Transformation of Undergraduate Medical Education in 2023

This Viewpoint discusses potential shifts in teaching and learning for undergraduate medical education with the advent of artificial intelligence tools.

Advanced Integrated Science Courses: Building a Skill Set to Engage With the Interface of Research and Medicine

Scientific research has been changing medical practice at an increasing pace. To keep up with this change, physicians of the future will need to be lifelong learners with the skills to engage with emerging science and translate it into clinical care. How medical schools can best prepare students for ongoing scientific change remains unclear. Adding to the challenge is reduced time allocated to basic science in curricula and rapid expansion of relevant scientific fields. A return to science with greater depth after clinical clerkships has been suggested, although few schools have adopted such curricula and implementation can present challenges. The authors describe an innovation at Harvard Medical School, the Advanced Integrated Science Courses (AISCs), which are taken after core clerkships. Students are required to take 2 such courses, which are offered in a variety of topics. Rather than factual content, the learning objectives are a set of generalizable skills to enable students to critically evaluate emerging research and its relationship to medical practice. Making these generalizable skills the defining principle of the courses has several important advantages: it allows standardization of acquired skills to be combined with diverse course topics ranging from basic to translational and population sciences; students can choose courses and projects aligned with their interests, thereby enhancing engagement, curiosity, and career relevance; schools can tailor course offerings to the interests of local faculty; and the generalizable skills delineate a unique purpose of these courses within the overall medical school curriculum. For the 3 years AISCs have been offered, students rated the courses highly and reported learning the intended skill set effectively. The AISC concept addresses the challenge of preparing students for this era of rapidly expanding science and should be readily adaptable to other medical schools.

The Harvard Medical School Pathways Curriculum: Reimagining Developmentally Appropriate Medical Education for Contemporary Learners

As the U.S. health care system changes and technology alters how doctors work and learn, medical schools and their faculty are compelled to modify their curricula and teaching methods. In this article, educational leaders and key faculty describe how the Pathways curriculum was conceived, designed, and implemented at Harvard Medical School. Faculty were committed to the principle that educators should focus on how students learn and their ability to apply what they learn in the evaluation and care of patients. Using the best evidence from the cognitive sciences about adult learning, they made major changes in the pedagogical approach employed in the classroom and clinic. The curriculum was built upon 4 foundational principles: to enhance critical thinking and provide developmentally appropriate content; to ensure both horizontal integration between courses and vertical integration between phases of the curriculum; to engage learners, foster curiosity, and reinforce the importance of student ownership and responsibility for their learning; and to support students' transformation to a professional dedicated to the care of their patients and to their obligations for lifelong, self-directed learning.The practice of medicine is rapidly evolving and will undoubtedly change in multiple ways over the career of a physician. By emphasizing personal responsibility, professionalism, and thinking skills over content transfer, the authors believe this curriculum will prepare students not only for the first day of practice but also for an uncertain future in the biological sciences, health and disease, and the nation's health care system, which they will encounter in the decades to come.

Precise Identification of Cell and Tissue Features Important for Histopathologic Diagnosis by a Whole Slide Imaging System

Background:

Previous studies have demonstrated the noninferiority of pathologists’ interpretation of whole slide images (WSIs) compared to microscopic slides in diagnostic surgical pathology; however, to our knowledge, no published studies have tested analytical precision of an entire WSI system.

Methods:

In this study, five pathologists at three locations tested intra-system, inter-system/site, and intra- and inter-pathologist precision of the Aperio AT2 DX System (Leica Biosystems, Vista, CA, USA). Sixty-nine microscopic slides containing 23 different morphologic features suggested by the Digital Pathology Association as important to diagnostic pathology were identified and scanned. Each of 202 unique fields of view (FOVs) had 1–3 defined morphologic features, and each feature was represented in three different tissues. For intra-system precision, each site scanned 23 slides at three different times and one pathologist interpreted all FOVs. For inter-system/site precision, all 69 slides were scanned once at each of three sites, and FOVs from each site were read by one pathologist. To test intra- and inter-pathologist precision, all 69 slides were scanned at one site, FOVs were saved in three different orientations, and the FOVs were transferred to a different site. Three different pathologists then interpreted FOVs from all 69 slides. Wildcard (unscored) slides and washout intervals were included in each study. Agreement estimates with 95% confidence intervals were calculated.

Results:

Combined precision from all three studies, representing 606 FOVs in each of the three studies, showed overall intra-system agreement of 97.9%; inter-system/site agreement was 96%, intra-pathologist agreement was 95%, and inter-pathologist agreement was 94.2%.

Conclusions:

Pathologists using the Aperio AT2 DX System identified histopathological features with high precision, providing increased confidence in using WSI for primary diagnosis in surgical pathology.

Epilepsy Benchmarks Area I: Understanding the Causes of the Epilepsies and Epilepsy-Related Neurologic, Psychiatric, and Somatic Conditions

The 2014 NINDS Benchmarks for Epilepsy Research included area I: Understand the causes of the epilepsies and epilepsy-related neurologic, psychiatric, and somatic conditions. In preparation for the 2020 Curing Epilepsies Conference, where the Benchmarks will be revised, this review will cover scientific progress toward that Benchmark, with emphasize on studies since 2016.

Beam Energy and Centrality Dependence of Direct-Photon Emission from Ultrarelativistic Heavy-Ion Collisions

The PHENIX collaboration presents first measurements of low-momentum (0.4<p_{T}<3  GeV/c) direct-photon yields from Au+Au collisions at sqrt[s_{NN}]=39 and 62.4 GeV. For both beam energies the direct-photon yields are substantially enhanced with respect to expectations from prompt processes, similar to the yields observed in Au+Au collisions at sqrt[s_{NN}]=200. Analyzing the photon yield as a function of the experimental observable dN_{ch}/dη reveals that the low-momentum (>1  GeV/c) direct-photon yield dN_{γ}^{dir}/dη is a smooth function of dN_{ch}/dη and can be well described as proportional to (dN_{ch}/dη)^{α} with α≈1.25. This scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and the Large Hadron Collider, for centrality selected samples, as well as for different A+A collision systems. At a given beam energy, the scaling also holds for high p_{T} (>5  GeV/c), but when results from different collision energies are compared, an additional sqrt[s_{NN}]-dependent multiplicative factor is needed to describe the integrated-direct-photon yield.

Fostering Student-Faculty Partnerships for Continuous Curricular Improvement in Undergraduate Medical Education

PROBLEM

A number of medical schools have used curricular reform as an opportunity to formalize student involvement in medical education, but there are few published assessments of these programs. Formal evaluation of a program's acceptability and use is essential for determining its potential for sustainability and generalizability.

APPROACH

Harvard Medical School's Education Representatives (Ed Reps) program was created in 2015 to launch alongside a new curriculum. The program aimed to foster partnerships between faculty and students for continuous and real-time curricular improvement. Ed Reps, course directors, and core faculty met regularly to convey bidirectional feedback to optimize the learning environment in real time.

OUTCOMES

A survey to assess the program's impact was sent to students and faculty. The majority of students (202/222; 91.0%) reported Ed Reps had a positive impact on the curriculum. Among faculty, 35/37 (94.6%) reported making changes to their courses as a result of Ed Reps feedback, and 34/37 (91.9%) agreed the program had a positive impact on the learning environment. Qualitative feedback from students and faculty demonstrated a change in school culture, reflecting the primary goals of partnership and continuous quality improvement (CQI).

NEXT STEPS

This student-faculty partnership demonstrated high rates of awareness, use, and satisfaction among faculty and students, suggesting its potential for local sustainability and implementation at other schools seeking to formalize student engagement in CQI. Next steps include ensuring the feedback provided is representative of the student body and identifying new areas for student CQI input as the curriculum becomes more established.

A Multimodal Imaging- and Stimulation-based Method of Evaluating Connectivity-related Brain Excitability in Patients with Epilepsy

Resting-state functional connectivity MRI (rs-fcMRI) is a technique that identifies connectivity between different brain regions based on correlations over time in the blood-oxygenation level dependent signal. rs-fcMRI has been applied extensively to identify abnormalities in brain connectivity in different neurologic and psychiatric diseases. However, the relationship among rs-fcMRI connectivity abnormalities, brain electrophysiology and disease state is unknown, in part because the causal significance of alterations in functional connectivity in disease pathophysiology has not been established. Transcranial Magnetic Stimulation (TMS) is a technique that uses electromagnetic induction to noninvasively produce focal changes in cortical activity. When combined with electroencephalography (EEG), TMS can be used to assess the brain's response to external perturbations. Here we provide a protocol for combining rs-fcMRI, TMS and EEG to assess the physiologic significance of alterations in functional connectivity in patients with neuropsychiatric disease. We provide representative results from a previously published study in which rs-fcMRI was used to identify regions with abnormal connectivity in patients with epilepsy due to a malformation of cortical development, periventricular nodular heterotopia (PNH). Stimulation in patients with epilepsy resulted in abnormal TMS-evoked EEG activity relative to stimulation of the same sites in matched healthy control patients, with an abnormal increase in the late component of the TMS-evoked potential, consistent with cortical hyperexcitability. This abnormality was specific to regions with abnormal resting-state functional connectivity. Electrical source analysis in a subject with previously recorded seizures demonstrated that the origin of the abnormal TMS-evoked activity co-localized with the seizure-onset zone, suggesting the presence of an epileptogenic circuit. These results demonstrate how rs-fcMRI, TMS and EEG can be utilized together to identify and understand the physiological significance of abnormal brain connectivity in human diseases.

Measurements of Elliptic and Triangular Flow in High-Multiplicity 3He+Au Collisions at √(s(NN))=200 GeV

We present the first measurement of elliptic (v(2)) and triangular (v(3)) flow in high-multiplicity (3)He+Au collisions at √(s(NN))=200  GeV. Two-particle correlations, where the particles have a large separation in pseudorapidity, are compared in (3)He+Au and in p+p collisions and indicate that collective effects dominate the second and third Fourier components for the correlations observed in the (3)He+Au system. The collective behavior is quantified in terms of elliptic v(2) and triangular v(3) anisotropy coefficients measured with respect to their corresponding event planes. The v(2) values are comparable to those previously measured in d+Au collisions at the same nucleon-nucleon center-of-mass energy. Comparisons with various theoretical predictions are made, including to models where the hot spots created by the impact of the three (3)He nucleons on the Au nucleus expand hydrodynamically to generate the triangular flow. The agreement of these models with data may indicate the formation of low-viscosity quark-gluon plasma even in these small collision systems.

Third International Congress on Epilepsy, Brain, and Mind: Part 2

Epilepsy is both a disease of the brain and the mind. Here, we present the second of two papers with extended summaries of selected presentations of the Third International Congress on Epilepsy, Brain and Mind (April 3-5, 2014; Brno, Czech Republic). Humanistic, biologic, and therapeutic aspects of epilepsy, particularly those related to the mind, were discussed. The extended summaries provide current overviews of epilepsy, cognitive impairment, and treatment, including brain functional connectivity and functional organization; juvenile myoclonic epilepsy; cognitive problems in newly diagnosed epilepsy; SUDEP including studies on prevention and involvement of the serotoninergic system; aggression and antiepileptic drugs; body, mind, and brain, including pain, orientation, the "self-location", Gourmand syndrome, and obesity; euphoria, obsessions, and compulsions; and circumstantiality and psychiatric comorbidities.

Physiological consequences of abnormal connectivity in a developmental epilepsy

OBJECTIVE

Many forms of epilepsy are associated with aberrant neuronal connections, but the relationship between such pathological connectivity and the underlying physiological predisposition to seizures is unclear. We sought to characterize the cortical excitability profile of a developmental form of epilepsy known to have structural and functional connectivity abnormalities.

METHODS

We employed transcranial magnetic stimulation (TMS) with simultaneous electroencephalographic (EEG) recording in 8 patients with epilepsy from periventricular nodular heterotopia and matched healthy controls. We used connectivity imaging findings to guide TMS targeting and compared the evoked responses to single-pulse stimulation from different cortical regions.

RESULTS

Heterotopia patients with active epilepsy demonstrated a relatively augmented late cortical response that was greater than that of matched controls. This abnormality was specific to cortical regions with connectivity to subcortical heterotopic gray matter. Topographic mapping of the late response differences showed distributed cortical networks that were not limited to the stimulation site, and source analysis in 1 subject revealed that the generator of abnormal TMS-evoked activity overlapped with the spike and seizure onset zone.

INTERPRETATION

Our findings indicate that patients with epilepsy from gray matter heterotopia have altered cortical physiology consistent with hyperexcitability, and that this abnormality is specifically linked to the presence of aberrant connectivity. These results support the idea that TMS-EEG could be a useful biomarker in epilepsy in gray matter heterotopia, expand our understanding of circuit mechanisms of epileptogenesis, and have potential implications for therapeutic neuromodulation in similar epileptic conditions associated with deep lesions.

The adhesion G protein-coupled receptor GPR56 is a cell-autonomous regulator of oligodendrocyte development

Mutations in GPR56, a member of the adhesion G protein-coupled receptor family, cause a human brain malformation called bilateral frontoparietal polymicrogyria (BFPP). Magnetic resonance imaging (MRI) of BFPP brains reveals myelination defects in addition to brain malformation. However, the cellular role of GPR56 in oligodendrocyte development remains unknown. Here, we demonstrate that loss of Gpr56 leads to hypomyelination of the central nervous system in mice. GPR56 levels are abundant throughout early stages of oligodendrocyte development, but are downregulated in myelinating oligodendrocytes. Gpr56-knockout mice manifest with decreased oligodendrocyte precursor cell (OPC) proliferation and diminished levels of active RhoA, leading to fewer mature oligodendrocytes and a reduced number of myelinated axons in the corpus callosum and optic nerves. Conditional ablation of Gpr56 in OPCs leads to a reduced number of mature oligodendrocytes as seen in constitutive knockout of Gpr56. Together, our data define GPR56 as a cell-autonomous regulator of oligodendrocyte development.

Somatic mutations in cerebral cortical malformations

BACKGROUND

Although there is increasing recognition of the role of somatic mutations in genetic disorders, the prevalence of somatic mutations in neurodevelopmental disease and the optimal techniques to detect somatic mosaicism have not been systematically evaluated.

METHODS

Using a customized panel of known and candidate genes associated with brain malformations, we applied targeted high-coverage sequencing (depth, ≥200×) to leukocyte-derived DNA samples from 158 persons with brain malformations, including the double-cortex syndrome (subcortical band heterotopia, 30 persons), polymicrogyria with megalencephaly (20), periventricular nodular heterotopia (61), and pachygyria (47). We validated candidate mutations with the use of Sanger sequencing and, for variants present at unequal read depths, subcloning followed by colony sequencing.

RESULTS

Validated, causal mutations were found in 27 persons (17%; range, 10 to 30% for each phenotype). Mutations were somatic in 8 of the 27 (30%), predominantly in persons with the double-cortex syndrome (in whom we found mutations in DCX and LIS1), persons with periventricular nodular heterotopia (FLNA), and persons with pachygyria (TUBB2B). Of the somatic mutations we detected, 5 (63%) were undetectable with the use of traditional Sanger sequencing but were validated through subcloning and subsequent sequencing of the subcloned DNA. We found potentially causal mutations in the candidate genes DYNC1H1, KIF5C, and other kinesin genes in persons with pachygyria.

CONCLUSIONS

Targeted sequencing was found to be useful for detecting somatic mutations in patients with brain malformations. High-coverage sequencing panels provide an important complement to whole-exome and whole-genome sequencing in the evaluation of somatic mutations in neuropsychiatric disease. (Funded by the National Institute of Neurological Disorders and Stroke and others.).

Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning

The human neocortex has numerous specialized functional areas whose formation is poorly understood. Here, we describe a 15-base pair deletion mutation in a regulatory element of GPR56 that selectively disrupts human cortex surrounding the Sylvian fissure bilaterally including "Broca's area," the primary language area, by disrupting regional GPR56 expression and blocking RFX transcription factor binding. GPR56 encodes a heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor required for normal cortical development and is expressed in cortical progenitor cells. GPR56 expression levels regulate progenitor proliferation. GPR56 splice forms are highly variable between mice and humans, and the regulatory element of gyrencephalic mammals directs restricted lateral cortical expression. Our data reveal a mechanism by which control of GPR56 expression pattern by multiple alternative promoters can influence stem cell proliferation, gyral patterning, and, potentially, neocortex evolution.

Integration of gray matter nodules into functional cortical circuits in periventricular heterotopia

Alterations in neuronal circuitry are recognized as an important substrate of many neurological disorders, including epilepsy. Patients with the developmental brain malformation of periventricular nodular heterotopia (PNH) often have both seizures and dyslexia, and there is evidence to suggest that aberrant neuronal connectivity underlies both of these clinical features. We used task-based functional MRI (fMRI) to determine whether heterotopic nodules of gray matter in this condition are integrated into functional cortical circuits. Blood oxygenation level-dependent (BOLD) fMRI was acquired in eight participants with PNH during the performance of reading-related tasks. Evidence of neural activation within heterotopic gray matter was identified, and regions of cortical coactivation were then mapped systematically. Findings were correlated with resting-state functional connectivity results and with performance on the fMRI reading-related tasks. Six participants (75%) demonstrated activation within at least one region of gray matter heterotopia. Cortical areas directly overlying the heterotopia were usually coactivated (60%), as were areas known to have functional connectivity to the heterotopia in the task-free resting state (73%). Six of seven (86%) primary task contrasts resulted in heterotopia activation in at least one participant. Activation was most commonly seen during rapid naming of visual stimuli, a characteristic impairment in this patient population. Our findings represent a systematic demonstration that heterotopic gray matter can be metabolically coactivated in a neuronal migration disorder associated with epilepsy and dyslexia. Gray matter nodules were most commonly coactivated with the anatomically overlying cortex and other regions with resting-state connectivity to heterotopia. These results have broader implications for understanding the network pathogenesis of both seizures and reading disabilities.

Estimation of temporal scales of variation in long-term scalp electroencephalograms from epilepsy patients

Long-term neurophysiological recordings, such as scalp encephalograms (EEG), have been routinely used in studies that aim to characterize dynamic changes in brain activity associated with normal biological processes, such as sleep, but are also becoming increasingly common for clinical evaluation of patients with neurological disorders, such as epilepsy. Analysis of non-stationary recordings from multiple days poses new signal processing challenges, in regard to algorithm efficiency and computational cost, as well as adequate dimensionality data reduction. We compared four approaches for estimating the underlying temporal dynamics of long-term recordings from patients with medically refractory epilepsy: (i) model order selection using the minimum description length principle, (ii) approximate entropy, (iii) mutual information, and (iv) Detrended Fluctuation Analysis (DFA). Individual approaches were found to be sensitive only to specific scales of variation. Approximate entropy and mutual information were sensitive to local dynamics, whereas dynamic model order estimation captured only slowly varying dynamics. DFA was sensitive to multiple temporal scales.

Medium modification of jet fragmentation in Au+Au collisions at √[s(NN)]=200 GeV measured in direct photon-hadron correlations

The jet fragmentation function is measured with direct photon-hadron correlations in p+p and Au+Au collisions at √[s(NN)]=200 GeV. The p(T) of the photon is an excellent approximation to the initial p(T) of the jet and the ratio z(T)=p(T)(h)/p(T)(γ) is used as a proxy for the jet fragmentation function. A statistical subtraction is used to extract the direct photon-hadron yields in Au+Au collisions while a photon isolation cut is applied in p+p. I(AA), the ratio of hadron yield opposite the photon in Au+Au to that in p+p, indicates modification of the jet fragmentation function. Suppression, most likely due to energy loss in the medium, is seen at high z(T). The associated hadron yield at low z(T) is enhanced at large angles. Such a trend is expected from redistribution of the lost energy into increased production of low-momentum particles.

Information theoretic measures of network coordination in high-frequency scalp EEG reveal dynamic patterns associated with seizure termination

How a seizure terminates is still under-studied and, despite its clinical importance, remains an obscure phase of seizure evolution. Recent studies of seizure-related scalp EEGs at frequencies >100 Hz suggest that neural activity, in the form of oscillations and/or neuronal network interactions, may play an important role in preictal/ictal seizure evolution (Andrade-Valenca et al., 2011; Stamoulis et al., 2012). However, the role of high-frequency activity in seizure termination, is unknown, if it exists at all. Using information theoretic measures of network coordination, this study investigated ictal and immediate postictal neurodynamic interactions encoded in scalp EEGs from a relatively small sample of 8 patients with focal epilepsy and multiple seizures originating in temporal and/or frontal brain regions, at frequencies ≤ 100 Hz and >100 Hz, respectively. Despite some heterogeneity in the dynamics of these interactions, consistent patterns were also estimated. Specifically, in several seizures, linear or non-linear increase in high-frequency neuronal coordination during ictal intervals, coincided with a corresponding decrease in coordination at frequencies <100 Hz, suggesting a potential interference role of high-frequency activity, to disrupt abnormal ictal synchrony at lower frequencies. These changes in network synchrony started at least 20-30s prior to seizure offset, depending on the seizure duration. Opposite patterns were estimated at frequencies ≤ 100 Hz in several seizures. These results raise the possibility that high-frequency interference may occur in the form of progressive network coordination during the ictal interval, which continues during the postictal interval. This may be one of several possible mechanisms that facilitate seizure termination. In fact, inhibition of pairwise interactions between EEGs by other signals in their spatial neighborhood, quantified by negative interaction information, was estimated at frequencies ≤ 100 Hz, at least in some seizures.

Space-time adaptive processing for improved estimation of preictal seizure activity

Detection of precursory, seizure-related activity in electroencephalograms (EEG) is a clinically important and difficult problem in the field of epilepsy. Seizure detection methods often aim to identify specific features and correlations between preictal EEG signals that differentiate them from interictal/nonictal signals. Typically, these methods use information from nonictal EEGs to establish detection thresholds, and do not otherwise incorporate their characteristics into the detection. A space-time adaptive approach is proposed to improve detection of seizure-related preictal activity in scalp EEG, using multiple patient-specific baseline signals to optimize the estimate of the baseline covariance matrix. A simplified model of the preictal EEG is assumed, which describes this signal as a linear superposition of seizure-related activity and baseline activity (treated as an interference signal). It is shown that when an improved estimate of the baseline covariance is included in the preictal detector, the true positive rate increases significantly and also the false positive rate decreases significantly.

Schizencephaly: association with young maternal age, alcohol use, and lack of prenatal care

Schizencephaly is a rare malformation of cortical development characterized by congenital clefts extending from the pial surface to the lateral ventricle that are lined by heterotopic gray matter. The clinical presentation is variable and can include motor or cognitive impairment and epilepsy. The causes of schizencephaly are heterogeneous and can include teratogens, prenatal infection, or maternal trauma. Reported genetic causes include chromosomal aneuploidy, EMX2 mutations, and possible autosomal recessive familial cases based on recurrence in siblings. In an effort to identify risk factors for schizencephaly, we conducted a survey of 48 parents or primary caretakers of patients with schizencephaly born between 1983 and 2004. We discovered that young maternal age, lack of prenatal care, and alcohol use were all significantly associated with risk of schizencephaly. Our results suggest that there are important nongenetic, intrauterine events that predispose to schizencephaly.

Signal subspace integration for improved seizure localization

A subspace signal processing approach is proposed for improved scalp EEG-based localization of broad-focus epileptic seizures, and estimation of the directions of source arrivals (DOA). Ictal scalp EEGs from adult and pediatric patients with broad-focus seizures were first decomposed into dominant signal modes, and signal and noise subspaces at each modal frequency, to improve the signal-to-noise ratio while preserving the original data correlation structure. Transformed (focused) modal signals were then resynthesized into wideband signals from which the number of sources and DOA were estimated. These were compared to denoised signals via principal components analysis (PCA). Coherent subspace processing performed better than PCA, significantly improved the localization of ictal EEGs and the estimation of distinct sources and corresponding DOAs.

Filamin A mutation associated with normal reading skills and dyslexia in a family with periventricular heterotopia

Periventricular heterotopia (PH) is a disorder of neuronal migration during fetal development that is characterized by morphologically normal neurons being located in an anatomically abnormal position in the mature brain. PH is usually diagnosed in patients presenting with a seizure disorder, when neuroimaging demonstrates the ectopically placed nodules of neurons. PH is a genetically and phenotypically heterogeneous disorder. The most commonly identified genetic cause is the X-linked dominant inheritance of mutations in the Filamin A (FLNA) gene. Multiple lines of evidence support the contribution of genetic factors in dyslexia. As dyslexia does not show a single-gene pattern of inheritance, it is classified as a complex genetic disorder. We have recently identified a specific reading fluency deficit in a variable group of patients with PH, in the context of normal intelligence. Here, we present a study of a mother-daughter pair who share bilateral widespread gray matter heterotopia caused by a novel mutation in FLNA and the same pattern of X-chromosome inactivation but who exhibit divergent reading and cognitive profiles. This novel observation highlights the uncertainty of using heterotopia anatomy in clinical practice to predict behavioral outcome.

Multiscale information for network characterization in epilepsy

We have developed a multiscale approach for the estimation of neuronal network coordination in the epileptic brain, from continuous (long-term) non-invasive electroencephalograms (EEG). The proposed approach specifically assesses the effect of large-scale network behavior on local network coordination, at individual dominant frequencies (modes) of the EEG spectrum. For this purpose a set of conditional information parameters is proposed to explicitly quantify the effect of global network correlation in the brain on pairwise (local) mutual information, via conditioning. These parameters are shown to be modulated in a frequency-specific manner at baseline, as well as during seizure evolution.

Modeling noninvasive neurostimulation in epilepsy as stochastic interference in brain networks

Noninvasive brain stimulation is one of very few potential therapies for medically refractory epilepsy. However, its efficacy remains suboptimal and its therapeutic value has not been consistently assessed. This is in part due to the nonoptimized spatio-temporal application of stimulation protocols for seizure prevention or arrest, and incomplete knowledge of the neurodynamics of seizure evolution. Through simulations, this study investigated electroencephalography (EEG)-guided, stochastic interference with aberrantly coordinated neuronal networks, to prevent seizure onset or interrupt a propagating partial seizure, and prevent it from spreading to large areas of the brain. Brain stimulation was modeled as additive white or band-limited noise, and simulations using real EEGs and data generated from a network of integrate-and-fire neuronal ensembles were used to quantify spatio-temporal noise effects. It was shown that additive stochastic signals (noise) may destructively interfere with network dynamics and decrease or abolish synchronization associated with progressively coupled networks. Furthermore, stimulation parameters, particularly amplitude and spatio-temporal application, may be optimized based on patient-specific neurodynamics estimated directly from noninvasive EEGs.

Abnormal structural and functional brain connectivity in gray matter heterotopia

PURPOSE

Periventricular nodular heterotopia (PNH) is a malformation of cortical development associated with epilepsy and dyslexia. Evidence suggests that heterotopic gray matter can be functional in brain malformations and that connectivity abnormalities may be important in these disorders. We hypothesized that nodular heterotopia develop abnormal connections and systematically investigated the structural and functional connectivity of heterotopia in patients with PNH.

METHODS

Eleven patients were studied using diffusion tensor tractography and resting-state functional connectivity MRI with bold oxygenation level-dependent (BOLD) imaging. Fiber tracks with a terminus within heterotopic nodules were visualized to determine structural connectivity, and brain regions demonstrating resting-state functional correlations to heterotopic nodules were analyzed. Relationships between these connectivity results and measures of clinical epilepsy and cognitive disability were examined.

KEY FINDINGS

A majority of heterotopia (69%) showed structural connectivity to discrete regions of overlying cortex, and almost all (96%) showed functional connectivity to these regions (mean peak correlation coefficient 0.61). Heterotopia also demonstrated connectivity to regions of contralateral cortex, other heterotopic nodules, ipsilateral but nonoverlying cortex, and deep gray matter structures or the cerebellum. Patients with the longest durations of epilepsy had a higher degree of abnormal functional connectivity (p = 0.036).

SIGNIFICANCE

Most heterotopic nodules in PNH are structurally and functionally connected to overlying cortex, and the strength of abnormal connectivity is higher among patients with the longest duration of epilepsy. Along with prior evidence that cortico-cortical tract defects underlie dyslexia in this disorder, the current findings suggest that altered connectivity is likely a critical substrate for neurologic dysfunction in brain malformations.

High-frequency neuronal network modulations encoded in scalp EEG precede the onset of focal seizures

Modulations of neuronal network interactions by seizure precursors are only partially understood and difficult to measure, in part due to inherent intra- and inter-patient seizure heterogeneities and EEG variability. This study investigated preictal neuromodulations associated with seizures originating in the temporal and/or frontal lobes, using information theoretic parameters estimated from awake scalp EEGs in two frequency ranges, ≤100 Hz and >100 Hz, respectively. Seizure-related activity at high frequencies has not been extensively estimated in awake scalp EEGs. Based on the statistical similarity of preictal and ictal information parameters, preictal network interactions appeared to be specifically modulated at frequencies >100 Hz, but not at lower frequencies. The dynamics of these parameters varied distinctly according to the origin of seizure onset (temporal versus frontal). Although preliminary, and based on a small patient sample for which the potential heterogeneity of multiple anticonvulsive medications was difficult to control, these results suggest that preictal modulations may be estimated from high-frequency scalp EEGs using directional information measures with high specificity to ictal events, and may thus be promising for improving seizure prediction.

Early cognitive and behavioral problems in children with nodular heterotopia

Adults with periventricular nodular heterotopia (PNH) have epilepsy and dyslexia, but most have normal intelligence. It is not known whether PNH-related reading difficulty can be detected earlier in childhood or whether associated behavioral problems are present. We studied 10 children with PNH, 3 of whom did not have seizures, and 10 matched controls with neuropsychological testing and parental rating instruments at two time points separated by about 1 year. Children with PNH performed significantly worse than controls on a task related to reading fluency. In addition, those with PNH showed significantly worse adaptive skills, and a measure of conduct problems significantly worsened over time. Mood and behavioral problems were reported more commonly, though not significantly so, in children with PNH. These findings demonstrate that reading dysfluency can be evident in children with nodular heterotopia, even in the absence of epilepsy, but also highlight difficulties with behavior in this population.

Cold nuclear matter effects on J/ψ yields as a function of rapidity and nuclear geometry in d+A collisions at sqrt[s(NN)]=200 GeV

We present measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200  GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2<y<2.4) with high statistical precision and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects. In order to remove model dependent systematic uncertainties we also compare the data to a simple geometric model. The forward rapidity data are inconsistent with nuclear modifications that are linear or exponential in the density weighted longitudinal thickness, such as those from the final state breakup of the bound state.

ESTIMATION OF DIRECTIONAL BRAIN ANISOTROPY FROM EEG SIGNALS USING THE MELLIN TRANSFORM AND IMPLICATIONS FOR SOURCE LOCALIZATION

This paper presents a novel approach for the estimation of frequency-specific EEG scale modulations by the directional anisotropy of the brain, using the Mellin transform [1, 2, 3]. In the case of epileptic sources, the activity recorded by routine scalp EEG includes contributions not only from a seizure's primary propagation path but also from secondary paths and unrelated to the seizure activity. In addition, the anisotropy of the brain directionally modulates the seizure-related signal component. We estimated patient-specific direction-specific, frequency-locked scale shifts. During the ictal interval, these shifts occurred at frequencies ≥50 Hz. We further estimated the effect of scale modulations on time-delay estimation. Larger time-delays were estimated from EEGs that had been corrected by a scale factor prior to this estimation. Thus, corrections for non-linear scaling of EEGs may ultimately improve time-delay estimation for source localization, particularly in cases of seizures rapidly propagating to large areas of the brain.

Candidate gene sequencing of LHX2, HESX1, and SOX2 in a large schizencephaly cohort

Schizencephaly is a malformation of cortical development characterized by gray matter-lined clefts in the cerebral cortex and a range of neurological presentations. In some cases, there are features of septo-optic dysplasia concurrently with schizencephaly. The etiologies of both schizencephaly and septo-optic dysplasia are thought to be heterogeneous, but there is evidence that at least some cases have genetic origin. We hypothesized that these disorders may be caused by mutations in three candidate genes: LHX2, a gene with an important cortical patterning role, and HESX1 and SOX2, genes that have been associated with septo-optic dysplasia. We sequenced a large cohort of patients with schizencephaly, some with features of septo-optic dysplasia, for mutations in these genes. No pathogenic mutations were observed, suggesting that other genes or non-genetic factors influencing genes critical to brain development must be responsible for schizencephaly. © 2010 Wiley-Liss, Inc.

Cerebral volumetric analysis over time in children with malformations of cortical development: a quantitative investigation

Malformations of cortical development are common neurological disorders characterized by disruptions in the normal development of cerebral gray and white matter during fetal life. We performed a quantitative, partly longitudinal investigation of cerebral volumes in a cohort of children with cortical malformations to investigate how their anatomical abnormalities change over time. Cortical malformation subjects showed volumetric curves that were comparable with those reported for healthy individuals, and reached peak cerebral volume, gray matter volume, and white matter volume at ages similar to those reported for healthy children. Volumes of heterotopic gray matter, however, demonstrated increases that were out of proportion to changes in cortical volume or caudate nucleus volume, suggesting that misplaced gray matter can have a unique pattern of maturation. Our findings demonstrate that overall brain growth in children with cortical malformations appears to mirror that of the healthy population, although malformed regions can show distinct growth patterns.

Network dynamics of the epileptic brain at rest

Baseline neurodynamics are believed to play an important role in normal brain function. A potentially intrinsic property of the brain is the weak coupling between networks at rest, which enables it to be flexible, adapt, process novel stimuli, and learn. Brain regions become differentially coordinated in response to cognitive task and behavior demands and external stimuli. However, abnormally synchronized resting brain networks may also be associated with different pathologies. We investigated baseline network dynamics in the epileptic brain using information theoretic parameters to quantify coupling and directionality of information flow between different cortical regions. We estimated relative entropy, conditional mutual information and a related measure of directional coupling, from EEGs of patients with epilepsy and healthy subjects. At rest, the healthy brain appears to be characterized by low and non-directional network coupling, whereas the epileptic brain appears to be transiently and directionally synchronized.

The syndrome of perisylvian polymicrogyria with congenital arthrogryposis

BACKGROUND

Bilateral perisylvian polymicrogyria (BPP) is a well-recognized malformation of cortical development commonly associated with epilepsy, cognitive impairment, and oromotor apraxia. Reports have suggested the association of BPP with arthrogryposis multiplex congenita. We sought to investigate the clinical, electrophysiological, and neuroradiological features of this combined syndrome to determine if there are unique features that distinguish BPP with arthrogryposis from BPP alone.

METHODS

Cases of BPP with congenital arthrogryposis were identified from a large research database of individuals with polymicrogyria. Clinical features (including oromotor function, seizures, and joint contractures), MR brain imaging, and results of neuromuscular testing were reviewed.

RESULTS

Ten cases of BPP with congenital arthrogryposis were identified. Most cases had some degree of oromotor apraxia. Only a few had seizures, but a majority of cases were still young children. Electrophysiological studies provided evidence for lower motor neuron or peripheral nervous system involvement. On brain imaging, bilateral polymicrogyria (PMG) centered along the Sylvian fissures was seen, with variable extension frontally or parietally; no other cortical malformations were present. We did not identify obvious neuroimaging features that distinguish this syndrome from that of BPP without arthrogryposis.

CONCLUSIONS

The clinical and neuroimaging features of the syndrome of BPP with congenital arthrogryposis appear similar to those seen in cases of isolated BPP without joint contractures, but electrophysiological studies often demonstrate coexistent lower motor neuron or peripheral nervous system pathology. These findings suggest that BPP with arthrogryposis may have a genetic etiology with effects at two levels of the neuraxis.

Transition in yield and azimuthal shape modification in dihadron correlations in relativistic heavy ion collisions

Hard-scattered parton probes produced in collisions of large nuclei indicate large partonic energy loss, possibly with collective produced-medium response to the lost energy. We present measurements of π^{0} trigger particles at transverse momenta p{T}{t}=4-12  GeV/c and associated charged hadrons (p{T}{a}=0.5-7  GeV/c) vs relative azimuthal angle Δϕ in Au+Au and p+p collisions at sqrt[s{NN}]=200  GeV. The Au+Au distribution at low p{T}{a}, whose shape has been interpreted as a medium effect, is modified for p{T}{t}<7  GeV/c. At higher p{T}{t}, the data are consistent with unmodified or very weakly modified shapes, even for the lowest measured p{T}{a}, which quantitatively challenges some medium response models. The associated yield of hadrons opposing the trigger particle in Au+Au relative to p+p (I{AA}) is suppressed at high p{T} (I{AA}≈0.35-0.5), but less than for inclusive suppression (R{AA}≈0.2).

Enhanced production of direct photons in Au + Au collisions at square root(S(NN)) = 200 GeV and implications for the initial temperature

The production of e+ e- pairs for m(e+ e-)<0.3 GeV/c2 and 1<p(T)<5 GeV/c is measured in p+p and Au+Au collisions at square root(S(NN))=200 GeV. An enhanced yield above hadronic sources is observed. Treating the excess as photon internal conversions, the invariant yield of direct photons is deduced. In central Au+Au collisions, the excess of the direct photon yield over p+p is exponential in transverse momentum, with an inverse slope T=221+/-19(stat)+/-19(syst) MeV. Hydrodynamical models with initial temperatures ranging from T(init) approximately 300-600 MeV at times of approximately 0.6-0.15 fm/c after the collision are in qualitative agreement with the data. Lattice QCD predicts a phase transition to quark gluon plasma at approximately 170 MeV.

Estimation of Eeg Signal Dispersion During Seizure Propagation

Localization of the seizure focus in the brain is a challenging problem in the field of epilepsy. The complexity of the seizure-related EEG waveform, its non-stationarity and degradation with distance due to the dispersive nature of the brain as a propagation medium, make localization difficult. Yet, precise estimation of the focus is critical, particularly when surgical resection is the only therapeutic option. The first step to solving this inverse problem is to estimate and account for frequency- or mode-specific signal dispersion, which is present in both scalp and intracranial EEG recordings during seizures. We estimated dispersion curves in both types of signals using a spatial correlation method and mode-based semblance analysis. We showed that, despite the assumption of spatial stationarity and a simplified array geometry, there is measurable inter-modal and intra-modal dispersion during seizures in both types of EEG recordings, affecting the estimated arrival times and consequently focus localization.

Measurement of bottom versus charm as a function of transverse momentum with electron-hadron correlations in p + p collisions at square root of s = 200 GeV

The momentum distribution of electrons from semileptonic decays of charm and bottom quarks for midrapidity |y|<0.35 in p+p collisions at square root of s=200 GeV is measured by the PHENIX experiment at the Relativistic Heavy Ion Collider over the transverse momentum range 2<pT<7 GeV/c. The ratio of the yield of electrons from bottom to that from charm is presented. The ratio is determined using partial D/D-->e(+/-)K(-/+)X (K unidentified) reconstruction. It is found that the yield of electrons from bottom becomes significant above 4 GeV/c in pT. A fixed-order-plus-next-to-leading-log perturbative quantum chromodynamics calculation agrees with the data within the theoretical and experimental uncertainties. The extracted total bottom production cross section at this energy is sigma(bb)=3.2(-1.1)(+1.2)(stat)(-1.3)(+1.4)(syst)mub.

Gray matter volumes and cognitive ability in the epileptogenic brain malformation of periventricular nodular heterotopia

Periventricular nodular heterotopia (PNH) is a brain malformation clinically characterized by the triad of epilepsy, normal intelligence, and dyslexia. We investigated the structure-function relationship between cerebral volumes and cognitive ability in this disorder by studying 12 subjects with PNH and 6 controls using volumetric analysis of high-resolution anatomical MRI and neuropsychological testing. Total cerebral volumes and specific brain compartment volumes (gray matter, white matter, and cerebrospinal fluid) in subjects with PNH were comparable to those in controls. There was a negative correlation between heterotopic gray matter volume and cortical gray matter volume. Cerebral and cortical volumes in PNH did not correlate with Full Scale IQ, unlike in normal individuals. Our findings support the idea that heterotopic nodules contain misplaced neurons that would normally have migrated to the cortex, and suggest that structural correlates of normal cognitive ability may be different in the setting of neuronal migration failure.

Gluon-spin contribution to the proton spin from the double-helicity asymmetry in inclusive pi0 production in polarized p+p collisions at [sqrt]s=200 GeV

The double helicity asymmetry in neutral pion production for pT=1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, DeltaG, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of micro2=4 GeV2 a next to leading order QCD analysis gives DeltaG[0.02,0.3]=0.2, with a constraint of -0.7<DeltaG[0.02,0.3]<0.5 at Deltachi2=9 (approximately 3sigma) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the DeltaG constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.

Microdysgenesis: Historical roots of an important concept in epilepsy

Microdysgenesis (MD) is a term used to refer to subtle brain dysplasia based on structural tissue characteristics seen exclusively under the microscope. Although MD is often referred to within the field of modern epileptology, the term and its implications have actually evolved over a long period in neurology, starting in the late 19th century. This article undertakes a careful evaluation of original publications in the epilepsy literature and demonstrates that the concept of MD is anchored within a set of papers written from 1890 to 1930 and their contemporaneous reception in classic neuropsychiatric handbooks. Both the text of these early publications and the development of the MD concept are examined and illustrated. This perspective provides insight into historical scientific views of epilepsy as a mental disease that was thought to be dependent largely on hereditary or developmental factors.

Application of Matched-Filtering to Extract EEG Features and Decouple Signal Contributions from Multiple Seizure Foci in Brain Malformations

Developmental brain malformations often cause intractable and in many cases generalized and/or multifocal seizures. Surgical intervention is not possible in these cases as it is difficult to isolate the epileptogenic foci. Scalp EEG signals recorded during such seizures include coupled contributions from different sources. If it was possible to decouple these contributions based on differences in both their signatures and inter-arrival times at different electrodes, it would subsequently be possible to estimate the locations of the seizure foci. For this purpose, we applied matched filtering to scalp EEG data from 3 patients with multifocal seizures, using patient-specific source-related short EEG segments as the template waveforms. These segments were assumed to be seizure-related based on distinct sets of inter-arrival times at different channels and alternating signal polarities. We present preliminary results and demonstrate that matched filtering can be successfully applied to extract decoupled signal components from the EEG, generated by potentially distinct sources, and thus with distinct inter-arrival times but partially overlapping spectra.

Sleep spindle alterations in patients with malformations of cortical development

Malformations of cortical development are disorders of altered brain anatomy and architecture that arise from abnormalities in the usual processes of cerebral cortical development. Although they often lead to epilepsy, cognitive delay, and motor impairment, little is known about their effect on sleep. Since malformations may anatomically or functionally disrupt the cerebral circuits that mediate sleep spindles, we hypothesized that these disorders would be associated with abnormal spindle characteristics. We analyzed the density, maximum frequency, laterality and distribution of sleep spindles seen in routine and long-term electroencephalographic recordings performed in ten brain malformation subjects and ten matched controls. There were no significant differences in spindle density or maximum frequency between the two groups, but malformation subjects had a significantly lower proportion of bilateral spindles and a significantly higher proportion of anterior and diffuse spindles compared to controls. In addition, unilateral malformations appeared to be associated with a skewing of unilateral spindles toward the contralateral side. Our findings suggest that brain malformations disrupt the thalamocortical circuits responsible for sleep spindle generation, and support the need for further studies on the relationships between cortical maldevelopment and sleep.

Estimation of brain state changes associated with behavior, stimulation and epilepsy

Brain state dynamics vary at different spatiotemporal scales with behavior, stimulation, and disease, and may be unobserved (latent). Using a state-space model framework and subspace identification, we estimated spatiotemporally localized, latent state changes associated with the application of transcranial magnetic stimulation (TMS), to assess the effect of stimulation on brain state dynamics. State appeared to be modulated by behavior in a spatially-specific manner and small-amplitude state fluctuations were temporally locked to stimulus presentations. In addition, during and following TMS, an overall, bilateral and spatially nonspecific decrease in brain state was observed. We also estimated brain state changes during seizure evolution (independent of TMS), in focal and generalized seizures, which have very different epileptogenesis and propagation mechanisms, possibly resulting also in distinct spatiotemporal dynamics. Indeed, our preliminary results showed that in focal seizures, temporally localized dynamic state changes occur at least 1 min prior to seizure onset, with a decrease in steady-state followed by an increase which reaches a maximum during the ictal interval. In contrast, no such dynamic pattern was evident in state estimates during generalized seizures.

Ethnically diverse causes of Walker-Warburg syndrome (WWS): FCMD mutations are a more common cause of WWS outside of the Middle East

Walker-Warburg syndrome (WWS) is a genetically heterogeneous autosomal recessive disease characterized by congenital muscular dystrophy, cobblestone lissencephaly, and ocular malformations. Mutations in six genes involved in the glycosylation of á-dystroglycan (POMT1, POMT2, POMGNT1, FCMD, FKRP and LARGE) have been identified in WWS patients, but account for only a portion of WWS cases. To better understand the genetics of WWS and establish the frequency and distribution of mutations across WWS genes, we genotyped all known loci in a cohort of 43 WWS patients of varying geographical and ethnic origin. Surprisingly, we reached a molecular diagnosis for 40% of our patients and found mutations in POMT1, POMT2, FCMD and FKRP, many of which were novel alleles, but no mutations in POMGNT1 or LARGE. Notably, the FCMD gene was a more common cause of WWS than previously expected in the European/American subset of our cohort, including all Ashkenazi Jewish cases, who carried the same founder mutation.