Development of white matter tracts between and within the dorsal and ventral streams.

The degree of interaction between the ventral and dorsal visual streams has been discussed in multiple scientific domains for decades. Recently, several white matter tracts that directly connect cortical regions associated with the dorsal and ventral streams have become possible to study due to advancements in automated and reproducible methods. The developmental trajectory of this set of tracts, here referred to as the posterior vertical pathway (PVP), has yet to be described. We propose an input-driven model of white matter development and provide evidence for the model by focusing on the development of the PVP. We used reproducible, cloud-computing methods and diffusion imaging from adults and children (ages 5-8 years) to compare PVP development to that of tracts within the ventral and dorsal pathways. PVP microstructure was more adult-like than dorsal stream microstructure, but less adult-like than ventral stream microstructure. Additionally, PVP microstructure was more similar to the microstructure of the ventral than the dorsal stream and was predicted by performance on a perceptual task in children. Overall, results suggest a potential role for the PVP in the development of the dorsal visual stream that may be related to its ability to facilitate interactions between ventral and dorsal streams during learning. Our results are consistent with the proposed model, suggesting that the microstructural development of major white matter pathways is related, at least in part, to the propagation of sensory information within the visual system.

Visual Information Routes in the Posterior Dorsal and Ventral Face Network Studied with Intracranial Neurophysiology and White Matter Tract Endpoints.

Occipitotemporal regions within the face network process perceptual and socioemotional information, but the dynamics and information flow between different nodes of this network are still debated. Here, we analyzed intracerebral EEG from 11 epileptic patients viewing a stimulus sequence beginning with a neutral face with direct gaze. The gaze could avert or remain direct, while the emotion changed to fearful or happy. N200 field potential peak latencies indicated that face processing begins in inferior occipital cortex and proceeds anteroventrally to fusiform and inferior temporal cortices, in parallel. The superior temporal sulcus responded preferentially to gaze changes with augmented field potential amplitudes for averted versus direct gaze, and large effect sizes relative to other network regions. An overlap analysis of posterior white matter tractography endpoints (from 1066 healthy brains) relative to active intracerebral electrodes in the 11 patients showed likely involvement of both dorsal and ventral posterior white matter pathways. Overall, our data provide new insight into the timing of face and social cue processing in the occipitotemporal brain and anchor the superior temporal cortex in dynamic gaze processing.

The Rheumatic Fever and Rheumatic Heart Disease Control programme--Jamaica.

BACKGROUND: Rheumatic fever (RF) and rheumatic heart disease (RHD) are significant causes of World Health Organization (WHO) and International Society and Federation of Cardiology (ISFC) initiated an International Programme for Prevention of RF/RHD in 16 developing countries, including Jamaica. The Jamaican RF/RHD National Control Programme began in July 1985. SUBJECTS AND METHOD: The Control Programme promotes the primary prevention of RF/RHD through the appropriate treatment of streptococcal throat infections. Secondary prevention has been the main focus of the Control Programme by administration of benzathine penicillin injections every four weeks to RF/RHD patients. Case finding activities have included two retrospective surveys of case records of RF/RHD patients admitted to the major hospitals in Kingston and St Andrew in the period 1975-1985 (Survey A) and 1989-1995 (Survey B). These surveys provided clinical and laboratory data on RF/RHD in Jamaican patients which were documented and analysed. RESULTS: Records of 1079 patients were reviewed in Survey A and records of 512 patients were reviewed in Survey B. Seventy-seven per cent of 524 patients were aged 5-15 years in initial attacks of RF in Survey A and in Survey B, 82% of 119 patients were between 5 and 15 years in initial attacks. There was no significant sex difference in RF in Survey A and Survey B. A diagnosis of RF had been made in 54% of records in Survey A and 55% of records in Survey B. Diagnosis conformed to the Modified Jones criteria. Carditis occurred in 41% and 70% of RF patients, respectively in survey A and B. Polyarthritis occurred in 73% in Survey A and 74% in Survey B. Chorea occurred in 3% of RF patients in both surveys. Erythema marginatum and subcutaneous nodules occurred rarely in both surveys. Evidence of recent streptococcal infections in RF was found in 74% and 64% in Survey A and B, respectively. Severe carditis occurred in 7% of initial attacks of RF in A and 26% in B. In RHD, mitral incompetence was the commonest valvular lesion, occurring in 82% and 68% in A and B, respectively Rheumatic fever and rheumatic heart disease have relatively long and expensive hospital stays which are preventable by careful adherence to prevention programmes. CONCLUSION: The National Control Programme for RF/RHD in Jamaica began in 1985 and deserves careful monitoring and support to reduce the burden of RF/RHD. Analysis of clinical and laboratory data obtained in the retrospective surveys conducted for case finding provides important data on RF/RHD in Jamaica.

The rheumatic fever and rheumatic heart disease control programme: Jamaica / Programa de control de la fiebre reumática y la enfermedad reumática del corazón: Jamaica

BACKGROUND: Rheumatic fever (RF) and rheumatic heart disease (RHD) are significant causes of cardiovascular disease in young adults and children especially in developing countries. In 1984, the World Health Organization (WHO) and International Society and Federation of Cardiology (ISFC) initiated an International Programme for Prevention of RF/RHD in 16 developing countries, including Jamaica. The Jamaican RF/RHD National Control Programme began in July 1985. SUBJECTS AND METHOD: The Control Programme promotes the primary prevention of RF/RHD through the appropriate treatment of streptococcal throat infections. Secondary prevention has been the main focus of the Control Programme by administration of benzathine penicillin injections every four weeks to RF/RHD patients. Case finding activities have included two retrospective surveys of case records of RF/RHD patients admitted to the major hospitals in Kingston and St Andrew in the period 1975 - 1985 (Survey A) and 1989 - 1995 (Survey B). These surveys provided clinical and laboratory data on RF/RHD in Jamaican patients which were documented and analysed. RESULTS: Records of 1079 patients were reviewed in Survey A and records of 512 patients were reviewed in Survey B. Seventy-seven per cent of 524 patients were aged 5−15 years in initial attacks of RF in Survey A and in Survey B, 82% of 119 patients were between 5 and 15 years in initial attacks. There was no significant sex difference in RF in Survey A and Survey B. A diagnosis of RF had been made in 54% of records in Survey A and 55% of records in Survey B. Diagnosis conformed to the Modified Jones criteria. Carditis occurred in 41% and 70% of RF patients, respectively in survey A and B. Polyarthritis occurred in 73% in Survey A and 74% in Survey B. Chorea occurred in 3% of RF patients in both surveys. Erythema marginatum and subcutaneous nodules occurred rarely in both surveys. Evidence of recent streptococcal infections in RF was found in 74% and 64% in Survey A and B, respectively. Severe carditis occurred in 7% of initial attacks of RF in A and 26% in B. In RHD, mitral incompetence was the commonest valvular lesion, occurring in 82% and 68% in A and B, respectively. Rheumatic fever and rheumatic heart disease have relatively long and expensive hospital stays which are preventable by careful adherence to prevention programmes. CONCLUSION: The National Control Programme for RF/RHD in Jamaica began in 1985 and deserves careful monitoring and support to reduce the burden of RF/RHD. Analysis of clinical and laboratory data obtained in the retrospective surveys conducted for case finding provides important data on RF/RHD in Jamaica.

ANTECEDENTES: La fiebre reumática (FR) y la enfermedad reumática del corazón (ERC) constituyen causas significativas de la enfermedad cardiovascular en adultos jóvenes y niños en los países en vías de desarrollo. En 1984 la Organización Mundial de la (OMS) y la Sociedad y Federación Internacional de Cardiología (ISFC) iniciaron un Programa Internacional para la Prevención de FR/ERC en 16 países en vías de desarrollo, incluyendo Jamaica. El Programa Nacional de Jamaica para el control de FR/ERC, comenzó en julio de 1985. SUJETOS Y MÉTODO: El Programa de Control promueve la prevención primaria de FR/ERC a través del tratamiento apropiado de infecciones estreptocócicas de la garganta la prevención secundaria ha sido el foco principal del Programa de Control mediante la administración de inyecciones de penicilina benzatinica cada cuatro semanas a los pacientes de FR/ERC. Las actividades de detección de casos han incluido dos estudios retrospectivos de historias clínicas de casos de pacientes de FR/ERC ingresados en los hospitales principales de Kingston y Saint Andrew en el periodo 1975 - 1985 (Estudio A) y 1989 - 1995 (Estudio B). Estos estudios proporcionaron datos clínicos y de laboratorio de FR/ERC en pacientes jamaicanos. Dichos datos fueron documentados y analizados. RESULTADOS: Se examinaron las historias clínicas de 1079 pacientes en el Estudio A y se revisaron las historias clínicas de 512 pacientes en el Estudio B. El 77% de 524 pacientes tenían entre 5 - 15 años de edad al inicio de lo ataques de FR en el Estudio A, en tanto que en el Estudio B el 82% de 119 pacientes tenían entre 5 y 15 años de edad al inicio de los ataques. No hubo ninguna diferencia significativa en cuanto a sexo en FR en el Estudio A y el Estudio B. Se había realizado un diagnóstico de FR en el 54% de las historias clínicas del Estudio A y el 55% de las historias clínicas del Estudio B. El diagnóstico se ajustaba a los criterios de Jones modificados. Se presentó carditis en 41% y 70% de los pacientes de FR respectivamente en el estudio A y B. La poliartritis ocurrió en 73% en el Estudio A y 74% en el Estudio B. La corea ocurrió en 3% de pacientes de FR en ambos estudios. Ls manifestaciones de eritema marginatum y los nódulos subcutáneos raramente ocurrieron en ambos estudios. En el 74% y 64% de los Estudios A y B, respectivamente, se halló evidencia de recientes infecciones estreptocócicas de FR. La carditis severa ocurrió en el 7% de los ataques iniciales de FR en A y 26% en B. En la ERC, la incompetencia mitral fue la lesión valvular más común, presentándose en el 82% y 68% de A y B, respectivamente. La fiebre reumática y la enfermedad reumática del corazón tienen estadías de hospitalización relativamente largas y costosas, las cuales pueden prevenirse mediante la adhesión cuidadosa a los programas de la prevención. CONCLUSIÓN: El Programa Nacional de Jamaica para el control de FR/ERC, empezó en 1985 y requiere un monitoreo cuidadoso y apoyo constante a fin de reducir la carga de FR/ERC. El análisis de los datos clínicos y los datos de laboratorio obtenidos en los estudios retrospectivos conducidos para la detección de casos proporcionan datos importantes sobre la FR/ERC en Jamaica.

Phosphorus runoff from incorporated and surface-applied liquid swine manure and phosphorus fertilizer.

Excessive fertilization with organic and/or inorganic P amendments to cropland increases the potential risk of P loss to surface waters. The objective of this study was to evaluate the effects of soil test P level, source, and application method of P amendments on P in runoff following soybean [Glycine max (L.) Merr.]. The treatments consisted of two rates of swine (Sus scrofa domestica) liquid manure surface-applied and injected, 54 kg P ha(-1) triple superphosphate (TSP) surface-applied and incorporated, and a control with and without chisel-plowing. Rainfall simulations were conducted one month (1MO) and six months (6MO) after P amendment application for 2 yr. Soil injection of swine manure compared with surface application resulted in runoff P concentration decreases of 93, 82, and 94%, and P load decreases of 99, 94, and 99% for dissolved reactive phosphorus (DRP), total phosphorus (TP), and algal-available phosphorus (AAP), respectively. Incorporation of TSP also reduced P concentration in runoff significantly. Runoff P concentration and load from incorporated amendments did not differ from the control. Factors most strongly related to P in runoff from the incorporated treatments included Bray P1 soil extraction value for DRP concentration, and Bray P1 and sediment content in runoff for AAP and TP concentration and load. Injecting manure and chisel-plowing inorganic fertilizer reduced runoff P losses, decreased runoff volumes, and increased the time to runoff, thus minimizing the potential risk of surface water contamination. After incorporating the P amendments, controlling erosion is the main target to minimize TP losses from agricultural soils.

Modelling the control of interceptive actions.

In recent years, several phenomenological dynamical models have been formulated that describe how perceptual variables are incorporated in the control of motor variables. We call these short-route models as they do not address how perception-action patterns might be constrained by the dynamical properties of the sensory, neural and musculoskeletal subsystems of the human action system. As an alternative, we advocate a long-route modelling approach in which the dynamics of these subsystems are explicitly addressed and integrated to reproduce interceptive actions. The approach is exemplified through a discussion of a recently developed model for interceptive actions consisting of a neural network architecture for the online generation of motor outflow commands, based on time-to-contact information and information about the relative positions and velocities of hand and ball. This network is shown to be consistent with both behavioural and neurophysiological data. Finally, some problems are discussed with regard to the question of how the motor outflow commands (i.e. the intended movement) might be modulated in view of the musculoskeletal dynamics.

Phosphorus runoff: effect of tillage and soil phosphorus levels.

Continued inputs of fertilizer and manure in excess of crop requirements have led to a build-up of soil phosphorus (P) levels and increased P runoff from agricultural soils. The objectives of this study were to determine the effects of two tillage practices (no-till and chisel plow) and a range of soil P levels on the concentration and loads of dissolved reactive phosphorus (DRP), algal-available phosphorus (AAP), and total phosphorus (TP) losses in runoff, and to evaluate the P loss immediately following tillage in the fall, and after six months, in the spring. Rain simulations were conducted on a Typic Argiudoll under a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation. Elapsed time after tillage (fall vs. spring) was not related to any form of P in runoff. No-till runoff averaged 0.40 mg L(-1) and 0.05 kg ha(-1) DRP and chisel-plow plots averaged 0.24 mg L(-1) and 0.02 kg ha(-1) DRP concentration and loads, respectively. The relationship between DRP and Bray P1 extraction values was approximated by a logistic function (S-shaped curve) for no-till plots and by a linear function for tilled plots. No significant differences were observed between tillage systems for TP and AAP in runoff. Bray P1 soil extraction values and sediment concentration in runoff were significantly related to the concentrations and amounts of AAP and TP in runoff. These results suggest that soil Bray P1 extraction values and runoff sediment concentration are two easily measured variables for adequate prediction of P runoff from agricultural fields.

Atomic-scale observation of temperature and pressure driven preroughening and roughening.

Preroughening and roughening transitions are observed on the GaAs(001) surface using scanning tunneling microscopy. By tuning the substrate temperature or As4 pressure the surface morphology can be made free of islands, covered with one monolayer high islands or covered with islands on top of islands forming a wedding-cake-type structure. These three distinct surface morphologies are classified as ordered flat (OF), disordered flat (DOF), and rough within the restricted solid-on-solid model. Here, the DOF phase is macroscopically flat; however, an up-down-up-down step pattern persists across the entire surface. Using this model we have determined the next-nearest-neighbor interaction energy to be about 0.05 eV.

A model of movement coordinates in the motor cortex: posture-dependent changes in the gain and direction of single cell tuning curves.

This article outlines a methodology for investigating the coordinate systems by which movement variables are encoded in the firing rates of individual motor cortical neurons. Recent neurophysiological experiments have probed the issue of underlying coordinates by examining how cellular preferred directions (as determined by the center-out task) change with posture. Several key experimental findings have resulted that constrain hypotheses about how motor cortical cells encode movement information. But while the significance of shifts in preferred direction is well known and widely accepted, posture-dependent changes in the depth of modulation of a cell's tuning curve--that is, gain changes--have not been similarly identified as a means of coordinate inference. This article develops a vector field framework in which the preferred direction and the gain of a cell's tuning curve are viewed as dual components of a unitary response vector. The formalism can be used to compute how each aspect of cell response covaries with posture as a function of the coordinate system in which a given cell is hypothesized to encode its movement information. Such an integrated approach leads to a model of motor cortical cell activity that codifies the following four observations: (i) cell activity correlates with hand movement direction; (ii) cell activity correlates with hand movement speed; (iii) preferred directions vary with posture; and (iv) the modulation depth of tuning curves varies with posture. Finally, the model suggests general methods for testing coordinate hypotheses at the single-cell level and simulates an example protocol for three possible coordinate systems: Cartesian spatial, shoulder-centered, and joint angle.

Spatially resolved spin-injection probability for gallium arsenide.

We report a large spin-polarized current injection from a ferromagnetic metal into a nonferromagnetic semiconductor, at a temperature of 100 Kelvin. The modification of the spin-injection process by a nanoscale step edge was observed. On flat gallium arsenide [GaAs(110)] terraces, the injection efficiency was 92%, whereas in a 10-nanometer-wide region around a [111]-oriented step the injection efficiency is reduced by a factor of 6. Alternatively, the spin-relaxation lifetime was reduced by a factor of 12. This reduction is associated with the metallic nature of the step edge. This study advances the realization of using both the charge and spin of the electron in future semiconductor devices.

Health-related quality-of-life measure enhances acute treatment response prediction in depressed inpatients.

BACKGROUND: Many nonbiological variables are reported to predict treatment response for major depression; however, there is little agreement about which variables are most predictive. METHOD: Inpatient subjects (N = 59) diagnosed with current DSM-IV major depressive disorder completed weekly depressive symptom ratings with the Hamilton Rating Scale for Depression (HAM-D-17) and Beck Depression Inventory (BDI), and weekly health-related quality-of-life (HRQL) ratings with the Quality of Well-Being Scale (QWB). Acute responders were identified by a 50% decrease in HAM-D-17 score from baseline within 4 weeks of medication treatment. Predictor variables were initially chosen from a literature review and then tested for their association with acute treatment response. RESULTS: An initial predictive model including age at first depression, admission BDI score, and melancholia predicted acute treatment response with 69% accuracy and was designated as the benchmark model. Adding the admission QWB index score to the benchmark model did not improve the prediction rate; however, adding the admission QWB subscales for physical and social activity to the benchmark model significantly improved acute treatment response prediction to 86% accuracy (p = .001). CONCLUSION: In addition to being designed for use in cost-effectiveness analyses, the QWB subscales appear to be useful HRQL variables for predicting acute inpatient depression treatment response.

Kinematic coordinates in which motor cortical cells encode movement direction.

During goal-directed reaching in primates, a sensorimotor transformation generates a dynamical pattern of muscle activation. Within the context of this sensorimotor transformation, a fundamental question concerns the coordinate systems in which individual cells in the primary motor cortex (MI) encode movement direction. This article develops a mathematical framework that computes, as a function of the coordinate system in which an individual cell is hypothesized to operate, the spatial preferred direction (pd) of that cell as the arm configuration and hand location vary. Three coordinate systems are explicitly modeled: Cartesian spatial, shoulder-centered, and joint angle. The computed patterns of spatial pds are distinct for each of these three coordinate systems, and experimental approaches are described that can capitalize on these differences to compare the empirical adequacy of each coordinate hypothesis. One particular experiment involving curved motion was analyzed from this perspective. Out of the three coordinate systems tested, the assumption of joint angle coordinates best explained the observed cellular response properties. The mathematical framework developed in this paper can also be used to design new experiments that are capable of disambiguating between a given set of specified coordinate hypotheses.

How the basal ganglia use parallel excitatory and inhibitory learning pathways to selectively respond to unexpected rewarding cues.

After classically conditioned learning, dopaminergic cells in the substantia nigra pars compacta (SNc) respond immediately to unexpected conditioned stimuli (CS) but omit formerly seen responses to expected unconditioned stimuli, notably rewards. These cells play an important role in reinforcement learning. A neural model explains the key neurophysiological properties of these cells before, during, and after conditioning, as well as related anatomical and neurophysiological data about the pedunculopontine tegmental nucleus (PPTN), lateral hypothalamus, ventral striatum, and striosomes. The model proposes how two parallel learning pathways from limbic cortex to the SNc, one devoted to excitatory conditioning (through the ventral striatum, ventral pallidum, and PPTN) and the other to adaptively timed inhibitory conditioning (through the striosomes), control SNc responses. The excitatory pathway generates CS-induced excitatory SNc dopamine bursts. The inhibitory pathway prevents dopamine bursts in response to predictable reward-related signals. When expected rewards are not received, striosomal inhibition of SNc that is unopposed by excitation results in a phasic drop in dopamine cell activity. The adaptively timed inhibitory learning uses an intracellular spectrum of timed responses that is proposed to be similar to adaptively timed cellular mechanisms in the hippocampus and cerebellum. These mechanisms are proposed to include metabotropic glutamate receptor-mediated Ca(2+) spikes that occur with different delays in striosomal cells. A dopaminergic burst in concert with a Ca(2+) spike is proposed to potentiate inhibitory learning. The model provides a biologically predictive alternative to temporal difference conditioning models and explains substantially more data than alternative models.

The application of near patient testing to microbiology.

Near patient testing (NPT) was the norm in days when urine was examined by smell and taste. More recently, general practitioners and physicians in genitourinary medicine began to use light microscopes in their consulting rooms to examine urine for pus cells and urethral and other swabs for pathogens. Increasing knowledge has led to specialisation, however, with clinicians obtaining specimens for examination by others. Improved technology has speeded up the practice of medicine, raising expectations of patients and doctors alike, and reductions in the size and expense of testing instruments have made a renaissance of NPT possible. Such a rebirth has already been seen in high dependency units and neonatal intensive care units, where arterial blood gases and serum bilirubin have to be tested in less time than it would take a sprinter to reach the laboratory. People with diabetes, rushing about in the community, stop and test their own blood glucose to determine the ideal dose of insulin, and patients with asthma measure peak expiratory flow rates to titrate doses of inhaled and oral corticosteroids. To what extent has NPT developed in microbiology? General practitioners have nitrite dipsticks and dipslides with which to identify urinary tract infections and elsewhere in this issue the prospect for testing for Helicobacter pylori infection is discussed. Do-it-yourself HIV testing kits can be bought in some countries. Are these desirable developments for communicable diseases, the results of whose investigation are used not only to benefit the individuals tested but also to monitor trends in populations and determine policies for the prevention and control of infection? If NPT is desirable, or inevitable, in microbiology, how can it be developed so as to ensure a high quality service both for patients and the population? This review considers the implications of NPT in the field of communicable diseases for microbiology laboratories, quality assurance, accreditation, and the legal framework in which medical devices are used.

A cortico-spinal model of reaching and proprioception under multiple task constraints.

A model of cortico-spinal trajectory generation for voluntary reaching movements is developed to functionally interpret a broad range of behavioral, physiological, and anatomical data. The model simulates how arm movements achieve their remarkable efficiency and accuracy in response to widely varying positional, speed, and force constraints. A key issue in arm movement control is how the brain copes with such a wide range of movement contexts. The model suggests how the brain may set automatic and volitional gating mechanisms to vary the balance of static and dynamic feedback information to guide the movement command and to compensate for external forces. For example, with increasing movement speed, the system shifts from a feedback position controller to a feedforward trajectory generator with superimposed dynamics compensation. Simulations of the model illustrate how it reproduces the effects of elastic loads on fast movements, endpoint errors in Coriolis fields, and several effects of muscle tendon vibration, including tonic and antagonist vibration reflexes, position and movement illusions, effects of obstructing the tonic vibration reflex, and reaching undershoots caused by antagonist vibration.

Cortical networks for control of voluntary arm movements under variable force conditions.

A neural model of voluntary movement and proprioception is developed that offers an integrated interpretation of the functional roles of diverse cell types in movement-related areas of primate cortex. The model circuit maintains accurate proprioception while controlling voluntary reaches to spatial targets, exertion of force against obstacles, posture maintenance despite perturbations, compliance with an imposed movement, and static and inertial load compensations. Computer simulations show that properties of model elements correspond to the properties of many known cells types in areas 4 and 5. Among these properties are delay period activation, response profiles during movement, kinematic and kinetic sensitivities, and latency of activity onset. In particular, area 4 phasic and tonic cells, respectively, compute velocity and position commands that are capable of activating alpha and gamma motor neurons, thereby shifting the mechanical equilibrium point. Anterior area 5 cells compute the position of the limb using corollary discharges from area 4 and feedback from muscle spindles. Posterior area 5 neurons use the position perception signal and a target position signal to compute a desired movement vector. The cortical loop is closed by a volition-gated projection of this movement vector to the area 4 phasic cells. An auxiliary circuit allows phasic-tonic cells in area 4 to incorporate force command components needed to compensate for static and inertial loads. After reporting simulations of prior experimental results, predictions are made for both motor and parietal cell types under novel experimental protocols.