Adenosine receptor antagonists including caffeine alter fetal brain development in mice.

Consumption of certain substances during pregnancy can interfere with brain development, leading to deleterious long-term neurological and cognitive impairments in offspring. To test whether modulators of adenosine receptors affect neural development, we exposed mouse dams to a subtype-selective adenosine type 2A receptor (A2AR) antagonist or to caffeine, a naturally occurring adenosine receptor antagonist, during pregnancy and lactation. We observed delayed migration and insertion of γ-aminobutyric acid (GABA) neurons into the hippocampal circuitry during the first postnatal week in offspring of dams treated with the A2AR antagonist or caffeine. This was associated with increased neuronal network excitability and increased susceptibility to seizures in response to a seizure-inducing agent. Adult offspring of mouse dams exposed to A2AR antagonists during pregnancy and lactation displayed loss of hippocampal GABA neurons and some cognitive deficits. These results demonstrate that exposure to A2AR antagonists including caffeine during pregnancy and lactation in rodents may have adverse effects on the neural development of their offspring.

Route and survey processing of topographical memory during navigation.

We investigated the characteristics of route and survey processing of a unique complex virtual environment both at the behavioral and brain levels. Prior to fMRI scanning, participants were trained to follow a route and to learn the spatial relationships between several places, acquiring both route and survey knowledge from a ground-level perspective. During scanning, snapshots of the environment were presented, and participants were required to either indicate the direction to take to follow the route (route task), or to locate unseen targets (survey task). Data suggest that route and survey processing are mainly supported by a common occipito-fronto-parieto-temporal neural network. Our results are consistent with those gathered in studies concerning the neural bases of route versus survey knowledge acquired either from different perspectives or in different environments. However, rather than arguing for a clear distinction between route and survey processing, "mixed" strategies are likely to be involved when both types of encoding take place in the same environment.

Differentiated forgetting rates of spatial knowledge in humans in the absence of repeated testing.

Spatial knowledge, necessary for efficient navigation, comprises route knowledge (memory of the landmarks along a route) and survey knowledge (map-like). Available data on the retention in humans of spatial knowledge show that this does not decline systematically over months or years. Here, two groups of participants elaborated route and survey knowledge during navigation in a complex virtual environment before performing route and survey tasks. Both groups were tested 5 minutes after learning and 3 months later, while one group was also tested 1 week and 1 month later (repeated testing). Performance was similar in both groups on the first testing session, remained stable in the repeated tested group, but decreased in the non-repeated tested group, especially on route tasks. These results are the first to reveal a substantial and selective decline of spatial knowledge, occurring only if there is no possibility of reactivating knowledge along repeated testing.

Comparing distances in mental images constructed from visual experience or verbal descriptions: the impact of survey versus route perspective.

Mental images constructed after visual examination of a spatial configuration or after processing a verbal description of that configuration have been shown to share similar properties, in particular the capacity to preserve metric information contained in the configuration represented. In the present study, we investigated the properties of mental images constructed under learning conditions resulting from the combination of a visual or a verbal mode of acquisition and a survey or route perspective. Participants memorized a virtual environment (a garden containing six objects) under one of four learning conditions: (a) viewing a map of the garden (visual-survey); (b) viewing a video presentation of a journey along the path around the garden (visual-route); (c) listening to a verbal description of the map of the garden (verbal-survey); and (d) listening to a verbal description of the journey around the garden (verbal-route). The participants were then invited to compare the distances separating objects in the garden mentally. Experiment 1, where the pairs of distances to be compared had a common starting point, revealed that the frequency of correct responses was higher, and response times were shorter when participants had learned about the environment visually rather than by a verbal description. The conditions involving a survey perspective resulted in a higher frequency of correct responses and shorter response times than those involving a route perspective. Lastly, a symbolic distance effect was obtained in the first three conditions, in that the greater the difference between the two distances being compared, the higher the frequency of correct responses, and the shorter the response times. Experiment 2, where the pairs of distances had different starting points, replicated these results, although longer response times revealed that the comparison process was more costly. Taken together, these findings support the view that mental spatial representations derived from different sources and adopting different perspectives contain genuine metric properties, except when the verbal modality and the route perspective are combined during learning.