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Recent studies have found that hippocampus of mammals and birds and the lateral pallium of the fish telencephalon are critical for learning the geometric properties of space. Nevertheless, other studies suggest that navigation based on geometric information is primarily supported by proximal cues near the target location. According to this hypothesis, animals could use a taxon strategy to navigate an environment where only geometric cues are available and the results from lesion studies could be masking other effects related to the use of featural information. In the present study, we examined the effects of lesions to the lateral pallium of goldfish in the encoding of geometric spatial information. Goldfish with telencephalic lesions were trained to search for a goal in a rectangular-shaped arena with either one or two possible goals. Lateral pallium lesions do not interfere with goal location when the geometric information defined the goal unambiguously. Present results suggest that the geometric information is sensitive to be encoded in taxon strategies and therefore it could not depend directly on the correct functioning of the hippocampal system., (Copyright © 2011 Elsevier B.V. All rights reserved.)

On the basis of results of a probe trial in 2 different experiments, K. Cheng (2005) has proposed a common mechanism for orientation in fish trained in both a map-like or relational procedure and a directly cued procedure. However, K. Cheng's model is inconsistent with previous results of goldfish (Carassius auratus) trained in these 2 tasks. Given that K. Cheng's proposal assumes that fish choose the goal by using a matching strategy in which they try to match as many properties as possible, including geometric and featural properties, future research is necessary to clarify what properties of the environmental space are codified and used for navigation., (((c) 2005 APA, all rights reserved).)

Sign and goal tracker animals show different behavioral patterns in response to conditioned stimuli, which may be driven by different neural circuits involved in processing stimuli. Here, we explored whether sign and goal-tracker profiles implicated different brain regions and responses to incentive salience of stimuli. We performed three experiments using male Wistar rats. Experiment 1 showed that lesioning the medial prefrontal cortex increased the prevalence of the goal-tracker phenotype. Experiment 2 assessed the developmental trajectory of the salience incentive attribution to a conditioned stimulus, showing that increased incentive salience of stimuli increased the prevalence of the sign-tracker phenotype in mature, but not preadolescent rats. In experiment 3, the functional impact of the medial prefrontal cortex circuits was analyzed with a latent inhibition procedure. Sign tracker rats showed a reduced latent inhibition to stimuli previously exposed when compared to goal tracker or intermediate rats. The overall results of this study highlight a key role of the medial prefrontal cortex for sign tracking behavior. The expression of sign and goal tracker phenotypes changed after lesion to the medial prefrontal cortex (experiment 1), differed across development (experiment 2), and showed differences in the attentional processes to previously exposed stimuli, as preexposure to CS was ineffective in sign tracker animals (experiment 3). These data indicate that the responses to the incentive salience of stimuli in sign tracker and goal tracker profiles are likely driven by different neural circuitry, with a different role of prefrontal cortical function. [ABSTRACT FROM AUTHOR]

Recent studies support the idea that stimulus processing in latent inhibition can vary during the course of preexposure. Controlled attentional mechanisms are said to be important in the early stages of preexposure, while in later stages animals adopt automatic processing of the stimulus to be used for conditioning. Given this distinction, it is possible that both types of processing are governed by different neural systems, affecting differentially the retrieval of information about the stimulus. In the present study we tested if a lesion to the dorso-lateral striatum or to the medial prefrontal cortex has a selective effect on exposure to the future conditioned stimulus (CS). With this aim, animals received different amounts of exposure to the future CS. The results showed that a lesion to the medial prefrontal cortex enhanced latent inhibition in animals receiving limited preexposure to the CS, but had no effect in animals receiving extended preexposure to the CS. The lesion of the dorso-lateral striatum produced a decrease in latent inhibition, but only in animals with an extended exposure to the future conditioned stimulus. These results suggest that the dorsal striatum and medial prefrontal cortex play essential roles in controlled and automatic processes. Automatic attentional processes appear to be impaired by a lesion to the dorso-lateral striatum and facilitated by a lesion to the prefrontal cortex. [ABSTRACT FROM AUTHOR]

The geometric properties of bounded space have attracted considerable attention as a source of spatial information that can guide goal navigation. Although the use of geometric information to navigate has been observed in every species studied to date, the neural mechanisms that support the representation of geometric information are still debated. With the purpose of investigating this topic, we trained pigeons with lesion to the hippocampal formation to search for food in a rectangular-shaped arena containing one wall of a different color that served as the only distinctive environmental feature. Although lesioned pigeons learned the task even faster than control animals, probe trials showed that they were insensitive to geometric information. Control animals could encode and use both geometric and feature information to locate the goal. By contrast, lesioned pigeons relied exclusively on the feature information provided by the wall of a different color. The results indicate that the avian hippocampal formation is critical for learning the geometric properties of space in homing pigeons. [ABSTRACT FROM AUTHOR]