The influence of learning history on anterograde interference.

Classically interpreted as a competition between opposite memories (A vs B), anterograde interference (AI) also emerges in the absence of competing memories (A vs A), suggesting that mechanisms other than those involved in memory competition contribute to AI. To investigate this, we tested the hypothesis that extending motor practice would enhance a first memory, but come at the cost of reduced learning capabilities when subsequently exposed to a second learning session of the same task. Based on converging biological evidence, AI was expected to depend upon the degree of extended practice of the initial exposure. During a first Session, four conditions were carried out where participants (n = 24) adapted to a gradually introduced -20° visual deviation while the extent of the initial exposure was manipulated by varying the duration or type of the performance asymptote. Specifically, the performance asymptote at -20° was either Short (40 trials), Moderate (160 trials), Long (320 trials), or absent due to continuously changing perturbations around the mean of -20° (Jagged; 160 trials). After a 2-min interval, participants re-adapted to the same (-20°) visual deviation, which was meant to probe the effect of extended practice in the first Session on the learning capabilities of a second identical memory (A vs A). The results first confirmed that the duration of exposure in the first Session enhanced immediate aftereffects in the Moderate, Long, and Jagged conditions as compared to the Short condition, suggesting that extended practice enhanced retention of the first memory. When comparing the second Session to the first one, results revealed a different pattern of re-adaptation depending on the duration of initial exposure: in the Short condition, there was evidence for facilitated re-adaptation and similar aftereffects. However, in the Moderate, Long and Jagged conditions, re-adaptation was similar and aftereffects were impaired, suggestive of AI. This suggests that extended practice initially enhances memory formation, but comes at the cost of reduced subsequent learning capabilities. One possibility is that AI occurs because extended practice induces the emergence of network-specific homeostatic constraints, which limit subsequent neuroplastic and learning capabilities in the same neural network.

Punishments and rewards both modestly impair visuomotor memory retention.

While the effects of rewards on memory appear well documented, the effects of punishments remain uncertain. Based on neuroimaging data, this study tested the hypothesis that, as compared to a neutral condition, a context allowing successful punishment avoidance would enhance memory to a similar extent as rewards. In a fully within-subject and counter-balanced design, participants (n = 18) took part in 3 distinct learning sessions during which the delivery of performance-contingent monetary punishments and rewards was manipulated. Specifically, participants had to reach towards visual targets while compensating for a gradually introduced visual deviation. Accuracy at achieving targets was either punished (Hit: "+0$"; Miss: "-0.5$), rewarded (Hit: "+0.5$"; Miss: "-0$"), or associated with neutral binary feedback (Hit: "Hit"; Miss: "Miss"). Retention was assessed through reach aftereffects both immediately and 24 h after initial acquisition. The results disconfirmed the hypothesis by showing that the punishment and reward learning sessions both impaired retention as compared to the neutral session, suggesting that both types of incentives similarly impaired memory formation and consolidation. Two alternative but complementary interpretations are discussed. One interpretation is that the presence of punishments and rewards induced a negative learning context, which - based on neurobiological data - could have been sufficient to interfere with memory formation and consolidation. Another interpretation is that punishments and rewards emphasized the disrupting effects of target hits on implicit learning processes, therefore yielding retention impairments. Altogether, these results suggest that incentives can have counter-productive effects on memory.

Learning the same motor task twice impairs its retention in a time- and dose-dependent manner.

Anterograde interference emerges when two differing tasks are learned in close temporal proximity, an effect repeatedly attributed to a competition between differing task memories. However, recent development alternatively suggests that initial learning may trigger a refractory period that occludes neuroplasticity and impairs subsequent learning, consequently mediating interference independently of memory competition. Accordingly, this study tested the hypothesis that interference can emerge when the same motor task is being learned twice, that is when competition between memories is prevented. In a first experiment, the inter-session interval (ISI) between two identical motor learning sessions was manipulated to be 2 min, 1 h or 24 h. Results revealed that retention of the second session was impaired as compared to the first one when the ISI was 2 min but not when it was 1 h or 24 h, indicating a time-dependent process. Results from a second experiment replicated those of the first one and revealed that adding a third motor learning session with a 2 min ISI further impaired retention, indicating a dose-dependent process. Results from a third experiment revealed that the retention impairments did not take place when a learning session was preceded by simple rehearsal of the motor task without concurrent learning, thus ruling out fatigue and confirming that retention is impaired specifically when preceded by a learning session. Altogether, the present results suggest that competing memories is not the sole mechanism mediating anterograde interference and introduce the possibility that a time- and dose-dependent refractory period-independent of fatigue-also contributes to its emergence. One possibility is that learning transiently perturbs the homeostasis of learning-related neuronal substrates. Introducing additional learning when homeostasis is still perturbed may not only impair performance improvements, but also memory formation.

Neurophysiological basis of contrast dependent BOLD orientation tuning.

Recent work in early visual cortex of humans has shown that the BOLD signal exhibits contrast dependent orientation tuning, with an inverse oblique effect (oblique > cardinal) at high contrast and a horizontal effect (vertical > horizontal) at low contrast. This finding is at odds with decades of neurophysiological research demonstrating contrast invariant orientation tuning in primate visual cortex, yet the source of this discrepancy is unclear. We hypothesized that contrast dependent BOLD orientation tuning may arise due to contrast dependent influences of feedforward (FF) and feedback (FB) synaptic activity, indexed through gamma and alpha rhythms, respectively. To quantify this, we acquired EEG and BOLD in healthy humans to generate and compare orientation tuning curves across all neural frequency bands with BOLD. As expected, BOLD orientation selectivity in V1 was contrast dependent, preferring oblique orientations at high contrast and vertical at low contrast. On the other hand, EEG orientation tuning was contrast invariant, though frequency-specific, with an inverse-oblique effect in the gamma band (FF) and a horizontal effect in the alpha band (FB). Therefore, high-contrast BOLD orientation tuning closely matched FF activity, while at low contrast, BOLD best resembled FB orientation tuning. These results suggest that contrast dependent BOLD orientation tuning arises due to the reduced contribution of FF input to overall neurophysiological activity at low contrast, shifting BOLD orientation tuning towards the orientation preferences of FB at low contrast.

Visuomotor Prediction Errors Modulate EEG Activity Over Parietal Cortex.

The parietal cortex is thought to be involved in visuomotor adaptation, yet it remains unclear whether it is specifically modulated by visuomotor prediction errors (i.e. PEs; mismatch between the predicted and actual visual consequences of the movement). One reason for this is that PEs tend to be associated with task errors, as well as changes in motor output and visual input, making them difficult to isolate. Here this issue is addressed using electroencephalography. A strategy (STR) condition, in which participants were instructed on how to counter a 45° visuomotor rotation, was compared to a condition in which participants had adapted to the rotation (POST). Both conditions were matched for task errors and movement kinematics, with the only difference being the presence of PEs in STR. Results revealed strong parietal modulations in current source density and low theta (2-4 Hz) power shortly after movement onset in STR vs. POST, followed by increased alpha/low beta (8-18 Hz) power during much of the post-movement period. Given recent evidence showing that feedforward and feedback information is respectively carried by theta and alpha/beta oscillations, the observed power modulations may reflect the bottom-up propagation of PEs and the top-down revision of predictions.

Patient-reported dietetic care post hospital for free-living patients: a Canadian Malnutrition Task Force Study.

BACKGROUND: Transitions out of hospital can influence recovery. Ideally, malnourished patients should be followed by someone with nutrition expertise, specifically a dietitian, post discharge from hospital. Predictors of dietetic care post discharge are currently unknown. The present study aimed to determine the patient factors independently associated with 30-days post hospital discharge dietetic care for free-living patients who transitioned to the community. METHODOLOGY: Nine hundred and twenty-two medical or surgical adult patients were recruited in 16 acute care hospitals in eight Canadian provinces on admission. Eligible patients could speak English or French, provide their written consent, were anticipated to have a hospital stay of ≥2 days and were not considered palliative. Telephone interviews were completed with 747 (81%) participants using a standardised questionnaire to determine whether dietetic care occurred post discharge; 544 patients discharged to the community were included in the multivariate analyses, excluding those who were admitted to nursing homes or rehabilitation facilities. Covariates during and post hospitalisation were collected prospectively and used in logistic regression analyses to determine independent patient-level predictors. RESULTS: Dietetic care post discharge was reported by 61/544 (11%) of participants and was associated with severe malnutrition [Subjective Global Assessment category C: odd's ratio (OR) 2.43 (1.23-4.83)], weight loss post discharge [(OR 2.86 (1.45-5.62)], comorbidity [(OR 1.09 (1.02-1.17)] and a dietitian consultation on admission [(OR 3.41 (1.95-5.97)]. CONCLUSIONS: Dietetic care post discharge occurs in few patients, despite the known high prevalence of malnutrition on admission and discharge. Dietetic care in hospital was the most influential predictor of post-hospital care.

Prevalence and predictors of weight change post discharge from hospital: a study of the Canadian Malnutrition Task Force.

BACKGROUND/OBJECTIVES: Little is known about factors associated with weight change post discharge from hospital; yet poor nutritional status in the transition from hospital to community can result in readmission. This exploratory study aimed to determine the factors associated with weight change 30 days post discharge defined as weight gain (WG; 5+ pounds), weight loss (WL; 5+pounds) or weight stable (WS). SUBJECTS/METHODS: A total of 922 medical or surgical patients were recruited from 16 acute care hospitals in 8 Canadian provinces. Telephone interviews were completed with 747 (81%) participants 30 days post discharge using a standardized questionnaire that included: self-reported weight change, assessment of appetite, usage of healthcare services and supports for food-related activities of daily living. Covariates collected during hospitalization, including nutritional status at discharge evaluated by subjective global assessment (SGA), were used in logistic regressions. RESULTS: Among the 747 patients, 26% reported WL, 16.7% had WG and 57.2% were WS. Those with WG were: younger (odds ratio (OR) 0.77 (0.69, 0.85)), male (OR 1.71 (1.12, 2.61)), malnourished at discharge (SGA B OR 2.13 (1.36, 3.33), SGA C OR 2.76 (1.19, 6.62)), and had a good appetite based on the low OR for fair/poor appetite (OR 0.28 (0.11, 0.66)). WL was associated with being on a special diet (OR 1.45 (1.07,1.96)) and reporting fair/poor appetite (OR 2.67 (1.76, 4.07)). CONCLUSIONS: Weight change was relatively common with WL predominating. Several variables were identified to be predictors of WL or weight gain, with appetite being common to both. Future work to further define and confirm these associations is warranted.

Moving beyond the concept of "primary forest" as a metric of forest environment quality.

The United Nations Food and Agriculture Organization (FAO) has been reporting country-level area in primary forests in its Global Forest Resource Assessment since 2005. The FAO definition of a primary forest (naturally regenerated forest of native species where there are no clearly visible indications of human activities and the ecological processes are not significantly disturbed) is generally accepted as authoritative and is being used in policy making. However, problems with this definition undermine our capacity to obtain globally coherent estimates. In addition, the current reporting on primary forests fails to consider the complementarily of non-primary forests toward the maintenance of ecosystem services. These issues undermine the appropriate tracking of changes in primary and non-primary forests, and the assessment of impacts of such changes on ecosystem services. We present the case for an operational reconsideration of the primary forest concept and discuss how alternatives or supplements might be developed.

Suprarrenalectomía larascópica single port / Single port laparoscopic adrenalectomy

Introducción: La Suprarrenalectomía quirúrgica es el tratamiento de elección en lesiones tumorales de la glándula suprarrenal mayores de 4 cm o aquellos que resulten funcionales. La técnica laparoscópica esta asociada a menor sangrado, morbilidad perioperatoria y estadía hospitalaria. El apoyo del abordaje single-port (LESS) se asocia además a menor dolor y mejores resultados estéticos, pero conlleva a una mayor complejidad técnica, sin embargo esta dificultad puede ser eliminada con el apoyo robótico, conservando los beneficios de la técnica single port.(AU)

Introduction: Surgical adrenalectomy is the treatment of choice in tumors of the adrenal gland larger than 4 cm or those that are functional. The laparoscopic technique is associated with less bleeding, perioperative morbidity and hospital stay. The support of the single-port approach (LESS) is also associated with less pain and better aesthetic results, but it leads to greater technical complexity, however this difficulty can be eliminated with robotic support, while retaining the benefits of the single port technique.

Boreal forest health and global change.

The boreal forest, one of the largest biomes on Earth, provides ecosystem services that benefit society at levels ranging from local to global. Currently, about two-thirds of the area covered by this biome is under some form of management, mostly for wood production. Services such as climate regulation are also provided by both the unmanaged and managed boreal forests. Although most of the boreal forests have retained the resilience to cope with current disturbances, projected environmental changes of unprecedented speed and amplitude pose a substantial threat to their health. Management options to reduce these threats are available and could be implemented, but economic incentives and a greater focus on the boreal biome in international fora are needed to support further adaptation and mitigation actions.

Barriers to food intake in acute care hospitals: a report of the Canadian Malnutrition Task Force.

BACKGROUND: Poor food intake is common in acute care patients and can exacerbate or develop into malnutrition, influencing both recovery and outcome. Yet, research on barriers and how they can be alleviated is lacking. The present study aimed to (i) describe the prevalence of food intake barriers in diverse hospitals and (ii) determine whether patient, care or hospital characteristics are associated with the experience of these barriers. METHODS: Patients (n = 890; 87%) completed a validated questionnaire on barriers to food intake, including perceptions of food quality, just before their discharge from a medical or surgical unit in each of 18 hospitals across Canada. Scores were created for barrier domains. Associations between these barriers and selected patient characteristics collected at admission or throughout the hospital stay and site characteristics were determined using bivariate analyses. RESULTS: Common barriers were being interrupted at meals (41.8%), not being given food when a meal was missed (69.2%), not wanting ordered food (58%), loss of appetite (63.9%) and feeling too sick (42.7%) or tired (41.1%) to eat. Younger patients were more likely (P < 0.0001) to report being disturbed at meals (44.6%) than older patients (33.9%) and missing a meal for tests (39.0% versus 31.0%, P < 0.05). Patients who were malnourished, women, those with more comorbidity, and those who ate <50% of the meal reported several barriers across domains. CONCLUSIONS: The present study confirms that barriers to food intake are common in acute care hospitals. This analysis also identifies that specific patient subgroups are more likely to experience food intake barriers. Because self-reported low food intake in hospital was associated with several barriers, it is relevant to consider assessing, intervening and monitoring barriers to food intake during the hospital stay.

Validity and reliability of the new Canadian Nutrition Screening Tool in the 'real-world' hospital setting.

BACKGROUND/OBJECTIVES: Nutrition screening should be initiated on hospital admission by non-dietitians. This research aimed to validate and assess the reliability of the Canadian Nutrition Screening Tool (CNST) in the 'real-world' hospital setting. SUBJECTS/METHODS: Adult patients were admitted to surgical and medical wards only (no palliative patients). Study 1--Nutrition Care in Canadian Hospitals (n=1014): development of the CNST (3 items: weight loss, decrease food intake, body mass index (BMI)) and exploratory assessment of its criterion and predictive validity. Study 2--Inter-rater reliability and criterion validity assessment of the tool completed by untrained nursing personnel or diet technician (DT) (n=150). Subjective Global Assessment performed by site coordinators was used as a gold standard for comparison. RESULTS: Study 1: The CNST completed by site coordinators showed good sensitivity (91.7%) and specificity (74.8%). Study 2: In the subsample of untrained personnel (160 nurses; one DT), tool's reliability was excellent (Kappa=0.88), sensitivity was good (>90%) but specificity was low (47.8%). However, using a two-item ('yes' on both weight change and food intake) version of the tool improved the specificity (85.9%). BMI was thus removed to promote feasibility. The final two-item tool (study 1 sample) has a good predictive validity: length of stay (P<0.001), 30-day readmission (P=0.02; X(2) 5.92) and mortality (P<0.001). CONCLUSIONS: The simple and reliable CNST shows good sensitivity and specificity and significantly predicts adverse outcomes. Completion by several untrained nursing personnel confirms its utility in the nursing admission assessment.

Providing quality nutrition care in acute care hospitals: perspectives of nutrition care personnel.

BACKGROUND: Malnutrition is common in acute care hospitals worldwide and nutritional status can deteriorate during hospitalisation. The aim of the present qualitative study was to identify enablers and challenges and, specifically, the activities, processes and resources, from the perspective of nutrition care personnel, required to provide quality nutrition care. METHODS: Eight hospitals participating in the Nutrition Care in Canadian Hospitals study provided focus group data (n = 8 focus groups; 91 participants; dietitians, dietetic interns, diet technicians and menu clerks), which were analysed thematically. RESULTS: Five themes emerged from the data: (i) developing a nutrition culture, where nutrition practice is considered important to recovery of patients and teams work together to achieve nutrition goals; (ii) using effective tools, such as screening, evidence-based protocols, quality, timely and accurate patient information, and appropriate and quality food; (iii) creating effective systems to support delivery of care, such as communications, food production and delivery; (iv) being responsive to care needs, via flexible food systems, appropriate menus and meal supplements, up to date clinical care and including patient and family in the care processes; and (v) uniting the right person with the right task, by delineating roles, training staff, providing sufficient time to undertake these important tasks and holding staff accountable for their care. CONCLUSIONS: The findings of the present study are consistent with other work and provide guidance towards improving the nutrition culture in hospitals. Further empirical work on how to support successful implementation of nutrition care processes is needed.

Changes in net ecosystem productivity of boreal black spruce stands in response to changes in temperature at diurnal and seasonal time scales.

Net ecosystem productivity (NEP) of boreal coniferous forests is believed to rise with climate warming, thereby offsetting some of the rise in atmospheric CO(2) concentration (C(a)) by which warming is caused. However, the response of conifer NEP to warming may vary seasonally, with rises in spring and declines in summer. To gain more insight into this response, we compared changes in CO(2) exchange measured by eddy covariance and simulated by the ecosystem process model ecosys under rising mean annual air temperatures (T(a)) during 2004-2006 at black spruce stands in Saskatchewan, Manitoba and Quebec. Hourly net CO(2) uptake was found to rise with warming at T(a) < 15 degrees C and to decline with warming at T(a) > 20 degrees C. As mean annual T(a) rose from 2004 to 2006, increases in net CO(2) uptake with warming at lower T(a) were greater than declines with warming at higher T(a) so that annual gross primary productivity and hence NEP increased. Increases in net CO(2) uptake measured at lower T(a) were explained in the model by earlier recovery of photosynthetic capacity in spring, and by increases in carboxylation activity, using parameters for the Arrhenius temperature functions of key carboxylation processes derived from independent experiments. Declines in net CO(2) uptake measured at higher T(a) were explained in the model by sharp declines in mid-afternoon canopy stomatal conductance (g(c)) under higher vapor pressure deficits (D). These declines were modeled from a hydraulic constraint to water uptake imposed by low axial conductivity of conifer roots and boles that forced declines in canopy water potential (psi(c)), and hence in g(c) under higher D when equilibrating water uptake with transpiration. In a model sensitivity study, the contrasting responses of net CO(2) uptake to specified rises in T(a) caused annual NEP of black spruce in the model to rise with increases in T(a) of up to 6 degrees C, but to decline with further increases at mid-continental sites with lower precipitation. However, these contrasting responses to warming also indicate that rises in NEP with climate warming would depend on the seasonality (spring versus summer) as well as the magnitude of rises in T(a).

[Intraoperative transesophageal echocardiography to guide removal of a hypernephroma with vena cava and right atrial extension]. / Ecocardiografía transesofágica intraoperatoria en el manejo de resección de hipernefroma con compromiso de vena cava y aurícula derecha.

We describe the case of a 70-year-old man who underwent resection of a right hypernephroma with vena caval and right atrial extension with continuous monitoring by transesophageal echocardiography. The monitoring technique brought important advantages, providing images that facilitated anatomical and functional evaluation of cardiac structures without obstructing the surgical field. Images of the heart and great vessels obtained in real time allowed the surgeon to make operative decisions based on accurate assessment of the cephalad extension of the tumor to the right chambers. Transesophageal echocardiography also allowed the anesthesiologist to monitor hemodynamic status throughout surgery and watch for tumoral emboli. The imaging technique proved to be highly useful for both anesthetic and surgical management of the patient.

Ecocardiografía transesofágica intraoperatoria en el manejo de resección de hipernefroma con compromiso de vena cava y aurícula derecha / Intraoperative transesophageal echocardiography to guide removal of a hypernephroma with vena cava and right atrial extension

Se presenta el caso clínico de un paciente varón de 70 años sometido a resección de un hipernefroma derecho con extensión tumoral a vena cava y aurícula derecha. Durante la cirugía se mantuvo con monitorización ecocardiográfica transesofágica continua. Los beneficios de la ecocardiografía transesofágica (ETE) intraoperatoria fueron altos, al tratarse de una tecnología de imágenes permitió el diagnóstico anatómico y funcional de las estructuras cardíacas y no interfirió con el campo quirúrgico. La obtención de estas imágenes en tiempo real del corazón y sus grandes vasos, permitió al cirujano evaluar la extensión cefálica del tumor y la afectación de las cavidades cardíacas derechas pudiendo precisar su conducta quirúrgica. A su vez la ETE permitió al anestesiólogo monitorizar el estado de la hemodinamia durante la cirugía y vigilar en forma continuada la presencia de eventuales embolizaciones tumorales. Se demostró así la alta utilidad de la ETE intraoperatoria en el manejo anestésico y quirúrgico de este paciente

We describe the case of a 70-year-old man who underwent resection of a right hypernephroma with vena caval and right atrial extension with continuous monitoring by transesophageal echocardiography. The monitoring technique brought important advantages, providing images that facilitated anatomical and functional evaluation of cardiac structures without obstructing the surgical field. Images of the heart and great vessels obtained in real time allowed the surgeon to make operative decisions based on accurate assessment of the cephalad extension of the tumor to the right chambers. Transesophageal echocardiography also allowed the anesthesiologist to monitor hemodynamic status throughout surgery and watch for tumoral emboli. The imaging technique proved to be highly useful for both anesthetic and surgical management of the patient

Synthesis of highly nitrogen-doped multi-walled carbon nanotubes.

We present a new synthesis route for nitrogen doped carbon nanotubes (CNx) based on the aerosol method. Tubes with a record high concentration of nitrogen (approximately 20 atom%) have been synthesized, confirmed by electron energy loss spectroscopy (EELS). A strong correlation between the N/C ratio and morphology of the tubes is observed and discussed.

Litotripsia extracorpórea en litiasis ureteral distal / Extracorporeal shock ware litotripsy in distal ureteral lithiasis

La litotripsia extracorpórea por ondas de choque (LEC), ha ganado su espacio en el tratamiento de los cálculos de la vía urinaria. Una de las indicaciones más ccontrovertidas para la LEC son los grandes cálculos renales y los de uréter distal. El objetivo de nuestro trabajo es evaluar la efectividad de la litotripsia extracorpórea (LEC) en cálculos de uréter distal. Se realizó una revisión retrospectiva de 70 pacientes sometidos a LEC por cálculo de uréter distal en nuestro hospital, durante el período diciembre 1996 a mayo del 2002. Se utilizó el litotriptor electrohidráulico Direx Tripter Compact. De nuestros 70 pacientes, el 68,6 porciento era de sexo masculino y el 31,4 porciento femenino, con un promedio de edad de 41,9 años. Tres de estos pacientes presentaban cálculos dobles, lo que da un total de 73 unidades de litiasis. El 53,4 porciento son derechos y 46,6 porciento izquierdos. El tamaño promedio de los cálculos fue de 8,5 mm y el promedio de ondas de choque aplicadas fue de 3211. El 19,2 porciento de los cálculos no se fragmentó o lo hizo en sólo 2 fragmentos, produciéndose fragmentación y posterior eliminación en el 80,8 porciento. En 14 pacientes (20 porciento) se requirió tratamiento complementario (9 ureterolitectomías : 8 endoscópicas yuna vía abierta, y 5 LEC adicionales).