Hippocampal formation is required for geometric navigation in pigeons

Is there an innate geometric module? Effects of experience with angular geometric cues on spatial re-orientation based on the shape of the environment

Non-human animals and human children can make use of the geometric shape of an environment for spatial reorientation and in some circumstances reliance on purely geometric information (metric properties of surfaces and sense) can overcome the use of local featural cues. Little is known as to whether the use of geometric information is in some way reliant on past experience or, as would likely be argued by advocates of the notion of a geometric module, it is innate. We tested the navigational abilities of newborn domestic chicks reared in either rectangular or circular cages. Chicks were trained in a rectangular-shaped enclosure with panels placed at the corners to provide salient featural cues. Rectangular-reared and circular-reared chicks proved equally able to learn the task. When tested after removal of the featural cues, both rectangular- and circular-reared chicks showed evidence that they had spontaneously encoded geometric information. Moreover, when trained in a rectangular-shaped enclosure without any featural cues, chicks reared in rectangular-, circular-, or c-shaped cages proved to be equally able to learn and perform the task using geometric information. These results suggest that effective use of geometric information for spatial reorientation does not require experience in environments with right angles and metrically distinct surfaces, thus supporting the hypothesis of a predisposed geometric module in the animal brain.

Asymmetrical participation of the left and right hippocampus for representing environmental geometry in homing pigeons

Control, right and left HF lesioned homing pigeons (Columba livia) were trained to locate a goal in one corner of a rectangular enclosure with a distinctive feature cue. Probe tests revealed that all groups were able to encode in parallel geometric (enclosure shape) and feature information, and in the absence of one of them, they could us the other to locate the goal. However, left HF lesioned pigeons learned the task at a faster rate, and when the geometric and feature information were set in conflict, they relied more on the feature cue compared to control and right HF lesioned pigeons. It was also found that pigeons, independent of group, trained to a goal adjacent to the feature cue learned the task in fewer sessions and relied more on feature information compared to pigeons trained to a goal opposite the feature cue. The latter group relied more on geometric information. The results support the hypothesis that the left HF plays a more important role in the representation of a goal location with respect to environmental shape/geometry. We further propose that the observed functional asymmetry can be explained by the lateralized properties of the pigeon tectofugal visual system.

Telencephalon and geometric space in goldfish

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.

Mammalian and avian neuroanatomy and the question of consciousness in birds

Some birds display behavior reminiscent of the sophisticated cognition and higher levels of consciousness usually associated with mammals, including the ability to fashion tools and to learn vocal sequences. It is thus important to ask what neuroanatomical attributes these taxonomic classes have in common and whether there are nevertheless significant differences. While the underlying brain structures of birds and mammals are remarkably similar in many respects, including high brain-body ratios and many aspects of brain circuitry, the architectural arrangements of neurons, particularly in the pallium, show marked dissimilarity. The neural substrate for complex cognitive functions that are associated with higher-level consciousness in mammals and birds alike may thus be based on patterns of circuitry rather than on local architectural constraints. In contrast, the corresponding circuits in reptiles are substantially less elaborated, with some components actually lacking, and in amphibian brains, the major thalamopallial circuits involving sensory relay nuclei are conspicuously absent. On the basis of these criteria, the potential for higher-level consciousness in these taxa appears to be lower than in birds and mammals.

Calcium-binding proteins, neuronal nitric oxide synthase, and GABA help to distinguish different pallial areas in the developing and adult chicken. I. Hippocampal formation and hyperpallium

To better understand the formation and adult organization of the avian pallium, we studied the expression patterns of gamma-aminobutyric acid (GABA), calbindin (CB), calretinin (CR), and neuronal nitric oxide synthase (nNOS) in the hippocampal formation and hyperpallium of developing and adult chicks. Each marker showed a specific spatiotemporal expression pattern and was expressed in a region (area)-specific but dynamic manner during development. The combinatorial expression of these markers was very useful for identifying and following the development of subdivisions of the chicken hippocampal formation and hyperpallium. In the hyperpallium, three separate radially arranged subdivisions were present since early development showing distinct expression patterns: the apical hyperpallium (CB-rich); the intercalated hyperpallium (nNOS-rich, CB-poor); the dorsal hyperpallium (nNOS-poor, CB-moderate). Furthermore, a novel division was identified (CB-rich, CR-rich), interposed between hyper- and mesopallium and related to the lamina separating both, termed laminar pallial nucleus. This gave rise at its surface to part of the lateral hyperpallium. Later in development, the interstitial nucleus of the apical hyperpallium became visible as a partition of the apical hyperpallium. In the hippocampal formation, at least five radial divisions were observed, and these were compared with the divisions proposed recently in adult pigeons. Of note, the corticoid dorsolateral area (sometimes referred as caudolateral part of the parahippocampal area) contained CB immunoreactivity patches coinciding with Nissl-stained cell aggregates, partially resembling the patches described in the mammalian entorhinal cortex. Each neurochemical marker was present in specific neuronal subpopulations and axonal networks, providing insights into the functional maturation of the chicken pallium.

Spared feature-structure discrimination but diminished salience of environmental geometry in hippocampal-lesioned homing pigeons (Columba livia)

Homing pigeons (Columba livia) were trained to locate a goal in one corner of a rectangular arena by either its shape (geometry) or the left-right configuration of colored features located in each corner (feature structure). Control and hippocampal-lesioned pigeons learned at a similar rate, but the control birds made proportionally more geometric errors during acquisition. On conflict probe trials, the control birds preferred geometrically correct corners, whereas the hippocampal-lesioned birds displayed a greater preference for the correct corner defined by feature structure. On geometry-only probe trials, both groups demonstrated an ability to identify the goal location. Hippocampal lesions do not interfere with goal recognition by the feature structure of local cues but diminish the salience of arena shape.

Adult but not aged C57BL/6 male mice are capable of using geometry for orientation

Geometry, e.g., the shape of the environment, can be used by numerous animal species to orientate, but data concerning the mouse are lacking. We addressed the question of whether mice are capable of using geometry for navigating. To test whether aging could affect searching strategies, we compared adult (3- to 5-mo old) and aged (20- to 21-mo old) C57BL/6 male mice. We established a water maze task in which spatial information is provided by one landmark proximal to the target (featural information) and by the rectangular shape of the maze (geometric information). By means of probe trials in which we manipulated the presence of these two kinds of information, we show that adult mice can use both geometry and landmark to orientate. By contrast, aged mice do not use geometry and rely exclusively on the landmark to locate the platform. This study provides the first evidence that mice are capable of using geometric information for orientation and that this ability declines in aged animals.

Potentiation, overshadowing, and blocking of spatial learning based on the shape of the environment

Rats were trained in Experiment 1 to find a submerged platform in 1 corner of either a rectangular or a kite-shaped pool. When the walls creating this corner were a different color than the opposite walls, then learning about the shape of the pool was potentiated in the kite but not in the rectangle. Experiments 2-4 revealed that learning about the rectangle can be overshadowed and blocked when information about the wall color indicates the location of the platform. The results mimic findings that have been obtained with Pavlovian conditioning, and they challenge the claim that learning about the shape of the environment takes places in a dedicated geometric module.

Small-scale spatial cognition in pigeons

Roberts and Van Veldhuizen's [Roberts, W.A., Van Veldhuizen, N., 1985. Spatial memory in pigeons on the radial maze. J. Exp. Psychol.: Anim. Behav. Proc. 11, 241-260] study on pigeons in the radial maze sparked research on landmark use by pigeons in lab-based tasks as well as variants of the radial-maze task. Pigeons perform well on open-field versions of the radial maze, with feeders scattered on the laboratory floor. Pigeons can also be trained to search precisely for buried food. The search can be based on multiple landmarks, but is sometimes controlled by just one or two landmarks, with the preferred landmarks varying across individuals. Findings are similar in landmark-based searching on a computer monitor and on a lab floor, despite many differences between the two kinds of tasks. A number of general learning principles are found in landmark-based searching, such as cue competition, generalization and peak shift, and selective attention. Pigeons also learn the geometry of the environment in which they are searching. Neurophysiological studies have implicated the hippocampal formation (HF) in avian spatial cognition, with the right hippocampus hypothesized to play a more important role in the spatial recognition of goal locations. Most recently, single-cell recording from the pigeon's hippocampal formation has revealed cells with different properties from the classic 'place' cells of rats, as well as differences in the two sides of the hippocampus.

The study of hemispheric specialization for categorical and coordinate spatial relations in animals

This article reviews some of the most representative studies in the animal literature pertaining to the processing of categorical and coordinate spatial relations and of their hemispheric control. Although the processing of coordinate and categorical cognition has been studied directly with nonhuman primates, experiments on cerebral asymmetries in avian spatial orientation are also reviewed. It turns out that Kosslyn's model concerning the existence of two types of spatial representations each with a specific lateralization pattern has received some support in nonhuman primates and is only weakly verified in the avian studies. Procedural differences might explain some but certainly not all of the discrepancies between the human and the animal literature. It is especially the laterality hypothesis of a left hemisphere advantage in relational cognition and a right hemispheric superiority in judging absolute distances that is not supported by the animal data. Studies specifically addressing Kosslyn's hypotheses and bearing on the use of similar stimuli, procedures and methods between the species tested are needed in order to lead to firm conclusions about the existence of coordinate versus categorical processing systems in animals.

The influence of hippocampal lesions on the discrimination of structure and on spatial memory in pigeons (Columba livia)

Pigeons (Columba livia) were trained with a spatial structural discrimination, which was based on the spatial relationship among the components of a pattern, and a feature-binding structural discrimination, which was based on how different visual features within a pattern were combined. Neither discrimination was impaired by damage to the hippocampus and area parahippocampalis. The lesions impaired performance on a spatial working memory and a spatial reference memory task in open field. The results indicate an intact hippocampus is not essential for the solution of structural discriminations in pigeons and the hippocampus is important for processing some types of spatial information--that used in navigation, but not other types--that used in spatial structural discriminations.

Shape Parameters Explain Data From Spatial Transformations: Comment on Pearce et al. (2004) and Tommasi & Polli (2004)

In 2 recent studies on rats (J. M. Pearce, M. A. Good, P. M. Jones, & A. McGregor, see record 2004-12429-006) and chicks (L. Tommasi & C. Polli, see record 2004-15642-007), the animals were trained to search in 1 corner of a rectilinear space. When tested in transformed spaces of different shapes, the animals still showed systematic choices. Both articles rejected the global matching of shape in favor of local matching processes. The present authors show that although matching by shape congruence is unlikely, matching by the shape parameter of the 1st principal axis can explain all the data. Other shape parameters, such as symmetry axes, may do even better. Animals are likely to use some global matching to constrain and guide the use of local cues; such use keeps local matching processes from exploding in complexity.

Goldfish (Carassius auratus) matching geometric and featural cues: A reinterpretation of some of the data of Vargas, López, Salas, and Thinus-Blanc (2004)

Vargas, López, Salas, and Thinus-Blanc showed that goldfish (Carassius auratus) can use both geometric and featural cues in relocating a target corner in a rectangular enclosure. When featural cues (arrangement of striped walls) were put in conflict with geometric cues, results differed according to target location during training. Vargas, López, et al. explained the results of their cue conflict in terms of 2 different strategies: mapping and cue guidance. I provide an alternative, more parsimonious interpretation in which the same strategy of attempting to match as many cues as possible applies to both cases.

Different ways of encoding geometric information by goldfish (Carassius auratus)

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.