Putting memory in context: dissociating memories by distinguishing the nature of context.

In recent years, spontaneous recognition tasks have become commonplace methods of assessing memory in animals. Adaptations of these tasks allow us to look at the role of objects, contexts and spatial locations in memory. Recent findings have highlighted that not all types of contexts in these tasks rely on the same neural systems. Similarly, asking different questions about the same types of context can allow the dissociation of neural systems underlying these memories. Here we review the current position in how context is used in such tasks, and we consider the fundamental importance of clearly defining both the nature of the context being used, and the questions asked of it in order to fully appreciate the neural and cognitive mechanisms being studied in such tasks.

Exotic species of zooplankton in the Upper Paraná River floodplain, Daphnia lumholtzi Sars, 1885 (Crustacea: Branchiopoda)

The integrity of aquatic ecosystems is being challenged worldwide by invading species, which has been one of the frequent causes of biodiversity loss. The invader may cause extinctions of vulnerable native species through predation, grazing, competition and habitat alteration. Daphnia lumholtzi G. O. Sars, 1885, a native cladoceran from Australia, Southwestern Asia and North Africa, has recently been found in the Neotropical region. The D. lumholtzi records from the Upper Paraná River floodplain were restricted to the Pombas floodplain lake (22º 47' 55.92" S and 53º 21' 32.58" W) and Pau Véio Backwater (22º 44' 50.76" S and 53º 15' 11.16" W), in 2003 and 2008, respectively. This species can be distinguished from the other Daphnia species registered in Brazil by the conspicuous pointed fornix, the sizes of the tail spine and helmet, and a carapace ventral margin with strong spines. The high temperatures in the tropical region, as well as the increase in water transparency and the decrease in nutrient concentration observed in the environments of the Upper Paraná River floodplain due to the upstream retention by dams, may favor the development of D. lumholtzi populations. The development of populations of D. lumholtzi in natural environments of the Upper Paraná River floodplain may suggest that this species is establishing in the Neotropical region.

A integridade dos ecossistemas aquáticos está sendo desafiada no mundo inteiro por espécies invasoras, as quais tem sido uma das causas freqüentes de perda de biodiversidade. Um invasor pode causar extinções de espécies nativas vulneráveis através de predação, herbivoría, competição e alteração de habitat. Daphnia lumholtzi G. O. Sars, 1885, cladócero nativo da Austrália, sudeste da Ásia e norte da África, recentemente tem sido registrado na região neotropoical. Os registros de D. lumholtzi na planície de inundação do Alto Rio Paraná foram restritos a lagoa das Pombas (22º 47' 55.92" S e 53º 21' 32.58" O) e Ressaco do Pau Véio (22º 44' 50.76" S e 53º 15' 11.16" O), em 2003 e 2008, respectivamente. Esta espécie pode ser diferenciada das demais espécies de Daphnia encontradas no Brasil pelos conspícuos fórnices pontiagudos, tamanho dos espinhos caudal e elmo, e margem ventral com espinhos fortes. As elevadas temperaturas na região tropical, o aumento da transparência da água e a redução das concentrações de nutrientes nos ambientes da planície de inundação do alto rio Paraná, devido aos represamentos a montante, podem estar favorecendo o desenvolvimento de populações de D. lumholtzi. O desenvolvimento de populações de D. lumholtzi em ambientes naturais da planície de inundação do alto rio Paraná pode representar o estabelecimento desta espécie na região neotropical.

The working memory capabilities of the spontaneously hypertensive rat.

This study addresses the working memory capabilities of the male spontaneously hypertensive rat (SHR) strain as compared to the normotensive inbred strain, Wistar Kyoto (WKY), and the out bred Sprague Dawley (SD) rat as a normal control. The objective was to use two working memory tasks in the water maze with different strategic demands: forced alternation (FA) which allows the use of either an allocentric ("place") or egocentric ("response") localisation strategy and delayed matching-to-place (DMP) which requires an allocentric strategy. In the FA task, SHR reached criterion at the same rate as WKY and SD controls and were impaired to the same extent as WKY at the long (1 h) delay. Furthermore, both SHR and WKY were impaired relative to SD when the memory load was increased through the use of massed trials. In the DMP task, the performance of SHR did not differ from that of either of the control strains, either during training or in response to delay. These findings do not provide evidence of short-term memory impairments in the SHR, which is a commonly-used animal model of Attention Deficit Hyperactivity Disorder (ADHD) in humans.

Spontaneously hypertensive, Wistar Kyoto and Sprague-Dawley rats differ in their use of place and response strategies in the water radial arm maze.

This study further characterises the use of mnemonic systems in the spontaneously hypertensive rat (SHR), which is frequently used as a rodent model of attention deficit hyperactivity disorder. The objective of this study was to assess the preference of male SHR, Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats for a place or response strategy when trained on an ambiguous T-maze task, and also to examine whether all strains acquired information about both strategies during ambiguous training, regardless of their preferred strategy. In the first experiment, SHR and WKY showed a preference for a response strategy on the ambiguous T-maze task; in contrast, SD displayed a preference for a place strategy. In the second experiment, all strains demonstrated that they learned information about both the response and place strategies during ambiguous training. However, on a conditioned place preference test SHR did not display as strong a preference for the place arm as WKY and SD. This finding supports previous research in a conditioned cue preference test, in which SHR did not display a preference for the cue associated with the platform. These observations that the strains differ with respect to behavioural strategy in a learning task suggest that they differ in the underlying neural circuitry that serves goal-directed behaviour, and are consistent with SHR having deficits associated with the nucleus accumbens.