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• Spatial learning in fish are dependent of telencephalic NO. • NO synthesis has scarcely any effect on retrieval process of information in fish. • Inhibition of NO production produced a selective deficit in place learning. Nitric oxide plays a role in the long term potentiation mechanisms produced in the mammalian hippocampus during spatial learning. A great deal of data has demonstrated that the dorsolateral telencephalon of fish could be homologous to the mammalian hippocampus sharing functional similarities. In the present study, we analyzed the role of nitric oxide in spatial learning in teleost fish. In Experiment 1, we studied the effects of the inhibition of telencephalic nitric oxide in goldfish during the acquisition of a spatial task. The results showed that nitric oxide is involved in the learning of a spatial task. Experiment 2 evaluated the effects of the inhibition of telencephalic nitric oxide in goldfish for the retrieval of a learned spatial response. The results indicated that the retrieval of the information previously stored is not dependent of the nitric oxide. The last experiment analyzed the role of the telencephalic nitric oxide in place and cue learning. Results showed a clear impairment in place but not in cue learning. As a whole, these results indicate that fish and mammals, could have a relational memory system mediated by similar biochemical mechanisms. [ABSTRACT FROM AUTHOR]

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]

The present study analyzed the functional activity of granular and agranular insular cortices in contextual specificity of latent inhibition using a conditioned taste aversion paradigm. c-Fos immunolabeling was examined in insular cortex in preexposed and no preexposed groups under similar and different context conditions. Result showed that the exposition to a novel taste increased c-fos activity in insular cortex. However, a context shift caused an increase in immunolabeling in animals preexposed to saccharine. These results suggest insular cortex is part of a complex system to evaluate taste-response, and it may read the meaning of taste stimuli depending on the context. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dls has been associated to S–R or habits and the dms with controlled processes. [•] This study analyzed if dls could be involved in cognitive processes. [•] Results showed that dls is important for the retrieval of overtrained association. [•] However, it is not necessary for retrieval processes requiring increased attention. [•] Data give support for theories of failure retrieval of LI. [ABSTRACT FROM AUTHOR]

Abstract: 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 &y& Elsevier]

Vertebrates use geometric and featural information for spatial navigation. When both geometric and featural cues are available, animals can use a variety of spatial strategies based on this information. To examine the nature of these strategies, we manipulated the spatial relationship between a conspicuous cue and the position of the goal when goldfish (Carassius auratus) were searching for the exit of a rectangular environment with one distinctive wall. Two groups of fish were used, one with the distinctive wall close to the goal and the other with the distinctive wall on the other end of the enclosure. Results showed that fish encoded featural and geometric information in both conditions but the spatial relationship between the goal and the distinctive wall influences the characteristics of the encoding of the spatial cues and the strategy used to locate the goal. These results suggest that fish in both procedures use the local featural cues associated with the goal instead of the whole set of spatial cues as previous studies propose. [ABSTRACT FROM AUTHOR]

Abstract: There is some experimental evidence that the pallial areas of a fish''s brain are involved in distincted learning functions. Recently published data suggest that the medial pallium is essential for avoidance learning and the lateral pallium is crucial for spatial learning and is also involved in temporal aspects of the learning processes. This data joined to the proposal of homologies between medial and lateral fish pallia and pallial amygdala and hippocampus respectively, suggest that the pallial areas could have preserved their functions throughout vertebrates’ evolution. However, the functional implication of dorsal pallium that has been proposed as homologous to mammalian isocortex and transition cortex is largely unknown. In this study we analyze the role of dorsal pallium in trace and non-trace avoidance learning. Our results show the implication of this area in trace conditioning, but not in non-trace conditioning. This result allows discussion of homology proposals among lateral, dorsal, and medial pallia and hippocampus, isocortex, and pallial amygdala respectively. [Copyright &y& Elsevier]

Neuroanatomical evidence indicates that the lateral pallium (LP) of ray-finned fishes could be homologous to the hippocampus of mammals and birds. Recent studies have found that hippocampus of mammals and birds is critical for learning geometric properties of space. In this work, we studied the effects of lesions to the lateral pallium of goldfish on the encoding of geometric spatial information. Goldfish with telencephalic lesions were trained to search for a goal in a rectangular-shaped arena containing one different wall that served as the only distinctive environmental feature. Although fish with lateral pallium lesions learned the task even faster than sham and medial pallium (MP)-lesioned animals, subsequent probe trials showed that they were insensitive to geometric information. Sham and medial pallium-lesioned animals could use both geometric and feature information to locate the goal. By contrast, fish with lateral palium lesions relied exclusively on the feature information provided by the wall of a different colour. These results indicate that lesions to the lateral pallium of goldfish, like hippocampal lesions in mammals and birds, selectively impair the encoding of geometric spatial information of environmental space. Thus, the forebrain structures of teleost fish that are neuroanatomically equivalent to the mammalian and avian hippocampus also share a central role in supporting spatial cognition. Present results suggest that the presence of a hippocampal-dependent memory system implicated in the processing of geometric spatial information is an ancient feature of the vertebrate forebrain that has been conserved during the divergent evolution of different vertebrate groups. [ABSTRACT FROM AUTHOR]

Abstract: The central representation of geomagnetic information in the avian brain continues to challenge researchers. Although the homing pigeon hippocampal formation primarily participates in the map-like representation of landmarks, some suggestive data indicate that it may also participate in spatial behavior guided by geomagnetic information. Forty-four isolated neurons were recorded from the hippocampal formation of homing pigeons trained to shuttle between two goal locations under changing (direction and intensity, and direction only) magnetic field conditions. Of the 37 slow-firing cells sampled (<14spikes/s), none displayed a change in firing rate at the time of magnetic field transitions or during different ambient magnetic field conditions. By contrast, three of seven fast firing cells (>17spikes/s) clearly displayed a phasic increase in firing during at least one of the magnetic field transitions used. The results are consistent with the hypothesis that a subset of hippocampal formation neurons receives information regarding changes in the earth''s magnetic field that may be used to guide behavior. [Copyright &y& Elsevier]

Abstract: Recent results have demonstrated that the mammalian hippocampus and the dorso-lateral telencephalon of ray-finned fishes share functional similarities in relation to spatial memory systems. In the present study, we investigated whether the physiological mechanisms of this hippocampus-dependent spatial memory system were also similar in mammals and ray-finned fishes, and therefore possibly conserved through evolution in vertebrates. In Experiment 1, we studied the effects of the intracranial administration of the noncompetitive NMDA receptor antagonist MK-801 during the acquisition of a spatial task. The results indicated dose-dependent drug-induced impairment of spatial memory. Experiment 2 evaluated if the MK-801 produced disruption of retrieval of a learned spatial response. Data showed that the administration of MK-801 did not impair the retrieval of the information previously stored. The last experiment analyzed the involvement of the telencephalic NMDA receptors in a spatial and in a cue task. Results showed a clear impairment in spatial learning but not in cue learning when NMDA receptors were blocked. As a whole, these results indicate that physiological mechanisms of this hippocampus-dependent system could be a general feature in vertebrate, and therefore phylogenetically conserved. [Copyright &y& Elsevier]

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]

Goldfish (Carassius auratus) were trained in different place-finding tasks as a means of analyzing their ability to encode the geometric and the featural properties of the environment. Results showed that goldfish could encode and use both geometric and featural information to navigate. Goldfish trained in a maplike, or relational, procedure encoded both types of information in a single representation. In contrast, fish trained in a directly cued procedure developed 2 independent and competing strategies. These results suggest that the geometric properties of the spatial arrangement and discrete landmarks are sensitive to encoding in a maplike or relational system, whereas different sources of spatial information are encoded in a single and flexible representation of the environment. [ABSTRACT FROM AUTHOR]

Surprising violations of outcome expectancies have long been known to enhance the associability of Pavlovian cues; that is, the rate at which the cue enters into further associations. The adaptive value of such enhancements resides in promoting new learning in the face of uncertainty. However, it is unclear whether associability enhancements reflect increased associative plasticity within a particular behavior system, or whether they can facilitate learning between a cue and any arbitrary outcome, as suggested by attentional models of conditioning. Here, we show evidence consistent with the latter hypothesis. Violating the outcome expectancies generated by a cue in an appetitive setting (feeding behavior system) facilitated subsequent learning about the cue in an aversive setting (defense behavior system). In addition to shedding light on the nature of associability enhancements, our findings offer the neuroscientist a behavioral tool to dissociate their neural substrates from those of other, behavior system- or valence-specific changes. Moreover, our results present an opportunity to utilize associability enhancements to the advantage of counterconditioning procedures in therapeutic contexts. [ABSTRACT FROM AUTHOR]

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 maplike or relational procedure and a directly cued procedure. However, K. Cheng's medal 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. [ABSTRACT FROM AUTHOR]

Abstract: The subiculum is the main structure linking the hippocampus with several cortical and subcortical areas. In particular, ventral subiculum might act as an interface between the hippocampus, a contextual information processor, and cortical and subcortical processing systems related to motivation, such as the ventral striatum. Electrophysiological studies have shown a relationship between ventral subiculum and ventral striatum, namely a strong influence on mesolimbic system and the activity of dopaminergic neurons in the ventral tegmental area. Dopamine activity in this system has received special attention for its role in the latent inhibition phenomenon. However, the functional relationship between mesolimbic system and this behavioral process remains unclear. Two experiments were performed to analyze the role of ventral subiculum on latent inhibition. The results showed that ventral subiculum is involved in contextual processing that modulates the expression of latent inhibition. These findings are consistent with electrophysiological studies revealing the ventral subiculum as a structure modulating the mesolimbic DA system and DA release in the nucleus accumbens. [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]

Attentional biomarkers in attention deficit hyperactivity disorder are difficult to detect using only behavioural testing. We explored whether attention measured by a low-cost EEG system might be helpful to detect a possible disorder at its earliest stages. The GokEvolution application was designed to train attention and to provide a measure to identify attentional problems in children early on. Attention changes registered with NeuroSky MindWave in combination with the CARAS-R psychological test were used to characterise the attentional profiles of 52 non-ADHD and 23 ADHD children aged 7 to 12 years old. The analyses revealed that the GokEvolution was valuable in measuring attention through its use of EEG–BCI technology. The ADHD group showed lower levels of attention and more variability in brain attentional responses when compared to the control group. The application was able to map the low attention profiles of the ADHD group when compared to the control group and could distinguish between participants who completed the task and those who did not. Therefore, this system could potentially be used in clinical settings as a screening tool for early detection of attentional traits in order to prevent their development. [ABSTRACT FROM AUTHOR]

• Goal directed behavior and habit are differentially affected for 2 models of PD. • 6-OHDA neurotoxic model disrupted Stimulus-Response mechanism. • LPS neuroinflammatory model facilitated habit formation. • Both models are involved in Substantia Nigra and striatum dopamine depletion. • Both models could help to understand different stages in PD. Instrumental conditioning involves two different processes: Goal-directed behavior, characterized by its dependence on the causal relationship between action and outcome and the sensitivity of actions to changes in the value of the outcome; and habits, characterized for its persistence and insensitivity to changes after conditioning. It is known that the dopaminergic system is involved in both kind of learning. The present experiments analyzed two animal models of Parkinson's disease. The 6-OHDA model causes selective damage of the catecholaminergic neurons, specifically affecting the dopaminergic neurons in nigro-striatal system. This model simulates degenerative process symptomatology of Parkinson's disease. On the other hand, the LPS model generates an inflammation process in the infusion area. This model simulates the early symptoms of this disorder, including neuroinflammation and microglia activation. In order to validate both parkinsonian models, we studied if 6-OHDA and LPS models cause the same behavioral effects. The results showed that the 6-OHDA model interfered with the process involved in habit formation. In contrast, animals treated with LPS showed a goal-directed learning deficit. Differences between these models could be due to the different effects on Substantia Nigra neurons. 6-OHDA model might disrupt the nigrostriatal pathway, while LPS could interfere on efferences and afferences to Substantia Nigra. [ABSTRACT FROM AUTHOR]