, and electrophysiological identification of coexisting subpopulations of cells. These data would enlighten how cellular attributes determine neuron type-specific connectivity and brain wiring for our diverse aptitudes and behavior.

The salience network is activated during self-recognition from both first-person and third-person perspectives

We usually observe ourselves from two perspectives. One is the first-person perspective, which we perceive directly with our own eyes, and the other is the third-person perspective, which we observe ourselves in a mirror or a picture. However, whether the self-recognition associated with these two perspectives has a common or separate neural basis remains unclear. To address this, we used functional magnetic resonance imaging to examine brain activity while participants viewed pretaped video clips of themselves and others engaged in meal preparation taken from first-person and third-person perspectives. We found that the first-person behavioral videos of the participants and others induced greater activation in the premotor-intraparietal region. In contrast, the third-person behavioral videos induced greater activation in the default mode network compared with the first-person videos. Regardless of the perspective, the videos of the participants induced greater activation in the salience network than the videos of others. On the other hand, the videos of others induced greater activation in the precuneus and lingual gyrus than the videos of the participants. These results suggest that the salience network is commonly involved in self-recognition from both perspectives, even though the brain regions involved in action observation for the two perspectives are distinct.

In the Body’s Eye: The computational anatomy of interoceptive inference

A growing body of evidence highlights the intricate linkage of exteroceptive perception to the rhythmic activity of the visceral body. In parallel, interoceptive inference theories of affective perception and self-consciousness are on the rise in cognitive science. However, thus far no formal theory has emerged to integrate these twin domains; instead, most extant work is conceptual in nature. Here, we introduce a formal model of cardiac active inference, which explains how ascending cardiac signals entrain exteroceptive sensory perception and uncertainty. Through simulated psychophysics, we reproduce the defensive startle reflex and commonly reported effects linking the cardiac cycle to affective behaviour. We further show that simulated ‘interoceptive lesions’ blunt affective expectations, induce psychosomatic hallucinations, and exacerbate biases in perceptual uncertainty. Through synthetic heart-rate variability analyses, we illustrate how the balance of arousal-priors and visceral prediction errors produces idiosyncratic patterns of physiological reactivity. Our model thus offers a roadmap for computationally phenotyping disordered brain-body interaction.

Understanding interactions between the brain and the body has become a topic of increased interest in computational neuroscience and psychiatry. A particular question here concerns how visceral, homeostatic rhythms such as the heart beat influence sensory, affective, and cognitive processing. To better understand these and other oscillatory brain-body interactions, we here introduce a novel computational model of interoceptive inference in which a synthetic agent’s perceptual beliefs are coupled to the rhythm of the heart. Our model both helps to explain emerging empirical data indicating that perceptual inference depends upon beat-to-beat heart rhythms, and can be used to better quantify intra- and inter-individual differences in heart-brain coupling. Using proof-of-principle simulations, we demonstrate how future empirical works could utilize our model to better understand and stratify disorders of interoception and brain-body interaction.

Von Economo neurons: Cellular specialization of human limbic cortices?

Von Economo neurons (VENs) have been mentioned in the medical literature since the second half of the 19th century; however, it was not until the second decade of the 20th century that their cytomorphology was described in detail. To date, VENs have been found in limbic sectors of the frontal, temporal and insular lobes. In humans, their density seems to decrease in the caudo-rostral and ventro-dorsal direction; that is, from the anterior regions of the cingulate and insular cortices towards the frontal pole and the superior frontal gyrus. Several studies have provided similar descriptions of the shape of the VEN soma, but the size of the soma varies from one cortical region to another. There is consensus among different authors about the selective vulnerability of VENs in certain pathologies, in which a deterioration of the capacities involved in social behaviour is observed. In this review, we propose that the restriction of VENs towards the sectors linked to limbic information processing in Homo sapiens gives them a possible functional role in relation to the structures in which they are located. However, given the divergence in characteristics such as location, density, size and biochemical profile among VENs of different cortical sectors, the activities in which they participate could allow them to partake in a wide spectrum of neurological functions, including autonomic responses and executive functions.

Anterior insula as a gatekeeper of executive control

Executive control is a complex high-level cognitive function that relies on distributed brain circuitry. We propose that the anterior insular cortex plays an under-appreciated role in executive processes, acting as a gatekeeper to other brain regions and networks by virtue of primacy of action and effective connectivity. The flexible functional profile of the anterior insular subdivision renders it a key hub within the broader midcingulo-insular 'salience network', allowing it to orchestrate and drive activity of other major functional brain networks including the medial frontoparietal 'default mode network' and lateral frontoparietal 'central executive network'. The microanatomy and large-scale connectivity of the insular cortex positions it to play a critical role in triaging and integrating internal and external multisensory stimuli in the service of initiating higher-order control functions. Multiple lines of evidence scaffold the novel hypothesis that, as a key hub for integration and a lever of network switching, the anterior insula serves as a critical gatekeeper to executive control.

Anatomical and functional connectivity support the existence of a salience network node within the caudal ventrolateral prefrontal cortex

Three large-scale networks are considered essential to cognitive flexibility: the ventral and dorsal attention (VANet and DANet) and salience (SNet) networks. The ventrolateral prefrontal cortex (vlPFC) is a known component of the VANet and DANet, but there is a gap in the current knowledge regarding its involvement in the SNet. Herein, we used a translational and multimodal approach to demonstrate the existence of a SNet node within the vlPFC. First, we used tract-tracing methods in non-human primates (NHP) to quantify the anatomical connectivity strength between different vlPFC areas and the frontal and insular cortices. The strongest connections were with the dorsal anterior cingulate cortex (dACC) and anterior insula (AI) - the main cortical SNet nodes. These inputs converged in the caudal area 47/12, an area that has strong projections to subcortical structures associated with the SNet. Second, we used resting-state functional MRI (rsfMRI) in NHP data to validate this SNet node. Third, we used rsfMRI in the human to identify a homologous caudal 47/12 region that also showed strong connections with the SNet cortical nodes. Taken together, these data confirm a SNet node in the vlPFC, demonstrating that the vlPFC contains nodes for all three cognitive networks: VANet, DANet, and SNet. Thus, the vlPFC is in a position to switch between these three networks, pointing to its key role as an attentional hub. Its additional connections to the orbitofrontal, dorsolateral, and premotor cortices, place the vlPFC at the center for switching behaviors based on environmental stimuli, computing value, and cognitive control.

Methodological aspects of studying the mechanisms of consciousness

There are at least two approaches to the definition of consciousness. In the first case, certain aspects of consciousness, called qualia, are considered inaccessible for research from a third person and can only be described through subjective experience. This approach is inextricably linked with the so-called "hard problem of consciousness", that is, the question of why consciousness has qualia or how any physical changes in the environment can generate subjective experience. With this approach, some aspects of consciousness, by definition, cannot be explained on the basis of external observations and, therefore, are outside the scope of scientific research. In the second case, a priori constraints do not constrain the field of scientific investigation, and the best explanation of the experience in the first person is included as a possible subject of empirical research. Historically, in the study of cause-and-effect relationships in biology, it was customary to distinguish between proximate causation and ultimate causation existing in biological systems. Immediate causes are based on the immediate influencing factors [1]. Proximate causation has evolutionary explanations. When studying biological systems themselves, such an approach is undoubtedly justified, but it often seems insufficient when studying the interaction of consciousness and the brain [2,3]. Current scientific communities proceed from the assumption that the physical substrate for the generation of consciousness is a neural network that unites various types of neurons located in various brain structures. Many neuroscientists attach a key role in this process to the cortical and thalamocortical neural networks. This question is directly related to experimental and clinical research in the field of disorder of consciousness. Progress in this area of medicine depends on advances in neuroscience in this area and is also a powerful source of empirical information. In this area of consciousness research, a large amount of experimental data has been accumulated, and in this review an attempt was made to generalize and systematize.

Autonomic Dysfunction in Autism Spectrum Disorder

Background: There have been previous reports of enhanced sympathoexcitation in autism spectrum disorder (ASD). However, there has been no formal investigation of autonomic dysfunction in ASD. Also, the joint hypermobile form of Ehlers-Danlos syndrome (hE-DS) that maybe overrepresented in ASD and orthostatic related autonomic dysfunction. This study examined the comorbidity of ASD, autonomic dysfunction and hE-DS in two UK autonomic national referral centers. Proven, documented and globally accepted clinical autonomic investigations were used to assess neuro-cardiovascular autonomic function in a cohort of ASD subjects and in age-matched healthy controls. Methods: Clinical data from 28 referrals with a confirmed diagnosis of ASD over a 10-year period were compared with 19 age-matched healthy controls. Autonomic function was determined using methods established in the centers previously described in detail. Results: 20/28 ASD had a diagnosed autonomic condition; 9 had the postural tachycardia syndrome (PoTS), 4 PoTS and vasovagal syncope (VVS), 3 experienced presyncope, 1 essential hyperhidrosis, 1 orthostatic hypotension, 1 VVS alone and 1 a combination of PoTS, VVS and essential hyperhidrosis. 16/20 ASD with autonomic dysfunction had hE-DS. In ASD, basal heart rate and responses to orthostatic tests of autonomic function were elevated, supporting previous findings of increased sympathoexcitation. However, sympathetic vasoconstriction was impaired in ASD. Conclusion: Intermittent neuro-cardiovascular autonomic dysfunction affecting heart rate and blood pressure was over-represented in ASD. There is a strong association with hE-DS. Autonomic dysfunction may further impair quality of life in ASD, particularly in those unable to adequately express their experience of autonomic symptoms.

Evolution of prefrontal cortex

Subdivisions of the prefrontal cortex (PFC) evolved at different times. Agranular parts of the PFC emerged in early mammals, and rodents, primates, and other modern mammals share them by inheritance. These are limbic areas and include the agranular orbital cortex and agranular medial frontal cortex (areas 24, 32, and 25). Rodent research provides valuable insights into the structure, functions, and development of these shared areas, but it contributes less to parts of the PFC that are specific to primates, namely, the granular, isocortical PFC that dominates the frontal lobe in humans. The first granular PFC areas evolved either in early primates or in the last common ancestor of primates and tree shrews. Additional granular PFC areas emerged in the primate stem lineage, as represented by modern strepsirrhines. Other granular PFC areas evolved in simians, the group that includes apes, humans, and monkeys. In general, PFC accreted new areas along a roughly posterior to anterior trajectory during primate evolution. A major expansion of the granular PFC occurred in humans in concert with other association areas, with modifications of corticocortical connectivity and gene expression, although current evidence does not support the addition of a large number of new, human-specific PFC areas.

Neural Representation of the Parent-Child Attachment from Infancy to Adulthood

Attachment theory is built on the assumption of consistency; the mother–infant bond is thought to underpin the life-long representations individuals construct of attachment relationships. Still, consistency in the individual’s neural response to attachment-related stimuli representing his or her entire relational history has not been investigated. Mothers and children were followed across two decades and videotaped in infancy (3–6 months), childhood (9–12 years) and young adulthood (18–24 years). In adulthood, participants underwent functional magnetic resonance imaging while exposed to videos of own mother–child interactions (Self) vs unfamiliar interactions (Other). Self-stimuli elicited greater activations across preregistered nodes of the human attachment network, including thalamus-to-brainstem, amygdala, hippocampus, anterior cingulate cortex (ACC), insula and temporal cortex. Critically, self-stimuli were age-invariant in most regions of interest despite large variability in social behavior, and Bayesian analysis showed strong evidence for lack of age-related differences. Psycho–physiological interaction analysis indicated that self-stimuli elicited tighter connectivity between ACC and anterior insula, consolidating an interface associating information from exteroceptive and interceptive sources to sustain attachment representations. Child social engagement behavior was individually stable from infancy to adulthood and linked with greater ACC and insula response to self-stimuli. Findings demonstrate overlap in circuits sustaining parental and child attachment and accord with perspectives on the continuity of attachment across human development.

Overt speech critically changes lateralization index and did not allow determination of hemispheric dominance for language: an fMRI study

Background

Pre-surgical mapping of language using functional MRI aimed principally to determine the dominant hemisphere. This mapping is currently performed using covert linguistic task in way to avoid motion artefacts potentially biasing the results. However, overt task is closer to natural speaking, allows a control on the performance of the task, and may be easier to perform for stressed patients and children. However, overt task, by activating phonological areas on both hemispheres and areas involved in pitch prosody control in the non-dominant hemisphere, is expected to modify the determination of the dominant hemisphere by the calculation of the lateralization index (LI).

Objective

Here, we analyzed the modifications in the LI and the interactions between cognitive networks during covert and overt speech task.

Methods

Thirty-three volunteers participated in this study, all but four were right-handed. They performed three functional sessions consisting of (1) covert and (2) overt generation of a short sentence semantically linked with an audibly presented word, from which we estimated the “Covert” and “Overt” contrasts, and a (3) resting-state session. The resting-state session was submitted to spatial independent component analysis to identify language network at rest (LANG), cingulo-opercular network (CO), and ventral attention network (VAN). The LI was calculated using the bootstrapping method.

Results

The LI of the LANG was the most left-lateralized (0.66 ± 0.38). The LI shifted from a moderate leftward lateralization for the Covert contrast (0.32 ± 0.38) to a right lateralization for the Overt contrast (− 0.13 ± 0.30). The LI significantly differed from each other. This rightward shift was due to the recruitment of right hemispheric temporal areas together with the nodes of the CO.

Conclusion

Analyzing the overt speech by fMRI allowed improvement in the physiological knowledge regarding the coordinated activity of the intrinsic connectivity networks. However, the rightward shift of the LI in this condition did not provide the basic information on the hemispheric language dominance. Overt linguistic task cannot be recommended for clinical purpose when determining hemispheric dominance for language.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12868-021-00671-y.

Constantin von Economo´s 90th death anniversary

The year of 2021 marks 90 year since the death of the neuroscientist Constantin von Economo, whose research in various areas was extremely relevant for the field of neurology. He described lethargic epidemic encephalitis, published an atlas of the cytoarchitecture of the human cerebral cortex, and conducted multiple studies in neuroanatomy, neurophysiology, and clinical neurology. Von Economo's genius extended into other nonmedical fields such as aeronautics, and he had renowned artistic skills.

Ideas on a possible neural pathway in depression

Depression is the second leading cause of disability in the world. Despite developing some efficacious treatments, many patients do not respond to the treatment well due to the complexity of depression and unknown mechanisms involved in its pathogenesis. It has been reported that patients with major depressive disorder (MDD) experience autonomic dysfunctions in different aspects. Evidence suggests that modulation of the autonomic nervous system may improve depression. Von Economo neurons (VENs) are shown to be involved in the pathophysiology of some of the neurological and psychological diseases. VENs are also important for the "ego" formation, sense of empathy, intuition, and cognition. These neurons express a high level of adrenoreceptor alpha 1a, which confirms their role in the autonomic function. Here, based on some evidence, I propose the hypothesis that these neurons may play a role in depression, possibly through being involved in the autonomic function. More focused studies on VENs and their possible role in depression is suggested in future. This pathway may open a new window in the treatment of depression.

Von Economo Neurons - Primate-Specific or Commonplace in the Mammalian Brain?

The pioneering work by von Economo in 1925 on the cytoarchitectonics of the cerebral cortex revealed a specialized and unique cell type in the adult human fronto-insular (FI) and anterior cingulate cortex (ACC). In modern studies, these neurons are termed von Economo neurons (VENs). In his work, von Economo described them as stick, rod or corkscrew cells because of their extremely elongated and relatively thin cell body clearly distinguishable from common oval or spindle-shaped infragranular principal neurons. Before von Economo, in 1899 Cajal depicted the unique somato-dendritic morphology of such cells with extremely elongated soma in the FI. However, although VENs are increasingly investigated, Cajal’s observation is still mainly being neglected. On Golgi staining in humans, VENs have a thick and long basal trunk with horizontally oriented terminal branching (basilar skirt) from where the axon arises. They are clearly distinguishable from a spectrum of modified pyramidal neurons found in infragranular layers, including oval or spindle-shaped principal neurons. Spindle-shaped cells with highly elongated cell body were also observed in the ACC of great apes, but despite similarities in soma shape, their dendritic and axonal morphology has still not been described in sufficient detail. Studies identifying VENs in non-human species are predominantly done on Nissl or anti-NeuN staining. In most of these studies, the dendritic and axonal morphology of the analyzed cells was not demonstrated and many of the cells found on Nissl or anti-NeuN staining had a cell body shape characteristic for common oval or spindle-shaped cells. Here we present an extensive literature overview on VENs, which demonstrates that human VENs are specialized elongated principal cells with unique somato-dendritic morphology found abundantly in the FI and ACC of the human brain. More research is needed to properly evaluate the presence of such specialized cells in other primates and non-primate species.

Stress and central autonomic network

The central autonomic network (CAN) plays a critical role in the stress response, which is triggered by challenges on the homeostasis (physiological stressors) or unpleasant social or environmental situations. This review focuses on the role of areas of the CAN including the insular and anterior cingulate cortices, extended amygdala, hypothalamus, periaqueductal gray and locus coeruleus in the stress response. These areas are interconnected and affect sympathetic or parasympathetic output via their influence on premotor or preganglionic autonomic neurons in the lower brainstem and spinal cord. The insula integrates multiple inputs to create a sense of the physiological state of the body, whereas the anterior cingulate initiates predictive visceromotor commands. The amygdala and bed nucleus of the stria terminalis provide automatic emotional tagging and trigger automatic survival responses to threat via their outputs to the hypothalamus, periaqueductal gray, and lower brainstem. Several regions of the hypothalamus, including the paraventricular nucleus, dorsomedial nucleus and lateral hypothalamic area participate in different patterns of stress response according to the type of stimulus and projections to premotor and preganglionic autonomic neurons. The periaqueductal gray initiates different patterns of autonomic, pain modulatory, and motor responses, including the "fight or flight" or "playing dead" responses. The locus coeruleus promotes emotional learning in the amygdala associated with states of anxiety. Neurons of the C1 area of the rostral ventrolateral medulla elicit sympathoexcitatory responses to internal stressors such as hypoxia and inflammation. The ventromedial medulla, including the nucleus raphe pallidus, initiates sympathoexcitatory responses to social and other external stressors.

Three genetic-environmental networks for human personality

Phylogenetic, developmental, and brain-imaging studies suggest that human personality is the integrated expression of three major systems of learning and memory that regulate (1) associative conditioning, (2) intentionality, and (3) self-awareness. We have uncovered largely disjoint sets of genes regulating these dissociable learning processes in different clusters of people with (1) unregulated temperament profiles (i.e., associatively conditioned habits and emotional reactivity), (2) organized character profiles (i.e., intentional self-control of emotional conflicts and goals), and (3) creative character profiles (i.e., self-aware appraisal of values and theories), respectively. However, little is known about how these temperament and character components of personality are jointly organized and develop in an integrated manner. In three large independent genome-wide association studies from Finland, Germany, and Korea, we used a data-driven machine learning method to uncover joint phenotypic networks of temperament and character and also the genetic networks with which they are associated. We found three clusters of similar numbers of people with distinct combinations of temperament and character profiles. Their associated genetic and environmental networks were largely disjoint, and differentially related to distinct forms of learning and memory. Of the 972 genes that mapped to the three phenotypic networks, 72% were unique to a single network. The findings in the Finnish discovery sample were blindly and independently replicated in samples of Germans and Koreans. We conclude that temperament and character are integrated within three disjoint networks that regulate healthy longevity and dissociable systems of learning and memory by nearly disjoint sets of genetic and environmental influences.

Roles of the MPFC and insula in impression management under social observation

People often engage in impression management by presenting themselves and others as socially desirable. However, specific behavioral manifestations and underlying neural mechanisms of impression management remain unknown. In this study, we investigated the neural mechanism of impression management during self- and friend-evaluation. Only participants assigned to the observation (OBS) group, not the control (CON) group, were informed that their responses would be monitored. They answered how well positive and negative trait adjectives described themselves or their friends. The behavioral results showed that the OBS group was more likely to reject negative traits for self-evaluation and to accept positive traits for friend-evaluation. An independent study revealed that demoting negative traits for oneself and promoting positive traits for a friend helps manage one’s impression. In parallel with the behavioral results, in the OBS vs the CON group, the rostromedial prefrontal cortex (rmPFC) and anterior insula (AI) activity showed a greater increase as the negativity of negatively valenced adjectives increased during self-evaluation and also showed a greater increase as the positivity of positively valenced adjectives increased during friend-evaluation. The present study suggests that rmPFC and AI are critically involved in impression management, promoting socially desirable target evaluations under social observation.

The Difficult Integration between Human and Animal Studies on Emotional Lateralization: A Perspective Article

Even if for many years hemispheric asymmetries have been considered as a uniquely human feature, an increasing number of studies have described hemispheric asymmetries for various behavioral functions in several nonhuman species. An aspect of animal lateralization that has attracted particular attention has concerned the hemispheric asymmetries for emotions, but human and animal studies on this subject have been developed as independent lines of investigation, without attempts for their integration. In this perspective article, after an illustration of factors that have hampered the integration between human and animal studies on emotional lateralization, I will pass to analyze components and stages of the processing of emotions to distinguish those which point to a continuum between humans and many animal species, from those which suggest a similarity only between humans and great apes. The right lateralization of sympathetic functions (involved in brain and bodily activities necessary in emergency situations) seems consistent across many animal species, whereas asymmetries in emotional communication and in structures involved in emotional experience, similar to those observed in humans, have been documented only in primates.

Empathetic Factors and Influences on Physical Performance: A Topical Review

Performance is dependent upon both physical and psychological factors. As a social animal, human behaviors are influenced by interactions with others. Empathy is based on social interactions and is defined as the understanding, awareness of, sensitivity to, and ability to vicariously experience the feelings, thoughts, and experience of another. There are few investigations on the influence of empathy in relation to individual and team performance and activity. There is some initial research suggesting that observing sad photos or videos or fatiguing exercise can adversely affect subsequent performance. Possible mechanisms may be attributed to mirror neurons or the affordance competition hypothesis. The relative degree of empathetic influences can be modulated by sex, age, personal familiarity, cultures and other factors. With the limited research in sport and exercise science, there is a need for more research to investigate the role of empathy on individual and team performances. The objective of this topical review was to examine the possible effects of empathy on physical performance, the potential underlying mechanisms and influencing variables moderating the association between empathy and performance?

A semiological marker of emotional insulo-cingulate network activation in epileptic human brain

There are limited reports on the "chapeau de gendarme" (CDG) sign, which is considered reliable evidence for the verification of frontal epilepsy. However, several recent reports of scattered cases of extra-frontal epilepsy suggest the complexity of the cortical networks underlying CDG generation. The present study aimed to investigate the anatomo-electro-clinical correlations and explore the cortical mechanisms of the generation of CDG via video-stereoelectroencephalography (SEEG). Patients with focal epilepsy who underwent SEEG and epilepsy surgery in our center from March 2017 to December 2019 were retrospectively reviewed. Ten patients with epilepsy with habitual seizures presenting with CDG were included. Most CDG signs were discerned visually into two chronological components referred to as the "prodromal component" and the "major component." The CDG signs occurred at 2.4-26.1 s after electrical onset and lasted for 2.2-16.6 s. The two sequential components were visually discerned in 64 included seizures of the six patients. The epileptogenic zones were diverse in distribution. Cluster analysis was performed based on the neurophysiological features of distinct cortical areas, and the agranulo-dysgranular insular and cingulate cortices were emphasized. Pearson correlation and linear regression showed a linear relationship between the latencies of CDG onset and the latencies of co-activation of agranulo-dysgranular cingulate and insular cortex in gamma bands. Our results suggest that (1) the CDG sign should be interpreted as a type of facial behavior with social-emotional features and considered a semiological marker of emotional insulo-cingulate cortex involvement in focal epilepsy, and (2) epileptic discharges arising directly from or propagating indirectly into this anterior limbic network have a high likelihood of evoking the CDG sign.

MRI-based Parcellation and Morphometry of the Individual Rhesus Monkey Brain: the macaque Harvard-Oxford Atlas (mHOA), a translational system referencing a standardized ontology

Investigations of the rhesus monkey (Macaca mulatta) brain have shed light on the function and organization of the primate brain at a scale and resolution not yet possible in humans. A cornerstone of the linkage between non-human primate and human studies of the brain is magnetic resonance imaging, which allows for an association to be made between the detailed structural and physiological analysis of the non-human primate and that of the human brain. To further this end, we present a novel parcellation method and system for the rhesus monkey brain, referred to as the macaque Harvard-Oxford Atlas (mHOA), which is based on the human Harvard-Oxford Atlas (HOA) and grounded in an ontological and taxonomic framework. Consistent anatomical features were used to delimit and parcellate brain regions in the macaque, which were then categorized according to functional systems. This system of parcellation will be expanded with advances in technology and, like the HOA, will provide a framework upon which the results from other experimental studies (e.g., functional magnetic resonance imaging (fMRI), physiology, connectivity, graph theory) can be interpreted.

Anterior insula regulates brain network transitions that gate conscious access

Conscious access to sensory information is likely gated at an intermediate site between primary sensory and transmodal association cortices, but the structure responsible remains unknown. We perform functional neuroimaging to determine the neural correlates of conscious access using a volitional mental imagery task, a report paradigm not confounded by motor behavior. Titrating propofol to loss of behavioral responsiveness in healthy volunteers creates dysfunction of the anterior insular cortex (AIC) in association with an impairment of dynamic transitions of default-mode and dorsal attention networks. Candidate subcortical regions mediating sensory gating or arousal (thalamus, basal forebrain) fail to show this association. The gating role of the AIC is consistent with findings in awake participants, whose conscious access is predicted by pre-stimulus AIC activity near perceptual threshold. These data support the hypothesis that AIC, situated at an intermediate position of the cortical hierarchy, regulates brain network transitions that gate conscious access.

In a human neuroimaging study, Huang et al. manipulate the level and content of consciousness using independent experimental protocols to demonstrate that the anterior insula, situated between unimodal and transmodal cortical areas along the brain’s functional hierarchy, serves as a gate for conscious access of sensory information.

Von Economo Neuron Pathology in Familial Dysautonomia: Quantitative Assessment and Possible Implications

Von Economo neurons (VENs) and fork cells are principally located in the anterior cingulate cortex (ACC) and the frontoinsular cortex (FI). Both of these regions integrate inputs from the autonomic nervous system (ANS) and are involved in decision-making and perception of the emotional states of self and others. Familial dysautonomia (FD) is an orphan disorder characterized by autonomic dysfunction and behavioral abnormalities including repetitive behavior and emotional rigidity, which are also seen in autism spectrum disorder. To understand a possible link between the ANS and the cortical regions implicated in emotion regulation we studied VENs and fork cells in an autonomic disorder. We determined the densities of VENs, fork cells, and pyramidal neurons and the ratio of VENs and fork cells to pyramidal neurons in ACC and FI in 4 FD patient and 6 matched control brains using a stereologic approach. We identified alterations in densities of VENs and pyramidal neurons and their distributions in the ACC and FI in FD brains. These data suggest that alterations in migration and numbers of VENs may be involved in FD pathophysiology thereby supporting the notion of a functional link between VENs, the ANS and the peripheral nervous system in general.

Updating and characterizing neuroanatomical markers in high-risk subjects, recently diagnosed and chronic patients with schizophrenia: A revised coordinate-based meta-analysis

Characterizing neuroanatomical markers of different stages of schizophrenia (SZ) to assess pathophysiological models of how the disorder develops is an important target for the clinical practice. We performed a meta-analysis of voxel-based morphometry studies of genetic and clinical high-risk subjects (g-/c-HR), recently diagnosed (RDSZ) and chronic SZ patients (ChSZ). We quantified gray matter (GM) changes associated with these four conditions and compared them with contrast and conjunctional data. We performed the behavioral analysis and networks decomposition of alterations to obtain their functional characterization. Results reveal a cortical-subcortical, left-to-right homotopic progression of GM loss. The right anterior cingulate is the only altered region found altered among c-HR, RDSZ and ChSZ. Contrast analyses show left-lateralized insular, amygdalar and parahippocampal GM reduction in RDSZ, which appears bilateral in ChSZ. Functional decomposition shows involvement of the salience network, with an enlargement of the sensorimotor network in RDSZ and the thalamus-basal nuclei network in ChSZ. These findings support the current neuroprogressive models of SZ and integrate this deterioration with the clinical evolution of the disease.

Crying with depressed affect induced by electrical stimulation of the anterior insula: A stereo EEG case study

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Anterior insular stimulation produces reproducible episodes of emotional crying.

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This is due to activation of complex neural network with its connectivity to the anterior cingulate cortex.

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This study increases our understanding of the complex functionality of the insula.

Stereo-EEG (sEEG) is an invasive recording technique used to localize the seizure-onset zone for epilepsy surgery in people with drug-resistant focal seizures. Pathological crying reflects disordered emotional expression and the anterior insula is known to play a role in empathy and socio-emotional processing. We describe a patient where electrical stimulation mapping (ESM) of the anterior insula during sEEG generated pathological crying and profound sadness that was time-locked to the electrical stimulus.

We evaluated a 35-year-old left-handed female for repeat epilepsy surgery. The patient had drug resistant focal impaired awareness seizures despite a previous left temporal neocortical resection informed by an invasive study using subdural grid and strip electrodes seven years earlier. She was studied invasively with 10 sEEG electrodes sampling temporal, occipital, and insular targets. In the process of functional mapping, stimulation of the anterior insular cortex provoked tearful crying with sad affect, reproducible upon repeat stimulation.

Our case is unique in demonstrating transitory pathological crying with profound sadness provoked by ESM of the left anterior insula. Furthermore we demonstrate repeated time-synched crying from electrical stimulation, which supports the hypothesis that the anterior insula in the brain plays an important role in the biology of emotion, as implicated by previous studies.

How Do You Feel Now? The Salience Network Functional Connectivity in End-Stage Renal Disease

Objective

The network connectivity basis of cognitive declines in end-stage renal disease (ESRD) remains unclear. A triple-network model of the salience (SN), executive control, and default mode networks has been suggested to be critical for efficient cognition. Here, we aimed to test the hypothesis that SN may play a role in cognitive impairment in patients with ESRD.

Materials and Methods

We investigated functional connectivity (FC) alterations within the SN between 43 ESRD patients (19 females/24 males, 46 ± 10 years) and 43 healthy controls (HC) (19 females/24 males, 47 ± 10 years), and performed linear support vector machine (LSVM) analysis on significant FC pairs within the SN to discriminate the two groups, and tested the accuracy of the classifier. Association and mediation analyses were conducted among the significant FC pairs within the SN nodes, clinical indicators, and neuropsychological tests scores.

Results

We identified significant between-group FC pairs within the SN and fairly good classification efficiency with significant accuracy (72.09%, p < 0.001). We found that FC between the right supramarginal gyrus and right anterior insula (AISL) was positively correlated with MoCA (r = 0.4010, p = 0.008); FC between the dorsal anterior cingulate cortex (dACC) and left AISL was positively correlated with the level of hemoglobin (r = 0.4979, p < 0.001). Mediation analysis found that the indirect effect of hemoglobin on forward digit span test scores via the FC between the dACC and right AISL (p < 0.05).

Conclusion

Disrupted SN connectivity may help explain cognitive declines in ESRD patients and act as a potential early biomarker. Moreover, the SN connectivity may interact with anemia to promote cognitive impairment.

Social Cognition and White Matter: Connectivity and Cooperation

Humans are highly social animals whose survival and well-being depend on their capacity to cooperate in complex social settings. Advances in anthropology and psychology have demonstrated the importance of cooperation for enhancing social cohesion and minimizing conflict. The understanding of social behavior is informed by the notion of social cognition, a set of mental operations including emotion perception, mentalizing, and empathy. The social brain hypothesis posits that the mammalian brain has enlarged over evolution to meet the challenges of social life, culminating in a large human brain well adapted for social cognition. The structures subserving social cognition are mainly located in the frontal and temporal lobes, and although gray matter is critical, social cognition also requires white matter. Whereas the social brain hypothesis assumes that brain enlargement has been driven by neocortical expansion, cerebral white matter has expanded even more robustly than the neocortex, coinciding with the emergence of social cognition. White matter expansion is most evident in the frontal and temporal lobes, where it enhances connectivity between regions critical for social cognition. Myelination has, in turn, conferred adaptive social advantages by enabling prompt empathic concern for offspring and by strengthening networks that support cooperation and the related capacities of altruism and morality. Social cognition deficits related to myelinated tract involvement occur in many disorders, including stroke, Binswanger disease, traumatic brain injury, multiple sclerosis, glioma, and behavioral variant frontotemporal dementia. The contribution of white matter to social cognition can be conceptualized as the enhancement of cooperation through brain connectivity.

Empathic pain evoked by sensory and emotional-communicative cues share common and process-specific neural representations

Pain empathy can be evoked by multiple cues, particularly observation of acute pain inflictions or facial expressions of pain. Previous studies suggest that these cues commonly activate the insula and anterior cingulate, yet vicarious pain encompasses pain-specific responses as well as unspecific processes (e.g. arousal) and overlapping activations are not sufficient to determine process-specific shared neural representations. We employed multivariate pattern analyses to fMRI data acquired during observation of noxious stimulation of body limbs (NS) and painful facial expressions (FE) and found spatially and functionally similar cross-modality (NS versus FE) whole-brain vicarious pain-predictive patterns. Further analyses consistently identified shared neural representations in the bilateral mid-insula. The vicarious pain patterns were not sensitive to respond to non-painful high-arousal negative stimuli but predicted self-experienced thermal pain. Finally, a domain-general vicarious pain pattern predictive of self-experienced pain but not arousal was developed. Our findings demonstrate shared pain-associated neural representations of vicarious pain.

Salience Network Atrophy Links Neuron Type-Specific Pathobiology to Loss of Empathy in Frontotemporal Dementia

Each neurodegenerative syndrome reflects a stereotyped pattern of cellular, regional, and large-scale brain network degeneration. In behavioral variant of frontotemporal dementia (bvFTD), a disorder of social-emotional function, von Economo neurons (VENs), and fork cells are among the initial neuronal targets. These large layer 5 projection neurons are concentrated in the anterior cingulate and frontoinsular (FI) cortices, regions that anchor the salience network, a large-scale system linked to social-emotional function. Here, we studied patients with bvFTD, amyotrophic lateral sclerosis (ALS), or both, given that these syndromes share common pathobiological and genetic factors. Our goal was to determine how neuron type-specific TAR DNA-binding protein of 43 kDa (TDP-43) pathobiology relates to atrophy in specific brain structures and to loss of emotional empathy, a cardinal feature of bvFTD. We combined questionnaire-based empathy assessments, in vivo structural MR imaging, and quantitative histopathological data from 16 patients across the bvFTD/ALS spectrum. We show that TDP-43 pathobiology within right FI VENs and fork cells is associated with salience network atrophy spanning insular, medial frontal, and thalamic regions. Gray matter degeneration within these structures mediated loss of emotional empathy, suggesting a chain of influence linking the cellular, regional/network, and behavioral levels in producing signature bvFTD clinical features.

The Role of Alpha-Synuclein and Other Parkinson's Genes in Neurodevelopmental and Neurodegenerative Disorders

Neurodevelopmental and late-onset neurodegenerative disorders present as separate entities that are clinically and neuropathologically quite distinct. However, recent evidence has highlighted surprising commonalities and converging features at the clinical, genomic, and molecular level between these two disease spectra. This is particularly striking in the context of autism spectrum disorder (ASD) and Parkinson's disease (PD). Genetic causes and risk factors play a central role in disease pathophysiology and enable the identification of overlapping mechanisms and pathways. Here, we focus on clinico-genetic studies of causal variants and overlapping clinical and cellular features of ASD and PD. Several genes and genomic regions were selected for our review, including SNCA (alpha-synuclein), PARK2 (parkin RBR E3 ubiquitin protein ligase), chromosome 22q11 deletion/DiGeorge region, and FMR1 (fragile X mental retardation 1) repeat expansion, which influence the development of both ASD and PD, with converging features related to synaptic function and neurogenesis. Both PD and ASD display alterations and impairments at the synaptic level, representing early and key disease phenotypes, which support the hypothesis of converging mechanisms between the two types of diseases. Therefore, understanding the underlying molecular mechanisms might inform on common targets and therapeutic approaches. We propose to re-conceptualize how we understand these disorders and provide a new angle into disease targets and mechanisms linking neurodevelopmental disorders and neurodegeneration.

Associations between age and brain microstructure in older community-dwelling men and women: the Rancho Bernardo Study

Cytoarchitectural brain changes during normal aging remain poorly characterized, and it is unclear whether patterns of brain aging differ by sex. This study used restriction spectrum imaging to examine associations between age and brain microstructure in 147 community-dwelling participants (aged 56-99 years). Widespread associations with age in multiple diffusion compartments, including increased free water, decreased restricted and hindered diffusion, and reduced neurite complexity, were observed in the cortical gray matter, the white matter tracts, and the hippocampus. Age differences in cortical microstructure were largely independent of atrophy. Associations were mostly global, although foci of stronger effects emerged in the fornix, anterior thalamic radiation and commissural fibers, and the medial temporal, orbitofrontal, and occipital cortices. Age differences were stronger and more widespread for women than men, even after adjustment for education, hypertension, and body mass index. Restriction spectrum imaging may be a convenient, noninvasive tool for monitoring changes in diffusion properties that are thought to reflect reduced cellular fractions and neurite density or complexity, which occur with typical aging, and for detecting sex differences in patterns of brain aging.