Hippocampal Interneurons are Required for Trace Eyeblink Conditioning in Mice / 神经科学通报·英文版

While the hippocampus has been implicated in supporting the association among time-separated events, the underlying cellular mechanisms have not been fully clarified. Here, we combined in vivo multi-channel recording and optogenetics to investigate the activity of hippocampal interneurons in freely-moving mice performing a trace eyeblink conditioning (tEBC) task. We found that the hippocampal interneurons exhibited conditioned stimulus (CS)-evoked sustained activity, which predicted the performance of conditioned eyeblink responses (CRs) in the early acquisition of the tEBC. Consistent with this, greater proportions of hippocampal pyramidal cells showed CS-evoked decreased activity in the early acquisition of the tEBC. Moreover, optogenetic suppression of the sustained activity in hippocampal interneurons severely impaired acquisition of the tEBC. In contrast, suppression of the sustained activity of hippocampal interneurons had no effect on the performance of well-learned CRs. Our findings highlight the role of hippocampal interneurons in the tEBC, and point to a potential cellular mechanism subserving associative learning.

Navegación espacial en niños en un laberinto circular: la interacción entre diferentes marcos geométricos de referencia / Spatial Navigation in Children in a Circular Maze: he Interaction between different frames of reference

Diversas teorías intentan explicar las estrategias de navegación que utilizan los niños menores de 6 años, siendo el uso de la geometría el principal tema de debate. El objetivo del estudio fue estudiar los sistemas de navegación espacial en niños de 3 y 6 años y su utilización de diversos marcos de referencia geométricos y de la guía proximal. Los niños emplearán la geometría como predice la teoría de la combinación adaptativa. Dos grupos de 20 niños de 6 y 3 años, respectivamente. Se utilizó un laberinto circular donde los niños tenían que buscar un objeto escondido. Se formaron dos grupos: desorientados respecto a la habitación exterior y no desorientados. Los niños de 3 años necesitaron la información geométrica de la habitación exterior, los de 6 años también son capaces de emplear la guía proximal y pueden usar la geometría del recinto experimental si su aprendizaje se ha realizado en presencia de la geometría de la habitación. Los resultados apoyan la teoría de la combinación adaptativa, en lugar de la de módulos geométricos. Por otro lado, la presencia de marcos de referencia geométricos fiables facilita la utilización de otros tipos de claves que en su ausencia no son empleadas.

Various theories attempt to explain the strategies of navigation used by children under 6 years old, principle amongst which is the use of geometry. The aim of this study was the spatial orientation applied by 3 and 6-year-old children and their use of different geometric frames of reference and the proximal guide. Children use geometry as the theory of the adaptive combination predicts. 20 six-year-old children and 20 three-year-old children. The experimental study used a circular maze in which the children had to find a hidden object. The children were split into two groups: those who were disoriented with respect to the outer room, and those who were not disoriented. The 3-year-old children need the geometric information of the outer room, the 6-year-old are also able to use the proximal guide and can use the geometry of the experimental enclosure when their learning has made available the geometry of the room. The results support the theory of adaptive combination, rather than the geometric modules. Furthermore, the presence of reliable geometric frames of reference facilitates the use of other types of keys that are not used in their absence.

Extinción y renovación de la memoria espacial en humanos / Extinction and renewal of spatial memory in humans

Participantes humanos fueron entrenados en un laberinto virtual de agua para localizar en dos fases sucesivas una plataforma cuya ubicación fue específica a la fase vigente. Posteriormente realizaron una prueba sin plataforma. El Grupo ABA realizó la primera fase y la prueba en un contexto A, y la segunda fase en un contexto B. El Grupo ABB realizó la primera fase en el contexto A, y la segunda fase y la prueba en el contexto B. Ambos grupos localizaron la plataforma en cada fase. Durante la prueba, la última ubicación de la plataforma fue preferida por el Grupo ABB, mientras que la primera ubicación fue preferida por el Grupo ABA. Estos resultados indican renovación de la memoria espacial en humanos.

Human participants were trained in a virtual water maze throughout two immediate phases, in order to locate a platform which particular location was specific to each phase. Afterwards, a trial without the platform was conducted.The ABA group experienced phase 1 and the test trial in Context A, while the second phase occurred in Context B. The ABB group received the first phase in Context A and the phase 2 and test trial training in Context B. Both groups had to locate the platform in each phase. During the test trial, the last platform location was preferred by the ABB group but the first platform location was preferred by the group ABA. These results suggest renewal of spatial memory in humans.

Determining sensitive stages for learning to detect predators in larval bronzed frogs: Importance of alarm cues in learning.

Successful survival and reproduction of prey organisms depend on their ability to detect their potential predators accurately and respond effectively with suitable defences. Predator detection can be innate or can be acquired through learning.We studied prey–predator interactions in the larval bronzed frogs (Sylvirana temporalis), which have the innate ability to detect certain predators. We conducted a series of experiments to determine if the larval S. temporalis rely solely on innate predator detection mechanisms or can also learn to use more specific cues such as conspecific alarm cues for the purpose. The results of our study clearly indicate that larval S. temporalis use both innate and learned mechanisms for predator detection. Predator-naïve tadpoles could detect kairomones alone as a potential threat and responded by reducing activity, suggesting an innate predator detection mechanism. Surprisingly, predator-naïve tadpoles failed to detect conspecific alarm cues as a potential threat, but learned to do so through experience. After acquiring the ability to detect conspecific alarm cues, they could associate novel predator cues with conspecific alarm cues. Further, post feeding stages of larval S. temporalis are sensitive for learning to detect conspecific alarm cues to label novel predators.

Magnitude and valence of outcomes as determinants of causal judgments / Magnitud y valencia de las consecuencias como determinantes de la atribución de juicios causales

This study examines if the blocking effect paradigm predicts causal judgments when consequences of events vary in valence and magnitude. The procedure consists on presenting participants with reports describing the positive or negative effects produced by different substances, when these are consumed either separately or simultaneously with others. Two groups of participants were exposed to high and low magnitude consequences, respectively. The extent to which behavior with respect to causal judgments is consistent with the predictions of the blocking effect was evaluated in in both groups using two types of questions. One of them asked whether or not substance X produced the effect, while the other one asked about the probability of substance X producing the effect. Differences in causal judgments as a product of logical or intuitive reasoning were examined. Even though the blocking effect was not observed, a significant interaction was obtained between the factors valence and experimental condition (blocking and control). Findings are discussed in terms of the differences between associative learning in humans and in non-human animals, and in terms of the theoretical differences between evaluative conditioning and predictive or causal conditioning.

El propósito de este proyecto es examinar si el modelo de bloqueo predice la atribución de juicios causales al variar la valencia y la magnitud de las consecuencias. El arreglo experimental consiste en la presentación de reportes sobre los efectos positivos y negativos que producen diferentes sustancias al ser consumidas solas o en conjunto con otras. Los participantes del primer grupo estuvieron expuestos a consecuencias de alta magnitud y los del segundo grupo, a consecuencias de baja magnitud. Se evaluó si la atribución de causalidad es consistente con las predicciones del efecto bloqueo mediante dos tipos de pregunta: una pregunta acerca si la sustancia X produce o no el efecto, y una pregunta sobre la probabilidad de que X produzca el efecto. Se examinaron las diferencias en los juicios causales cuando las atribuciones son producto del razonamiento lógico o intuitivo. Si bien no se observó evidencia del efecto bloqueo, se obtuvieron efectos de interacción entre los factores valencia y condición experimental (sustancias bloqueo y control). Se discuten los hallazgos en términos de las diferencias entre el aprendizaje asociativo en humanos y animales no humanos, y en términos de las implicaciones sobre las diferencias teóricas entre el condicionamiento evaluativo y el condicionamiento predictivo.

Aprendizagem associativa em fêmeas e machos de Anastrepha obliqua (Diptera, Tephritidae) com diferentes idades e estados nutricionais / Associative learning in anastrepha obliqua (diptera, tephritidae) wild females and males of different ages and nutritional states

Adult Anastrepha obliqua fruit-flies need protein sources to promote sexual maturation and egg production. Learning can be a mechanism to improve the foraging behavior to acquire this nutrient. Learning could be defined as the acquisition of a new representation of neuronal information, and it can only be indirectly observed through its potential effect on behavior. In the present study, the occurrence or not of associative learning in A. obliqua females and males of different ages and nutritional states concerning sucrose (carbohydrate) and brewer´s yeast (protein source) was observed. Associative learning for sucrose was demonstrated in young and old females and males only when deprived of food for 2 days after the experience period. As concerns yeast, the associative learning was demonstrated in deprived young and old females only.

Adultos de moscas-das-frutas, Anastrepha obliqua, necessitam de fontes proteicas para promover a maturação sexual e produção de ovos. A aprendizagem pode ser um mecanismo para melhorar o comportamento de forrageamento na aquisição deste nutriente. Dentre as diferentes definições de aprendizagem uma delas a define como a aquisição de uma nova representação de informação neuronal e pode ser indiretamente observada através de seu efeito potencial no comportamento. No presente estudo, a ocorrência ou não de aprendizagem em fêmeas e machos de A. obliqua de diferentes idades e estados nutricionais foram observadas em relação à sacarose (carboidrato) e lêvedo de cerveja (fonte de proteína). A aprendizagem associativa para sacarose foi demonstrada em fêmeas e machos jovens e velhos somente quando privados de alimento por dois dias depois do período de experiência. Em relação ao lêvedo, a aprendizagem associativa foi demonstrada em fêmeas jovens e velhas, mas não nos machos.

The time course of ethanol tolerance: associative learning

The effect of different contextual stimuli on different ethanol-induced internal states was investigated during the time course of both the hypothermic effect of the drug and of drug tolerance. Minimitters were surgically implanted in 16 Wistar rats to assess changes in their body temperature under the effect of ethanol. Rat groups were submitted to ethanol or saline trials every other day. The animals were divided into two groups, one receiving a constant dose (CD) of ethanol injected intraperitoneally, and the other receiving increasing doses (ID) during the 10 training sessions. During the ethanol training sessions, conditioned stimuli A (tone) and B (buzzer) were presented at "state +" (35 min after drug injection) and "state -" (170 min after drug injection), respectively. Conditioned stimuli C (bip) and D (white noise) were presented at moments equivalent to stimuli A and B, respectively, but during the saline training sessions. All stimuli lasted 15 min. The CD group, but not the ID group, developed tolerance to the hypothermic effect of ethanol. Stimulus A (associated with drug "state +") induced hyperthermia with saline injection in the ID group. Stimulus B (associated with drug "state -") reduced ethanol tolerance in the CD group and modulated the hypothermic effect of the drug in the ID group. These results indicate that contextual stimuli acquire modulatory conditioned properties that are associated with the time course of both the action of the drug and the development of drug tolerance.