Deep latent variable joint cognitive modeling of neural signals and human behavior.

As the field of computational cognitive neuroscience continues to expand and generate new theories, there is a growing need for more advanced methods to test the hypothesis of brain-behavior relationships. Recent progress in Bayesian cognitive modeling has enabled the combination of neural and behavioral models into a single unifying framework. However, these approaches require manual feature extraction, and lack the capability to discover previously unknown neural features in more complex data. Consequently, this would hinder the expressiveness of the models. To address these challenges, we propose a Neurocognitive Variational Autoencoder (NCVA) to conjoin high-dimensional EEG with a cognitive model in both generative and predictive modeling analyses. Importantly, our NCVA enables both the prediction of EEG signals given behavioral data and the estimation of cognitive model parameters from EEG signals. This novel approach can allow for a more comprehensive understanding of the triplet relationship between behavior, brain activity, and cognitive processes.

Does achieving clinically important thresholds after first shoulder arthroplasty predict similar outcomes of the contralateral shoulder?

BACKGROUND: Patients are increasingly undergoing bilateral total shoulder arthroplasty (TSA). At present, it is unknown whether success after the first TSA is predictive of success after contralateral TSA. We aimed to determine whether exceeding clinically important thresholds of success after primary TSA predicts similar outcomes for subsequent contralateral TSA. METHODS: We performed a retrospective review of a prospectively collected shoulder arthroplasty database for patients undergoing bilateral primary anatomic (aTSA) or reverse (rTSA) total shoulder arthroplasty since January 2000 with preoperative and 2- or 3-year clinical follow-up. Our primary outcome was whether exceeding clinically important thresholds in the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) score for the first TSA was predictive of similar success of the contralateral TSA; thresholds for the ASES score were adopted from prior literature and included the minimal clinically important difference (MCID), the substantial clinical benefit (SCB), 30% of maximal possible improvement (MPI), and the patient acceptable symptomatic state (PASS). The PASS is defined as the highest level of symptom beyond which patients consider themselves well, which may be a better indicator of a patient's quality of life. To determine whether exceeding clinically important thresholds was independently predictive of similar success after second contralateral TSA, we performed multivariable logistic regression adjusted for age at second surgery, sex, BMI, and type of first and second TSA. RESULTS: Of the 134 patients identified that underwent bilateral shoulder arthroplasty, 65 (49%) had bilateral rTSAs, 45 (34%) had bilateral aTSAs, 21 (16%) underwent aTSA/rTSA, and 3 (2%) underwent rTSA/aTSA. On multivariable logistic regression, exceeding clinically important thresholds after first TSA was not associated with greater odds of achieving thresholds after second TSA when success was evaluated by the MCID, SCB, and 30% MPI. In contrast, exceeding the PASS after first TSA was associated with 5.9 times greater odds (95% confidence interval 2.5-14.4, P < .001) of exceeding the PASS after second TSA. Overall, patients who exceeded the PASS after first TSA exceeded the PASS after second TSA at a higher rate (71% vs. 29%, P < .001); this difference persisted when stratified by type of prosthesis for first and second TSA. CONCLUSIONS: Patients who achieve the ASES score PASS after first TSA have greater odds of achieving the PASS for the contralateral shoulder regardless of prostheses type.

A tutorial on fitting joint models of M/EEG and behavior to understand cognition.

We present motivation and practical steps necessary to find parameter estimates of joint models of behavior and neural electrophysiological data. This tutorial is written for researchers wishing to build joint models of human behavior and scalp and intracranial electroencephalographic (EEG) or magnetoencephalographic (MEG) data, and more specifically those researchers who seek to understand human cognition. Although these techniques could easily be applied to animal models, the focus of this tutorial is on human participants. Joint modeling of M/EEG and behavior requires some knowledge of existing computational and cognitive theories, M/EEG artifact correction, M/EEG analysis techniques, cognitive modeling, and programming for statistical modeling implementation. This paper seeks to give an introduction to these techniques as they apply to estimating parameters from neurocognitive models of M/EEG and human behavior, and to evaluate model results and compare models. Due to our research and knowledge on the subject matter, our examples in this paper will focus on testing specific hypotheses in human decision-making theory. However, most of the motivation and discussion of this paper applies across many modeling procedures and applications. We provide Python (and linked R) code examples in the tutorial and appendix. Readers are encouraged to try the exercises at the end of the document.

Establishing the diagnosis of radial tunnel syndrome: a systematic review of published clinical series.

PURPOSE: Radial tunnel syndrome (RTS) is a controversial diagnosis due to non-specific exam findings and frequent absence of positive electromyography (EMG) and nerve conduction study (NCS) findings. The purpose of this study was to identify the methods used to diagnose RTS in the literature. METHODS: We queried PubMed, Embase, Web of Science, and Cochrane databases per PRISMA guidelines. Extracted data included article and patient characteristics, diagnostic assessments utilized and their respective findings, and treatments. Objective data were summarized descriptively. The relationship between reported diagnostic findings (i.e., physical exam and diagnostic tests) and treatments was assessed via a descriptive synthesis. RESULTS: Our review included 13 studies and 391 upper extremities. All studies utilized physical exam in diagnosing RTS; most commonly, patients had tenderness over the radial tunnel (381/391, 97%). Preoperative EMG/NCS was reported by 11/13 studies, with abnormal findings in 8.9% (29/327) of upper extremities. Steroid and/or lidocaine injection for presumed lateral epicondylitis was reported by 9/13 studies (46/295 upper extremities, 16%), with RTS being diagnosed after patients received little to no relief. It was also common to inject the radial tunnel to make the diagnosis (218/295, 74%). The most common reported intraoperative finding was narrowing of the PIN (38/137, 28%). The intraoperative compressive site most commonly reported was the arcade of Frohse (142/306, 46%). CONCLUSIONS: There is substantial heterogeneity in modalities used to diagnose RTS and the reported definition of RTS. This, in conjunction with many patients having concomitant lateral epicondylitis, makes it difficult to compare treatment outcomes for RTS. LEVEL OF EVIDENCE: Level III. Systematic review of retrospective and prospective cohort studies.

A Measure of Neural Function Provides Unique Insights into Behavioral Deficits in Acute Stroke.

BACKGROUND: Clinical and neuroimaging measures incompletely explain behavioral deficits in the acute stroke setting. We hypothesized that electroencephalography (EEG)-based measures of neural function would significantly improve prediction of acute stroke deficits. METHODS: Patients with acute stroke (n=50) seen in the emergency department of a university hospital from 2017 to 2018 underwent standard evaluation followed by a 3-minute recording of EEG at rest using a wireless, 17-electrode, dry-lead system. Artifacts in EEG recordings were removed offline and then spectral power was calculated for each lead pair. A primary EEG metric was DTABR, which is calculated as a ratio of spectral power: [(Delta*Theta)/(Alpha*Beta)]. Bivariate analyses and least absolute shrinkage and selection operator (LASSO) regression identified clinical and neuroimaging measures that best predicted initial National Institutes of Health Stroke Scale (NIHSS) score. Multivariable linear regression was then performed before versus after adding EEG findings to these measures, using initial NIHSS score as the dependent measure. RESULTS: Age, diabetes status, and infarct volume were the best predictors of initial NIHSS score in bivariate analyses, confirmed using LASSO regression. Combined in a multivariate model, these 3 explained initial NIHSS score (adjusted r2=0.47). Adding any of several different EEG measures to this clinical model significantly improved prediction; the greatest amount of additional variance was explained by adding contralesional DTABR (adjusted r2=0.60, P<0.001). CONCLUSIONS: EEG measures of neural function significantly add to clinical and neuroimaging for explaining initial NIHSS score in the acute stroke emergency department setting. A dry-lead EEG system can be rapidly and easily implemented. EEG contains information that may be useful early after stroke.

Study Design and Analysis in Hand Surgery Research: Tips for Success.

Hand surgeons are constantly faced with evaluation of new evidence to identify best practices in clinical care. However, even the most rigorous study designs have limitations due to biases, generalizability, and other flaws. Here, we highlight seven common aspects of study design and analysis that should be considered by hand surgeons when interpreting findings. The evaluation of these practices can optimize the peer-review process and assess the value of evidence to be incorporated into clinical practice.

The association between humeral lengthening and clinical outcomes after reverse shoulder arthroplasty: a systematic review and meta-analysis.

BACKGROUND: The purpose of this study was to evaluate the relationship between humeral lengthening and clinical outcomes after reverse shoulder arthroplasty (RSA) with stratification based on measurement method and implant design. METHODS: This systematic review was performed using PRISMA-P guidelines. PubMed/Medline, Cochrane Trials, and Embase were queried for articles evaluating the relationship between humeral lengthening and clinical outcomes inclusive of range of motion (ROM), strength, outcome scores, and pertinent complications (acromial and scapular spine fractures, nerve injury) after RSA. The relationship between humeral lengthening and clinical outcomes was reported descriptively overall and stratified by measurement method and implant design (globally medialized vs. lateralized). A positive association was defined as increased humeral lengthening being associated with greater ROM, outcome scores, or a greater incidence of complications, whereas a negative association denoted that increased humeral lengthening was associated with poorer ROM, outcome scores, or a lower incidence of complications. Meta-analysis was performed to compare humeral lengthening between patients with and without fractures of the acromion or scapular spine. RESULTS: Twenty-two studies were included. Humeral lengthening was assessed as the acromiohumeral distance (AHD), the distance from the acromion to the greater tuberosity (AGT), the acromion to the deltoid tuberosity (ADT), and the acromion to the distal humerus (ADH). Of 11 studies that assessed forward elevation, a positive association with humeral lengthening was found in 6, a negative association was found in 1, and 4 studies reported no association. Of studies assessing internal rotation (n = 9), external rotation (n = 7), and abduction (n = 4), all either identified a positive or lack of association with humeral lengthening. Studies assessing outcome scores (n = 11) found either a positive (n = 5) or no (n = 6) association with humeral lengthening. Of the studies that assessed fractures of the acromion and/or scapular spine (n = 6), 2 identified a positive association with humeral lengthening, 1 identified a negative association, and 3 identified no association. The single study that assessed the incidence of nerve injury identified a positive association with humeral lengthening. Meta-analysis was possible for AGT (n = 2) and AHD (n = 2); greater humeral lengthening was found in patients with fractures for studies using the AGT (mean difference 4.5 mm, 95% CI 0.7-8.3) but not the AHD. Limited study inclusion and heterogeneity prohibited identification of trends based on method of measuring humeral lengthening and implant design. CONCLUSION: The relationship between humeral lengthening and clinical outcomes after RSA remains unclear and requires future investigation using a standardized assessment method.

Two-year outcomes of the reverse humeral reconstruction prosthesis.

BACKGROUND: Extensive proximal humeral bone loss in the setting of shoulder arthroplasty represents a difficult challenge for the treating surgeon. Achieving adequate fixation with standard humeral prostheses can be problematic. Allograft-prosthetic composites are a viable solution for this problem; however, high rates of complications have been reported. Modular proximal humeral replacement systems are another potential solution, but there is a paucity of outcome data on these implants. This study reports the 2-year minimum follow-up outcomes and complications of a single system reverse proximal humeral reconstruction prosthesis (RHRP) for patients with extensive proximal humeral bone loss. METHODS: We retrospectively reviewed all patients with minimum 2-year follow-up who underwent implantation of an RHRP for either (1) failed shoulder arthroplasty or (2) proximal humerus fracture with severe bone loss (Pharos 2 and 3) and/or sequelae thereof. Forty-four patients met inclusion criteria (average age 68.3 ± 13.1 years). The average follow-up was 36.2 ± 12.4 months. Demographic information, operative data, and complications were recorded. Pre- and postoperative range of motion (ROM), pain, and outcome scores were assessed and compared to the minimal clinically important difference (MCID) and substantial clinical benefit (SCB) for primary rTSA where available. RESULTS: Of the 44 RHRPs evaluated, 93% (n = 39) had undergone prior surgery and 70% (n = 30) were performed for failed arthroplasty. ROM improved significantly in abduction by 22° (P = .006) and forward elevation by 28° (P = .003). Average pain on a daily basis and pain at worst improved significantly, by 2.0 points (P < .001) and 2.7 points (P < .001), respectively. Mean Simple Shoulder Test score improved by 3.2 (P < .001), Constant score by 10.9 (P = .030), American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) score by 29.7 (P < .001), University of California, Los Angeles (UCLA), score by 10.6 (P < .001), and Shoulder Pain and Disability Index score by 37.4 (P < .001). A majority of patients achieved the MCID for all outcome measures assessed (56%-81%). The SCB was exceeded by half of patients for forward elevation and the Constant score (50%), and exceeded by the majority of patients for the ASES score (58%) and UCLA score (58%). The complication rate was 28%; the most common complication was dislocation requiring closed reduction. Notably, there were no occurrences of humeral loosening requiring revision surgery. DISCUSSION: These data demonstrate that the RHRP resulted in significant improvements in ROM, pain, and patient-reported outcome measures, without the risk of early humeral component loosening. RHRP represents another potential solution for shoulder arthroplasty surgeons when addressing extensive proximal humerus bone loss.

Glenoid component placement accuracy in total shoulder arthroplasty with preoperative planning and standard instrumentation is not influenced by supero-inferior glenoid erosion.

PURPOSE: Accurate glenoid component placement in total shoulder arthroplasty (TSA) remains challenging even with preoperative planning, especially for variable glenoid erosion patterns in the coronal plane. METHODS: We retrospectively reviewed 170 primary TSAs in which preoperative planning software was used. After registration of intraoperative bony landmarks, surgeons were blinded to the navigation screen and attempted to implement their plan by simulating placement of a central-axis guide pin: 230 screenshots of simulated guide pin placement were included (aTSA = 66, rTSA = 164). Displacement, error in version and inclination, and overall malposition from the preoperatively-planned target point were stratified by the Favard classification describing superior-inferior glenoid wear: E0 (n = 89); E1 (n = 81); E2 (n = 29); E3(n = 29); E4(n = 2). Malposition was considered > 10° for version/inclination errors or > 4 mm displacement from the starting point. RESULTS: Mean displacement error was 3.5 ± 2.7 mm (aTSA = 2.7 ± 2.3 mm, rTSA = 3.8 ± 2.9 mm), version error was 5.7 ± 4.7° (aTSA = 5.8 ± 4.4°, rTSA = 5.7 ± 4.8°), inclination error was 7.1 ± 5.6 (aTSA = 4.8 ± 4.8°, rTSA = 8.1 ± 5.7°), and malposition rate was 53% (aTSA = 38%, rTSA = 59%). When compared by Favard classification, there were no differences in any measure; when stratified by TSA type, version error differed for rTSAs (P = .038), with E1 having the greatest version error (6.9 ± 5.2°) and E3 the least (4.2 ± 3.4°). When comparing glenoids without wear (E0) and glenoids with superior wear (E2 and E3), the only difference was greater version error in glenoids without wear (6.0 ± 4.9° vs. 4.6 ± 3.7°, P = .041). CONCLUSIONS: Glenoid malposition did not differ based on coronal glenoid morphology. Although, malposition was relatively high, suggesting surgeons should consider alternate techniques beyond preoperative planning and standard instrumentation in TSA. LEVEL OF EVIDENCE III: Retrospective Cohort Study.

Clinical Profile and Outcome Following Exchange Transfusion for Neonatal Jaundice in a Tertiary Care Centre.

INTRODUCTION: Phototherapy has reduced the need for exchange transfusion (ET) to manage jaundiced neonates. Hence there are concerns about increased risk of complication due to lack of opportunity to sustain skills in performing ET. We studied the complications and treatment outcomes of neonates treated for jaundice with ET. METHODOLOGY: A retrospective observational study was conducted from June 2013 to June 2020 in a tertiary care hospital in India. All neonates treated with ET for jaundice were included. RESULTS: Twenty-eight neonates underwent 31 ET during the study period. Their mean gestational age and birth weight were 37 weeks and 3200 g, respectively. Predisposing factor for jaundice observed were Coomb's positive status (11), hepatosplenomegaly suggesting hemolysis (3), cephalhematoma (2) and birth asphyxia (1). Abnormal neurological status before ET was seen in seven neonates. Adverse clinical events that happened during or within 8 h after ET were desaturation (4), tachycardia (3), tachypnea (2), bradycardia (2), shock (2) and temperature instability (2). One neonate developed acute kidney injury after ET and required peritoneal dialysis. Abnormal lab parameters observed during or within 8 h after ET were hypocalcemia (20), anemia (8), hypokalemia (7), hypernatremia (3), thrombocytopenia (3) and hyperkalemia (2). Post ET sepsis was seen in five neonates: two had only blood culture positive sepsis, two had bone and joint infection and one had liver abscess. CONCLUSION: The neonates undergoing ET are at high risk of developing complications which may be life threatening. Hence careful monitoring during the procedure is needed.

Exchange transfusion is a treatment done for newborn babies with severe jaundice. This procedure is done by removing baby's blood in small quantities and replacing it with donor's blood. This life-saving procedure is associated with many complications. We did this study to estimate the complications associated with this procedure in our newborn unit. Twenty-eight patients underwent exchange transfusion from June 2013 to June 2020 in our hospital. We found out that temperature disturbance, abnormal heart rate, abnormal breathing and fall in oxygen levels occurred during exchange transfusion. After the procedure blood circulation disturbances, low platelet count, low blood calcium levels and low blood potassium levels were commonly observed. One patient developed renal failure after the procedure and was treated with dialysis. Five patients developed infection after the procedure and were treated with antibiotics. Thus newborn patients undergoing exchange transfusion are at high risk of developing complications which may be life threatening. Hence careful monitoring during the procedure is needed to prevent these complications.

How to Shoot and Edit High-Quality Surgical Videos for Hand and Upper Extremity Surgery.

A surgical video can improve patient care, surgical education, as well as scientific presentations and publications. Previous authors have outlined a basic understanding of how to produce high-quality surgical videos. With continuous technological improvements in video-filming hardware and editing software, multiple options for producing high-quality surgical videos are available. This article described important aspects of filming and editing videos to create a video that the surgeon can watch before performing the procedure. The authors reviewed camera terminology, including resolution, optical and digital zoom, shutter speed, and frame rate, as well as equipment options or setup for recording high-quality surgical videos. We provided information regarding computer requirements and editing on Windows and Macintosh operating systems, optimizing educational value for the viewer.

Coherent neural oscillations inform early stroke motor recovery.

Neural oscillations may contain important information pertaining to stroke rehabilitation. This study examined the predictive performance of electroencephalography-derived neural oscillations following stroke using a data-driven approach. Individuals with stroke admitted to an inpatient rehabilitation facility completed a resting-state electroencephalography recording and structural neuroimaging around the time of admission and motor testing at admission and discharge. Using a lasso regression model with cross-validation, we determined the extent of motor recovery (admission to discharge change in Functional Independence Measurement motor subscale score) prediction from electroencephalography, baseline motor status, and corticospinal tract injury. In 27 participants, coherence in a 1-30 Hz band between leads overlying ipsilesional primary motor cortex and 16 leads over bilateral hemispheres predicted 61.8% of the variance in motor recovery. High beta (20-30 Hz) and alpha (8-12 Hz) frequencies contributed most to the model demonstrating both positive and negative associations with motor recovery, including high beta leads in supplementary motor areas and ipsilesional ventral premotor and parietal regions and alpha leads overlying contralesional temporal-parietal and ipsilesional parietal regions. Electroencephalography power, baseline motor status, and corticospinal tract injury did not significantly predict motor recovery during hospitalization (R2  = 0-6.2%). Findings underscore the relevance of oscillatory synchronization in early stroke rehabilitation while highlighting contributions from beta and alpha frequency bands and frontal, parietal, and temporal-parietal regions overlooked by traditional hypothesis-driven prediction models.

Rotator Cuff Repair and Reconstruction.

Rotator cuff pathology is the most common shoulder condition for which patients seek treatment. Schmidt et al covered the relevant anatomy, natural history, nonsurgical and surgical treatment, biological augmentation, and postoperative rehabilitation in their comprehensive review published in 2015. This current review builds upon the last update, discussing the most recent evidence-based medicine regarding rotator cuff repair: primary repair, revision repair, and reconstructive techniques for superior capsular reconstruction, subacromial balloon spacers, tendon transfer options (pectoralis major, latissimus dorsi, and lower trapezius), and reverse total shoulder arthroplasty.

Low-Frequency Oscillations Are a Biomarker of Injury and Recovery After Stroke.

Background and Purpose- Low-frequency oscillations reflect brain injury but also contribute to normal behaviors. We examined hypotheses relating electroencephalography measures, including low-frequency oscillations, to injury and motor recovery poststroke. Methods- Patients with stroke completed structural neuroimaging, a resting-state electroencephalography recording and clinical testing. A subset admitted to an inpatient rehabilitation facility also underwent serial electroencephalography recordings. The relationship that electroencephalography measures (power and coherence with leads overlying ipsilesional primary motor cortex [iM1]) had with injury and motor status was assessed, focusing on delta (1-3 Hz) and high-beta (20-30 Hz) bands. Results- Across all patients (n=62), larger infarct volume was related to higher delta band power in bilateral hemispheres and to higher delta band coherence between iM1 and bilateral regions. In chronic stroke, higher delta power bilaterally correlated with better motor status. In subacute stroke, higher delta coherence between iM1 and bilateral areas correlated with poorer motor status. These coherence findings were confirmed in serial recordings from 18 patients in an inpatient rehabilitation facility. Here, interhemispheric coherence between leads overlying iM1 and contralesional M1 was elevated at inpatient rehabilitation facility admission compared with healthy controls (n=22), declining to control levels over time. Decreases in interhemispheric coherence between iM1 and contralesional M1 correlated with better motor recovery. Conclusions- Delta band coherence with iM1 related to greater injury and poorer motor status subacutely, while delta band power related to greater injury and better motor status chronically. Low-frequency oscillations reflect both injury and recovery after stroke and may be useful biomarkers in stroke recovery and rehabilitation.

Electroencephalography Might Improve Diagnosis of Acute Stroke and Large Vessel Occlusion.

BACKGROUND AND PURPOSE: Clinical methods have incomplete diagnostic value for early diagnosis of acute stroke and large vessel occlusion (LVO). Electroencephalography is rapidly sensitive to brain ischemia. This study examined the diagnostic utility of electroencephalography for acute stroke/transient ischemic attack (TIA) and for LVO. METHODS: Patients (n=100) with suspected acute stroke in an emergency department underwent clinical exam then electroencephalography using a dry-electrode system. Four models classified patients, first as acute stroke/TIA or not, then as acute stroke with LVO or not: (1) clinical data, (2) electroencephalography data, (3) clinical+electroencephalography data using logistic regression, and (4) clinical+electroencephalography data using a deep learning neural network. Each model used a training set of 60 randomly selected patients, then was validated in an independent cohort of 40 new patients. RESULTS: Of 100 patients, 63 had a stroke (43 ischemic/7 hemorrhagic) or TIA (13). For classifying patients as stroke/TIA or not, the clinical data model had area under the curve=62.3, whereas clinical+electroencephalography using deep learning neural network model had area under the curve=87.8. Results were comparable for classifying patients as stroke with LVO or not. CONCLUSIONS: Adding electroencephalography data to clinical measures improves diagnosis of acute stroke/TIA and of acute stroke with LVO. Rapid acquisition of dry-lead electroencephalography is feasible in the emergency department and merits prehospital evaluation.

Forearm Nonunion: Characterization and Management.

Adult forearm nonunion should be investigated prior to developing a treatment strategy: "Why did the fracture not heal?" Optimizing the patient's biology and the stability at the nonunion site are critical for a successful outcome. This review concisely discusses the initial work-up, including history, physical examination, imaging, and laboratory testing, as well as available surgical techniques-irrigation and debridement with deep cultures, revision open reduction internal fixation with or without biological adjuvant therapies, cancellous autograft, tricortical iliac crest, reamer/irrigator/aspirator, allograft, vascularized free-fibula and induced-membrane technique.

Distal Biceps Tendon Repair and Reconstruction.

Distal biceps tendon ruptures can result in functionally significant loss of supination and flexion strength, as well as decreased resistance to fatigue. Although the diagnosis of distal biceps tendon ruptures remains straightforward, substantial debate continues with regards to surgical indications, pertinent surgical anatomy, single- versus double-incision surgical technique, and fixation options. This review discusses the latest evidence-based literature regarding distal biceps tendon repair/reconstruction including types of tears, demographics, clues for diagnosis, surgical indications, anatomy with special attention to how the distal tendon inserts distally and the relevant tuberosity anatomy (height and cam effect), common reconstruction techniques (single- vs double-incision and single-incision power optimizing cost-effective technique), fixation techniques (bone tunnels, distal biceps button, interference screw, button plus screw), surgical technique pearls, postoperative rehabilitation, postoperative outcomes, as well as the treatment of chronic tears with special reconstruction techniques including Achilles allograft, pedicled latissimus transfer, and the use of a free innervated gracilis.

Hierarchical organization of melodic sequences is encoded by cortical entrainment.

Natural speech is organized according to a hierarchical structure, with individual speech sounds combining to form abstract linguistic units, and abstract linguistic units combining to form higher-order linguistic units. Since the boundaries between these units are not always indicated by acoustic cues, they must often be computed internally. Signatures of this internal computation were reported by Ding et al. (2016), who presented isochronous sequences of mono-syllabic words that combined to form phrases that combined to form sentences, and showed that cortical responses simultaneously encode boundaries at multiple levels of the linguistic hierarchy. In the present study, we designed melodic sequences that were hierarchically organized according to Western music conventions. Specifically, isochronous sequences of "sung" nonsense syllables were constructed such that syllables combined to form triads outlining individual chords, which combined to form harmonic progressions. EEG recordings were made while participants listened to these sequences with the instruction to detect when violations in the sequence structure occurred. We show that cortical responses simultaneously encode boundaries at multiple levels of a melodic hierarchy, suggesting that the encoding of hierarchical structure is not unique to speech. No effect of musical training on cortical encoding was observed.

The latency of a visual evoked potential tracks the onset of decision making.

Encoding of a sensory stimulus is believed to be the first step in perceptual decision making. Previous research has shown that electrical signals recorded from the human brain track evidence accumulation during perceptual decision making (Gold and Shadlen, 2007; O'Connell et al., 2012; Philiastides et al., 2014). In this study we directly tested the hypothesis that the latency of the N200 recorded by EEG (a negative peak occurring between 150 and 275 ms after stimulus presentation in human participants) reflects the visual encoding time (VET) required for completion of figure-ground segregation before evidence accumulation. We show that N200 latencies vary across individuals, are modulated by external visual noise, and increase response time by x milliseconds when they increase by x milliseconds, reflecting a linear regression slope of 1. Simulations of cognitive decision-making theory show that variation in human response times not related to evidence accumulation (non-decision time; NDT), including VET, are tracked by the fastest response times. Evidence that VET is tracked by N200 latencies was found by fitting a linear model between trial-averaged N200 latencies and the 10th percentiles of response times, a model-independent estimate of NDT. Fitting a novel neuro-cognitive model of decision making also yielded a slope of 1 between N200 latency and model-estimated NDT in multiple visual noise conditions, indicating that N200 latencies track the completion of visual encoding and the onset of evidence accumulation. The N200 waveforms were localized to the cortical surface at distributed temporal and extrastriate locations, consistent with a distributed network engaged in figure-ground segregation of the target stimulus.

Multi-Scale Neural Sources of EEG: Genuine, Equivalent, and Representative. A Tutorial Review.

A biophysical framework needed to interpret electrophysiological data recorded at multiple spatial scales of brain tissue is developed. Micro current sources at membrane surfaces produce local field potentials, electrocorticography, and electroencephalography (EEG). We categorize multi-scale sources as genuine, equivalent, or representative. Genuine sources occur at the micro scale of cell surfaces. Equivalent sources provide identical experimental outcomes over a range of scales and applications. In contrast, each representative source distribution is just one of many possible source distributions that yield similar experimental outcomes. Macro sources ("dipoles") may be defined at the macrocolumn (mm) scale and depend on several features of the micro sources-magnitudes, micro synchrony within columns, and distribution through the cortical depths. These micro source properties are determined by brain dynamics and the columnar structure of cortical tissue. The number of representative sources underlying EEG data depends on the spatial scale of neural tissue under study. EEG inverse solutions (e.g. dipole localization) and high resolution estimates (e.g. Laplacian, dura imaging) have both strengths and limitations that depend on experimental conditions. The proposed theoretical framework informs studies of EEG source localization, source characterization, and low pass filtering. It also facilitates interpretations of brain dynamics and cognition, including measures of synchrony, functional connections between cortical locations, and other aspects of brain complexity.