Nfib Promotes Metastasis through a Widespread Increase in Chromatin Accessibility.

Metastases are the main cause of cancer deaths, but the mechanisms underlying metastatic progression remain poorly understood. We isolated pure populations of cancer cells from primary tumors and metastases from a genetically engineered mouse model of human small cell lung cancer (SCLC) to investigate the mechanisms that drive the metastatic spread of this lethal cancer. Genome-wide characterization of chromatin accessibility revealed the opening of large numbers of distal regulatory elements across the genome during metastatic progression. These changes correlate with copy number amplification of the Nfib locus, and differentially accessible sites were highly enriched for Nfib transcription factor binding sites. Nfib is necessary and sufficient to increase chromatin accessibility at a large subset of the intergenic regions. Nfib promotes pro-metastatic neuronal gene expression programs and drives the metastatic ability of SCLC cells. The identification of widespread chromatin changes during SCLC progression reveals an unexpected global reprogramming during metastatic progression.

Zmat3 Is a Key Splicing Regulator in the p53 Tumor Suppression Program.

Although TP53 is the most commonly mutated gene in human cancers, the p53-dependent transcriptional programs mediating tumor suppression remain incompletely understood. Here, to uncover critical components downstream of p53 in tumor suppression, we perform unbiased RNAi and CRISPR-Cas9-based genetic screens in vivo. These screens converge upon the p53-inducible gene Zmat3, encoding an RNA-binding protein, and we demonstrate that ZMAT3 is an important tumor suppressor downstream of p53 in mouse KrasG12D-driven lung and liver cancers and human carcinomas. Integrative analysis of the ZMAT3 RNA-binding landscape and transcriptomic profiling reveals that ZMAT3 directly modulates exon inclusion in transcripts encoding proteins of diverse functions, including the p53 inhibitors MDM4 and MDM2, splicing regulators, and components of varied cellular processes. Interestingly, these exons are enriched in NMD signals, and, accordingly, ZMAT3 broadly affects target transcript stability. Collectively, these studies reveal ZMAT3 as a novel RNA-splicing and homeostasis regulator and a key component of p53-mediated tumor suppression.

Sudden Cardiac Death and Myocardial Fibrosis, Determined by Autopsy, in Persons with HIV.

BACKGROUND: The incidence of sudden cardiac death and sudden death caused by arrhythmia, as determined by autopsy, in persons with human immunodeficiency virus (HIV) infection has not been clearly established. METHODS: Between February 1, 2011, and September 16, 2016, we prospectively identified all new deaths due to out-of-hospital cardiac arrest among persons 18 to 90 years of age, with or without known HIV infection, for comprehensive autopsy and toxicologic and histologic testing. We compared the rates of sudden cardiac death and sudden death caused by arrhythmia between groups. RESULTS: Of 109 deaths from out-of-hospital cardiac arrest among 610 unexpected deaths in HIV-positive persons, 48 met World Health Organization criteria for presumed sudden cardiac death; of those, fewer than half (22) had an arrhythmic cause. A total of 505 presumed sudden cardiac deaths occurred between February 1, 2011, and March 1, 2014, in persons without known HIV infection. Observed incidence rates of presumed sudden cardiac death were 53.3 deaths per 100,000 person-years among persons with known HIV infection and 23.7 deaths per 100,000 person-years among persons without known HIV infection (incidence rate ratio, 2.25; 95% confidence interval [CI], 1.37 to 3.70). Observed incidence rates of sudden death caused by arrhythmia were 25.0 and 13.3 deaths per 100,000 person-years, respectively (incidence rate ratio, 1.87; 95% CI, 0.93 to 3.78). Among all presumed sudden cardiac deaths, death due to occult drug overdose was more common in persons with known HIV infection than in persons without known HIV infection (34% vs. 13%). Persons who were HIV-positive had higher histologic levels of interstitial myocardial fibrosis than persons without known HIV infection. CONCLUSIONS: In this postmortem study, the rates of presumed sudden cardiac death and myocardial fibrosis were higher among HIV-positive persons than among those without known HIV infection. One third of apparent sudden cardiac deaths in HIV-positive persons were due to occult drug overdose. (Supported by the National Heart, Lung, and Blood Institute.).

A Randomized Controlled Trial of Topical Analgesia Post-Hemorrhoidectomy (TAPH Trial).

BACKGROUND: Postoperative pain remains the greatest problem after hemorrhoidectomy. Pain is hypothesized to arise from bacterial infection, sphincter spasm, and local inflammation. OBJECTIVE: A randomized controlled factorial trial was conducted to assess the effects of metronidazole, diltiazem, and lidocaine on post-hemorrhoidectomy pain. DESIGN: A double blinded randomized controlled factorial trial. SETTINGS: A multicenter trial was conducted in Auckland, New Zealand. PATIENTS: 192 Participants were randomized (1:1:1:1) into four parallel arms. INTERVENTIONS: Participants were randomized into one of four groups receiving topical treatment with 10% metronidazole (M), 10% metronidazole + 2% diltiazem (MD), 10% metronidazole + 4% lidocaine (ML), or 10% metronidazole + 2% diltiazem + 4% lidocaine (MDL). Participants were instructed to apply to the anal verge 3 times daily for 7 days. MAIN OUTCOME MEASURES: The primary outcome was pain on the visual analogue scale on day 4. The secondary outcomes included analgesia usage, pain on bowel motion, and functional recovery index. RESULTS: There was no significant difference in the pain and recovery scores when diltiazem or lidocaine was added to metronidazole (score difference between presence and absence of D in the formulation: -3.69, 95% CI: -13.3, 5.94, p = 0.46; between presence and absence of L: -5.67, 95% CI: -15.5, 3.80, p = 0.24). The combination of MDL did not further reduce pain. Secondary analysis revealed a significant difference between the best (ML) and worst (MDL) groups in both pain and functional recovery scores. There were no significant differences in analgesic usage, complications, or return to work between the groups. No clinically important adverse events were reported. The adverse event rate did not change in the intervention groups. LIMITATIONS: Topical metronidazole was utilized in the control group, rather than a pure placebo. CONCLUSION: There was no significant difference in pain when topical diltiazem or lidocaine, or both, was added to topical metronidazole. CLINICAL TRIAL REGISTRATION IDENTIFIER: NCT04276298.

Hypoimmune induced pluripotent stem cell-derived cell therapeutics treat cardiovascular and pulmonary diseases in immunocompetent allogeneic mice.

The emerging field of regenerative cell therapy is still limited by the few cell types that can reliably be differentiated from pluripotent stem cells and by the immune hurdle of commercially scalable allogeneic cell therapeutics. Here, we show that gene-edited, immune-evasive cell grafts can survive and successfully treat diseases in immunocompetent, fully allogeneic recipients. Transplanted endothelial cells improved perfusion and increased the likelihood of limb preservation in mice with critical limb ischemia. Endothelial cell grafts transduced to express a transgene for alpha1-antitrypsin (A1AT) successfully restored physiologic A1AT serum levels in mice with genetic A1AT deficiency. This cell therapy prevented both structural and functional changes of emphysematous lung disease. A mixture of endothelial cells and cardiomyocytes was injected into infarcted mouse hearts, and both cell types orthotopically engrafted in the ischemic areas. Cell therapy led to an improvement in invasive hemodynamic heart failure parameters. Our study supports the development of hypoimmune, universal regenerative cell therapeutics for cost-effective treatments of major diseases.

PD-1 expression by tumour-associated macrophages inhibits phagocytosis and tumour immunity.

Programmed cell death protein 1 (PD-1) is an immune checkpoint receptor that is upregulated on activated T cells for the induction of immune tolerance. Tumour cells frequently overexpress the ligand for PD-1, programmed cell death ligand 1 (PD-L1), facilitating their escape from the immune system. Monoclonal antibodies that block the interaction between PD-1 and PD-L1, by binding to either the ligand or receptor, have shown notable clinical efficacy in patients with a variety of cancers, including melanoma, colorectal cancer, non-small-cell lung cancer and Hodgkin's lymphoma. Although it is well established that PD-1-PD-L1 blockade activates T cells, little is known about the role that this pathway may have in tumour-associated macrophages (TAMs). Here we show that both mouse and human TAMs express PD-1. TAM PD-1 expression increases over time in mouse models of cancer and with increasing disease stage in primary human cancers. TAM PD-1 expression correlates negatively with phagocytic potency against tumour cells, and blockade of PD-1-PD-L1 in vivo increases macrophage phagocytosis, reduces tumour growth and lengthens the survival of mice in mouse models of cancer in a macrophage-dependent fashion. This suggests that PD-1-PD-L1 therapies may also function through a direct effect on macrophages, with substantial implications for the treatment of cancer with these agents.

A hybrid type Ia supernova with an early flash triggered by helium-shell detonation.

Type Ia supernovae arise from the thermonuclear explosion of white-dwarf stars that have cores of carbon and oxygen. The uniformity of their light curves makes these supernovae powerful cosmological distance indicators, but there have long been debates about exactly how their explosion is triggered and what kind of companion stars are involved. For example, the recent detection of the early ultraviolet pulse of a peculiar, subluminous type Ia supernova has been claimed as evidence for an interaction between a red-giant or a main-sequence companion and ejecta from a white-dwarf explosion. Here we report observations of a prominent but red optical flash that appears about half a day after the explosion of a type Ia supernova. This supernova shows hybrid features of different supernova subclasses, namely a light curve that is typical of normal-brightness supernovae, but with strong titanium absorption, which is commonly seen in the spectra of subluminous ones. We argue that this early flash does not occur through previously suggested mechanisms such as the companion-ejecta interaction. Instead, our simulations show that it could occur through detonation of a thin helium shell either on a near-Chandrasekhar-mass white dwarf, or on a sub-Chandrasekhar-mass white dwarf merging with a less-massive white dwarf. Our finding provides evidence that one branch of previously proposed explosion models-the helium-ignition branch-does exist in nature, and that such a model may account for the explosions of white dwarfs in a mass range wider than previously supposed.

Positive Controls in Adults and Children Support That Very Few, If Any, New Neurons Are Born in the Adult Human Hippocampus.

Adult hippocampal neurogenesis was originally discovered in rodents. Subsequent studies identified the adult neural stem cells and found important links between adult neurogenesis and plasticity, behavior, and disease. However, whether new neurons are produced in the human dentate gyrus (DG) during healthy aging is still debated. We and others readily observe proliferating neural progenitors in the infant hippocampus near immature cells expressing doublecortin (DCX), but the number of such cells decreases in children and few, if any, are present in adults. Recent investigations using dual antigen retrieval find many cells stained by DCX antibodies in adult human DG. This has been interpreted as evidence for high rates of adult neurogenesis, even at older ages. However, most of these DCX-labeled cells have mature morphology. Furthermore, studies in the adult human DG have not found a germinal region containing dividing progenitor cells. In this Dual Perspectives article, we show that dual antigen retrieval is not required for the detection of DCX in multiple human brain regions of infants or adults. We review prior studies and present new data showing that DCX is not uniquely expressed by newly born neurons: DCX is present in adult amygdala, entorhinal and parahippocampal cortex neurons despite being absent in the neighboring DG. Analysis of available RNA-sequencing datasets supports the view that DG neurogenesis is rare or absent in the adult human brain. To resolve the conflicting interpretations in humans, it is necessary to identify and visualize dividing neuronal precursors or develop new methods to evaluate the age of a neuron at the single-cell level.

Decoding neural representational spaces using multivariate pattern analysis.

A major challenge for systems neuroscience is to break the neural code. Computational algorithms for encoding information into neural activity and extracting information from measured activity afford understanding of how percepts, memories, thought, and knowledge are represented in patterns of brain activity. The past decade and a half has seen significant advances in the development of methods for decoding human neural activity, such as multivariate pattern classification, representational similarity analysis, hyperalignment, and stimulus-model-based encoding and decoding. This article reviews these advances and integrates neural decoding methods into a common framework organized around the concept of high-dimensional representational spaces.

A systematic review and meta-analysis of the efficacy of topical sphincterotomy treatments for anal fissure.

BACKGROUND: Anal fissure is a common condition that can be treated medically or surgically. Chemical sphincterotomy is often used before surgical intervention. This study aims to evaluate the effectiveness of topical agents for chemical sphincterotomy on healing of anal fissures and side-effects. METHODS: A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) compliant systematic review was performed using MEDLINE, EMBASE, Scopus, and CENTRAL databases. Eligible studies included randomized controlled trials which compared topical sphincterotomy agents with topical placebo agents or each other. Studies that included surgical treatments were excluded. Overall evidence was synthesized according to the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. RESULTS: Thirty-seven studies met the study selection criteria. Seventeen studies show that glyceryl trinitrate (GTN) was significantly more likely to heal anal fissure than placebo (relative risk (RR) = 1.96, 95% confidence interval (95%CI) = 1.35-2.84, I2 = 80%). Eleven studies showed a marginally significant difference between healing rates for diltiazem vs GTN, RR = 1.16, (1.01-1.33) I2 = 48%. There was no significant difference in healing between diltiazem and placebo, RR = 1.65, (0.64-4.23), I2 = 92%. GTN significantly reduced pain on the visual analog scale compared to the placebo group, MD-0.97 (-1.64 to -0.29) I2 = 92%. There was high certainty of evidence that GTN was significantly more likely to cause headache than placebo (RR = 2.73 (1.82-4.10) I2 = 58%) and diltiazem RR = 6.88 (2.19-21.63) I2 = 17%. CONCLUSION: There is low certainty evidence topical nitrates are an effective treatment for anal fissure healing and pain reduction compared to placebo. Despite widespread use of topical diltiazem, more evidence is required to establish the effectiveness of calcium channel blockers compared to placebo.

CD47-blocking antibodies restore phagocytosis and prevent atherosclerosis.

Atherosclerosis is the disease process that underlies heart attack and stroke. Advanced lesions at risk of rupture are characterized by the pathological accumulation of diseased vascular cells and apoptotic cellular debris. Why these cells are not cleared remains unknown. Here we show that atherogenesis is associated with upregulation of CD47, a key anti-phagocytic molecule that is known to render malignant cells resistant to programmed cell removal, or 'efferocytosis'. We find that administration of CD47-blocking antibodies reverses this defect in efferocytosis, normalizes the clearance of diseased vascular tissue, and ameliorates atherosclerosis in multiple mouse models. Mechanistic studies implicate the pro-atherosclerotic factor TNF-α as a fundamental driver of impaired programmed cell removal, explaining why this process is compromised in vascular disease. Similar to recent observations in cancer, impaired efferocytosis appears to play a pathogenic role in cardiovascular disease, but is not a fixed defect and may represent a novel therapeutic target.

BRD4 (Bromodomain-Containing Protein 4) Interacts with GATA4 (GATA Binding Protein 4) to Govern Mitochondrial Homeostasis in Adult Cardiomyocytes.

BACKGROUND: Gene regulatory networks control tissue homeostasis and disease progression in a cell type-specific manner. Ubiquitously expressed chromatin regulators modulate these networks, yet the mechanisms governing how tissue specificity of their function is achieved are poorly understood. BRD4 (bromodomain-containing protein 4), a member of the BET (bromo- and extraterminal domain) family of ubiquitously expressed acetyl-lysine reader proteins, plays a pivotal role as a coactivator of enhancer signaling across diverse tissue types in both health and disease and has been implicated as a pharmacological target in heart failure. However, the cell-specific role of BRD4 in adult cardiomyocytes remains unknown. METHODS: We combined conditional mouse genetics, unbiased transcriptomic and epigenomic analyses, and classic molecular biology and biochemical approaches to understand the mechanism by which BRD4 in adult cardiomyocyte homeostasis. RESULTS: Here, we show that cardiomyocyte-specific deletion of Brd4 in adult mice leads to acute deterioration of cardiac contractile function with mutant animals demonstrating a transcriptomic signature characterized by decreased expression of genes critical for mitochondrial energy production. Genome-wide occupancy data show that BRD4 enriches at many downregulated genes (including the master coactivators Ppargc1a, Ppargc1b, and their downstream targets) and preferentially colocalizes with GATA4 (GATA binding protein 4), a lineage-determining cardiac transcription factor not previously implicated in regulation of adult cardiac metabolism. BRD4 and GATA4 form an endogenous complex in cardiomyocytes and interact in a bromodomain-independent manner, revealing a new functional interaction partner for BRD4 that can direct its locus and tissue specificity. CONCLUSIONS: These results highlight a novel role for a BRD4-GATA4 module in cooperative regulation of a cardiomyocyte-specific gene program governing bioenergetic homeostasis in the adult heart.

Anatomically specific reactive oxygen species production participates in Marfan syndrome aneurysm formation.

Marfan syndrome (MFS) is a connective tissue disorder that results in aortic root aneurysm formation. Reactive oxygen species (ROS) seem to play a role in aortic wall remodelling in MFS, although the mechanism remains unknown. MFS Fbn1C1039G/+ mouse root/ascending (AS) and descending (DES) aortic samples were examined using DHE staining, lucigenin-enhanced chemiluminescence (LGCL), Verhoeff's elastin-Van Gieson staining (elastin breakdown) and in situ zymography for protease activity. Fbn1C1039G/+ AS- or DES-derived smooth muscle cells (SMC) were treated with anti-TGF-ß antibody, angiotensin II (AngII), anti-TGF-ß antibody + AngII, or isotype control. ROS were detected during early aneurysm formation in the Fbn1C1039G/+ AS aorta, but absent in normal-sized DES aorta. Fbn1C1039G/+ mice treated with the unspecific NADPH oxidase inhibitor, apocynin reduced AS aneurysm formation, with attenuated elastin fragmentation. In situ zymography revealed apocynin treatment decreased protease activity. In vitro SMC studies showed Fbn1C1039G/+ -derived AS SMC had increased NADPH activity compared to DES-derived SMC. AS SMC NADPH activity increased with AngII treatment and appeared TGF-ß dependent. In conclusion, ROS play a role in MFS aneurysm development and correspond anatomically with aneurysmal aortic segments. ROS inhibition via apocynin treatment attenuates MFS aneurysm progression. AngII enhances ROS production in MFS AS SMCs and is likely TGF-ß dependent.

Novel and lethal case of cardiac involvement in DNM1L mitochondrial encephalopathy.

Pathogenic DNM1L mutations cause a mitochondrial disorder with a highly variable clinical phenotype characterized by developmental delay, hypotonia, seizures, microcephaly, poor feeding, ocular abnormalities, and dysarthria. We report the case of an 8-month-old female with autosomal dominant, de novo DNM1L c. 1228G>A (p. E410K) mutation and mitochondrial disorder, septo-optic dysplasia, hypotonia, developmental delay, elevated blood lactate, and severe mitochondrial cardiomyopathy leading to nonischemic congestive heart failure and cardiogenic shock resulting in death. This case suggests that cardiac involvement, previously undescribed, can be a clinically important feature of this syndrome and should be screened for at diagnosis.

Putting the pieces together: Generating a novel representational space through deductive reasoning.

How does the brain represent a newly-learned mental model? Representational similarity analysis (RSA) has revealed the neural basis of common representational spaces learned early in development, such as categories of natural kinds. This study uses RSA to examine the neural implementation of a newly-learned mental model-i.e., a representational space created through deductive reasoning-and study the structure of previously found parietal activity in reasoning tasks. Specifically, all the information in this mental model could only be obtained through abstract transitive reasoning, as there were no predictive differences between observable features in the stimuli, and stimuli were counterbalanced across participants. Participants were shown unfamiliar face portraits paired with names and asked to learn about the height of each person pictured in the portraits through comparison to other individuals in the set. Participants learned the relative heights only of adjacent pairs in the set and then used transitive reasoning to generate a linear ranking of heights (e.g., "Matthew is taller than Thomas; Thomas is taller than Andrew; therefore Matthew is taller than Andrew"). During fMRI, participants recalled the approximate height of each individual based on these inferences. Using a predictive model based on the relative heights of the set of individuals, RSA revealed three brain regions in the right hemisphere that encoded this newly-learned representational space, located within the intraparietal sulcus, precuneus, and inferior frontal gyrus. These findings demonstrate the value of RSA for analyzing structure within patterns of activity and support theories asserting that logical reasoning recruits spatial processing mechanisms.

Brief Report: External Beam Radiation Therapy for the Treatment of Human Pluripotent Stem Cell-Derived Teratomas.

Human pluripotent stem cells, including human embryonic stem cells (hESCs) and human induced PSCs (hiPSCs), have great potential as an unlimited donor source for cell-based therapeutics. The risk of teratoma formation from residual undifferentiated cells, however, remains a critical barrier to the clinical application of these cells. Herein, we describe external beam radiation therapy (EBRT) as an attractive option for the treatment of this iatrogenic growth. We present evidence that EBRT is effective in arresting growth of hESC-derived teratomas in vivo at day 28 post-implantation by using a microCT irradiator capable of targeted treatment in small animals. Within several days of irradiation, teratomas derived from injection of undifferentiated hESCs and hiPSCs demonstrated complete growth arrest lasting several months. In addition, EBRT reduced reseeding potential of teratoma cells during serial transplantation experiments, requiring irradiated teratomas to be seeded at 1 × 103 higher doses to form new teratomas. We demonstrate that irradiation induces teratoma cell apoptosis, senescence, and growth arrest, similar to established radiobiology mechanisms. Taken together, these results provide proof of concept for the use of EBRT in the treatment of existing teratomas and highlight a strategy to increase the safety of stem cell-based therapies. Stem Cells 2017;35:1994-2000.

Two patients with FOXF1 mutations with alveolar capillary dysplasia with misalignment of pulmonary veins and other malformations: Two different presentations and outcomes.

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) describes a group of developmental disorders affecting the lungs with its pulmonary vasculature. Mutations in the FOXF1 gene have been reported in most cases, and extrapulmonary findings were described. We present two patients with ACDMPV and FOXF1 mutations that illustrate the variability in presentation and outcome of their disease. Patient 1 was a full-term infant with imperforate anus and pulmonary hypertension. He required Extracorporeal Membrane Oxygenation on day of life (DOL) 3, and passed away on DOL 13 after no clinical improvement. Postmortem findings were consistent with ACDMPV. FOXF1 testing revealed a heterozygous pathogenic frameshift de novo mutation, c.1057_1078dup, p.(Gly360Valfs*58). Patient 2 is a 6-month-old female, with a small omphalocele. She had intermittent retractions at 1 week of age. She was admitted with pulmonary hypertension at 7 weeks of age. Lung biopsy confirmed ACDMPV. FOXF1 testing revealed a de novo, heterozygous likely pathogenic missense mutation c.253T>C, p.(Phe85Leu]). Our two patients had different presentations, ages of onset, and progression of their disease. Our second patient had patchy lung involvement on biopsy, which may explain the relatively delayed onset and longer survival. ACDMPV is an important consideration for full-term infants with worsening pulmonary hypertension early in life.

CDKN2B Regulates TGFß Signaling and Smooth Muscle Cell Investment of Hypoxic Neovessels.

RATIONALE: Genetic variation at the chromosome 9p21 cardiovascular risk locus has been associated with peripheral artery disease, but its mechanism remains unknown. OBJECTIVE: To determine whether this association is secondary to an increase in atherosclerosis, or it is the result of a separate angiogenesis-related mechanism. METHODS AND RESULTS: Quantitative evaluation of human vascular samples revealed that carriers of the 9p21 risk allele possess a significantly higher burden of immature intraplaque microvessels than carriers of the ancestral allele, irrespective of lesion size or patient comorbidity. To determine whether aberrant angiogenesis also occurs under nonatherosclerotic conditions, we performed femoral artery ligation surgery in mice lacking the 9p21 candidate gene, Cdkn2b. These animals developed advanced hindlimb ischemia and digital autoamputation, secondary to a defect in the capacity of the Cdkn2b-deficient smooth muscle cell to support the developing neovessel. Microarray studies identified impaired transforming growth factor ß (TGFß) signaling in cultured cyclin-dependent kinase inhibitor 2B (CDKN2B)-deficient cells, as well as TGFß1 upregulation in the vasculature of 9p21 risk allele carriers. Molecular signaling studies indicated that loss of CDKN2B impairs the expression of the inhibitory factor, SMAD-7, which promotes downstream TGFß activation. Ultimately, this manifests in the upregulation of a poorly studied effector molecule, TGFß1-induced-1, which is a TGFß-rheostat known to have antagonistic effects on the endothelial cell and smooth muscle cell. Dual knockdown studies confirmed the reversibility of the proposed mechanism, in vitro. CONCLUSIONS: These results suggest that loss of CDKN2B may not only promote cardiovascular disease through the development of atherosclerosis but may also impair TGFß signaling and hypoxic neovessel maturation.

Attention Selectively Reshapes the Geometry of Distributed Semantic Representation.

Humans prioritize different semantic qualities of a complex stimulus depending on their behavioral goals. These semantic features are encoded in distributed neural populations, yet it is unclear how attention might operate across these distributed representations. To address this, we presented participants with naturalistic video clips of animals behaving in their natural environments while the participants attended to either behavior or taxonomy. We used models of representational geometry to investigate how attentional allocation affects the distributed neural representation of animal behavior and taxonomy. Attending to animal behavior transiently increased the discriminability of distributed population codes for observed actions in anterior intraparietal, pericentral, and ventral temporal cortices. Attending to animal taxonomy while viewing the same stimuli increased the discriminability of distributed animal category representations in ventral temporal cortex. For both tasks, attention selectively enhanced the discriminability of response patterns along behaviorally relevant dimensions. These findings suggest that behavioral goals alter how the brain extracts semantic features from the visual world. Attention effectively disentangles population responses for downstream read-out by sculpting representational geometry in late-stage perceptual areas.

How the Human Brain Represents Perceived Dangerousness or "Predacity" of Animals.

UNLABELLED: Common or folk knowledge about animals is dominated by three dimensions: (1) level of cognitive complexity or "animacy;" (2) dangerousness or "predacity;" and (3) size. We investigated the neural basis of the perceived dangerousness or aggressiveness of animals, which we refer to more generally as "perception of threat." Using functional magnetic resonance imaging (fMRI), we analyzed neural activity evoked by viewing images of animal categories that spanned the dissociable semantic dimensions of threat and taxonomic class. The results reveal a distributed network for perception of threat extending along the right superior temporal sulcus. We compared neural representational spaces with target representational spaces based on behavioral judgments and a computational model of early vision and found a processing pathway in which perceived threat emerges as a dominant dimension: whereas visual features predominate in early visual cortex and taxonomy in lateral occipital and ventral temporal cortices, these dimensions fall away progressively from posterior to anterior temporal cortices, leaving threat as the dominant explanatory variable. Our results suggest that the perception of threat in the human brain is associated with neural structures that underlie perception and cognition of social actions and intentions, suggesting a broader role for these regions than has been thought previously, one that includes the perception of potential threat from agents independent of their biological class. SIGNIFICANCE STATEMENT: For centuries, philosophers have wondered how the human mind organizes the world into meaningful categories and concepts. Today this question is at the core of cognitive science, but our focus has shifted to understanding how knowledge manifests in dynamic activity of neural systems in the human brain. This study advances the young field of empirical neuroepistemology by characterizing the neural systems engaged by an important dimension in our cognitive representation of the animal kingdom ontological subdomain: how the brain represents the perceived threat, dangerousness, or "predacity" of animals. Our findings reveal how activity for domain-specific knowledge of animals overlaps the social perception networks of the brain, suggesting domain-general mechanisms underlying the representation of conspecifics and other animals.