Análisis comparado del aprendizaje aversivo en anfibios

El presente artículo desarrolla con un enfoque comparado una revisión completa y actualizada de los estudios de aprendizaje aversivo en anfibios. La mayoría de ellos utilizaron como estímulo aversivo descargas eléctricas, obteniéndose resultados inconsistentes o negativos. Las investigaciones más recientes mostraron que otra clase de estímulos (soluciones salinas de alta concentración, o aumento de la temperatura del agua) han resultado ser más eficientes para producir modificaciones estables en el comportamiento. Se analizan también algunos aspectos neurofisiológicos relacionados con el aprendizaje aversivo y los miedos aprendidos. Si bien se cuenta con datos comparativos de estudios neurofisiológicos en peces, aún no existen referencias con información funcional sobre las bases neurales del aprendizaje aversivo en anfibios. Sin embargo, sí se conoce en anfibios las regiones cerebrales homólogas a las estructuras que en mamíferos mostraron estar implicadas con dicho aprendizaje (especialmente la amígdala), abriendo así el camino para abordar en el futuro el estudio de esta cuestión.Comparative analysis of aversive learning in amphibians: This article develops with a comparative approach a comprehensive and updated review of studies of aversive learning in amphibians. Most of them used electric shock as aversive stimulus, resulting in inconsistent or negative results. Recent research showed that another class of stimuli (saline solutions highly concentrated or warm water) has been more efficient to produce steady changes in behavior. Some neurophysiological aspects of aversive and fear learning are also discussed. While comparative data from neurophysiological studies in fish is available, there are no references on functional information on the neural basis of aversive learning in amphibians. However, it is known in amphibian homologous brain areas to the mammalian structures shown to be involved with such learning (especially the amygdala), opening the way to address the study of this question in the future.Fil: Puddington, Martin Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biologia y Medicina Experimental (i); Argentina; Universidad de Buenos Aires. Facultad de Psicologia; Argentina;Fil: Muzio, Ruben Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biologia y Medicina Experimental (i); Argentina; Universidad de Buenos Aires. Facultad de Psicologia; Argentina

Experimental model in amphibians: unidimensionality of the processing of appetitive and aversive stimuli in associative learning

En el condicionamiento clásico,un animal es expuesto a un estímulo neutro (estímulo condicionado) seguido deun estímulo apetitivo o aversivo (estímulo incondicionado). Sucesivasrepeticiones de esta asociación generan una respuesta frente al estímulo neutrocomo si se tratara del estímulo incondicionado, fenómeno ampliamente exploradoen distintas clases zoológicas (desde invertebrados hasta humanos). En general,los estímulos incondicionados apetitivos y aversivos corresponden a víassensoriales diferentes (típicamente el estímulo utilizado como apetitivo escomida, excitando mayormente receptores gustativos; mientras que como estímuloaversivo se usa una descarga eléctrica, actuando sobre las vías táctiles ynociceptivas). Los estudios en anfibios, en particular el sapo terrestre,reproducen en buena medida los hallazgos en otras especies animales, perotienen características que los hacen únicos al poseer receptores a electrolitosen su piel que intervienen en la regulación del balance hidrosalino corporal.Un sapo expuesto a una solución salina levemente hipertónica (concentraciónmenor a 250 mM NaCl), gana peso y exhibe conductas de aproximación. Alcontrario, si la solución salina es altamente hipertónica (concentraciónsuperior a 400 mM NaCl), pierde peso y exhibe conductas de escape. Así, unmismo estímulo (una solución salina de NaCl), actúa como estímulo apetitivo oaversivo dependiendo de su concentración, característica que denominamosunidimensionalidad de los estímulos motivacionales. El presente trabajodescribe los procedimientos y revisa los resultados de estudios de aprendizajeasociativo en sapos, resaltando el uso de este modelo experimental para elanálisis de los mecanismos neurales implicados en el procesamiento de señalesambientales apetitivas y aversivas.In classical conditioning, an animal is exposed to a neutral stimulus (conditioned stimulus) followed by an appetitive or aversive stimulus (unconditioned stimulus). With successive repetitions of this association, the animal will respond to the neutral stimulus as if it were the unconditioned stimulus. is phenomenon has been widely explored in different zoological classes, covering animal species ranging from mollusks to humans. In most cases, appetitive and aversive unconditioned stimuli correspond to different sensory pathways. For example, the appetitive stimulus typically used is food and the typical aversive stimulus is electric shock. us one type of stimulus will excite the receptors related to the sense of taste, while the other type will do so mostly on the tactile and nociceptive pathways. Studies on amphibians, particularly the terrestrial toad, reproduce to a large extent the findings in other animal species, but they have characteristics that make them unique by having electrolyte receptors in their skin that are involved in the regulation of their body's hydrosaline balance. A toad exposed to a slightly hypertonic saline solution (concentration less than 250 mM NaCl) gains weight and exhibits approximation behaviors. Whereas if it takes contact with a highly hypertonic saline solution (concentration higher than 400 mM NaCl), it loses weight and exhibits escape behaviors. us, the same stimulus (a saline solution of NaCl), can act as an appetitive or aversive stimulus depending on its concentration. is particularity has been called unidimensionality of motivational stimuli. In the present work we describe the procedures and review the results of associative learning studies in toads, highlighting the use of this experimental model for the study of the possible neural mechanisms involved in the processing of appetitive and aversive environmental signals.Fil: Muzio, Ruben Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad de Buenos Aires. Facultad de Psicología; ArgentinaFil: Puddington, Martin Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad de Buenos Aires. Facultad de Psicología; Argentin

Relationship between behavior and activation of brain areas: using the agnoR technique in comparative psychology

Se presenta una revisión de distintos estudios que emplearon la técnica de AgNOR en el campo de las neurociencias del comportamiento. AgNOR es una técnica histológica que permite estudiar la activación cerebral de una región específica. Esta técnica ha sido utilizada en distintos grupos zoológicos que comprenden desde peces y anfibios hasta mamíferos, incluyendo actividad neural tanto en procesos normales como patológicos. En conjunto, la técnica de AgNOR tiene tres notables ventajas con respecto a otras técnicas histológicas como las técnicas inmunohistoquímicas. En primer lugar, su bajo costo. En segundo lugar, su robustez. Finalmente, la posibilidad de ser aplicada con facilidad a cualquier especie animal, siendo esto último particularmente relevante en el campo de la Psicología Comparada. Paradójicamente, a pesar de estas ventajas es una técnica poco conocida y empleada. El propósito de este artículo es contribuir a su difusión dentro de la comunidad decientíficos del comportamiento.In this paper we review the use of AgNOR technique in the field of behavioral neuroscience. AgNOR is a histological technique used to study the activation of a specific brain region. NORs (nucleolar organizer regions) are the cell nucleus compartments where part of the ribosomal synthesis occurs. When a neuron enhances its protein synthesis demand, for example during a learning process, NORs increase their size. Staining with silver nitrate, colors the cell nucleus in brown and the cell nucleolus in dark brown, nearly black. Thus, the size of the nucleus and the nucleolus can be easily measured in histological preparations treated with silver nitrate through any appropriated image processing software. In this manner, AgNOR technique consist in staining the tissue of subjects that have received different treatments and comparing the average size of the nucleolus of a particular brain region, which is an indirect marker of cellular activity. The use of AgNOR technique in the study of neural basis of learning, typically involves: (1) training animals in a particular task, (2) after acquisition, animals in the trained group along with animals from a control condition are sacrificed in order to obtain a brain sample, (3) brains of animals from both conditions are processed and compared. This procedure was successfully used to study telencephalic activation during spatial learning in fish (Carassius auratus). The task consisted in using visual cues to identify the correct exit from a trap. In the case of fish, the histological analysis showed an increase of the nucleolus size in the lateral pallium, proposed as homologous to the mammalian hippocampus, observing that this area is involved in spatial memory. In our laboratory this technique was also used to analyze the neural activity after spatial learning in the terrestrial toad Rhinella arenarum. We conducted several studies where dehydrated animals had to use visual cues to locate the correct position of a water source. In accordance with fish’s data, our results indicated a higher activity of the hippocampal homologous region (the amphibian medial pallium), showing a high degree of functional equivalence. On the other hand, we also studied in toads the telencephalic activity during an aversive learning task. Here, it was observed an increase in the average of NORs size in the ventrolateral telencephalic region, the striatum (proposed as homologous to the mammalian amygdala), also showing a highly preserved functional equivalence. In mammals, AgNOR technique was used with different purposes, such as the study of changes in hippocampal activity during development in rats, the comparison of the basal activity of two regions of the rats hippocampus, the CA1 and the CA3, both strongly related with learning, or the the hippocampal activity in two different situations in which the liver activity was altered (by an artificial cholestasis, or by alcohol consumption). Finally, AgNOR technique was also used in the study of human brain activity of subjects that had committed suicide. On the whole, the AgNOR technique has three distinct advantages over other histological techniques such as the immunohistochemical. First, their low cost. Second, their robustness. Finally, the fact that it can be easily applied to any animal species, which makes it particularly attractive to the field of the Comparative Psychology. But paradoxically, despite these advantages it is a poorly known and used technique. The aim of this paper is to contribute to the diffusion of the AgNOR technique in the community of behavioral scientists, showing that its use has provided a valuable contribution to research in different fields and animal species.Fil: Puddington, Martin Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Muzio, Ruben Nestor. Universidad de Buenos Aires. Facultad de Psicología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentin

Adaptation to the spanish language of the invalidating childhood environmental

El ambiente invalidante es un concepto central del Modelo Biosocial de Marsha Linehan (1993). La Escala de Ambiente Invalidante Infantil (ICES) es un cuestionario diseñado específicamente para evaluar este constructo de manera retrospectiva. Se presenta la adaptación al español de esta escala, junto con datos sobre las cualidades psicométricas del instrumento.La escala exhibió una buena consistencia interna. Según el análisis factorialexploratorio, mostró una estructura de dos factores, diferenciando los ítems relacionados con la reacción negativa del padre hacia la expresión emocional del niño, de los que reflejan la respuesta de apoyo de los padres hacia el niño.Estos primeros ensayos muestran que esta adaptación del ICES es una prueba adecuada para evaluar el ambiente invalidante infantil en sujetos de habla hispana.The invalidating environment is a central concept in Linehan’s Biosocial Theory. The Invalidating Childhood Environment Scale (ICES) is a questionnaire specifically designed to assess this construct retrospectively. We present a Spanish adaptation of the ICES, along with data about its’ psychometric properties. The instrument showed good internal consistency. An explorative factorial analysis revealed a 2 factor structure differentiating the items that assess the parental negative reaction towards the child emotional expression, from the items that reflect a positive and supportive parental behavior. These early trials show that this adaptation of the ICES is a proper instrument to assess the childhood invalidating environment in Spanish speaking population.Fil: Puddington, Martin Miguel. Universidad de Buenos Aires. Facultad de Psicología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Duthu, Florencia. Fundación Foro; ArgentinaFil: Gagliesi, Pablo. Fundación Foro; Argentin

Duration of extinction trials as a determinant of instrumental extinction in terrestrial toads (Rhinella arenarum)

Instrumental learning guides behavior toward resources. When such resources are no longer available, approach to previously reinforced locations is reduced, a process called extinction. The present experiments are concerned with factors affecting the extinction of acquired behaviors in toads. In previous experiments, total reward magnitude in acquisition and duration of extinction trials were confounded. The present experiments were designed to test the effects of these factors in factorial designs. Experiment 1 varied reward magnitude (900, 300, or 100 s of water access per trial) and amount of acquisition training (5 or 15 daily trials). With total amount of water access equated in acquisition, extinction with large rewards was faster (longer latencies in 900/5 than 300/15), but with total amount of training equated, extinction with small rewards was faster (longer latencies in 100/15 than 300/15). Experiment 2 varied reward magnitude (1200 or 120 s of water access per trial) while holding constant the number of acquisition trials (5 daily trials) and the duration of extinction trials (300 s). Extinction performance was lower with small, rather than large reward magnitude (longer latencies in 120/300 than in 1200/300). Thus, instrumental extinction depends upon the amount of time toads are exposed to the empty goal compartment during extinction trials.Fil: Puddington, Martin Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Papini, Mauricio Roberto. Texas Christian University; Estados UnidosFil: Muzio, Ruben Nestor. Universidad de Buenos Aires. Facultad de Psicología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentin

Vulnerability of long-term memory to temporal delays in amphibians

Two experiments with toads were designed to test the hypothesis that extinction (i.e., nonreinforced) performance is a function of time since the last reinforced trial (the memory-decay hypothesis). in experiment 1, groups of toads (rhinella arenarum, formerly bufo arenarum) received 15 daily acquisition trials each reinforced with access to water during 300 s in a runway. after the last acquisition trial, animals were assigned to one of 6 retention intervals: 1, 4, 8, 16, 32, and 64 days. extinction started after the retention interval and lasted 8 additional daily trials. overall extinction performance was a logarithmic function of the length of the retention interval. in experiment 2, two groups of toads received 15 daily acquisition trials each reinforced with access to water in a runway for either 30 or 600 s, thus producing two reward magnitudes. after an 8-day retention interval, the extinction performance in 8 additional daily trials was weaker after training with the small, than with the large reward magnitude. these results support a memory-decay hypothesis and suggest that the instrumental performance of toads is strongly influenced by the time since the last reinforced trial.Fil: Puddington, Martin Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Papini, Mauricio Roberto. Texas Christian University; Estados UnidosFil: Muzio, Ruben Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); Argentin

Telencephalic neural activation following passive avoidance learning in a terrestrial toad

The present study explores passive avoidance learning and its neural basis in toads (Rhinella arenarum). In Experiment 1, two groups of toads learned to move from a lighted compartment into a dark compartment. After responding, animals in the experimental condition were exposed to an 800-mM strongly hypertonic NaCl solution that leads to weight loss. Control animals received exposure to a 300-mM slightly hypertonic NaCl solution that leads to neither weight gain nor loss. After 10 daily acquisition trials, animals in the experimental group showed significantly longer latency to enter the dark compartment. Additionally, 10 daily trials in which both groups received the 300-mM NaCl solution after responding eliminated this group effect. Thus, experimental animals showed gradual acquisition and extinction of a passive avoidance respond. Experiment 2 replicated the gradual acquisition effect, but, after the last trial, animals were sacrificed and neural activation was assessed in five brain regions using AgNOR staining for nucleoli?an index of brain activity. Higher activation in the experimental animals, relative to controls, was observed in the amygdala and striatum. Group differences in two other regions, lateral pallium and septum, were borderline, but nonsignificant, whereas group differences in the medial pallium were nonsignificant.These preliminary results suggest that a striatal-amygdala activation could be a key component of the brain circuit controlling passive avoidance learning in amphibians. The results are discussed in relationto the results of analogous experiments with other vertebrates.Fil: Puddington, Martin Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad de Buenos Aires. Facultad de Psicología; ArgentinaFil: Daneri, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad de Buenos Aires. Facultad de Psicología; ArgentinaFil: Papini, Mauricio Roberto. Texas Christian University; Estados UnidosFil: Muzio, Ruben Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad de Buenos Aires. Facultad de Psicología; Argentin