Biomedical subjects

David Eilam

Publications and source records attributed to David Eilam.

12 recordsLinked to original sources

PubMed2006

Sand rats see the light: short photoperiod induces a depression-like response in a diurnal rodent.

The present study examined the effect of simulated change in day length on the behavior of a diurnal rodent, the fat sand rat (a species of gerbil). Animals were housed under a short photoperiod (5/19 light/dark cycle) for 3 weeks and compared with controls living under a 12/12 light/dark cycle. All sand rats then underwent the forced swim test for depression-like behavior, and the open-field test for overall activity. Sand rats exposed to the short photoperiod displayed a significantly earlier sinking in the swim test, but there was no difference between their open-field activity compared with controls. Taking these responses as indicative of depression-like behavior, we suggest that a short photoperiod may induce affective-like changes, and that the sand rat may thus offer an appropriate animal model to explore the effect of photoperiod on normal, and perhaps also abnormal, seasonal mood changes (e.g., SAD), which in humans is a prevalent disorder, with winter depression episodes and spring/summer remissions.

Animals↗

PubMed2006

Exploration in a dark open field: a shift from directional to positional progression and a proposed model of acquiring spatial information.

Exploration in a dark open field undergoes three progressive changes: (i) an initial phase of spending equal amounts of time in various zones of the arena changes to staying in the corners, and ultimately spending most of the time in one corner; (ii) travel paths are first circular and scattered all over the arena, but gradually become anchored to one corner at which they start and end; (iii) traveled distance gradually decreases to that of the initial level seen in a lit open field. Altogether, rodents shift from a 'looping' exploration mechanism with feeble coupling with the environment, to 'home base' exploration which is firmly anchored to the environment. This shift also involves switching from momentary and sporadic to repeated returns to a specific, presumably familiar place, to which the animal navigates back from various other places. We suggest that this switching illustrates navigation first by directional and then by positional environmental cues, as hypothesized in the 'parallel map theory'. We also suggest that the transition from looping to home base behavior is part of a hierarchal construction of space representation via three modes of spatial information processing: (i) piloting--sequential processing, based on moving from one landmark to the next; (ii) orienting--parallel processing, based on moving from one point to the next, with the same starting and ending point; (iii) navigating--continuous processing, based on continuously updating the position in relation to several locations in the environment (map navigation).

Analysis of Variance↗

PubMed2005

Rituals, stereotypy and compulsive behavior in animals and humans.

From a survey of the behavior of animals in the wild, in captivity, under the influence of psychoactive drugs and in a model of obsessive-compulsive disorder (OCD), we identify that the behavioral repertoire invariably includes motor rituals, and that such rituals are performed at a few specific locations/objects in the environment with an orderly transition amongst locations/objects. The concept and parameters of this stable organization of rituals in time and space were used to analyze rituals of OCD patients, compared with control individuals performing the same actions (e.g. car locking). It was found that human rituals also converged to a few places/objects where repetitive acts were performed in a regular order, with the acts in OCD patients overlapping with those of control individuals. Across a very diverse range of animals and conditions, motor rituals are thus characterized by their close linkage to a few environmental locations and the repeated performance of relatively few acts. Such similarity in form may reflect a similarity in the mechanisms that control motor rituals in both animals and humans.

Animals↗

PubMed2005

Die hard: a blend of freezing and fleeing as a dynamic defense--implications for the control of defensive behavior.

Freezing, fleeing or fighting back are general defensive responses in many taxa. These defenses are mutually exclusive, since a prey cannot simultaneously flee and fight, or freeze and flee. Each of these defenses by itself is rudimentary and probably cannot provide a completely effective means to elude predation. Freezing is efficient only if employed before the prey is spotted by the predator, otherwise the prey becomes a stationary, easy to catch target. In fleeing, the prey can move directly away and maximize its distance from the predator, move toward the predator to confine it to a single clashing point, or dodge sideways to evade the attack. Prey can also run in a straight path that is efficient against slow or distant predators, or in a zigzag path that is efficient when a raptor is close or fast. In all, freezing and fleeing constitute together a complex and flexible defensive response, and are probably controlled by different motor systems that are inter-connected to allow fast switching between these behaviors, as required for an effective and versatile response.

Animals↗

PubMed2005

Psychostimulant-induced behavior as an animal model of obsessive-compulsive disorder: an ethological approach to the form of compulsive rituals.

Rats treated chronically with the D2/D3 dopamine receptor agonist quinpirole show a pattern of behavior that meets a set of ethologically derived criteria of compulsive behavior in obsessive-compulsive disorder (OCD). Moreover, in both quinpirole-treated rats and OCD patients, the structure of compulsive rituals appear similar in being composed of relatively few motor acts that are organized in a flexible yet recurrent manner. In addition, the development of compulsive behavior in quinpirole-treated rats is attenuated by the OCD pharmacotherapeutic drug clomipramine. These similarities support the validity of quinpirole-treated rats as a psychostimulant-induced animal model of OCD. Considering that the induction of compulsive behavior in the rat model involves chronic hyperstimulation of dopamine receptors, this raises the possibility that dopaminergic mechanisms may play a role in OCD, at least in some subtypes of this disorder.

Animals↗

PubMed2004

Protean behavior under barn-owl attack: voles alternate between freezing and fleeing and spiny mice flee in alternating patterns.

When attacking a spiny mouse in an experimental arena, a barn owl launched a few attacks from distant perches, made repetitive short-distance swoops in each attack and remained in the vicinity of the prey while chasing it. The spiny mouse fled in response, and typically oriented to face the owl whenever it stopped. When attacking a vole, the barn owl performed a greater number of attacks from distant perches, and left the vicinity of the prey after a few short-distance chases or capture attempts. Voles responded to these attacks in unspecific combinations of freezing and fleeing, and did not turn to face the owl when they stopped. Four conclusions are drawn from these encounters. First, two strategies characterized these predator-prey interactions; in one, both predator and prey continuously maintained awareness of each other's location; whereas in the other they continuously attempted to avoid the attention of the other. Second, responses of spiny mice and voles were a manifestation of protean behavior, with spiny mice fleeing in an alternating pattern and voles alternating between running and freezing. Third, locomotor response to owl attack comprised behavior that is an augmentation of normal behavior, with voles clinging to the walls and spiny mice running with frequent and irregular changes in direction. Fourth, the different defensive responses accord with the motor capacities and habitat of each rodent species. All in all, these results demonstrate the dynamic and multidimensional nature of predator-prey interactions.

Animals↗

PubMed2004

'Looping'-an exploration mechanism in a dark open field.

The behavior of Tristram's jird (a species of gerbil) in an illuminated open field resembled that of other rodents, comprising round trips to a home base and alternating between periods of progression (locomoting) and of stopping. In this study, we compared the characteristics of exploration in a dark arena with exploration by the same individuals in a lit arena. In the dark arena, stopping episodes were brief and fewer, suggesting almost continuous locomotion by the rodents. The clear distinction between progression and stopping that had characterized locomotion in an illuminated arena, thus diminished in the dark. There was also no apparent home base in the dark and traveling consisted in moving in a circular path, closing a loop to a recently traveled place that varied from one loop to the next. Locomotion in the dark may thus be regarded as a set of loops (round trips) to a continuously shifting home base, whereas with lights on the round trips converge to a home base using visible environmental landmarks. We suggest that a similar looping mechanism may be applicable to the behavior of hippocampal rats displaying hyperactivity and diversified locomotion, reminiscent of that seen in jirds in a dark arena.

Animals↗

PubMed2004

Locomotor activity in common spiny mice (Acomys cahirinuse): the effect of light and environmental complexity.

BACKGROUND: Rodents typically avoid illuminated and open areas, favoring dark or sheltered environments for activity. While previous studies focused on the effect of these environmental attributes on the level of activity, the present study tested whether the spatio-temporal structure of activity was also modified in illuminated compared with dark and complex compared with open arenas. For this, we tested common spiny mice (Acomys cahirinus) in empty or stone-containing arenas with lights on or lights off. RESULTS: In an illuminated or open arena, spiny mice moved in less frequent but longer trips with relatively long distances between consecutive stops. In contrast, in either a dark arena or an arena with stones, the animals took shorter and more frequent trips, with more stops per trip and shorter inter-stop distances. In illuminated arenas spiny mice remained mainly along the walls, whereas locomotion in the center was more prevalent in dark empty arenas, and was carried out along convoluted paths. Increasing environmental complexity by adding stones to either illuminated or dark arenas increased locomotion along straight trajectories and away from walls. CONCLUSIONS: Earlier findings of reduced activity in illuminated or open areas have been extended in the present study by demonstrating changes in the spatio-temporal structure of locomotor behavior. In the more complex arenas (with stones) spiny mice traveled along short straight segments whereas in the open their trips were longer and took the shape of a zigzag path which is more effective against fast or nearby predators. Alternatively, the zigzag path may reflect a difficulty in navigation.

Animals↗

PubMed2003

Rodents in open space adjust their behavioral response to the different risk levels during barn-owl attack.

BACKGROUND: Previous studies have revealed that the response of prey species to predatory risk comprised either freezing (when the prey remained immobile), or fleeing (when it ran frantically in order to remove itself from the vicinity of the predator). Other studies, however, have suggested that the prey will adjust its behavior to risk level. The present study was designed to follow the attacks of a barn owl (Tyto alba) on common spiny mice (Acomys cahirinus) and social voles (Microtus socialis guntherei), in order to reveal the correspondence between the behavior of the owl, the risk level at each phase of the owl's attack, and the defensive behavior of the rodents. RESULTS: Spiny mice dramatically increased the traveled distance upon the appearance of the owl, and kept moving during its attack while taking long trajectories of locomotion. Defensive response in voles dichotomized: in some voles traveled distance dropped when the owl appeared, reaching zero during its attack. In other voles, traveled distance dramatically increased once the owl appeared and further increased under its attack. These defensive responses developed by gradual tuning of normal locomotor behavior in accordance with the level of risk. CONCLUSIONS: The phenotypic difference in defensive behavior between voles and spiny mice probably stems from their different habitats and motor capacities. Agility and running capacity, together with a relatively sheltered natural habitat, make fleeing the most appropriate response for spiny mice during owl attack. Clumsiness and relatively limited motor capacities, together with an open natural habitat, account for the dichotomy to freezing or fleeing in voles. Thus, the apparent species-specific anti-predator response in spiny mice and voles is based on species-specific normal locomotor behavior, which depends on the species-specific ecology and motor capacity, and behaviors like defensive attack or escape jump that are specific to life threat. The latter behaviors are brief, and irregularly inlaid in the ongoing locomotor behavior. Finally, our results show that in both voles and spiny mice there is a gradual transition from normal to defensive behavior in accordance with the increase in risk level.

Animals↗

PubMed2003

Open-field behavior withstands drastic changes in arena size.

Individual voles were tested on successive days under increasing, decreasing, or randomly changing arena size. Locomotor behavior was adjusted to arena size by (i) preserving the same level of activity, (ii) taking longer but less frequent trips in smaller arenas in contrast to taking more frequent yet shorter trips in the larger arenas, and (iii) moving in the entire space available for exploration in the smaller arenas in contrast to remaining along the walls of the open field in the larger arenas. The effect of testing order was minimal, probably being related to increased novelty under increasing arena size, as opposed to habituation under decreasing arena size, when parts of the same area were re-explored. These behavioral changes averaged up to a two-fold difference compared with the larger six-fold change in the perimeter and 44-fold change in the area of the open field. The modest change in open-field behavior indicates that it has a solid spatio-temporal structure that withstands extensive environmental changes. This behavioral stability and consistency further validates studies of pharmacological, neurological, and genetic preparations that use behavior in a small open field as representation of the general pattern of behavior.

Animals↗

PubMed2003

Voles scale locomotion to the size of the open-field by adjusting the distance between stops: a possible link to path integration.

In this study we show that social voles (Microtus socialis guentheri) preserve the same level of activity and spatio-temporal organization of behavior whether exploring a small (1 x 1 m) or a large (2 x 2 m) open field. In each open field, a vole established a home base from which it set on to round-trips of exploration; taking fewer but longer trips in the large open field, compared with more frequent but shorter trips in the small open field. Each trip comprised bouts of progression (locomotion) interrupted by stops. The number of stops per trip was the same for both large open field (longer trips) and small open field (shorter trips), and achieved by scaling the distance between stops according to the size of the open field. Voles traveled more along the walls in the large compared with the small open field. These adjustments in locomotor behavior to open field size were observed immediately after the voles were introduced into the arena, indicating that the perceived distances available for locomotion were identified by the voles immediately at the beginning of exploration. It is suggested that these properties of spontaneous exploration are an expression of navigation using visual landmarks and path integration.

Animals↗

PubMed2002

Social vole parents force their mates to baby-sit.

Parental care has been categorized into direct and indirect investment. The former includes direct contact with the offspring, as in lactation or huddling with the pups, and the latter includes activities such as nest building or hoarding food for the guarding mate. We report here an unfamiliar type of parental behavior in which one parent aggressively forces its mate to stay in the nest with the pups. In this "forced baby-sitting," one parent grasps the fur of its mate and drags it toward the nest. The behavior was observed in 6 of 10 pairs of the social vole (Microtus socilalis guentheri) and was typically executed by the male. Dragging the mate to the nest was not correlated with other parental behaviors; neither could we explain why/when it occurred. However, this behavioral pattern was eye catching, and its goal was obviously to enforce the mate to stay in the nest with the pups.

Animals↗