Evaluating the effect of denoising submillimeter auditory fMRI data with NORDIC

Functional magnetic resonance imaging (fMRI) has emerged as an essential tool for exploring human brain function. Submillimeter fMRI, in particular, has emerged as a tool to study mesoscopic computations. The inherently low signal-to-noise ratio (SNR) at submillimeter resolutions warrants the use of denoising approaches tailored at reducing thermal noise - the dominant contributing noise component in high resolution fMRI. NORDIC PCA is one of such approaches, and has been benchmarked against other approaches in several applications. Here, we investigate the effects that two versions of NORDIC denoising have on auditory submillimeter data. As investigating auditory functional responses poses unique challenges, we anticipated that the benefit of this technique would be especially pronounced. Our results show that NORDIC denoising improves the detection sensitivity and the reliability of estimates in submillimeter auditory fMRI data. These effects can be explained by the reduction of the noise-induced signal variability. However, we also observed a reduction in the average response amplitude (percent signal), which may suggest that a small amount of signal was also removed. We conclude that, while evaluating the effects of the signal reduction induced by NORDIC may be necessary for each application, using NORDIC in high resolution auditory fMRI studies may be advantageous because of the large reduction in variability of the estimated responses.

Framewise multi-echo distortion correction for superior functional MRI

Functional MRI (fMRI) data are severely distorted by magnetic field (B0) inhomogeneities which currently must be corrected using separately acquired field map data. However, changes in the head position of a scanning participant across fMRI frames can cause changes in the B0 field, preventing accurate correction of geometric distortions. Additionally, field maps can be corrupted by movement during their acquisition, preventing distortion correction altogether. In this study, we use phase information from multi-echo (ME) fMRI data to dynamically sample distortion due to fluctuating B0 field inhomogeneity across frames by acquiring multiple echoes during a single EPI readout. Our distortion correction approach, MEDIC (Multi-Echo DIstortion Correction), accurately estimates B0 related distortions for each frame of multi-echo fMRI data. Here, we demonstrate that MEDIC's framewise distortion correction produces improved alignment to anatomy and decreases the impact of head motion on resting-state functional connectivity (RSFC) maps, in higher motion data, when compared to the prior gold standard approach (i.e., TOPUP). Enhanced framewise distortion correction with MEDIC, without the requirement for field map collection, furthers the advantage of multi-echo over single-echo fMRI.

Multi-echo Acquisition and Thermal Denoising Advances Infant Precision Functional Imaging

The characterization of individual functional brain organization with Precision Functional Mapping has provided important insights in recent years in adults. However, little is known about the ontogeny of inter-individual differences in brain functional organization during human development, but precise characterization of systems organization during periods of high plasticity might be most influential towards discoveries promoting lifelong health. Collecting and analyzing precision fMRI data during early development has unique challenges and emphasizes the importance of novel methods to improve data acquisition, processing, and analysis strategies in infant samples. Here, we investigate the applicability of two such methods from adult MRI research, multi-echo (ME) data acquisition and thermal noise removal with Noise reduction with distribution corrected principal component analysis (NORDIC), in precision fMRI data from three newborn infants. Compared to an adult example subject, T2* relaxation times calculated from ME data in infants were longer and more variable across the brain, pointing towards ME acquisition being a promising tool for optimizing developmental fMRI. The application of thermal denoising via NORDIC increased tSNR and the overall strength of functional connections as well as the split-half reliability of functional connectivity matrices in infant ME data. While our findings related to NORDIC denoising are coherent with the adult literature and ME data acquisition showed high promise, its application in developmental samples needs further investigation. The present work reveals gaps in our understanding of the best techniques for developmental brain imaging and highlights the need for further developmentally-specific methodological advances and optimizations, towards precision functional imaging in infants.

Low haemoglobin level predicts early hospital readmission in patients with cirrhosis and acute decompensation

Background & Aims

Patients with decompensated cirrhosis present frequent hospitalisations with a relevant clinical and socio-economic impact. This study aims to characterise unscheduled readmissions up to 1-year follow-up and identify predictors of 30-day readmission after an index hospitalisation for acute decompensation (AD).

Methods

We performed a secondary analysis of a prospectively collected cohort of patients admitted for AD. Laboratory and clinical data at admission and at discharge were collected. Timing and causes of unscheduled readmissions and mortality were recorded up to 1 year.

Results

A total of 329 patients with AD were included in the analysis. Acute-on-chronic liver failure was diagnosed in 19% of patients at admission or developed in an additional 9% of patients during the index hospitalisation. During the 1-year follow-up, 182 patients (55%) were rehospitalised and 98 (30%) more than once. The most frequent causes of readmission were hepatic encephalopathy (36%), ascites (22%), and infection (21%). Cumulative incidence of readmission was 20% at 30 days, 39% at 90 days, and 63% at 1 year. Fifty-four patients were readmitted for emergent liver-related causes within 30 days. Early readmission was associated with a higher 1-year mortality (47 vs. 32%, p = 0.037). Multivariable Cox regression analysis showed that haemoglobin (Hb) ≤8.7 g/dl (hazard ratio 2.63 [95% CI 1.38-5.02], p = 0.003) and model for end-stage liver disease-sodium score (MELD-Na) >16 at discharge (hazard ratio 2.23 [95% CI 1.27-3.93], p = 0.005), were independent predictors of early readmission. In patients with MELD-Na >16 at discharge, the presence of Hb ≤8.7 g/dl doubles the risk of early rehospitalisation (44% vs. 22%, p = 0.02).

Conclusion

Besides MELD-Na, a low Hb level (Hb ≤8.7 g/dl) at discharge emerged as a new risk factor for early readmission, contributing to identification of patients who require closer surveillance after discharge.

Impact and Implications

Patients with decompensated cirrhosis face frequent hospitalisations. In the present study, type and causes of readmissions were analysed during 1-year follow-up in patients discharged after the index hospitalisation for an acute decompensation of the disease. Early (30-day) liver-related readmission was associated with higher 1-year mortality. The model for end-stage liver disease-sodium score and low haemoglobin at discharge were identified as independent risk factors for early readmissions. Haemoglobin emerged as a new easy-to-use parameter associated with early readmission warranting further investigation.

Porto-Sinusoidal Vascular Disorder, report of a novel association with POEMS syndrome. Future challenge for the hepatologist

Porto-Sinusoidal Vascular Disorder (PSVD) is a recently introduced clinical entity. Since it is rare and often underrecognized, there is growing interest in identifying patients at increased risk. We present a case of a 59-year-old male with refractory ascites, pleural effusion, and high-risk varices meeting the diagnostic criteria for PSVD with a concomitant diagnosis of POEMS syndrome. The possible association between PSVD and POEMS syndrome has been described only in eight reports in literature, but it may be underrecognized due to the clinical manifestations overlap. To gain a wider comprehension of PSVD, it is fundamental to cooperate using international networks.

Evaluating increases in sensitivity from NORDIC for diverse fMRI acquisition strategies

As the neuroimaging field moves towards detecting smaller effects at higher spatial resolutions, and faster sampling rates, there is increased attention given to the deleterious contribution of unstructured, thermal noise. Here, we critically evaluate the performance of a recently developed reconstruction method, termed NORDIC, for suppressing thermal noise using datasets acquired with various field strengths, voxel sizes, sampling rates, and task designs. Following minimal preprocessing, statistical activation (t-values) of NORDIC processed data was compared to the results obtained with alternative denoising methods. Additionally, we examined the consistency of the estimates of task responses at the single-voxel, single run level, using a finite impulse response (FIR) model. To examine the potential impact on effective image resolution, the overall smoothness of the data processed with different methods was estimated. Finally, to determine if NORDIC alters or removes temporal information important for modeling responses, we employed an exhaustive leave-p-out cross validation approach, using FIR task responses to predict held out timeseries, quantified using R². After NORDIC, the t-values are increased, an improvement comparable to what could be achieved by 1.5 voxels smoothing, and task events are clearly visible and have less cross-run error. These advantages are achieved with smoothness estimates increasing by less than 4%, while 1.5 voxel smoothing is associated with increases of over 140%. Cross-validated R²s based on the FIR models show that NORDIC is not measurably distorting the temporal structure of the data under this approach and is the best predictor of non-denoised time courses. The results demonstrate that analyzing 1 run of data after NORDIC produces results equivalent to using 2 to 3 original runs and that NORDIC performs equally well across a diverse array of functional imaging protocols. Significance Statement: For functional neuroimaging, the increasing availability of higher field strengths and ever higher spatiotemporal resolutions has led to concomitant increase in concerns about the deleterious effects of thermal noise. Historically this noise source was suppressed using methods that reduce spatial precision such as image blurring or averaging over a large number of trials or sessions, which necessitates large data collection efforts. Here, we critically evaluate the performance of a recently developed reconstruction method, termed NORDIC, which suppresses thermal noise. Across datasets varying in field strength, voxel sizes, sampling rates, and task designs, NORDIC produces substantial gains in data quality. Both conventional t-statistics derived from general linear models and coefficients of determination for predicting unseen data are improved. These gains match or even exceed those associated with 1 voxel Full Width Half Max image smoothing, however, even such small amounts of smoothing are associated with a 52% reduction in estimates of spatial precision, whereas the measurable difference in spatial precision is less than 4% following NORDIC.

20-fold Accelerated 7T fMRI Using Referenceless Self-Supervised Deep Learning Reconstruction

High spatial and temporal resolution across the whole brain is essential to accurately resolve neural activities in fMRI. Therefore, accelerated imaging techniques target improved coverage with high spatio-temporal resolution. Simultaneous multi-slice (SMS) imaging combined with in-plane acceleration are used in large studies that involve ultrahigh field fMRI, such as the Human Connectome Project. However, for even higher acceleration rates, these methods cannot be reliably utilized due to aliasing and noise artifacts. Deep learning (DL) reconstruction techniques have recently gained substantial interest for improving highly-accelerated MRI. Supervised learning of DL reconstructions generally requires fully-sampled training datasets, which is not available for high-resolution fMRI studies. To tackle this challenge, self-supervised learning has been proposed for training of DL reconstruction with only undersampled datasets, showing similar performance to supervised learning. In this study, we utilize a self-supervised physics-guided DL reconstruction on a 5-fold SMS and 4-fold in-plane accelerated 7T fMRI data. Our results show that our self-supervised DL reconstruction produce high-quality images at this 20-fold acceleration, substantially improving on existing methods, while showing similar functional precision and temporal effects in the subsequent analysis compared to a standard 10-fold accelerated acquisition.

Statistical power or more precise insights into neuro-temporal dynamics? Assessing the benefits of rapid temporal sampling in fMRI

Functional magnetic resonance imaging (fMRI), a non-invasive and widely used human neuroimaging method, is most known for its spatial precision. However, there is a growing interest in its temporal sensitivity. This is despite the temporal blurring of neuronal events by the blood oxygen level dependent (BOLD) signal, the peak of which lags neuronal firing by 4-6 seconds. Given this, the goal of this review is to answer a seemingly simple question - "What are the benefits of increased temporal sampling for fMRI?". To answer this, we have combined fMRI data collected at multiple temporal scales, from 323 to 1000 milliseconds, with a review of both historical and contemporary temporal literature. After a brief discussion of technological developments that have rekindled interest in temporal research, we next consider the potential statistical and methodological benefits. Most importantly, we explore how fast fMRI can uncover previously unobserved neuro-temporal dynamics - effects that are entirely missed when sampling at conventional 1 to 2 second rates. With the intrinsic link between space and time in fMRI, this temporal renaissance also delivers improvements in spatial precision. Far from producing only statistical gains, the array of benefits suggest that the continued temporal work is worth the effort.

Lowering the thermal noise barrier in functional brain mapping with magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) has become an indispensable tool for investigating the human brain. However, the inherently poor signal-to-noise-ratio (SNR) of the fMRI measurement represents a major barrier to expanding its spatiotemporal scale as well as its utility and ultimate impact. Here we introduce a denoising technique that selectively suppresses the thermal noise contribution to the fMRI experiment. Using 7-Tesla, high-resolution human brain data, we demonstrate improvements in key metrics of functional mapping (temporal-SNR, the detection and reproducibility of stimulus-induced signal changes, and accuracy of functional maps) while leaving the amplitude of the stimulus-induced signal changes, spatial precision, and functional point-spread-function unaltered. We demonstrate that the method enables the acquisition of ultrahigh resolution (0.5 mm isotropic) functional maps but is also equally beneficial for a large variety of fMRI applications, including supra-millimeter resolution 3- and 7-Tesla data obtained over different cortical regions with different stimulation/task paradigms and acquisition strategies.

The signal-to-noise ratio is a key consideration when selecting a magnetic resonance imaging protocol. Thermal noise is major issue, especially in high resolution functional images. Here the authors introduce a method to suppress thermal noise in functional images without losses in spatial precision, increasing the signal-to-noise ratio.

Clarifying the role of higher-level cortices in resolving perceptual ambiguity using ultra high field fMRI

The brain is organized into distinct, flexible networks. Within these networks, cognitive variables such as attention can modulate sensory representations in accordance with moment-to-moment behavioral requirements. These modulations can be studied by varying task demands; however, the tasks employed are often incongruent with the postulated functions of a sensory system, limiting the characterization of the system in relation to natural behaviors. Here we combine domain-specific task manipulations and ultra-high field fMRI to study the nature of top-down modulations. We exploited faces, a visual category underpinned by a complex cortical network, and instructed participants to perform either a stimulus-relevant/domain-specific or a stimulus-irrelevant task in the scanner. We found that 1. perceptual ambiguity (i.e. difficulty of achieving a stable percept) is encoded in top-down modulations from higher-level cortices; 2. the right inferior-temporal lobe is active under challenging conditions and uniquely encodes trial-by-trial variability in face perception.

Heterotopic segmental liver transplantation on splenic vessels after splenectomy with delayed native hepatectomy after graft regeneration: A new technique to enhance liver transplantation

We describe a patient with liver metastases from colorectal cancer treated with chemotherapy and hepatic resection, who developed unresectable multifocal liver recurrence and who received liver transplantation using a novel planned technique: heterotopic transplantation of segment 2-3 in the splenic fossa with splenectomy and delayed hepatectomy after regeneration of the transplanted graft. We transplanted a segmental liver graft after in-situ splitting without any impact on the waiting list, as it was previously rejected for pediatric and adult transplantation. The volume of the graft was insufficient to provide liver function to the recipient, so we performed this novel operation. The graft was anastomosed to the splenic vessels after splenectomy, and the native liver portal flow was modulated to enhance graft regeneration, leaving the native recipient liver intact. The volume of the graft doubled during the next 2 weeks and the native liver was removed. After 8 months, the patient lives with a functioning liver in the splenic fossa and without abdominal tumor recurrence. This is the first case reported of a segmental graft transplanted replacing the spleen and modulating the portal flow to favor graft growth, with delayed native hepatectomy.

Liver transplantation in Italy in the era of COVID 19: reorganizing critical care of recipients

Transplant programs have been severely disrupted by the COVID-19 pandemic. Italy was one of the first countries with the highest number of deaths in the world due to SARS-CoV-2. Here we propose a management model for the reorganization of liver transplant (LT) activities and policies in a local intensive care unit (ICU) assigned to liver transplantation affected by restrictions on mobility and availability of donors and recipients as well as health personnel and beds. We describe the solutions implemented to continue transplantation activities throughout a given pandemic: management of donors and recipients' LT program, ICU rearrangement, healthcare personnel training and monitoring to minimize mortality rates of patients on the waiting list. Transplantation activities from February 22, 2020, the data of first known COVID-19 case in Italy's Emilia Romagna region to June 30, 2020, were compared with the corresponding period in 2019. During the 2020 study period, 38 LTs were performed, whereas 41 were performed in 2019. Patients transplanted during the COVID-19 pandemic had higher MELD and MELD-Na scores, cold ischaemia times, and hospitalization rates (p < 0.05); accordingly, they spent fewer days on the waitlist and had a lower prevalence of hepatocellular carcinoma (p < 0.05). No differences were found in the provenance area, additional MELD scores, age of donors and recipients, BMI, re-transplant rates, and post-transplant mortality. No transplanted patients contracted COVID-19, although five healthcare workers did. Ultimately, our policy allowed us to continue the ICU's operations by prioritizing patients hospitalized with higher MELD without any case of transplant infection due to COVID-19.

Liver transplantation in mitochondrial neurogastrointestinal encephalomyopathy (MNGIE): clinical long-term follow-up and pathogenic implications

We report the longest follow-up of clinical and biochemical features of two previously reported adult mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) patients treated with liver transplantation (LT), adding information on a third, recently transplanted, patient. All three patients overcame the early post-operative period and tolerated immunosuppressive therapy. Plasma nucleoside levels dramatically decreased, with evidence of clinical improvement of ambulation and neuropathy. Conversely, other features of MNGIE, as gastrointestinal dysmotility, low weight, ophthalmoparesis, and leukoencephalopathy were essentially unchanged. A similar picture characterized two patients treated with allogenic hematopoietic stem cell transplantation (AHSCT). In conclusion, LT promptly and stably normalizes nucleoside imbalance in MNGIE, stabilizing or improving some clinical parameters with marginal periprocedural mortality rate as compared to AHSCT. Nevertheless, restoring thymidine phosphorylase (TP) activity, achieved by both LT and AHSCT, does not allow a full clinical recovery, probably due to consolidated cellular damage and/or incomplete enzymatic tissue replacement.

Multivoxel Pattern of Blood Oxygen Level Dependent Activity can be sensitive to stimulus specific fine scale responses

At ultra-high field, fMRI voxels can span the sub-millimeter range, allowing the recording of blood oxygenation level dependent (BOLD) responses at the level of fundamental units of neural computation, such as cortical columns and layers. This sub-millimeter resolution, however, is only nominal in nature as a number of factors limit the spatial acuity of functional voxels. Multivoxel Pattern Analysis (MVPA) may provide a means to detect information at finer spatial scales that may otherwise not be visible at the single voxel level due to limitations in sensitivity and specificity. Here, we evaluate the spatial scale of stimuli specific BOLD responses in multivoxel patterns exploited by linear Support Vector Machine, Linear Discriminant Analysis and Naïve Bayesian classifiers across cortical depths in V1. To this end, we artificially misaligned the testing relative to the training portion of the data in increasing spatial steps, then investigated the breakdown of the classifiers’ performances. A one voxel shift led to a significant decrease in decoding accuracy (p < 0.05) across all cortical depths, indicating that stimulus specific responses in a multivoxel pattern of BOLD activity exploited by multivariate decoders can be as precise as the nominal resolution of single voxels (here 0.8 mm isotropic). Our results further indicate that large draining vessels, prominently residing in proximity of the pial surface, do not, in this case, hinder the ability of MVPA to exploit fine scale patterns of BOLD signals. We argue that tailored analytical approaches can help overcoming limitations in high-resolution fMRI and permit studying the mesoscale organization of the human brain with higher sensitivities.

A critical assessment of data quality and venous effects in sub-millimeter fMRI

Advances in hardware, pulse sequences, and reconstruction techniques have made it possible to perform functional magnetic resonance imaging (fMRI) at sub-millimeter resolution while maintaining high spatial coverage and acceptable signal-to-noise ratio. Here, we examine whether sub-millimeter fMRI can be used as a routine method for obtaining accurate measurements of fine-scale local neural activity. We conducted fMRI in human visual cortex during a simple event-related visual experiment (7 T, gradient-echo EPI, 0.8-mm isotropic voxels, 2.2-s sampling rate, 84 slices), and developed analysis and visualization tools to assess the quality of the data. Our results fall along three lines of inquiry. First, we find that the acquired fMRI images, combined with appropriate surface-based processing, provide reliable and accurate measurements of fine-scale blood oxygenation level dependent (BOLD) activity patterns. Second, we show that the highly folded structure of cortex causes substantial biases on spatial resolution and data visualization. Third, we examine the well-recognized issue of venous contributions to fMRI signals. In a systematic assessment of large sections of cortex measured at a fine scale, we show that time-averaged T₂*-weighted EPI intensity is a simple, robust marker of venous effects. These venous effects are unevenly distributed across cortex, are more pronounced in gyri and outer cortical depths, and are, to a certain degree, in consistent locations across subjects relative to cortical folding. Furthermore, we show that these venous effects are strongly correlated with BOLD responses evoked by the experiment. We conclude that sub-millimeter fMRI can provide robust information about fine-scale BOLD activity patterns, but special care must be exercised in visualizing and interpreting these patterns, especially with regards to the confounding influence of the brain's vasculature. To help translate these methodological findings to neuroscience research, we provide practical suggestions for both high-resolution and standard-resolution fMRI studies.

Accuracy of Lung Ultrasound in Patients with Acute Dyspnea: The Influence of Age, Multimorbidity and Cognitive and Motor Impairment

Discriminating between causes of dyspnea may be difficult, particularly in the elderly. The aim of this retrospective study of 83 inpatients with acute dyspnea was to assess the influence of age, multimorbidity and cognitive or motor impairment on the diagnostic accuracy of lung ultrasound (LUS) in discriminating acute heart failure (AHF) from noncardiogenic dyspnea (NCD). Univariate analysis indicates that LUS misdiagnosis was associated with the following parameters: history of stroke (p = 0.037), lower activity of daily living (p = 0.039), higher modified-Rankin scale (mRS) (p = 0.027) and need of two operators to complete LUS because of reduced patient compliance (p = 0.030). Regression analysis identified only history of stroke (p = 0.048) as an independent predictor of LUS misdiagnosis. This study supports LUS usefulness to differentiate AHF from NCD. Our data suggest that diagnostic accuracy of LUS is affected by history of stroke as a proxy for severe motor impairment but not by age, cognitive impairment and multimorbidity.

Contextual Feedback to Superficial Layers of V1

Neuronal cortical circuitry comprises feedforward, lateral, and feedback projections, each of which terminates in distinct cortical layers [1–3]. In sensory systems, feedforward processing transmits signals from the external world into the cortex, whereas feedback pathways signal the brain’s inference of the world [4–11]. However, the integration of feedforward, lateral, and feedback inputs within each cortical area impedes the investigation of feedback, and to date, no technique has isolated the feedback of visual scene information in distinct layers of healthy human cortex. We masked feedforward input to a region of V1 cortex and studied the remaining internal processing. Using high-resolution functional brain imaging (0.8 mm³) and multivoxel pattern information techniques, we demonstrate that during normal visual stimulation scene information peaks in mid-layers. Conversely, we found that contextual feedback information peaks in outer, superficial layers. Further, we found that shifting the position of the visual scene surrounding the mask parametrically modulates feedback in superficial layers of V1. Our results reveal the layered cortical organization of external versus internal visual processing streams during perception in healthy human subjects. We provide empirical support for theoretical feedback models such as predictive coding [10, 12] and coherent infomax [13] and reveal the potential of high-resolution fMRI to access internal processing in sub-millimeter human cortex.

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High-resolution MRI shows functional information patterns in non-stimulated V1

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Non-stimulated V1 receives cortical feedback information to superficial layers

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Feedback to non-stimulated V1 superficial layers is predictive of visual context

Neural microgenesis of personally familiar face recognition

Despite a wealth of information provided by neuroimaging research, the neural basis of familiar face recognition in humans remains largely unknown. Here, we isolated the discriminative neural responses to unfamiliar and familiar faces by slowly increasing visual information (i.e., high-spatial frequencies) to progressively reveal faces of unfamiliar or personally familiar individuals. Activation in ventral occipitotemporal face-preferential regions increased with visual information, independently of long-term face familiarity. In contrast, medial temporal lobe structures (perirhinal cortex, amygdala, hippocampus) and anterior inferior temporal cortex responded abruptly when sufficient information for familiar face recognition was accumulated. These observations suggest that following detailed analysis of individual faces in core posterior areas of the face-processing network, familiar face recognition emerges categorically in medial temporal and anterior regions of the extended cortical face network.

The Senile Lung as a Possible Source of Pitfalls on Chest Ultrasonography and Computed Tomography

BACKGROUND

Age-associated changes in the pulmonary system could be detected with imaging techniques. Widespread use of lung ultrasonography (US) requires characterization of a normal pattern.

OBJECTIVES

To compare US and computed tomography (CT) findings in healthy subjects undergoing both techniques (with CT as the gold standard).

METHODS

We prospectively selected 59 subjects undergoing chest CT and US on the same day, without a history of smoking, respiratory symptoms, or known pulmonary pathologies. There were 44 patients in group 1 (age ≥60 years - elderly) and 15 patients in group 2 (age ≤50 years - young). Lung US was performed with a convex and a linear probe, and 10 chest areas per patient were analyzed. Convex and linear probe agreement was evaluated by means of the Cohen κ statistic; Fisher's exact test was used to compare categorical variables between groups.

RESULTS

Isolated B-lines were frequent in both group 1 (54.5%) and group 2 (40.0%); the number of chest areas positive for B-lines increased with age (16.1% in group 1 vs. 5.3% in group 2, p = 0.0028). In group 2, we found that 37.5% of subjects with B-lines had at least 1 chest area with multiple B-lines, but only 2 subjects had 2 or more. Moreover, in group 1 the chest CT documented a reticular pattern (2.3%), areas of increased density (9.1%), ground glass (6.8%), cysts (2.3%), bronchiectasis (22.7%), and bronchial thickening (6.8%); in group 2, only cysts (6.7%) and bronchiectasis (6.7%) were found.

CONCLUSIONS

The senile lung is characterized by mild changes on CT and US. Chest areas positive for B-lines increase with age, and focal multiple B-lines can be found. However, diffuse patterns, especially in symptomatic subjects, suggest a different diagnosis.

Contributions of cortical feedback to sensory processing in primary visual cortex

Closing the structure-function divide is more challenging in the brain than in any other organ (Lichtman and Denk, 2011). For example, in early visual cortex, feedback projections to V1 can be quantified (e.g., Budd, 1998) but the understanding of feedback function is comparatively rudimentary (Muckli and Petro, 2013). Focusing on the function of feedback, we discuss how textbook descriptions mask the complexity of V1 responses, and how feedback and local activity reflects not only sensory processing but internal brain states.

Changes of liver enzymes and bilirubin during ischemic stroke: mechanisms and possible significance

Background

Small changes of bilirubin and liver enzymes are often detected during the acute phase of stroke, but their origin and significance are still poorly understood.

Methods

On days 0, 3, 7, and 14 after admission, 180 patients with ischemic stroke underwent serial determinations of bilirubin, GOT, GPT, γGT, alkaline phosphatase, C-reactive protein (CRP) and complete blood count. On days 0 and 7 common bile duct diameter was measured by ultrasound, and on day 3 cerebral infarct volume (IV) was calculated from CT scan slices.

Results

During the first week GOT, GPT, γGT (P < 0.001) and CRP (P = 0.03) increased with subsequent plateau, while significant decrements (P < 0.001) concerned unconjugated bilirubin, erythrocytes and haemoglobin. Alkaline phosphatase, direct bilirubin and common bile duct diameter remained stable. IV correlated with CRP, leukocytes, GOT, γGT (r > 0.3, P < 0.001 for all) and direct bilirubin (r = 0.23, P = 0.008). In multivariate analysis only CRP and GOT remained independently associated with IV (P < =0.001). The correlation of IV with GOT increased progressively from admission to day 14. GOT independently correlated with GPT which, in turn, correlated with γGT. γGT was also highly correlated with leukocytes. Unconjugated bilirubin correlated with haemoglobin, which was inversely correlated with CRP.

Conclusions

The changes of bilirubin and liver enzymes during ischemic stroke reflect two phenomena, which are both related to IV: 1) inflammation, with consequent increment of CRP, leukocytes and γGT, and decrease of haemoglobin and unconjugated bilirubin and 2) an unknown signal, independent from inflammation, leading to increasing GOT and GPT levels.

Adipocyte-fatty acid binding protein and non-alcoholic fatty liver disease in the elderly

BACKGROUND

Adipocyte-fatty acid binding protein (A-FABP) is an intracellular lipid transporter that mediates metabolically triggered inflammation, and it is associated with insulin resistance, atherogenic dyslipidemia, and cardiovascular risk.

AIMS

The aim of this study was to evaluate A-FABP behavior in elderly people, and especially its association with liver steatosis at abdominal ultrasound.

METHOD

Cross-sectional study of two cohort of individuals with and without steatosis, with assessment of several clinical and laboratory variables. Prospective evaluation of liver steatosis remodeling after six years of follow-up. One hundred and fifty-six subjects aged over 65 years were enrolled.

RESULTS

Serum A-FABP positively correlated with body fat percentage, total cholesterol, serum triglycerides and erythrocyte sedimentation rate. Unlike expected, high A-FABP levels were associated with absence of liver steatosis, while there was no evidence of association with steatosis grade changes after 6 years of follow-up.

CONCLUSION

Among individuals aging more than 65 years included in the study, A-FABP was inversely associated with liver steatosis. It can be argued, that still uncovered mechanisms modify A-FABP behavior in elderly people, especially its association with multifactorial diseases.

Predictors of short-term improvement of ischemic stroke

OBJECTIVES

Several studies have sought factors predictive of early neurological deterioration during acute stroke; however, no study carried out a systematic search for factors capable of predicting early improvement. This investigation is aimed at identifying the variables associated with short-term neurological improvement in patients with ischemic stroke not undergoing thrombolysis.

METHODS

Two-hundred and fifty-two patients with ischemic stroke were retrospectively examined (mean age: 76.7 ± 10.6 years, 120 males, median delay of admission 8 hours). Stroke severity was assessed both on admission and at discharge (median stay: 4 days) by the National Institutes of Health Stroke Scale (NIHSS). Improvement was defined as a difference between initial and final assessment (ΔNIHSS) ≥ the median value (2 points). Thus, 127 patients improved (mean change: +3.8 points) and 125 did not (mean change: -1.4 points).

RESULTS

During the first 48 hours of hospitalization, 263 clinical, laboratory, instrumental, and therapeutic variables were collected. These were preliminarily compared between two subgroups of patients, improved and non-improved, which were matched for initial NIHSS score, and 17 possible predictors of improvement were found. The subsequent multivariable analysis led to the identification of four factors independently associated with improvement (odds ratio, 95% confidence interval): total anterior circulation syndrome (TACS) (0.20, 0.10-0.39, P<0.0001), aphasia (3.58, 1.89-6.77, P = 0.0001), average systolic blood pressure (0.98 per mmHg, 0.96-0.99, P = 0.002), and age (0.97 per year, 0.94-0.99, P = 0.02).

CONCLUSIONS

The ischemic strokes that are not TACS, with aphasia, with normal/low blood pressure, or occurring in younger subjects, may have a significant tendency to short-term improvement.

Mapping Face Recognition Information Use across Cultures

Face recognition is not rooted in a universal eye movement information-gathering strategy. Western observers favor a local facial feature sampling strategy, whereas Eastern observers prefer sampling face information from a global, central fixation strategy. Yet, the precise qualitative (the diagnostic) and quantitative (the amount) information underlying these cultural perceptual biases in face recognition remains undetermined. To this end, we monitored the eye movements of Western and Eastern observers during a face recognition task, with a novel gaze-contingent technique: the Expanding Spotlight. We used 2° Gaussian apertures centered on the observers' fixations expanding dynamically at a rate of 1° every 25 ms at each fixation - the longer the fixation duration, the larger the aperture size. Identity-specific face information was only displayed within the Gaussian aperture; outside the aperture, an average face template was displayed to facilitate saccade planning. Thus, the Expanding Spotlight simultaneously maps out the facial information span at each fixation location. Data obtained with the Expanding Spotlight technique confirmed that Westerners extract more information from the eye region, whereas Easterners extract more information from the nose region. Interestingly, this quantitative difference was paired with a qualitative disparity. Retinal filters based on spatial-frequency decomposition built from the fixations maps revealed that Westerners used local high-spatial-frequency information sampling, covering all the features critical for effective face recognition (the eyes and the mouth). In contrast, Easterners achieved a similar result by using global low-spatial-frequency information from those facial features. Our data show that the face system flexibly engages into local or global eye movement strategies across cultures, by relying on distinct facial information span and culturally tuned spatially filtered information. Overall, our findings challenge the view of a unique putative process for face recognition.

Eyes like it, Brain Likes it: Tracking the Neural Tuning of Cultural Diversity in Eye Movements for Faces

Eye movement strategies deployed by humans to identify conspecifics are not universal. Westerners preferentially fixate the eyes and the mouth during face recognition, whereas strikingly Easterners focus more on the face central region. However, when, where and how Preferred Viewing Locations (PVLs) for high-level visual stimuli are coded in the human brain has never been directly investigated. Here, we simultaneously recorded eye-movements and electroencephalographic (EEG) signals of Westerners and Easterners during face identification of learnt identities. After defining 9 equidistant Viewing Positions (VPs) covering all facial internal features, we presented the learned faces centered on a random VP for 100ms. We then extracted from prior free-viewing fixation maps the average Z-scored fixation intensity for the nonoverlapping facial VP regions (VPZs). Finally, we computed a component-free data-driven spatio-temporal regression between the VPZs and EEG amplitudes. This analysis revealed a universal direct relationship between VPZ and EEG amplitudes over the face-sensitive N170 network at around 350ms, an effect unrelated to a burst of microsaccades occurring in this time-window. Our data show that the distinct cultural fixation preferences for faces are related to a universal post-perceptual tuning in the occipito-temporal cortex. Culture shapes visual information sampling, but does not regulate neural information coding.