Hippocampus lesions impair landmark array spatial learning in homing pigeons: a laboratory study

Hippocampal (HF)-lesioned pigeons display impaired homing ability when flying over familiar terrain, where they are presumably relying on a map-like representation of familiar landmarks to navigate. However, research carried out in the field precludes a direct test of whether hippocampal lesions compromise the ability of homing pigeons to navigate by familiar landmarks. To examine more thoroughly the relationship between hippocampus and landmark spatial learning, control, neostriatum-lesioned, and HF-lesioned homing pigeons were trained on two open field, laboratory, conditional discrimination tasks. One was a visual landmark array task, and the other was a room color discrimination task. For the tasks, the correct of three differently colored food bowls was determined by the spatial relationship among a group of five landmarks and room color, respectively. Intact control birds successfully learned both tasks, while neostriatum-lesioned birds successfully learned the landmark array task-the only task on which they were trained. By contrast, HF-lesioned birds successfully learned the room color task but were unable to learn the landmark array task. The data support the hypothesis that homing performance deficits observed in the field following hippocampal lesions are in part a consequence of an impairment in the ability of lesioned pigeons to use familiar visual landmarks for navigation.     

Use of slope and feature cues in pigeon (Columba livia) goal-searching behavior

Terrain slope provides a directional frame of reference for reorientation and navigation, similar to cardinal directions. Previous studies have shown that, in a goal location task, slope is a very salient cue and that pigeons tend to rely on it even if it is not the most informative cue. Such a strong dependence on one type of information, when there are more effective predictors of reward, is a key premise for a modular view of information processing. Here we tested the provocative hypothesis of a "slope module" for reorientation in slanted environments. Pigeons had to solve a goal location task using slope or another, theoretically salient cue: a beacon feature. Overall, searching behavior was controlled almost equally by the two cues. The fact that, for the first time, slope failed to capture most of the associative strength allows us to reject a strong modularity view and suggests instead that there is competition between cues based on salience. As an interesting additional finding, the reliance on slope and the feature was affected by training location (uphill vs. downhill), suggesting the possibility of a modulatory role of effort on the cue-weighting mechanism of reorientation.     

Nocturnal homing in the tropical amblypygid Phrynus pseudoparvulus (Class Arachnida,Order Amblypygi)

Arthropods are renowned for their navigational capabilities, with numerous examples known from insects and crustaceans. Early studies of amblypygids (Class Arachnida, Order Amblypygi) also suggest complex nocturnal navigation, despite their apparent lack of visual adaptations to the low-light conditions of a tropical understory. In a series of two studies, we use the tropical amblypygid, Phrynus pseudoparvulus, to assess their nocturnal homing ability. Our first experiment displaced and tracked resident and nonresident individuals. Resident individuals, displaced up to 4.5 m from their home refuges and released onto their home tree, were more likely to return to their previously occupied refuge than were nonresident individuals that were collected from trees outside the study area and released at the same locations. In a follow-up study, we displaced amblypygids longer distances (6–8.7 m) from their home trees and tracked them by telemetry. These individuals returned to home trees, typically within 1–3 nights, often via indirect paths. Taken together, our results provide evidence that P. pseudoparvulus are able to navigate home, often taking indirect routes, and can do so through a mechanism other than path integration.     

How focus at encoding affects children’s source monitoring

Retention of source information is enhanced by focus on speakers’ feelings about statements even though recognition is reduced for both adults and children. However, does any focus on another person lead to enhanced source monitoring, or is a particular kind of focus required? Does other-focus enhance source monitoring, or does self-focus detract from it? In Experiment 1, 4- and 6-year-olds watched two speakers make statements in a no-focus control or with focus directed on how they (or a speaker) felt about the statements or on perceptual features about themselves (or the speaker). Source monitoring decisions were enhanced by other-focus in both the perceptual and emotional conditions. However, the effect was larger for the emotional condition, and source monitoring exceeded no-focus controls only for this condition. Experiment 2 showed no effect of other-focus versus self-focus on source monitoring when questions were semantic.     

Septal area lesions impair spatial working memory in homing pigeons (Columba livia)

The septo-hippocampal system in birds resembles that of mammals, motivating research into the function of the avian hippocampus while surprisingly little attention has been given to the septum. To investigate a possible role of the avian septum in memory, the effects of septal area lesions on a spatial working memory (SpWM) task was tested in homing pigeons. After preoperative training on an analogue eight-arm (feeders) radial maze, now sham-operated control and septal lesioned pigeons were then trained again on the same task of locating the four feeders on the test phase of a trial that were not baited during the sample phase of a trial. During the test phase of a working memory trial, septal lesioned pigeons, compared to both their own preoperative performance and the performance of the controls, required significantly more choices to locate the four baited feeders not baited during the sample phase of a trial, and they made significantly fewer correct responses to the now baited feeders on their first four choices. The results demonstrate that, like its mammalian counterpart, the avian septum plays an important role in SpWM, suggesting that at least some functional properties of the septum are evolutionarily conserved in birds and mammals.     

Time-space learning in homing pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>): orientation to an artificial light source

Time-space learning reflects an ability to represent in memory event-stimulus properties together with the place and time of the event; a capacity well developed in birds. Homing pigeons were trained in an indoor octagonal arena to locate one food goal in the morning and a different food goal in the late afternoon. The goals differed with respect to their angular/directional relationship to an artificial light source located outside the arena. Further, the angular difference in reward position approximated the displacement of the sun's azimuth that would occur during the same time period. The experimental birds quickly learned the task, demonstrating the apparent ease with which birds can adopt an artificial light source to discriminate among alternative spatial responses at different times of the day. However, a novel midday probe session following successful learning revealed that the light source was interpreted as a stable landmark and not as a surrogate sun that would support compass orientation. Probe sessions following a phase shift of the light–dark cycle revealed that the mechanism employed to make the temporal discrimination was prevailingly based on an endogenous circadian rhythm and not an interval timing mechanism.     

Spatial and feature-based memory representation in free-flying homing pigeons

The memory-based recognition of a goal is a capacity well demonstrated in birds, and understanding this ability often involves determining the relative importance of spatial and feature information in representing the properties of a goal. However, surprisingly little avian research has examined goal recognition in a field setting. Here, we demonstrate that homing pigeons can be successfully trained outdoors to fly to and land on a goal platform located in an array of other platforms at a distance on the order of 100 m. They can do so under conditions when the properties of the goal are stable in time as well as when the properties of the goal periodically change; the latter condition indicating that homing pigeons can rapidly adapt their memory representations to take into account changing environmental conditions. When probed for preferential use of either spatial (location) or feature-based (color) information, the pigeons demonstrated an indifferent capacity to use both independent of task demands. The homing pigeon memory systems that support goal recognition appear to be opportunistic with respect to the information exploited, using spatial and feature information equally to guide their behavior. Therefore, and despite strong natural and artificial selection for navigational ability, spatial information is no more important than feature cues in representing a goal location for homing pigeons flying outdoors.     

On the transfer of spatial learning between geometrically different shaped environments in the terrestrial toad,Rhinella arenarum

Animal Cognition - When trained in a rectangular arena, some research has suggested that rats are guided by local features rather than overall boundary geometry. We explored this hypothesis using...