Novel Diagnostic Techniques in the Evaluation of Gastroesophageal Reflux Disease (GERD).

In our present clinical paradigm, patient symptoms and presentation in the setting of traditional findings from endoscopy (erosive esophagitis, Barrett's esophagus, reflux-mediated stenosis), esophageal high-resolution manometry, and/or ambulatory reflux monitoring (distal esophageal acid exposure time, numbers of reflux events, reflux-symptom association) guide the care of patients with suspected GERD. However, novel metrics and techniques acquired from or performed at endoscopy, manometry, or pH-impedance monitoring, beyond conventional evaluation, are of great interest to the gastroenterology community given the frequent (and sometimes challenging) presentation of suspected GERD. These novel and evolving diagnostic approaches have the potential to enhance the evaluation of these patients and optimize their management. In this invited review, we discuss the present evidence and potential clinical utility of selected GERD metrics and techniques of interest at endoscopy (dilated intercellular spaces, mucosal impedance), manometry (contractile integral, impedance analysis, straight leg raise, multiple rapid swallow maneuvers), and reflux monitoring (mean nocturnal baseline impedance, post-reflux swallow-induced peristaltic wave indices), and how these tools may be most optimally adopted and utilized for clinical care (Fig. 1).

Aberrant H3.3 dynamics in NAc promote vulnerability to depressive-like behavior.

Human major depressive disorder (MDD), along with related mood disorders, is among the world's greatest public health concerns; however, its pathophysiology remains poorly understood. Persistent changes in gene expression are known to promote physiological aberrations implicated in MDD. More recently, histone mechanisms affecting cell type- and regional-specific chromatin structures have also been shown to contribute to transcriptional programs related to depressive behaviors, as well as responses to antidepressants. Although much emphasis has been placed in recent years on roles for histone posttranslational modifications and chromatin-remodeling events in the etiology of MDD, it has become increasingly clear that replication-independent histone variants (e.g., H3.3), which differ in primary amino acid sequence from their canonical counterparts, similarly play critical roles in the regulation of activity-dependent neuronal transcription, synaptic connectivity, and behavioral plasticity. Here, we demonstrate a role for increased H3.3 dynamics in the nucleus accumbens (NAc)-a key limbic brain reward region-in the regulation of aberrant social stress-mediated gene expression and the precipitation of depressive-like behaviors in mice. We find that molecular blockade of these dynamics promotes resilience to chronic social stress and results in a partial renormalization of stress-associated transcriptional patterns in the NAc. In sum, our findings establish H3.3 dynamics as a critical, and previously undocumented, regulator of mood and suggest that future therapies aimed at modulating striatal histone dynamics may potentiate beneficial behavioral adaptations to negative emotional stimuli.

Sex Differences in Nucleus Accumbens Transcriptome Profiles Associated with Susceptibility versus Resilience to Subchronic Variable Stress.

Depression and anxiety disorders are more prevalent in females, but the majority of research in animal models, the first step in finding new treatments, has focused predominantly on males. Here we report that exposure to subchronic variable stress (SCVS) induces depression-associated behaviors in female mice, whereas males are resilient as they do not develop these behavioral abnormalities. In concert with these different behavioral responses, transcriptional analysis of nucleus accumbens (NAc), a major brain reward region, by use of RNA sequencing (RNA-seq) revealed markedly different patterns of stress regulation of gene expression between the sexes. Among the genes displaying sex differences was DNA methyltransferase 3a (Dnmt3a), which shows a greater induction in females after SCVS. Interestingly, Dnmt3a expression levels were increased in the NAc of depressed humans, an effect seen in both males and females. Local overexpression of Dnmt3a in NAc rendered male mice more susceptible to SCVS, whereas Dnmt3a knock-out in this region rendered females more resilient, directly implicating this gene in stress responses. Associated with this enhanced resilience of female mice upon NAc knock-out of Dnmt3a was a partial shift of the NAc female transcriptome toward the male pattern after SCVS. These data indicate that males and females undergo different patterns of transcriptional regulation in response to stress and that a DNA methyltransferase in NAc contributes to sex differences in stress vulnerability. SIGNIFICANCE STATEMENT: Women have a higher incidence of depression than men. However, preclinical models, the first step in developing new diagnostics and therapeutics, have been performed mainly on male subjects. Using a stress-based animal model of depression that causes behavioral effects in females but not males, we demonstrate a sex-specific transcriptional profile in brain reward circuitry. This transcriptional profile can be altered by removal of an epigenetic mechanism, which normally suppresses DNA transcription, creating a hybrid male/female transcriptional pattern. Removal of this epigenetic mechanism also induces behavioral resilience to stress in females. These findings shed new light onto molecular factors controlling sex differences in stress response.

Sex-Specific Regulation of Stress Susceptibility by the Astrocytic Gene Htra1.

Major depressive disorder (MDD) is linked to impaired structural and synaptic plasticity in limbic brain regions. Astrocytes, which regulate synapses and are influenced by chronic stress, likely contribute to these changes. We analyzed astrocyte gene profiles in the nucleus accumbens (NAc) of humans with MDD and mice exposed to chronic stress. Htra1 , which encodes an astrocyte-secreted protease targeting the extracellular matrix (ECM), was significantly downregulated in the NAc of males but upregulated in females in both species. Manipulating Htra1 in mouse NAc astrocytes bidirectionally controlled stress susceptibility in a sex-specific manner. Such Htra1 manipulations also altered neuronal signaling and ECM structural integrity in NAc. These findings highlight astroglia and the brain's ECM as key mediators of sex-specific stress vulnerability, offering new approaches for MDD therapies.

CREB Binding at the Zfp189 Promoter Within Medium Spiny Neuron Subtypes Differentially Regulates Behavioral and Physiological Adaptations Over the Course of Cocaine Use.

BACKGROUND: Over the course of chronic drug use, brain transcriptional neuroadaptation is thought to contribute to a change in drug use behavior over time. The function of the transcription factor CREB (cAMP response element binding protein) within the nucleus accumbens (NAc) has been well documented in opposing the rewarding properties of many classes of drugs, yet the gene targets through which CREB causally manifests these lasting neuroadaptations remain unknown. Here, we identify zinc finger protein 189 (Zfp189) as a CREB target gene that is transcriptionally responsive to acute and chronic cocaine use within the NAc of mice. METHODS: To investigate the role of the CREB-Zfp189 interaction in cocaine use, we virally delivered modified clustered regularly interspaced short palindromic repeats (CRISPR)/dCas9 constructs capable of selectively localizing CREB to the Zfp189 gene promoter in the NAc of mice. RESULTS: We observed that CREB binding to the Zfp189 promoter increased Zfp189 expression and diminished the reinforcing responses to cocaine. Furthermore, we showed that NAc Zfp189 expression increased within D1 medium spiny neurons in response to acute cocaine but increased in both D1- and D2-expressing medium spiny neurons in response to chronic cocaine. CREB-mediated induction of Zfp189 potentiated electrophysiological activity of D1- and D2-expressing medium spiny neurons, recapitulating the known effect of CREB on these neurons. Finally, targeting CREB to the Zfp189 promoter within NAc Drd2-expressing neurons, but not Drd1-expressing neurons, was sufficient to diminish cocaine-conditioned behaviors. CONCLUSIONS: Together, these findings point to the CREB-Zfp189 interaction within the NAc Drd2+ neurons as a molecular signature of chronic cocaine use that is causal in counteracting the reinforcing effects of cocaine.

Computational Analysis of Multidimensional Behavioral Alterations After Chronic Social Defeat Stress.

BACKGROUND: The study of depression in humans depends on animal models that attempt to mimic specific features of the human syndrome. Most studies focus on one or a few behavioral domains, with time and practical considerations prohibiting a comprehensive evaluation. Although machine learning has enabled unbiased analysis of behavior in animals, this has not yet been applied to animal models of psychiatric disease. METHODS: We performed chronic social defeat stress (CSDS) in mice and evaluated behavior with PsychoGenics' SmartCube, a high-throughput unbiased automated phenotyping platform that collects >2000 behavioral features based on machine learning. We evaluated group differences at several times post-CSDS and after administration of the antidepressant medication imipramine. RESULTS: SmartCube analysis after CSDS successfully separated control and defeated-susceptible mice, and defeated-resilient mice more resembled control mice. We observed a potentiation of CSDS effects over time. Treatment of susceptible mice with imipramine induced a 40.2% recovery of the defeated-susceptible phenotype as assessed by SmartCube. CONCLUSIONS: High-throughput analysis can simultaneously evaluate multiple behavioral alterations in an animal model for the study of depression, which provides a more unbiased and holistic approach to evaluating group differences after CSDS and perhaps can be applied to other mouse models of psychiatric disease.

Chronic stress and antidepressant treatment alter purine metabolism and beta oxidation within mouse brain and serum.

Major depressive disorder (MDD) is a complex condition with unclear pathophysiology. Molecular disruptions within limbic brain regions and the periphery contribute to depression symptomatology and a more complete understanding the diversity of molecular changes that occur in these tissues may guide the development of more efficacious antidepressant treatments. Here, we utilized a mouse chronic social stress model for the study of MDD and performed metabolomic, lipidomic, and proteomic profiling on serum plus several brain regions (ventral hippocampus, nucleus accumbens, and medial prefrontal cortex) of susceptible, resilient, and unstressed control mice. To identify how commonly used tricyclic antidepressants impact the molecular composition in these tissues, we treated stress-exposed mice with imipramine and repeated our multi-OMIC analyses. Proteomic analysis identified three serum proteins reduced in susceptible animals; lipidomic analysis detected differences in lipid species between resilient and susceptible animals in serum and brain; and metabolomic analysis revealed dysfunction of purine metabolism, beta oxidation, and antioxidants, which were differentially associated with stress susceptibility vs resilience by brain region. Antidepressant treatment ameliorated stress-induced behavioral abnormalities and affected key metabolites within outlined networks, most dramatically in the ventral hippocampus. This work presents a resource for chronic social stress-induced, tissue-specific changes in proteins, lipids, and metabolites and illuminates how molecular dysfunctions contribute to individual differences in stress sensitivity.

Sex-Specific Role for the Long Non-coding RNA LINC00473 in Depression.

Depression is a common disorder that affects women at twice the rate of men. Here, we report that long non-coding RNAs (lncRNAs), a recently discovered class of regulatory transcripts, represent about one-third of the differentially expressed genes in the brains of depressed humans and display complex region- and sex-specific patterns of regulation. We identified the primate-specific, neuronal-enriched gene LINC00473 as downregulated in prefrontal cortex (PFC) of depressed females but not males. Using viral-mediated gene transfer to express LINC00473 in adult mouse PFC neurons, we mirrored the human sex-specific phenotype by inducing stress resilience solely in female mice. This sex-specific phenotype was accompanied by changes in synaptic function and gene expression selectively in female mice and, along with studies of human neuron-like cells in culture, implicates LINC00473 as a CREB effector. Together, our studies identify LINC00473 as a female-specific driver of stress resilience that is aberrant in female depression.

Multidimensional Predictors of Susceptibility and Resilience to Social Defeat Stress.

BACKGROUND: Previous studies identified several separate risk factors for stress-induced disorders. However, an integrative model of susceptibility versus resilience to stress including measures from brain-body domains is likely to yield a range of multiple phenotypic information to promote successful adaptation to stress. METHODS: We used computational and molecular approaches to test whether 1) integrative brain-body behavioral, immunological, and structural domains characterized and predicted susceptibility or resilience to social defeat stress (SDS) in mice and 2) administration of acetyl-L-carnitine promoted resilience at the SDS paradigm. RESULTS: Our findings identified multidimensional brain-body predictors of susceptibility versus resilience to SDS. The copresence of anxiety, decreased hippocampal volume, and elevated systemic interleukin-6 characterized a susceptible phenotype that developed behavioral and neurobiological deficits after exposure to SDS. The susceptible phenotype showed social withdrawal and impaired transcriptomic-wide changes in the ventral dentate gyrus after SDS. At the individual level, a computational approach predicted whether a given animal developed SDS-induced social withdrawal, or remained resilient, based on the integrative in vivo measures of anxiety and immune system function. Finally, we provide initial evidence that administration of acetyl-L-carnitine promoted behavioral resilience at the SDS paradigm. CONCLUSIONS: The current findings of multidimensional brain-body predictors of susceptibility versus resilience to stress provide a starting point for in vivo models of mechanisms predisposing apparently healthy individuals to develop the neurobiological and behavioral deficits resulting from stress exposure. This framework can lead to novel therapeutic strategies to promote resilience in susceptible phenotypes.

Stress resilience is promoted by a Zfp189-driven transcriptional network in prefrontal cortex.

Understanding the transcriptional changes that are engaged in stress resilience may reveal novel antidepressant targets. Here we use gene co-expression analysis of RNA-sequencing data from brains of resilient mice to identify a gene network that is unique to resilience. Zfp189, which encodes a previously unstudied zinc finger protein, is the highest-ranked key driver gene in the network, and overexpression of Zfp189 in prefrontal cortical neurons preferentially activates this network and promotes behavioral resilience. The transcription factor CREB is a predicted upstream regulator of this network and binds to the Zfp189 promoter. To probe CREB-Zfp189 interactions, we employ CRISPR-mediated locus-specific transcriptional reprogramming to direct CREB or G9a (a repressive histone methyltransferase) to the Zfp189 promoter in prefrontal cortex neurons. Induction of Zfp189 with site-specific CREB is pro-resilient, whereas suppressing Zfp189 expression with G9a increases susceptibility. These findings reveal an essential role for Zfp189 and CREB-Zfp189 interactions in mediating a central transcriptional network of resilience.

In Vivo Fiber Photometry Reveals Signature of Future Stress Susceptibility in Nucleus Accumbens.

Recognizing why chronic stress causes only a subset of individuals to become depressed is critical to understanding depression on a basic level and, also, to developing treatments that increase resilience. Stress-induced alterations in the activity of reward-related brain regions, such as the nucleus accumbens (NAc), are linked to the pathophysiology of depression. However, it has been difficult to determine if differences in stress susceptibility are pre-existing or merely an effect of chronic stress. The NAc consists largely of medium spiny neurons (MSNs), distinguished by their predominant expression of either D1 or D2 dopamine receptors. Mice that develop depressive-like symptoms after chronic social defeat stress show distinct changes in the activity of these two cell subtypes. Until now it has not been possible to determine whether such effects are merely a consequence of stress or in fact precede stress and, thus, have utility in pre-identifying stress-susceptible individuals. The goal of this study was to define a cell-type specific signature of stress susceptibility and resilience. Using fiber photometry calcium imaging, we recorded calcium transients in NAc D1- and D2-MSNs in awake behaving mice and found that D1-MSN activity is a predictive marker of depression susceptibility: prior to stress, mice that will later become resilient had increased baseline D1- MSN activity, and increased calcium transients specific to social interaction. Differences in D2- MSN activity were not specific to social interaction. Our findings identify a pre-existing mechanism of stress-induced susceptibility, creating the potential to target preventative interventions to the most relevant populations.

Estrogen receptor α drives pro-resilient transcription in mouse models of depression.

Most people exposed to stress do not develop depression. Animal models have shown that stress resilience is an active state that requires broad transcriptional adaptations, but how this homeostatic process is regulated remains poorly understood. In this study, we analyze upstream regulators of genes differentially expressed after chronic social defeat stress. We identify estrogen receptor α (ERα) as the top regulator of pro-resilient transcriptional changes in the nucleus accumbens (NAc), a key brain reward region implicated in depression. In accordance with these findings, nuclear ERα protein levels are altered by stress in male and female mice. Further, overexpression of ERα in the NAc promotes stress resilience in both sexes. Subsequent RNA-sequencing reveals that ERα overexpression in NAc reproduces the transcriptional signature of resilience in male, but not female, mice. These results indicate that NAc ERα is an important regulator of pro-resilient transcriptional changes, but with sex-specific downstream targets.

Corrigendum: Sex-specific transcriptional signatures in human depression.

This corrects the article DOI: 10.1038/nm.4386.

Cocaine Self-administration Alters Transcriptome-wide Responses in the Brain's Reward Circuitry.

BACKGROUND: Global changes in gene expression underlying circuit and behavioral dysregulation associated with cocaine addiction remain incompletely understood. Here, we show how a history of cocaine self-administration (SA) reprograms transcriptome-wide responses throughout the brain's reward circuitry at baseline and in response to context and/or cocaine re-exposure after prolonged withdrawal (WD). METHODS: We assigned male mice to one of six groups: saline/cocaine SA + 24-hour WD or saline/cocaine SA + 30-day WD + an acute saline/cocaine challenge within the previous drug-paired context. RNA sequencing was conducted on six interconnected brain reward regions. Using pattern analysis of gene expression and factor analysis of behavior, we identified genes that are strongly associated with addiction-related behaviors and uniquely altered by a history of cocaine SA. We then identified potential upstream regulators of these genes. RESULTS: We focused on three patterns of gene expression that reflect responses to 1) acute cocaine, 2) context re-exposure, and 3) drug + context re-exposure. These patterns revealed region-specific regulation of gene expression. Further analysis revealed that each of these gene expression patterns correlated with an addiction index-a composite score of several addiction-like behaviors during cocaine SA-in a region-specific manner. Cyclic adenosine monophosphate response element binding protein and nuclear receptor families were identified as key upstream regulators of genes associated with such behaviors. CONCLUSIONS: This comprehensive picture of transcriptome-wide regulation in the brain's reward circuitry by cocaine SA and prolonged WD provides new insight into the molecular basis of cocaine addiction, which will guide future studies of the key molecular pathways involved.

Sex-specific transcriptional signatures in human depression.

Major depressive disorder (MDD) is a leading cause of disease burden worldwide. While the incidence, symptoms and treatment of MDD all point toward major sex differences, the molecular mechanisms underlying this sexual dimorphism remain largely unknown. Here, combining differential expression and gene coexpression network analyses, we provide a comprehensive characterization of male and female transcriptional profiles associated with MDD across six brain regions. We overlap our human profiles with those from a mouse model, chronic variable stress, and capitalize on converging pathways to define molecular and physiological mechanisms underlying the expression of stress susceptibility in males and females. Our results show a major rearrangement of transcriptional patterns in MDD, with limited overlap between males and females, an effect seen in both depressed humans and stressed mice. We identify key regulators of sex-specific gene networks underlying MDD and confirm their sex-specific impact as mediators of stress susceptibility. For example, downregulation of the female-specific hub gene Dusp6 in mouse prefrontal cortex mimicked stress susceptibility in females, but not males, by increasing ERK signaling and pyramidal neuron excitability. Such Dusp6 downregulation also recapitulated the transcriptional remodeling that occurs in prefrontal cortex of depressed females. Together our findings reveal marked sexual dimorphism at the transcriptional level in MDD and highlight the importance of studying sex-specific treatments for this disorder.

Social stress induces neurovascular pathology promoting depression.

Studies suggest that heightened peripheral inflammation contributes to the pathogenesis of major depressive disorder. We investigated the effect of chronic social defeat stress, a mouse model of depression, on blood-brain barrier (BBB) permeability and infiltration of peripheral immune signals. We found reduced expression of the endothelial cell tight junction protein claudin-5 (Cldn5) and abnormal blood vessel morphology in nucleus accumbens (NAc) of stress-susceptible but not resilient mice. CLDN5 expression was also decreased in NAc of depressed patients. Cldn5 downregulation was sufficient to induce depression-like behaviors following subthreshold social stress whereas chronic antidepressant treatment rescued Cldn5 loss and promoted resilience. Reduced BBB integrity in NAc of stress-susceptible or mice injected with adeno-associated virus expressing shRNA against Cldn5 caused infiltration of the peripheral cytokine interleukin-6 (IL-6) into brain parenchyma and subsequent expression of depression-like behaviors. These findings suggest that chronic social stress alters BBB integrity through loss of tight junction protein Cldn5, promoting peripheral IL-6 passage across the BBB and depression.

Essential Role of Mesolimbic Brain-Derived Neurotrophic Factor in Chronic Social Stress-Induced Depressive Behaviors.

BACKGROUND: Previous work has shown that chronic social defeat stress (CSDS) induces increased phasic firing of ventral tegmental area (VTA) dopamine (DA) neurons that project to the nucleus accumbens (NAc) selectively in mice that are susceptible to the deleterious effects of the stress. In addition, acute optogenetic phasic stimulation of these neurons promotes susceptibility in animals exposed to acute defeat stress. These findings are paradoxical, as increased DA signaling in NAc normally promotes motivation and reward, and the influence of chronic phasic VTA firing in the face of chronic stress is unknown. METHODS: We used CSDS with repeated optogenetic activation and pharmacologic manipulations of the mesolimbic VTA-NAc pathway to examine the role of brain-derived neurotrophic factor (BDNF) and DA signaling in depressive-like behaviors. We measured BDNF protein expression and DA release in this model. RESULTS: Pharmacologic blockade of BDNF-tyrosine receptor kinase B (TrkB) signaling, but not DA signaling, in NAc prevented CSDS-induced behavioral abnormalities. Chronic optogenetic phasic stimulation of the VTA-NAc circuit during CSDS exacerbated the defeat-induced behavioral symptoms, and these aggravated symptoms were also normalized by BDNF-TrkB blockade in NAc. The aggravated behavioral deficits induced by phasic stimulation of the VTA-NAc pathway were blocked as well by local knockdown of BDNF in VTA. CONCLUSIONS: These findings show that BDNF-TrkB signaling, rather than DA signaling, in the VTA-NAc circuit is crucial for facilitating depressive-like outcomes after CSDS and they establish BDNF-TrkB signaling as a pathologic mechanism during periods of chronic stress.

Integrative Analysis of Sex-Specific microRNA Networks Following Stress in Mouse Nucleus Accumbens.

Adult women are twice as likely as men to suffer from affective and anxiety disorders, although the mechanisms underlying heightened female stress susceptibility are incompletely understood. Recent findings in mouse Nucleus Accumbens (NAc) suggest a role for DNA methylation-driven sex differences in genome-wide transcriptional profiles. However, the role of another epigenetic process-microRNA (miR) regulation-has yet to be explored. We exposed male and female mice to Subchronic Variable Stress (SCVS), a stress paradigm that produces depression-like behavior in female, but not male, mice, and performed next generation mRNA and miR sequencing on NAc tissue. We applied a combination of differential expression, miR-mRNA network and functional enrichment analyses to characterize the transcriptional and post-transcriptional landscape of sex differences in NAc stress response. We find that male and female mice exhibit largely non-overlapping miR and mRNA profiles following SCVS. The two sexes also show enrichment of different molecular pathways and functions. Collectively, our results suggest that males and females mount fundamentally different transcriptional and post-transcriptional responses to SCVS and engage sex-specific molecular processes following stress. These findings have implications for the pathophysiology and treatment of stress-related disorders in women.

Circuit-wide Transcriptional Profiling Reveals Brain Region-Specific Gene Networks Regulating Depression Susceptibility.

Depression is a complex, heterogeneous disorder and a leading contributor to the global burden of disease. Most previous research has focused on individual brain regions and genes contributing to depression. However, emerging evidence in humans and animal models suggests that dysregulated circuit function and gene expression across multiple brain regions drive depressive phenotypes. Here, we performed RNA sequencing on four brain regions from control animals and those susceptible or resilient to chronic social defeat stress at multiple time points. We employed an integrative network biology approach to identify transcriptional networks and key driver genes that regulate susceptibility to depressive-like symptoms. Further, we validated in vivo several key drivers and their associated transcriptional networks that regulate depression susceptibility and confirmed their functional significance at the levels of gene transcription, synaptic regulation, and behavior. Our study reveals novel transcriptional networks that control stress susceptibility and offers fundamentally new leads for antidepressant drug discovery.

Operator experience determines performance in a simulated computer-based brain tumor resection task.

PURPOSE: Develop measures to differentiate between experienced and inexperienced neurosurgeons in a virtual reality brain surgery simulator environment. METHODS: Medical students (n = 71) and neurosurgery residents (n = 12) completed four simulated Glioblastoma multiforme resections. Simulated surgeries took place over four days with intermittent spacing in between (average time between surgeries of 4.77 ± 0.73 days). The volume of tumor removed (cc), volume of healthy brain removed (cc), and instrument path length (mm) were recorded. Additionally, surgical effectiveness (% tumor removed divided by % healthy brain removed) and efficiency (% tumor removed divided by instrument movement in mm) were calculated. Performance was compared (1) between groups, and (2) for each participant over time to assess the learning curve. In addition, the effect of real-time instruction ("coaching") was assessed with a randomly selected group of medical students. RESULTS: Neurosurgery residents removed less healthy brain, were more effective in removing tumor and sparing healthy brain tissue, required less instrument movement, and were more efficient in removing tumor tissue than medical students. Medical students approached the resident level of performance over serial sessions. Coached medical students showed more conservative surgical behavior, removing both less tumor and less healthy brain. In sum, neurosurgery residents removed more tumor, removed less healthy brain, and required less instrument movement than medical students. Coaching modified medical student performance. CONCLUSIONS: Virtual Reality brain surgery can differentiate operators based on both recent and long-term experience and may be useful in the acquisition and assessment of neurosurgical skills. Coaching alters the learning curve of naïve inexperienced individuals.