Ariane S. Etienne

Short-distance homing in the golden hamster after a passive outward journey

Abstract The golden hamster carries food back to its nest along a direct path. In a situation combining a passive outward journey with the elimination of visual and various other exteroceptive cues, the subjects continued to return to their nest site and were not influenced by alterations of the earths magnetic field. Experiments in which the animals started their hoarding trips from a changing point of departure, or were transferred to an unfamiliar experimental space, suggest that they orientate by path integration and that they assess the angular, but not the linear component of a passive outward journey.

Navigation through vector addition

During short foraging excursions away from their home, central place foragers update their position relative to their point of departure by processing signals generated by locomotion. They therefore can home along a self-generated vector without using learned references. In rodents,,,, and other mammals,, this path integration process (dead reckoning) can occur on the basis of purely internal signals, such as vestibular or proprioceptive (re)afferences. We report here that hamsters are also capable of proceeding to a previously learned feeding site through vector information from locomotion only. The subjects compute the direction and distance to the goal by subtracting their current-position vector from the stored nest-to-goal vector. This computation pertains to locations per se and therefore occurs in absolute space, independently of landmark objects. If available, prominent visual cues merely serve to confirm the path planned through the addition of self-generated vectors, whereas visual as well as non-visual references confirm that the subject has arrived at the goal site.

Resetting the path integrator: a basic condition for route-based navigation

SUMMARY During short excursions away from home, some mammals are known to update their position with respect to their point of departure through path integration (dead reckoning) by processing internal (idiothetic) signals generated by rotations and translations. Path integration (PI) is a continuously ongoing process in which errors accumulate. To remain functional over longer excursions, PI needs to be reset through position information from stable external references. We tested the homing behaviour of golden hamsters (Mesocricetus auratus W.) during hoarding excursions following a rotation of the arena and nest. In continuous darkness, the hamsters returned to their point of departure at the rotated nest, and therefore depended on PI only. In other trials, the animals were briefly presented with visual room cues during or at the end of the outward trip, visual cues being pitted by 67° or 98° against the animals current self-generated position vector. After a fix, the animals headed for the usual (unrotated) nest location, as defined by room cues, independent of the timing of the fix. These results were obtained in two different geometrical settings and showed that, after the fix, the animals update their position, and not merely their head direction or internal compass, in a new reference frame. Thus, episodic fixes on familiar external references reset the PI and therefore greatly enhance the functional signification of navigation that is based on feedback information from locomotion.

The orientation of the golden hamster to its nest-site after the elimination of various sensory cues

Golden hamsters hoard food by carrying it back to their nest-site along a fairly direct path. 7 out of 12 animals continued to orientate in this way after passive transportation to the food source and the simultaneous elimination of visual, olfactory and acoustical cues. Experiments in which the hamsters tried to reach their nest-box from an unfamiliar place suggest that they orientate in a given direction with respect to a ‘compass’, the nature of which has still to be determined.

Short-distance homing in a small mammal: the role of exteroceptive cues and path integration

When hoarding food under IR light, the golden hamster returns to its nest by path integration after an active outward journey, and it is capable of compensating the angular component of a passive outward journey independently of auditory, olfactory, tactile and geomagnetic cues. If, however, peripheral visual cues are available, they predominate over information which is gained during the active or passive outward journey. Further experiments show the limitations of homing by path integration, which is open to cumulative errors and therefore needs to be complemented by other categories of information.

A brief view of known landmarks reorientates path integration in hamsters

Abstract In darkness, hamsters commute between their nest and a feeding site through path integration only, and therefore show cumulative errors in the return direction to the nest. We examined whether a brief presentation of familiar room cues could reset the path integrator. The hamsters could see the room cues either during, or at the end of, the outward journey to the food place, in a conflict situation where motion cues and visual information were set at variance. In both conditions, the animals used mainly visual information to return home. Thus, hamsters can determine their azimuth, and possibly their location, through a visual fix, and can reset their path integrator through the fix. This allows them to update their position during further locomotion in the dark and thus to compute a correct homing vector with respect to a visually induced reference frame. Taking episodic positional fixes may greatly enhance the functional value of path integration.

The Control of Short-Distance Homing in the Golden Hamster

The aim of spatial orientation studies is to determine what information controls the subject’s orientation in space and how this information is integrated and organized. In the ethological approach of this field of research, the first step always consists of defining the cues which a particular species uses in a given situation on the basis of its sensory equipment and with respect to the requirements it has to fulfill in its natural way of life. At this point in our investigations we have not only to ask what sensory modalities are involved, but, more fundamentally, whether our subjects rely on information which is registered “on site”, i.e. at particular locations or whether they use information which has been generated “en route”, i.e. during a preceding phase of locomotion (Baker, 1981;1984; Mittelstaedt and Mittelstaedt, 1982). Adopting the terminology which R. Robin Baker has coined with respect to navigation (usually defined in the ethological literature as goal-directed orientation across unfamiliar space), we shall refer to these two categories of spatial information as “location-based” and as “route-based” information.

The Meaning of Object Permanence at Different Zoological Levels

The nature of the object concept is reviewed at various zoological levels, and special importance is given to the notion of its continued existence. Three fundamentally different types of response to

Learning to recalibrate the role of dead reckoning and visual cues in spatial navigation

In Experiment 1, hamsters started from their permanent home at the periphery of a circular arena and headed to a food source at the center. They then returned, fully laden with food, along a direct path to their home. On control trials, in which no manipulation takes place, visual cues outside the arena and dead reckoning (i.e., updated internal references generated during the outward journey to the food source) controlled the return journey. On experimental trials, the arena, with the hamster in its nest, was rotated by 90°, putting dead reckoning at variance with the distal visual environment. The animals were rewarded for going with dead reckoning. At first, they favored the distal cues, but later most of the subjects switched to using dead reckoning. Thus, hamsters are flexible enough to recalibrate the relative weight that they normally attribute to different sets of spatial cues. In Experiment 2, the reliance on dead-reckoning was greatly enhanced when a cue card at the nest entrance was rotated along with the arena, pitting one proximal cue plus dead reckoning against distal cues. Hence, dead reckoning and external cues seem to reinforce each other through their mutual correlation.

Enhancing the impact of visual extra-maze cues in a spatial orientation task

In a short-distance homing task, golden hamsters derive the homing direction both from visual extra-maze cues and from the integration of the outward journey. The relative importance of visual configurations in the control of homing was assessed by presenting these cues in conflict with path integration. The hamsters depended mainly on path integration during the presentation of 3 objects at the periphery of the experimental arena or of a background pattern which surrounded the arena at a certain distance. However, they switched to visually controlled behaviour when the objects were superimposed on the patterned background. The possibility is discussed that the enhancement of the depth dimension through the simultaneous presentation of a foreground and a background may increase the effectiveness of visual cues in spatial orientation.