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Biomedical subjects

A S Etienne

Publications and source records attributed to A S Etienne.

13 recordsLinked to original sources
PubMed2000

A brief view of known landmarks reorientates path integration in hamsters.

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.

Animals↗
PubMed1998

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 nonvisual references confirm that the subject has arrived at the goal site.

Animals↗
PubMed1996

Path integration in mammals and its interaction with visual landmarks.

During locomotion, mammals update their position with respect to a fixed point of reference, such as their point of departure, by processing inertial cues, proprioceptive feedback and stored motor commands generated during locomotion. This so-called path integration system (dead reckoning) allows the animal to return to its home, or to a familiar feeding place, even when external cues are absent or novel. However, without the use of external cues, the path integration process leads to rapid accumulation of errors involving both the direction and distance of the goal. Therefore, even nocturnal species such as hamsters and mice rely more on previously learned visual references than on the path integration system when the two types of information are in conflict. Recent studies investigate the extent to which path integration and familiar visual cues cooperate to optimize the navigational performance.

Animals↗
PubMed1995

Optimizing distal landmarks: horizontal versus vertical structures and relation to background.

During hoarding excursions, golden hamsters use distal landmarks and dead reckoning (updated signals derived from locomotion) to find their way back from a food source at the centre of a circular arena to their nest at the periphery. The preference for particular landmarks was assessed by setting landmark panoramas in conflict with dead reckoning. The hamsters tended to prefer horizontal landmarks to vertical ones when these landmarks were presented alone. However, in combination with a continuous background pattern including a single apex, vertical landmarks were more effective than horizontal ones. A panorama consisting of a vertical cylinder or bar and the background pattern was optimal provided the vertical landmark was aligned or superimposed on the apex of the background. The impact of a landmark panorama therefore depends on its particular components as well as on their mutual relationship.

Animals↗
PubMed1994

Golden hamsters on the eight-arm maze in light and darkness: the role of dead reckoning.

This paper examines whether golden hamsters can rely on dead reckoning (getting positional information from updated signals generated during locomotion) on an eight-arm maze. Two groups of hamsters were tested: Group L under ordinary room light, Group D in darkness. To enhance the role of dead reckoning, each subject could climb from its own home cage onto the central platform of the maze. In a first experimental phase (15 trials), the L subjects learned to master the maze through developing a locomotor rule (arm chaining) after three to four trials. The D subjects developed arm chaining less readily and fluctuated more in their performance than did the L subjects. In a second experimental phase (15 trials), four arms were blocked at the beginning of each trial. In both experimental groups the performance decreased, yet remained well above chance level. Success and arm chaining were positively correlated in Phase 1 and negatively correlated with success in Phase 2. We assume that in Phase 2 the L subjects switched to the predominant use of visual cues, and the D subjects to dead reckoning.

Animals↗
PubMed1993

Dead reckoning in a small mammal: the evaluation of distance.

When hoarding food under infra-red light, golden hamsters Mesocricetus auratus W. return fairly directly from a feeding place to their nest site by evaluating and updating internal signals that they have generated during the previous outward journey to the feeding place. To test more specifically the animals' capacity to evaluate the linear components of the outward journey, the subjects were led from their (cone-shaped) nest to a feeding place along a detour which comprised either 2 (experiment 1) or 5 (experiment 2) segments; adjoining segments were at right angles to each other. In these conditions, the subjects remained significantly oriented towards the nest and therefore were capable of assessing translations as well as rotations during the outward journey. In experiment 3, the nest was removed after the hamsters had started the direct outward journey to the feeding place and the hamsters were rotated during the food uptake. The animals were no longer oriented towards the starting point of their journey, but nonetheless covered, along a fairly straight path, the correct homing distance, and then changed over to a circular search path. These results confirm that mammals can derive the linear components of an outward journey from self-generated signals and therefore are able to judge the homing distance without relying on cues from the environment. For a number of detour outward journeys, our data yield an unexpectedly good fit to Müller and Wehner's (1988) model of dead reckoning in ants. However, this is no longer the case when the outward journey contains an initial loop which brings the subject back to the starting point. These findings are discussed in terms of the biological significance and limitations of an approximate form of path integration.

Algorithms↗
PubMed1990

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.

Animals↗
PubMed1984

Sensory modalities in depth perception by golden hamsters.

Golden hamsters are able to detect differences in the height of a platform from which they jump, as measured by their increasing latencies prior to jumping from increased elevations. This ability is very effective when optical information is available, but it is also present when hamsters jump in total darkness. A second experiment shows that, when hamsters are placed on a real physical cliff, they preferentially use tactile information over visual information to guide their choice of the side from which to descend. In a nonvisual setting, tactile stimulation is used in conjunction with other types of cues. Evidence is provided to suggest that these cues are of an acoustical nature.

Animals↗
PubMed1982

Depth perception by means of ambient sounds in a small mammal.

Golden hamsters placed on a jumping stand from which they can descend onto a shallow or deep landing platform prefer to descend on to the shallow platform, even when tested under IR-light without tactile cues. This preference disappears for subjects with plugged ears. The simultaneous recording of the animal's behaviour and possible emission of ultrasound as well as experiments in which the external acoustical conditions or the sound-reflecting properties of the jumping apparatus were altered suggest that the animals use certain parameters of the ambient sound field for depth perception.

Acoustics↗
PubMed1982

Ontogeny of hoarding in the golden hamster: the development of motor patterns and their sequential coordination.

The hoarding behavior of 4 litters of Golden hamster pups (n = 3) was observed every 2nd day between the age of 13 and 47 days (2 litters) or 13 and 55 (2 litters). Each litter lived with the mother until Day 30; then the pups were put in social isolation. Immature forms of pouch filling and emptying, which were not integrated into coherent behavior sequences, appeared from the beginning of the observation period. Coordinated hoarding trips were shown from Day 21 onwards, once the motor patterns of inserting and extracting food had gained their definitive form. The development of hoarding was correlated with the animal's body weight and therefore with maturational factors. Mature hoarding behavior was greatly enhanced by the subject's separation from its family unit.

Age Factors↗
PubMed1980

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 al unfamiliar place suggest that they orientate in a given direction with respect to a 'compass', the nature of which has still to be determined.

Animals↗