Discrimination reversal facilitates contextual conditioning in rats' appetitive conditioning / La inversión de la discriminación facilita el condicionamiento contextual en una preparación de condicionamiento apetitivo con ratas

Two experiments were conducted with the goal of exploring the effect of experiencing associative interference upon concurrent learning about conditioned stimuli and contexts in rats’ appetitive conditioning. During the first training phase, two groups of rats received a conditioned stimulus (CS1) followed by food, whereas another conditioned stimulus (CS2) was presented alone. During a second training phase, discrimination was reversed in group R, while it remained the same in group D. A new conditioned stimulus (CS3) was concurrently trained followed by food during this second Phase (Experiment 1). Reversal discrimination did not facilitate concurrent conditioning of the new stimulus, but there was a trend towards facilitation of contextual conditioning, measured by magazine entries in the absence of stimuli, that was confirmed in Experiment 2. These results suggest that the interference treatment may facilitate context conditioning under circumstances and with boundaries that are yet to be established

Se realizaron dos experimentos con el objetivo de explorar el efecto de experimentar una interferencia asociativa sobre el aprendizaje concurrente acerca de estímulos condicionados y contextos en condicionamiento apetitivo con ratas. Durante la primera fase de entrenamiento, dos grupos de ratas recibieron un estímulo condicionado (CS1) seguido de comida, mientras otro (CS2) se presentaba solo. Durante la segunda fase de entrenamiento, la discriminación se invirtió en el grupo R, mientras se mantuvo constante en el grupo D. Durante esta segunda fase, un estímulo condicionado nuevo (CS3) fue presentado seguido de comida (Experimento 1). La inversión de la discriminación no facilitó el aprendizaje concurrente acerca del nuevo estímulo, pero sí hubo una tendencia hacia la facilitación del condicionamiento contextual, medido a partir de la respuesta de entrada en el comedero en ausencia de estimulación, que se confirmó en el Experimento 2. Estos resultados sugieren que los tratamientos de interferencia pueden facilitar el condicionamiento contextual en circunstancias y con limitaciones que están aún por determinarse

Testing a cue outside the training context increases attention to the contexts and impairs performance in human predictive learning.

One experiment in human predictive learning explored the impact of a context change on attention to contexts and predictive ratings controlled by the cue. In Context A: cue X was paired with an outcome four times, while cue Y was presented without an outcome four times in Context B:. In both contexts filler cues were presented without the outcome. During the test, target cues X and Y were presented either in the context where they were trained, or in the alternative context. With the context change expectation of the outcome X, expressed as predictive ratings, decreased in the presence of X and increased in the presence of Y. Looking at the contexts, expressed as a percentage of the overall gaze dwell time on a trial, was high across the four training trials, and increased with the context change. Results suggest that the presentation of unexpected information leads to increases in attention to contextual cues. Implications for contextual control of behavior are discussed.

Flexible Configural Learning of Non-Linear Discriminations and Detection of Stimulus Compounds.

Previous work showed that prior experience with discriminations requiring configural solutions (e.g., biconditional discrimination) confers an advantage for the learning of new configural discriminations (e.g., negative patterning) in comparison to prior experience with elemental discriminations. This effect is well established but its mechanism is not well understood. In the studies described below we assessed whether the saliences of configural and element cues were affected by prior training. We observed positive transfer to a new configural discrimination after configural pre-training but we were unable to find evidence for changes in cue salience using a signal-detection task. Our results confirm previous work by demonstrating experience-dependent flexibility in cue processing but they also suggest that this flexibility occurs at a point in the stimulus processing pipeline later than 1-2 s after the presentation of stimulus inputs. (138 words).

Attention to irrelevant contexts decreases as training increases: Evidence from eye-fixations in a human predictive learning task.

Participants were trained in a human predictive learning task in which they had to predict whether the ingestion of a given food (cue) by the imaginary customer of an imaginary restaurant (context) was followed by gastric malaise (outcome). One food was always followed by gastric malaise in one of the contexts, while other foods were not followed by gastric malaise in the same, or in an alternative context. Predictive responses and eye-fixations were recorded throughout the 48 training trials with each cue involved in the task. In agreement with the predictions of the Attentional Theory of Context Processing, attention to the contexts measured through eye-fixations decreased while attention to the cues increased as training progressed. The results of this study give support to the idea that contexts are actively processed at the beginning of acquisition, and that this processing decreases as training increases.

Context specificity of extinguished schedule-induced drinking within an ABA renewal design in rats / Especificidad contextual de la extinción de la bebida inducida por programa en un diseño de renovación ABA en ratas

The main goal of this study was to explore whether extinction of schedule-induced adjunctive drinking (polydipsia) may become under contextual control. Drinking was induced by a Fixed-Time 30 sec food delivery schedule (FT30). Experiment 1 used a 2 x 2 factorial design with Schedule (FT30 vs. food a the start of the session), and Stimulus (Presenceor absence of a 10 sec tone at the end of each 30 sec period within a session) as factors. Acquisition and extinction were conducted in two different contexts, returning to the acquisition context at testing. Experiment 2 tested contextual control of extinction against a control that remained in the extinction context at testing. Recovery from extinction was observed as an increase in water intake (as well as in magazine entries) during the test, regardless of the presence of the tone. Implications for theunderstanding of schedule-induced drinking as a conditioned response are discusse (AU)

El objetivo principal de este estudio fue evaluar si la extinción de la bebida adjuntiva inducida por programa (polidipsia) podía quedar bajo control contextual. La bebida se indujo mediante un programa de administración de comida de tiempo fijo 30 segundos (TF30). El experimento 1 utilizó un diseño factorial 2 x 2 con Programa (TF30 vs. comida al inicio de la sesión) y Estímulo (presencia o ausencia de un sonido de 10s al final de cada periodo de 30s dentro de la sesión)como factores. La adquisición y la extinción se realizaron en contextos diferentes, regresando al contexto de adquisición durante la prueba. El experimento 2 introdujo una condición de control que recibió la prueba en el contexto de extinción. La recuperación de la extinción se observó como un aumento en la ingesta de agua (así como en las entradas en el comedero) durante la prueba, independientemente de la presencia del sonido. Se discuten las implicaciones de estos resultados para la interpretación de la bebida inducida por programa como una respuesta condicionada (AU)

Mesenchymal stem cells promote leukaemic cells aberrant phenotype from B-cell acute lymphoblastic leukaemia.

BACKGROUND AND OBJECTIVES: The role of bone marrow-mesenchymal stem cells (BM-MSC) in leukaemic cell control is controversial. The purpose of this work was to evaluate BM-MSC role regarding the viability, proliferation and immunophenotype of normal B-cell precursors from control (Ct) patients and leukaemic cells from B-acute lymphoblastic leukaemia (B-ALL) patients. PATIENTS AND METHODS: BM-MSC were isolated and characterised from voluntary donors. Mononuclear cells isolated from Ct and B-ALL bone marrow samples were cultured in the presence or absence of BM-MSC for 7days. Cell viability was determined with LIVE/DEAD and proliferation index evaluated by CFSE labelling. Cell population immunophenotypes were characterised by estimating CD19, CD10, CD20 and CD45 antigens by flow cytometry. RESULTS: After co-culture, B-ALL cells exhibited higher viability (20-40%) as compared to just cells (3-10%). Ct and B-ALL absolute cell counts were higher in the presence of BM-MSC (Ct: 25/mm(3)cf8/mm(3), B-ALL: 15/mm(3)cf3/mm(3)). Normal B-cell subpopulations in co-culture had increased expression of CD19 and CD10 (Pre-pre B) and CD45 and CD20 antigens (Pre-B). B-ALL cells co-cultured with BM-MSC showed an increase in CD19 and CD20, although the greatest increase was observed in the CD10 antigen. CONCLUSIONS: Lymphoid cell maintenance, at early stages of differentiation, was significantly promoted by BM-MSC in normal and leukaemic cells. Co-cultures also modulated the expression of antigens associated with the B-ALL asynchronous phenotype as CD10 co-expressed with CD19 and CD20. To our knowledge, this is the first time that CD10, CD19 and CD20 leukaemic antigens have been reported as being regulated by BM-MSC.