Polycomb repressive complex 2 is critical for mouse cortical glutamatergic neuron development.

The Polycomb Repressive Complex 2 (PRC2) regulates corticogenesis, yet the consequences of mutations to this epigenetic modifier in the mature brain are poorly defined. Importantly, PRC2 core genes are haploinsufficient and causative of several human neurodevelopmental disorders. To address the role of PRC2 in mature cortical structure and function, we conditionally deleted the PRC2 gene Eed from the developing mouse dorsal telencephalon. Adult homozygotes displayed smaller forebrain structures. Single-nucleus transcriptomics revealed that glutamatergic neurons were particularly affected, exhibiting dysregulated gene expression profiles, accompanied by aberrations in neuronal morphology and connectivity. Remarkably, homozygous mice performed well on challenging cognitive tasks. In contrast, while heterozygous mice did not exhibit clear anatomical or behavioral differences, they displayed dysregulation of neuronal genes and altered neuronal morphology that was strikingly different from homozygous phenotypes. Collectively, these data reveal how alterations to PRC2 function shape the mature brain and reveal a dose-specific role for PRC2 in determining glutamatergic neuron identity.

A protocol for high-resolution episcopic microscopy and 3D volumetric analyses of the adult mouse brain.

The rapid evolution of different imaging modalities in the last two decades has enabled the investigation of the role of different genes in development and disease to be studied in a range of model organisms. However, selection of the appropriate imaging technique depends on a number of constraints, including cost, time, image resolution, size of the sample, computational complexity and processing power. Here, we use the adult mouse central nervous system to investigate whether High-Resolution Episcopic Microscopy (HREM) can provide an effective means to study the volume of individual subregions within the brain. We find that HREM can provide precise volume quantification of different structures within the mouse brain, albeit with limitations regarding the time involved for analysis and the necessity of some estimations.

Is disgust more resistant to extinction than fear? A meta-analytic review of laboratory paradigms.

Disgust can be acquired via evaluative conditioning; a process by which a neutral stimulus (conditioned stimulus; CS) comes to be evaluated as disgusting due to its pairing with an inherently disgusting stimulus (unconditioned stimulus; US). Research has shown that conditioned disgust responses are resistant to extinction which may have implications for disorders (i.e., contamination-based obsessive-compulsive disorder, specific phobias, and post-traumatic stress disorder) in which heightened disgust has been implicated. Importantly, extinction is the primary mechanism by which exposure therapies are thought to achieve symptom reduction for these disorders. Exposure therapies were originally modeled on fear extinction, whereas disgust extinction was largely overlooked until recently. Accordingly, differences in the degree to which learned disgust and fear can be attenuated via extinction learning remains unclear. The present investigation was a meta-analysis directly comparing the degree of extinction of conditioned disgust (n = 14) and conditioned fear (n = 14) in laboratory paradigms. Extinction was operationalized as the standardized mean difference (SMD) in evaluative ratings between the CS+ (the CS paired with the US) and CS- (the unpaired CS) after extinction training. Results of a subgroup analysis indicated that disgust (SMD = 0.52) was significantly more resistant to extinction than fear (SMD = 0.37). Additionally, a series of meta-regression analyses indicated that extinction was not influenced by important study characteristics (e.g., sex, age, number of conditioning and extinction trials). The findings suggest that extinction-based approaches may be less effective at attenuating learned disgust and research is needed to better optimize treatments for disgust-related disorders.

Cellular and molecular functions of SETD2 in the central nervous system.

The covalent modification of histones is critical for many biological functions in mammals, including gene regulation and chromatin structure. Posttranslational histone modifications are added and removed by specialised 'writer' and 'eraser' enzymes, respectively. One such writer protein implicated in a wide range of cellular processes is SET domain-containing 2 (SETD2), a histone methyltransferase that catalyses the trimethylation of lysine 36 on histone H3 (H3K36me3). Recently, SETD2 has also been found to modify proteins other than histones, including actin and tubulin. The emerging roles of SETD2 in the development and function of the mammalian central nervous system (CNS) are of particular interest as several SETD2 variants have been implicated in neurodevelopmental disorders, such as autism spectrum disorder and the overgrowth disorder Luscan-Lumish syndrome. Here, we summarise the numerous roles of SETD2 in mammalian cellular functions and development, with a focus on the CNS. We also provide an overview of the consequences of SETD2 variants in human disease and discuss future directions for understanding essential cellular functions of SETD2.

Super-Resolution Ultrasound Localization Microscopy Using High-Frequency Ultrasound to Measure Ocular Perfusion Velocity in the Rat Eye.

Imaging of the ocular vasculature can provide new insights into the pathophysiology of ocular diseases. This study proposes a novel high-frequency super-resolution ultrasound localization microscopy (SRULM) technique and evaluates its ability to measure in vivo perfusion changes in the rat eye at elevated intraocular pressure (IOP). A 38.4 MHz center frequency linear array transducer on a VisualSonics Vevo F2 imaging platform was used to collect high frame rate (1 kHz) radiofrequency data of the posterior rat eye following systemic microbubble contrast injection. Following clutter and spatiotemporal non-local means filtering, individual microbubbles were localized and tracked. The microbubble tracks were accumulated over 10,000 frames to generate vascular images quantifying perfusion velocity and direction. Experiments were performed using physiologic relevant controlled flow states for algorithm validation and subsequently performed in vivo on the rat eye at 10 mm Hg IOP increments from 10 to 60 mm Hg. The posterior vasculature of the rat eye, including the ophthalmic artery, long posterior ciliary arteries and their branches, central retinal artery and retinal arterioles and venules were successfully visualized, and velocities quantified at each IOP level. Significant reductions in arterial flow were measured as IOP was elevated. High-frequency SRULM can be used to visualize and quantify the perfusion velocity of the rat eye in both the retrobulbar and intraocular vasculature simultaneously. The ability to detect ocular perfusion changes throughout the depth of the eye may help elucidate the role ischemia has in the pathophysiology of ocular diseases such as glaucoma.

Probing Edge/Support Electronic Cooperativity in Single Edge Fe/Co6Se8 Clusters.

This study provides insights into the electronic structure of an atomically precise Fe/Co6Se8 cluster and the extent of redox cooperativity between the Fe active site and the noninnocent Co6Se8 support. Chemical oxidation studies enable the isolation of two types of oxidized Fe/Co6Se8 clusters, in which the nature of the counterion (I- or OTf-) significantly impacts the structural interactions between Fe and the Co6Se8 unit. Experimental characterization by single crystal X-ray diffraction, 57Fe Mössbauer spectroscopy, and 31P{1H} NMR spectroscopy is complemented by computational analysis. In aggregate, the study reveals that upon oxidation, the charge is shared between the Fe edge site and the Co6Se8 core.

Temporal patterns of antibiotic prescribing for sore throat, otitis media, and sinusitis: a longitudinal study of general practitioner registrars.

BACKGROUND: Antibiotics provide minimal benefit for sore throat, otitis media, and sinusitis. Antibiotic stewardship, with reduced prescribing, is required to address antibiotic resistance. As most antibiotic prescribing occurs in general practice and prescribing habits develop early, general practitioner (GP) trainees (registrars) are important for effective antibiotic stewardship. OBJECTIVES: To establish temporal trends in Australian registrars' antibiotic prescribing for acute sore throat, acute otitis media, and acute sinusitis. DESIGN: A longitudinal analysis of data from the Registrar Clinical Encounters in Training (ReCEnT) study from 2010 to 2019. PARTICIPANTS: ReCEnT is an ongoing cohort study of registrars' in-consultation experiences and clinical behaviours. Pre-2016, 5 of 17 Australian training regions participated. From 2016, 3 of 9 regions (42% of Australian registrars) participate. MAIN MEASURES: The outcome was prescription of an antibiotic for a new acute problem/diagnosis of sore throat, otitis media, or sinusitis. The study factor was year (2010-2019). KEY RESULTS: Antibiotics were prescribed in 66% of sore throat diagnoses, 81% of otitis media, and in 72% of sinusitis. Prescribing frequencies decreased between 2010 and 2019 by 16% for sore throat (from 76% to 60%) by 11% for otitis media (from 88% to 77%) and by 18% for sinusitis (from 84% to 66%). In multivariable analyses, "Year" was associated with reduced prescribing for sore throat (OR 0.89; 95%CI 0.86-0.92; p < 0.001), otitis media (OR 0.90; 95%CI 0.86-0.94; p < 0.001), and sinusitis (OR 0.90; 95%CI 0.86, 0.94; p < 0.001). CONCLUSIONS: Registrars' prescribing rates for sore throat, otitis media, and sinusitis significantly decreased during the period 2010-2019. However, educational (and other) interventions to further reduce prescribing are warranted.

Metal/Support Interactions Regulate Substrate Binding in Fe/Co/Se Cluster Catalysts.

Here, we investigate the stereoelectronic requirements of a family of Fe/Co6Se8 molecular clusters to achieve a Goldilocks regime of substrate affinity for the catalytic coupling of tosyl azide and tert-butyl isocyanide. The reactivity of a catalytically competent iron-nitrenoid intermediate, observed in situ, is explored toward nitrene transfer and hydrogen-atom abstraction. The dual role of isocyanide, which, on the one hand, prevents catalyst degradation but, in large amounts, slows down reactivity, is exposed. The impact of distal changes (the number of neighboring active sites and the identity of supporting ligands) on the substrate affinity, electronic properties, and catalytic activity is investigated. Overall, the study reveals that the dynamic, push-pull interactions between the substrate (tBuNC), active site (Fe), and support (Co6Se8) create a regime where increased substrate activation occurs with facile dissociation.

Work-based feedback conversations with GP teachers.

INTRODUCTION: Feedback may play out in the general practice workplace less usefully than anticipated by educators. We investigated work-based feedback conversations about directly observed student tasks embedded in the supervisor's clinical consultations with patients. METHODS: Feedback conversations between GP teachers and medical students and subsequent student reflections were audio-recorded. Student and GP teacher focus groups were also conducted and transcribed professionally. An iterative, qualitative descriptive analysis integrating all transcripts was undertaken. Findings are discussed under the descriptive categories of feedback structure, content and perceived value. RESULTS: Twenty feedback conversations (total duration of 85 min) between five GP teachers, nine students and 20 student reflections (total duration of 58 min) were analysed. GP teachers actively engaged students in reflection and used balancing scripts and soft correction strategies. Students appeared to have some difficulty steering feedback conversations, which focused more on general skills than case-specific content knowledge. The recorded conversations were fragments of ongoing, in-practice teaching and learning, explicit and implicit. Student reflections suggested that they were able to grasp learning points effectively and identify room for growth. Praise and positive self-feedback appeared to reassure students, particularly when they were disappointed by their performances. DISCUSSION: Formal 'set-piece' feedback conversations may be a useful opportunity to explicitly surface and/or reinforce previous 'in-practice' reflection and feedback using a systematic structure. They may also reassure and encourage students and foster positive educational alliances. Students value in-practice and on-practice feedback but may prefer more control of the latter conversations.

Personality or pathology? Predictors of early substance use in first-year college students.

OBJECTIVE: The aim of the current study was to examine the dual role of personality and psychopathology in predicting substance use among first-year students. PARTICIPANTS: 103 first-semester undergraduate students were recruited via the university subject pool. METHODS: Participants completed personality questionnaires, structured clinical interviews, followed by the completion of diary entries each week reporting on substance use throughout their first semester. RESULTS: Results indicated that a past diagnosis of an affective (mood/anxiety/stress) disorder was the most significant predictor of substance use. Personality and current psychopathology had no association to substance use. CONCLUSION: This finding is consistent with developmental models of substance use relating to emotion-related disease and suggests that greater nuance is needed in understanding substance use risk in college students.

Interphotoreceptor matrix proteoglycans IMPG1 and IMPG2 proteolyze in the SEA domain and reveal localization mutual dependency.

The interphotoreceptor matrix (IPM) is a specialized extracellular mesh of molecules surrounding the inner and outer segments of photoreceptor neurons. Interphotoreceptor matrix proteoglycan 1 and 2 (IMPG1 and IMPG2) are major components of the IPM. Both proteoglycans possess SEA (sperm protein, enterokinase and agrin) domains, which may support proteolysis. Interestingly, mutations in the SEA domains of IMPG1 and IMPG2 are associated with vision disease in humans. However, if SEA domains in IMPG molecules undergo proteolysis, and how this contributes to vision pathology is unknown. Therefore, we investigated SEA-mediated proteolysis of IMPG1 and IMPG2 and its significance to IPM physiology. Immunoblot analysis confirmed proteolysis of IMPG1 and IMPG2 in the retinas of wildtype mice. Point mutations mimicking human mutations in the SEA domain of IMPG1 that are associated with vision disease inhibited proteolysis. These findings demonstrate that proteolysis is part of the maturation of IMPG1 and IMPG2, in which deficits are associated with vision diseases. Further, immunohistochemical assays showed that proteolysis of IMPG2 generated two subunits, a membrane-attached peptide and an extracellular peptide. Notably, the extracellular portion of IMPG2 trafficked from the IPM around the inner segment toward the outer segment IPM by an IMPG1-dependent mechanism. This result provides the first evidence of a trafficking system that shuttles IMPG1 and IMPG2 from the inner to outer IPM in a co-dependent manner. In addition, these results suggest an interaction between IMPG1-IMPG2 and propose that mutations affecting one IMPG could affect the localization of the normal IMPG partner, contributing to the disease mechanism of vision diseases associated with defective IMPG molecules.

Metal-Support Interactions in Molecular Single-Site Cluster Catalysts.

This study provides atomistic insights into the interface between a single-site catalyst and a transition metal chalcogenide support and reveals that peak catalytic activity occurs when edge/support redox cooperativity is maximized. A molecular platform MCo6Se8(PEt3)4(L)2 (1-M, M = Cr, Mn, Fe, Co, Cu, and Zn) was designed in which the active site (M)/support (Co6Se8) interactions are interrogated by systematically probing the electronic and structural changes that occur as the identity of the metal varies. All 3d transition metal 1-M clusters display remarkable catalytic activity for coupling tosyl azide and tert-butyl isocyanide, with Mn and Co derivatives showing the fastest turnover in the series. Structural, electronic, and magnetic characterization of the clusters was performed using single crystal X-ray diffraction, 1H and 31P nuclear magnetic resonance spectroscopy, electronic absorption spectroscopy, cyclic voltammetry, and computational methods. Distinct metal/support redox regimes can be accessed in 1-M based on the energy of the edge metal's frontier orbitals with respect to those of the cluster support. As the degree of electronic interaction between the edge and the support increases, a cooperative regime is reached wherein the support can deliver electrons to the catalytic site, increasing the reactivity of key metal-nitrenoid intermediates.

Multi-active Site Dynamics on a Molecular Cr/Co/Se Cluster Catalyst.

This study uncovers the interconnected reactivity of the three catalytically active sites of an atomically precise nanocluster Cr3(py)3Co6Se8L6 (1(py)3, L = Ph2PNTol-, Ph = phenyl, Tol = 4-tolyl). Catalytic and stoichiometric studies into tosyl azide activation and carbodiimide formation enabled the isolation and crystallographic characterization of key catalytically competent metal-imido intermediates, including the tris(imido) cluster 1(NTs)3, the catalytic resting state 1(NTs)3(CNtBu)3, and the site-differentiated mono(imido) cluster 1(NTs)(CNtBu)2. In the stoichiometric regime, nitrene transfer proceeds via a stepwise mechanism, with the three active sites engaging sequentially to produce carbodiimide. Moreover, the chemical state of neighboring active sites was found to regulate the affinity for substrates of an individual Cr-imido edge site, as revealed by comparative structural analysis and CNtBu binding studies.

Does past military experience impact fear reactivity in active-duty firefighters? Well, it is complicated.

OBJECTIVE: A significant proportion of military veterans successfully transition out of the military into civilian careers as first responders, such as firefighters. Like military service, being a firefighter is a high-risk profession involving exposure to aversive environments. Thus, it is possible that military experience might serve to buffer or exacerbate risk for negative psychological outcomes in firefighters. However, both occupations are associated with increased risk for psychopathology, such as PTSD, and little research has examined the effect of military service on processes that underlie stress in veterans serving as active-duty firefighters. The current study explores whether military service confers an adaptive advantage or an additional risk. METHOD: Using a case-control design, we examined differences in fear reactivity through electrodermal activity (EDA) and recording of fearful facial expressions, between 32 firefighters with and 32 firefighters without military veteran status (MVS; all men). Participants completed a semistructured, emotionally evocative interview with multiple contexts eliciting varying levels of emotion. RESULTS: MVS firefighters had relatively elevated EDA across contexts. However, lower baseline levels indicated calmer resting state in MVS firefighters. There was greater incidence of lifetime PTSD in MVS compared with non-MVS firefighters (40.6% vs. 15.6%). Overall, firefighters with past PTSD had less EDA reactivity. Finally, number of military deployments was associated with higher fear expressions throughout the interview. CONCLUSIONS: These findings highlight the need to consider interactions between military experience and psychiatric history in future investigations examining risk and resilience in first responders. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Patterns of concomitant injury in thoracic spine fractures.

Background: Thoracic spine fractures (TSFs) are rarely isolated injuries, and they tend to present with a characteristic set of vertebral and non-vertebral injuries based on mechanism of injury. There is limited research on the rates and distribution of injuries that occur concurrently with TSFs. The purpose of this study is to characterize the distributions of these injuries by region of the body and by mechanisms of injury, so that trauma and spine surgeons can efficiently evaluate and treat patients presenting with TSFs. Methods: We retrospectively reviewed the trauma database records of 683 patients presenting with a TSFs at a single institution from 2015 to 2019. We recorded patient demographics, comorbidities, and associated injuries by body region. We characterized the TSFs using the AO classification system, as well as the presenting physical exam and treatment. All associated injuries among the TSF patients were classified into the following categories: head injury (HI), thoracic injury (TI), non-thoracic vertebral injury (NTVI), abdominal injury (AI), upper extremity injury (UEI), lower extremity injury (LEI), and spinal cord injury (SCI). Results: The three leading causes of TSFs were mechanical falls (38.4%), falls from height (24.9%), and motor vehicle crashes (MVCs) (23.4%). Patients with a TSF from MVC were statistically more likely to have concomitant injuries of TI, NTVI, AI, HI, UEI, and LEI. TSFs from fall from height were statistically more likely to have TI, NTVI, and LEI. TSFs from mechanical falls had significantly lower rates of all injury locations, but still presented with high rates of additional injury. TSFs from motorcycle crashes (MCCs) presented with TI, AI, UEI, and LEI. There were high rates of treatment for TSFs, with surgery ranging from 5.3% to 20.0% and bracing from 52.3% to 65.7% depending on mechanism of injury. Conclusions: TSFs after MVCs, mechanical falls, falls from height, and MCCs presented with a predictable pattern of injuries and were rarely an isolated injury. This cross-sectional data may help spine and trauma surgeons better understand patterns of injury associated with TSFs, with the hope of preventing missed injuries and better advising patients with TSFs on severity of injuries.

Redox-Switchable Allosteric Effects in Molecular Clusters.

We demonstrate that allosteric effects and redox state changes can be harnessed to create a switch that selectively and reversibly regulates the coordination chemistry of a single site on the surface of a molecular cluster. This redox-switchable allostery is employed as a guiding force to assemble the molecular clusters Zn3Co6Se8L'6 (L' = Ph2PN(H)Tol, Ph = phenyl, Tol = 4-tolyl) into materials of predetermined dimensionality (1- or 2-D) and to encode them with emissive properties. This work paves the path to program the assembly and function of inorganic clusters into stimuli-responsive, atomically precise materials.

Were there losses in social support during the pandemic? Testing the impact of COVID-19 on psychological adjustment to trauma in United States adults.

Introduction: Social support is a key protective factor in the psychological adjustment of individuals to traumatic events. However, since March 2020, extant research has revealed evidence of increased loneliness, social isolation, and disconnection, likely due to COVID-19 pandemic-related recommendations that restricted day-to-day contact with others. Methods: In this investigation, we applied a case-control design to test the direct impacts of the pandemic on social support in United States adults recovering from a significant injury caused by PTSD-qualifying, traumatic events (e.g., motor vehicle crashes, violence, etc.). We compared individuals who experienced trauma during the pandemic, the "cases" recruited and evaluated between December 2020 to April 2022, to trauma-exposed "controls," recruited and evaluated pre-pandemic, from August 2018 through March 9, 2020 (prior to changes in public health recommendations in the region). Cohorts were matched on key demographics (age, sex, education, race/ethnicity, income) and injury severity variables. We tested to see if there were differences in reported social support over the first 5 months of adjustment, considering variable operationalizations of social support from social network size to social constraints in disclosure. Next, we tested to see if the protective role of social support in psychological adjustment to trauma was moderated by cohort status to determine if the impacts of the pandemic extended to changes in the process of adjustment. Results: The results of our analyses suggested that there were no significant cohort differences, meaning that whether prior to or during the pandemic, individuals reported similar levels of social support that were generally protective, and similar levels of psychological symptoms. However, there was some evidence of moderation by cohort status when examining the process of adjustment. Specifically, when examining symptoms of post-traumatic stress over time, individuals adjusting to traumatic events during COVID-19 received less benefit from social support. Discussion: Although negative mental health implications of the pandemic are increasingly evident, it has not been clear how the pandemic impacted normative psychological adjustment processes. These results are one of the first direct tests of the impact of COVID-19 on longitudinal adjustment to trauma and suggest some minimal impacts.

Internalized Nanoceria Modify the Radiation-Sensitivity Profile of MDA MB231 Breast Carcinoma Cells.

Owing to its unique redox properties, cerium oxide (nanoceria) nanoparticles have been shown to confer either radiosensitization or radioprotection to human cells. We investigated nanoceria's ability to modify cellular health and reactive oxygen species (ROS) at various absorbed doses (Gray) of ionizing radiation in MDA-MB231 breast carcinoma cells. We used transmission electron microscopy to visualize the uptake and compartmental localization of nanoceria within cells at various treatment concentrations. The effects on apoptosis and other cellular health parameters were assessed using confocal fluorescence imaging and flow cytometry without and with various absorbed doses of ionizing radiation, along with intracellular ROS levels. Our results showed that nanoceria were taken up into cells mainly by macropinocytosis and segregated into concentration-dependent large aggregates in macropinosomes. Confocal imaging and flow cytometry data showed an overall decrease in apoptotic cell populations in proportion to increasing nanoparticle concentrations. This increase in cellular health was observed with a corresponding reduction in ROS at all tested absorbed doses. Moreover, this effect appeared pronounced at lower doses compared to unirradiated or untreated populations. In conclusion, internalized nanoceria confers radioprotection with a corresponding decrease in ROS in MDA-MB231 cells, and this property confers significant perils and opportunities when utilized in the context of radiotherapy.

What Drives Preventive Health Behavior During a Global Pandemic? Emotion and Worry.

BACKGROUND & PURPOSE: Primary prevention of COVID-19 has focused on encouraging compliance with specific behaviors that restrict contagion. This investigation sought to characterize engagement in these behaviors in U.S. adults early during the pandemic and to build explanatory models of the psychological processes that drive them. METHODS: US adults were recruited through Qualtrics Research Panels (N = 324; 55% female; Mage = 50.91, SD = 15.98) and completed 10 days of online reports of emotion, COVID-19 perceived susceptibility and worry, and recommended behaviors (social distancing, hand washing, etc.). Factor analysis revealed behaviors loaded on two factors suggesting distinct motivational orientations: approach and avoidance. RESULTS: Changes in approach and avoidance behaviors over the 10 days indicated large individual differences consistent with three types of participants. Discrete emotions, including fear, guilt/shame, and happiness were associated with more recommended behaviors. Fear and COVID-19 worry indirectly influenced each other to facilitate more behavioral engagement. While emotions and worry strongly predicted individual differences in behavior across the 10 days, they did not predict as well why behaviors occurred on one day versus another. CONCLUSIONS: These findings suggest how daily affective processes motivate behavior, improving the understanding of compliance and efforts to target behaviors as primary prevention of disease.

Dealing with Multi-Dimensional Data and the Burden of Annotation: Easing the Burden of Annotation.

The need for huge data sets represents a bottleneck for the application of artificial intelligence. Substantially fewer annotated target lesions than normal tissues for comparison present an additional problem in the field of pathology. Organic brains overcome these limitations by utilizing large numbers of specialized neural nets arranged in both linear and parallel fashion, with each solving a restricted classification problem. They rely on local Hebbian error corrections as compared to the nonlocal back-propagation used in most artificial neural nets, and leverage reinforcement. For these reasons, even toddlers are able to classify objects after only a few examples. Rather than provide an overview of current AI research in pathology, this review focuses on general strategies for overcoming the data bottleneck. These include transfer learning, zero-shot learning, Siamese networks, one-class models, generative networks, and reinforcement learning. Neither an extensive mathematic background nor advanced programing skills are needed to make these subjects accessible to pathologists. However, some familiarity with the basic principles of deep learning, briefly reviewed here, is expected to be useful in understanding both the current limitations of machine learning and determining ways to address them.