In order to ascertain the typical pattern and amount of parental care in the social vole (Microtu... more In order to ascertain the typical pattern and amount of parental care in the social vole (Microtus socialis guentheri) as well as the individual investment of the female, male, or both parents simultaneously, we studied ten primiparous females and their mates. Results revealed that out of seven parental behaviors, only crouching was correlated with litter size, suggesting that parental care was relatively independent of litter size-that is, duration of time spent with the young, licking them, retrieving them to the nest, having them attached to the female's nipples, and searching for a nipple on the male were not correlated with litter size. Individual investment of caretakers also varied, with no typical proportion of shared nurturing by the female and male. Accordingly, overall parental investment varied greatly among different sets of parents without correlation to the relative contribution of the female, the male, or both. Finally, duration and frequency of most parental behaviors declined over the course of postnatal development. Altogether, these data suggest a surplus parental investment that was probably not required for survival of offspring but might have evolved either for other purposes such as the formation of social bonds or was selected for in captivity.
Behavior in obsessive compulsive disorder (OCD), in habitual daily tasks, and in sport and cultur... more Behavior in obsessive compulsive disorder (OCD), in habitual daily tasks, and in sport and cultural rituals is deconstructed into elemental acts and categorized into common acts, performed by all individuals completing a similar task, and idiosyncratic acts, not performed by all individuals. Never skipped, common acts establish the pragmatic part of motor tasks. Repetitive performance of a few common acts renders rituals a rigid form, whereby common acts may serve as memes for cultural transmission. While idiosyncratic acts are not pragmatically necessary for task completion, they fulfill important cognitive roles. They form a long preparatory phase in tasks that involve high stakes, and a long confirmatory phase in OCD rituals. Idiosyncratic acts also form transitional phases between motor tasks, and are involved in establishing identity and preserving the flexibility necessary for adapting to varying circumstances. Behavioral variability, as manifested in idiosyncrasy, thus does not seem to be a noise or by-product of motor activity, but an essential cognitive component that has been preserved in the evolution of behavioral patterns, similar to the genetic variability in biology.
One-day-old rat pups adopt a supine posture before attaching to the mother's nipple. Body rotatio... more One-day-old rat pups adopt a supine posture before attaching to the mother's nipple. Body rotations performed to reach the nipple occur in a typical kinematic structure. First, the pup rotates along the longitudinal axis of the trunk and lies on its side. Next, the pup arches the trunk to achieve a U-shaped posture and then rapidly relaxes the trunk. A second cephalocaudal rotation follows at the peak of trunk relaxation as the pup achieves a supine posture. After reaching a supine posture, the pup crawls to a nipple by performing "stepping" movements on the mother's ventral surface. The kinematic structure of these movements is reminiscent of the structure of righting as seen in the newborn rat. Both righting and achieving a supine posture under the mother involve the expression of common motor modules. During righting the modules are executed in the direction of gravity, and when achieving a supine posture the modules are executed against the force of gravity. Simple motor behaviors expressed by the rat pup during early postnatal development may have common origins and common control mechanisms.
The study compares the behavioral profiles induced in rats (N= 118) by the Dz-dopaminergic recept... more The study compares the behavioral profiles induced in rats (N= 118) by the Dz-dopaminergic receptor agonist quinpirole (0.03 and 0.5 mg/kg), and the Dl-agonist SKF38393 (1.25-40 mg/kg), and both agonists administered together. Locomotion and snout contact frequency were reduced by the low but increased by the high dose of quinpirole; SKF38393 also reduced these behaviors and attenuated the effect of the high quinpirole dose. Only the high dose of quinpirole increased the duration of snout contact bouts and the frequency of mouthing; SKF38393 had no effect but in combination with the high dose of quinpirole, it enhanced the performance of these behaviors greatly. The duration of mouthing bouts was not affected by either agonist but was greatly extended when SKF38393 was administered together with the high dose of quinpirole. Grooming was inhibited by both the low and the high dose of quinpirole, and stimulated by the injection of SKF38393 or its addition to the low dose of quinpirole. These findings suggest that snout contact is controlled by modulating the frequency of episodes whereas mouthing is controlled by modulating the duration of episodes. Moreover, although they do not disprove the prevailing notion of D 1-D2 receptor synergism, the present data are consistent also with an oppositional model of D~-D2 receptor interaction in the regulation of locomotion, snout contact, mouthing, and grooming in intact animals.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
ï‚· Rats with different spatial knowledge regarding food location were tested together ï‚· Food avail... more ï‚· Rats with different spatial knowledge regarding food location were tested together ï‚· Food availability was the prime factor in shaping spatial decisions ï‚· This primacy was further augmented by socializing with the other rat ï‚· Dyad partners displayed a greater tendency to visit baited locations together ï‚· Rats' familiarity with past locations was least influential in foraging decisions
Dwelling in a specific habitat requires adaptation to the habitat physical and biological propert... more Dwelling in a specific habitat requires adaptation to the habitat physical and biological properties in order to maximize fitness. Adaptations that are manifested in the organization of behavior in time and space reflect how the environment is perceived and utilized. Testing species from different habitats in the same laboratory environment can uncover the differences in their behavior and their adaptations to specific habitats. The question posed in this study is that of how two rodent species, one occupying flatlands (Tristram's jird; Meriones tristrami) and the other occupying structured rocky habitats (common spiny mouse; Acomys dimidiatus), differ in the way that they explore the same three-dimensional laboratory environment. Individuals of these two species were introduced into an arena with a five-level ziggurat in the center, and their behavior was followed for 60 min. We found that both species preserved the typical spatiotemporal rodents' behavior of establishing a home-base-a location that is a terminal from which they set out to explore the environment. However, the jirds, which live in flatlands, mainly travelled on the arena floor and the lower levels of the ziggurat; while, in contrast, the spiny mice, which live in rocky habitats and are used to climbing, mostly remained and travelled on the ziggurat, with some of them hardly descending to the arena floor. We suggest that the distinction in spatial behavior between the two species reflects their different motor abilities, different depth perception, and different umvelt (perceived world), in accordance with their different natural habitats.
Alzheimer's disease (AD) is associated with serum antibodies directed specifically agains... more Alzheimer's disease (AD) is associated with serum antibodies directed specifically against phosphorylated epitopes highly enriched in the heavy neurofilament protein NF-H of cholinergic neurons. Prolonged immunization of rats with these molecules but not with other NF-H isoforms results in cognitive impairments. This animal model, termed experimental autoimmune dementia (EAD), supports a role for such antibodies in neurodegeneration in AD. In the present study we investigated the cellular and immunological mechanisms underlying the cognitive defects in EAD. Immunohistochemical studies revealed that IgG accumulate in the septum, hippocampus and in the entorhinal cortex of the EAD rats. This is accompanied by a marked reduction in the density of septal cholinergic neurons. An inverse correlation was observed between the level of IgG in the septum of individual EAD rats and the density of their septal cholinergic neurons. Time course studies revealed that the decrease in the density of cholinergic neurons in the septum of EAD rats and the accumulation of IgG in this brain area have the same time course and are both significant by three to four months following the initiation of immunization with cholinergic NF-H. The cognitive deficits of the EAD rats evolve more slowly and are pronounced only after six months following the initation of immunization. In vitro studies revealed that anti NF-H IgG bind to the outer surface of neurons in tissue cultures of rat forebrain and can affect neuronal viability. These AD and in vitro findings provide model systems for studying the mechanisms underlying the neuropathological effects of specific anti NF-H antibodies.
In a large open field, rats injected repeatedly with the dopamine agonist quinpirole develop moto... more In a large open field, rats injected repeatedly with the dopamine agonist quinpirole develop motor rituals that, we show here, evolve through a cascade of four behavioral processes. The first process involves an increase in overall activity. The second process involves an increase in path stereotypy, reflected in traveling repeatedly along the same few paths. The third process is an increase in the frequency of stopping in few places, alongside a decrease in stopping in other places. The fourth process is a decrease in the repetition of movements performed in the specific stopping places. Altogether, these processes culminate in a typical short set of movements comprising a single performance of each movement type. The increased activity leads to a recurrent and stereotyped performance of the entire ritual. Thus, stereotypy does not arise from changes in the content of the behavior patterns used, but in how these patterns are organized temporally and spatially. These results provide a model for the development of motor rituals and their linkage to normal behavior and to the physical properties of the environment.
Spatial organization is an extensively studied field, in which most of the research has been on h... more Spatial organization is an extensively studied field, in which most of the research has been on how the physical environment is perceived and conceived. There is a consensus that physical attributes such as environment geometry and landmarks are key factors in shaping spatial cognition. Nevertheless, the numerous studies of spatial behavior have usually been carried out on individuals, thereby overlooking the possible impact of the social environment. In the present study, rats were exposed to an unfamiliar open-field, first alone and then in tetrads of unfamiliar individuals, in order to monitor and analyze when and how their individual spatial behavior converged to a group spatial behavior. We found that the unfamiliar rats spent most of their time in companionship, first with preferred partners and ultimately as a quartet. Specifically, group formation was dynamic and gradual, with the rats first forming duos, then trios, and ultimately a quartet. Trios and quartets mostly huddled in the same specific corner that became a shared home base, from which they took solo or duo roundtrips to the arena. The present study unveils how, by means of gradual interactions among self, place, and conspecifics, four unfamiliar rats organized together their social spatial behavior.
Here we present an empirical study that provides a basis for understanding the impact of the soci... more Here we present an empirical study that provides a basis for understanding the impact of the social environment on individuals with mental disorders. Rats treated chronically with the dopamine-agonist quinpirole offer a solid animal model for compulsive behavior that has been comprehensively evaluated and validated in numerous studies. Moreover, the method of behavioral analysis used in the quinpirole rat model has been similarly applied to the analysis of compulsive rituals in OCD patients, revealing similarities to the structure of compulsions in the quinpirole-sensitized rats. Here, we examined how compulsive checking by quinpirole-sensitized rats was modulated by the presence of a partner that was also treated with quinpirole or a partner that was treated with saline, compared to the typical expression of compulsive checking shown by rats tested alone. Our results demonstrate that the presence of a partner does indeed modulate the performance of checking behavior. Specifically, the vigor of compulsive checking was attenuated in the presence of a saline-treated partner, and augmented in the presence of a quinpirole-treated partner. This finding provides compelling evidence that social interactions modulate the expression of compulsive checking in the quinpirole rat model of OCD. This uncovering of the effectiveness of social modulation, indicates the quinpirole preparation as a paradigm for investigating the mechanisms by which the social environment modulates the development and expression of OCD. More generally, it presents a paradigm for the study of the influence of drug effects as a function of social interaction.
In order to uncover processes in the acquisition of spatial representation, we tested voles, jird... more In order to uncover processes in the acquisition of spatial representation, we tested voles, jirds, and mice in a dark grid maze-a relatively homogenous environment comprising 16 identical equispaced crossroads and similar choice of paths at each crossroad. The three species initially displayed a tendency to retrace sections of their recently traversed path, perhaps indicating exploration and learning of an unfamiliar environment by virtue of repetition. All three species displayed the same decision making at crossroads. They had an equal tendency to progress forward, turn sideways, or turn back to retrace their path upon the first arrival at each crossroad. Over repeated visits to the same crossroad, however, progressing forward increased along with a decrease in turning back, but there was no change in the incidence of turning sideways. It is suggested that progressing forward is easier than making turns, since the latter oblige the navigator to remember the location of turning in order to retrace or integrate the path and remain oriented. The incidence of turning sideways, in being more difficult than forward progression and retracing, yet necessary in a restricted maze space, did not change over repeated visits to crossroads. Altogether, decision making at a crossroad may be described as going straight ahead for simplicity, retracing a path to memorize it, or turning sideways at a constant rate. The present tests in the grid maze illustrate how tangible entities (crossroads, paths) are integrated during the early phase of acquiring an abstract representation (map) of the maze.
Ritualized behavior, intuitively recognizable by its stereotypy, rigidity, repetition, and appare... more Ritualized behavior, intuitively recognizable by its stereotypy, rigidity, repetition, and apparent lack of rational motivation, is found in a variety of life conditions, customs, and everyday practices: in cultural rituals, whether religious or non-religious; in many children's complicated routines; in the pathology of obsessive-compulsive disorders (OCD); in normal adults around certain stages of the life-cycle, birthing in particular. Combining evidence from evolutionary anthropology, neuropsychology and neuroimaging, we propose an explanation of ritualized behavior in terms of an evolved Precaution System geared to the detection of and reaction to inferred threats to fitness. This system, distinct from fear-systems geared to respond to manifest danger, includes a repertoire of clues for potential danger as well as a repertoire of species-typical precautions. In OCD pathology, this system does not supply a negative feedback to the appraisal of potential threats, resulting in doubts about the proper performance of precautions, and repetition of action. Also, anxiety levels focus the attention on low-level gestural units of behavior rather than on the goal-related higher-level units normally used in parsing the action-flow. Normally automatized actions are submitted to cognitive control. This "swamps" working memory, an effect of which is a temporary relief from intrusions but also their long-term strengthening. Normal activation of this Precaution System explains intrusions and ritual behaviors in normal adults. Gradual calibration of the system occurs through childhood rituals. Cultural mimicry of this system's normal input makes cultural rituals attention-grabbing and compelling. A number of empirical predictions follow from this synthetic model.
Open-field behavior is a common tool in studying exploration and navigation, as well as emotions ... more Open-field behavior is a common tool in studying exploration and navigation, as well as emotions and motivations. However, it has been suggested that this behavior might be parsimoniously interpreted as directed to optimize security, with no need to interpret the animal's mental state. This latter view was challenged here by providing voles with presumably sense of optimal security. For this, voles were introduced into a dark open-field inside a familiar shelter in which they previously lived in their home cage. Voles then emerged either to locomote only in the vicinity of the shelter, or to travel further out to explore the entire arena and only later to return to the shelter. While their staying near the shelter confirms the notion of optimizing security, their traveling further out along the perimeter negates this notion. This divergence of behavior under the same security conditions illustrates that open-field behavior, which is a multi-faceted and dynamic process, is also affected by an emotional component. That is, safety is a subjective emotional state dictated by various inputs and, therefore, the resulting dynamic behavior, which is the ultimate output of the central nervous system, may vary beyond the possibility of being parsimoniously interpreted by only one factor. In a similar vein, we show that the impact of the start point on the paths of locomotion is not an intrinsic property of that point, but depends on its physical location.
Pharmacology, Biochemistry and Behavior, Aug 1, 1990
EILAM, D. AND H. SZECHTMAN. Dosing regimen differentiates sensitization of locomotion and mouthin... more EILAM, D. AND H. SZECHTMAN. Dosing regimen differentiates sensitization of locomotion and mouthing to D2 agonist quinpirole. PHARMACOL BIOCHEM BEHAV 36(4) 989-991, 1990.-The study examines whether the order of administering 2
Mole rats were videotaped while locomoting in a Plexiglas tube to evaluate the effects of inclina... more Mole rats were videotaped while locomoting in a Plexiglas tube to evaluate the effects of inclination on locomotion. Animals moving uphill preferred to go backward using plantigrade foot postures, presumably to prevent sliding. Uphill backward locomotion also allowed animals to cope with changes in weight distribution between the hind and forelimbs without modifying footfall pattern relative to the direction of progression. When the animals did use uphill forward strides, they switched to asymmetrical gaits, which are associated with increased propulsive forces. These and prior results suggest that weight distribution and direction of progression can modify the natural pattern of stepping in mammalian quadrupeds. Walking Running Backward locomotion Symmetrical gaits Asymmetrical gaits Footfall patterns Stride Fossorial mammals Rodents Plantigrade Digitigrade
We sought to uncover the impact of the social environment on the spatial behavior of rats. Food-d... more We sought to uncover the impact of the social environment on the spatial behavior of rats. Food-deprived rats were trained in a spatial task of collecting food items from 16 equispaced objects. Following training, they were tested, first alone and then with a similarlytrained cage-mate. It was found that the presence of another rat substantially altered the rats' spatial behavior. Lone rats collected the food items faster while traveling a shorter distance, reflecting a higher efficiency of task completion. When accompanied by a partner, however, the rats traveled together, visiting the same set of objects in each trip with one of them leading. Whether alone or with a partner, rats continued to revisit the same objects; however, more such revisits occurred with a partner. We argue that revisiting objects is not necessarily an error, since returning to past places is an important aspect of rats' natural behavior. Revisiting an object following food depletion implies that searching for food was not the main driving force in the rats' spatial behavior. Specifically, despite food deprivation, rats were more attentive to one another than to the food. This could be adaptive, since foraging and feeding in groups is a way of poison avoidance in wild rats. Finally, the addition of a social component added complexity to the environment since the rats organized their spatial behavior in reference to one another in addition to their organization in the physical surrounding. Consequently, when tested with a partner, spatial behavior was less structured, less predictable and more chaotic.
Chronic intermittent injection of quinpirole (0.5mg/kg) to rats in a large non-standard open fiel... more Chronic intermittent injection of quinpirole (0.5mg/kg) to rats in a large non-standard open field (mirrored glass table without walls, 160 x 160cm and 60cm high) induces pronounced behavioral sensitization characterized by a 6-fold increase in locomotor distance and increased rigidity of travel along the same routes (path stereotype). Experiment 1 showed that equivalent treatment in the home cage induces much less sensitization of locomotor distance and no sensitization of path stereotypy, as evidenced by a test in the open field. In Experiment 2, transferring rats sensitized in one open field to a novel open field resulted in a 50% loss of sensitized locomotor distance and a virtual loss of sensitized path stereotypy. In Experiment 3, rotating the open field in relation to room cues did not affect sensitized responding, suggesting that the behavior is organized in relation to distal rather than local (open field) cues. Finally, an injection of saline in the sensitized environment failed to elicit conditioned locomotion (Experiment 4). These results are taken to indicate that the control of sensitization to quinpirole has components that are environment independent, behavior specific, and context dependent, each having a relatively different contribution and mechanism. It is suggested that under the experimental conditions of this study, the relative contributions to quinpirole sensitization were 50% for the context-dependent component, 30% for the behavior-specific component, and 20% for the environment-independent contribution. The mechanism for the context-dependent component may be related to development of path stereotypy and involve spatial learning.
In order to ascertain the typical pattern and amount of parental care in the social vole (Microtu... more In order to ascertain the typical pattern and amount of parental care in the social vole (Microtus socialis guentheri) as well as the individual investment of the female, male, or both parents simultaneously, we studied ten primiparous females and their mates. Results revealed that out of seven parental behaviors, only crouching was correlated with litter size, suggesting that parental care was relatively independent of litter size-that is, duration of time spent with the young, licking them, retrieving them to the nest, having them attached to the female's nipples, and searching for a nipple on the male were not correlated with litter size. Individual investment of caretakers also varied, with no typical proportion of shared nurturing by the female and male. Accordingly, overall parental investment varied greatly among different sets of parents without correlation to the relative contribution of the female, the male, or both. Finally, duration and frequency of most parental behaviors declined over the course of postnatal development. Altogether, these data suggest a surplus parental investment that was probably not required for survival of offspring but might have evolved either for other purposes such as the formation of social bonds or was selected for in captivity.
Behavior in obsessive compulsive disorder (OCD), in habitual daily tasks, and in sport and cultur... more Behavior in obsessive compulsive disorder (OCD), in habitual daily tasks, and in sport and cultural rituals is deconstructed into elemental acts and categorized into common acts, performed by all individuals completing a similar task, and idiosyncratic acts, not performed by all individuals. Never skipped, common acts establish the pragmatic part of motor tasks. Repetitive performance of a few common acts renders rituals a rigid form, whereby common acts may serve as memes for cultural transmission. While idiosyncratic acts are not pragmatically necessary for task completion, they fulfill important cognitive roles. They form a long preparatory phase in tasks that involve high stakes, and a long confirmatory phase in OCD rituals. Idiosyncratic acts also form transitional phases between motor tasks, and are involved in establishing identity and preserving the flexibility necessary for adapting to varying circumstances. Behavioral variability, as manifested in idiosyncrasy, thus does not seem to be a noise or by-product of motor activity, but an essential cognitive component that has been preserved in the evolution of behavioral patterns, similar to the genetic variability in biology.
One-day-old rat pups adopt a supine posture before attaching to the mother's nipple. Body rotatio... more One-day-old rat pups adopt a supine posture before attaching to the mother's nipple. Body rotations performed to reach the nipple occur in a typical kinematic structure. First, the pup rotates along the longitudinal axis of the trunk and lies on its side. Next, the pup arches the trunk to achieve a U-shaped posture and then rapidly relaxes the trunk. A second cephalocaudal rotation follows at the peak of trunk relaxation as the pup achieves a supine posture. After reaching a supine posture, the pup crawls to a nipple by performing "stepping" movements on the mother's ventral surface. The kinematic structure of these movements is reminiscent of the structure of righting as seen in the newborn rat. Both righting and achieving a supine posture under the mother involve the expression of common motor modules. During righting the modules are executed in the direction of gravity, and when achieving a supine posture the modules are executed against the force of gravity. Simple motor behaviors expressed by the rat pup during early postnatal development may have common origins and common control mechanisms.
The study compares the behavioral profiles induced in rats (N= 118) by the Dz-dopaminergic recept... more The study compares the behavioral profiles induced in rats (N= 118) by the Dz-dopaminergic receptor agonist quinpirole (0.03 and 0.5 mg/kg), and the Dl-agonist SKF38393 (1.25-40 mg/kg), and both agonists administered together. Locomotion and snout contact frequency were reduced by the low but increased by the high dose of quinpirole; SKF38393 also reduced these behaviors and attenuated the effect of the high quinpirole dose. Only the high dose of quinpirole increased the duration of snout contact bouts and the frequency of mouthing; SKF38393 had no effect but in combination with the high dose of quinpirole, it enhanced the performance of these behaviors greatly. The duration of mouthing bouts was not affected by either agonist but was greatly extended when SKF38393 was administered together with the high dose of quinpirole. Grooming was inhibited by both the low and the high dose of quinpirole, and stimulated by the injection of SKF38393 or its addition to the low dose of quinpirole. These findings suggest that snout contact is controlled by modulating the frequency of episodes whereas mouthing is controlled by modulating the duration of episodes. Moreover, although they do not disprove the prevailing notion of D 1-D2 receptor synergism, the present data are consistent also with an oppositional model of D~-D2 receptor interaction in the regulation of locomotion, snout contact, mouthing, and grooming in intact animals.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
ï‚· Rats with different spatial knowledge regarding food location were tested together ï‚· Food avail... more ï‚· Rats with different spatial knowledge regarding food location were tested together ï‚· Food availability was the prime factor in shaping spatial decisions ï‚· This primacy was further augmented by socializing with the other rat ï‚· Dyad partners displayed a greater tendency to visit baited locations together ï‚· Rats' familiarity with past locations was least influential in foraging decisions
Dwelling in a specific habitat requires adaptation to the habitat physical and biological propert... more Dwelling in a specific habitat requires adaptation to the habitat physical and biological properties in order to maximize fitness. Adaptations that are manifested in the organization of behavior in time and space reflect how the environment is perceived and utilized. Testing species from different habitats in the same laboratory environment can uncover the differences in their behavior and their adaptations to specific habitats. The question posed in this study is that of how two rodent species, one occupying flatlands (Tristram's jird; Meriones tristrami) and the other occupying structured rocky habitats (common spiny mouse; Acomys dimidiatus), differ in the way that they explore the same three-dimensional laboratory environment. Individuals of these two species were introduced into an arena with a five-level ziggurat in the center, and their behavior was followed for 60 min. We found that both species preserved the typical spatiotemporal rodents' behavior of establishing a home-base-a location that is a terminal from which they set out to explore the environment. However, the jirds, which live in flatlands, mainly travelled on the arena floor and the lower levels of the ziggurat; while, in contrast, the spiny mice, which live in rocky habitats and are used to climbing, mostly remained and travelled on the ziggurat, with some of them hardly descending to the arena floor. We suggest that the distinction in spatial behavior between the two species reflects their different motor abilities, different depth perception, and different umvelt (perceived world), in accordance with their different natural habitats.
Alzheimer's disease (AD) is associated with serum antibodies directed specifically agains... more Alzheimer's disease (AD) is associated with serum antibodies directed specifically against phosphorylated epitopes highly enriched in the heavy neurofilament protein NF-H of cholinergic neurons. Prolonged immunization of rats with these molecules but not with other NF-H isoforms results in cognitive impairments. This animal model, termed experimental autoimmune dementia (EAD), supports a role for such antibodies in neurodegeneration in AD. In the present study we investigated the cellular and immunological mechanisms underlying the cognitive defects in EAD. Immunohistochemical studies revealed that IgG accumulate in the septum, hippocampus and in the entorhinal cortex of the EAD rats. This is accompanied by a marked reduction in the density of septal cholinergic neurons. An inverse correlation was observed between the level of IgG in the septum of individual EAD rats and the density of their septal cholinergic neurons. Time course studies revealed that the decrease in the density of cholinergic neurons in the septum of EAD rats and the accumulation of IgG in this brain area have the same time course and are both significant by three to four months following the initiation of immunization with cholinergic NF-H. The cognitive deficits of the EAD rats evolve more slowly and are pronounced only after six months following the initation of immunization. In vitro studies revealed that anti NF-H IgG bind to the outer surface of neurons in tissue cultures of rat forebrain and can affect neuronal viability. These AD and in vitro findings provide model systems for studying the mechanisms underlying the neuropathological effects of specific anti NF-H antibodies.
In a large open field, rats injected repeatedly with the dopamine agonist quinpirole develop moto... more In a large open field, rats injected repeatedly with the dopamine agonist quinpirole develop motor rituals that, we show here, evolve through a cascade of four behavioral processes. The first process involves an increase in overall activity. The second process involves an increase in path stereotypy, reflected in traveling repeatedly along the same few paths. The third process is an increase in the frequency of stopping in few places, alongside a decrease in stopping in other places. The fourth process is a decrease in the repetition of movements performed in the specific stopping places. Altogether, these processes culminate in a typical short set of movements comprising a single performance of each movement type. The increased activity leads to a recurrent and stereotyped performance of the entire ritual. Thus, stereotypy does not arise from changes in the content of the behavior patterns used, but in how these patterns are organized temporally and spatially. These results provide a model for the development of motor rituals and their linkage to normal behavior and to the physical properties of the environment.
Spatial organization is an extensively studied field, in which most of the research has been on h... more Spatial organization is an extensively studied field, in which most of the research has been on how the physical environment is perceived and conceived. There is a consensus that physical attributes such as environment geometry and landmarks are key factors in shaping spatial cognition. Nevertheless, the numerous studies of spatial behavior have usually been carried out on individuals, thereby overlooking the possible impact of the social environment. In the present study, rats were exposed to an unfamiliar open-field, first alone and then in tetrads of unfamiliar individuals, in order to monitor and analyze when and how their individual spatial behavior converged to a group spatial behavior. We found that the unfamiliar rats spent most of their time in companionship, first with preferred partners and ultimately as a quartet. Specifically, group formation was dynamic and gradual, with the rats first forming duos, then trios, and ultimately a quartet. Trios and quartets mostly huddled in the same specific corner that became a shared home base, from which they took solo or duo roundtrips to the arena. The present study unveils how, by means of gradual interactions among self, place, and conspecifics, four unfamiliar rats organized together their social spatial behavior.
Here we present an empirical study that provides a basis for understanding the impact of the soci... more Here we present an empirical study that provides a basis for understanding the impact of the social environment on individuals with mental disorders. Rats treated chronically with the dopamine-agonist quinpirole offer a solid animal model for compulsive behavior that has been comprehensively evaluated and validated in numerous studies. Moreover, the method of behavioral analysis used in the quinpirole rat model has been similarly applied to the analysis of compulsive rituals in OCD patients, revealing similarities to the structure of compulsions in the quinpirole-sensitized rats. Here, we examined how compulsive checking by quinpirole-sensitized rats was modulated by the presence of a partner that was also treated with quinpirole or a partner that was treated with saline, compared to the typical expression of compulsive checking shown by rats tested alone. Our results demonstrate that the presence of a partner does indeed modulate the performance of checking behavior. Specifically, the vigor of compulsive checking was attenuated in the presence of a saline-treated partner, and augmented in the presence of a quinpirole-treated partner. This finding provides compelling evidence that social interactions modulate the expression of compulsive checking in the quinpirole rat model of OCD. This uncovering of the effectiveness of social modulation, indicates the quinpirole preparation as a paradigm for investigating the mechanisms by which the social environment modulates the development and expression of OCD. More generally, it presents a paradigm for the study of the influence of drug effects as a function of social interaction.
In order to uncover processes in the acquisition of spatial representation, we tested voles, jird... more In order to uncover processes in the acquisition of spatial representation, we tested voles, jirds, and mice in a dark grid maze-a relatively homogenous environment comprising 16 identical equispaced crossroads and similar choice of paths at each crossroad. The three species initially displayed a tendency to retrace sections of their recently traversed path, perhaps indicating exploration and learning of an unfamiliar environment by virtue of repetition. All three species displayed the same decision making at crossroads. They had an equal tendency to progress forward, turn sideways, or turn back to retrace their path upon the first arrival at each crossroad. Over repeated visits to the same crossroad, however, progressing forward increased along with a decrease in turning back, but there was no change in the incidence of turning sideways. It is suggested that progressing forward is easier than making turns, since the latter oblige the navigator to remember the location of turning in order to retrace or integrate the path and remain oriented. The incidence of turning sideways, in being more difficult than forward progression and retracing, yet necessary in a restricted maze space, did not change over repeated visits to crossroads. Altogether, decision making at a crossroad may be described as going straight ahead for simplicity, retracing a path to memorize it, or turning sideways at a constant rate. The present tests in the grid maze illustrate how tangible entities (crossroads, paths) are integrated during the early phase of acquiring an abstract representation (map) of the maze.
Ritualized behavior, intuitively recognizable by its stereotypy, rigidity, repetition, and appare... more Ritualized behavior, intuitively recognizable by its stereotypy, rigidity, repetition, and apparent lack of rational motivation, is found in a variety of life conditions, customs, and everyday practices: in cultural rituals, whether religious or non-religious; in many children's complicated routines; in the pathology of obsessive-compulsive disorders (OCD); in normal adults around certain stages of the life-cycle, birthing in particular. Combining evidence from evolutionary anthropology, neuropsychology and neuroimaging, we propose an explanation of ritualized behavior in terms of an evolved Precaution System geared to the detection of and reaction to inferred threats to fitness. This system, distinct from fear-systems geared to respond to manifest danger, includes a repertoire of clues for potential danger as well as a repertoire of species-typical precautions. In OCD pathology, this system does not supply a negative feedback to the appraisal of potential threats, resulting in doubts about the proper performance of precautions, and repetition of action. Also, anxiety levels focus the attention on low-level gestural units of behavior rather than on the goal-related higher-level units normally used in parsing the action-flow. Normally automatized actions are submitted to cognitive control. This "swamps" working memory, an effect of which is a temporary relief from intrusions but also their long-term strengthening. Normal activation of this Precaution System explains intrusions and ritual behaviors in normal adults. Gradual calibration of the system occurs through childhood rituals. Cultural mimicry of this system's normal input makes cultural rituals attention-grabbing and compelling. A number of empirical predictions follow from this synthetic model.
Open-field behavior is a common tool in studying exploration and navigation, as well as emotions ... more Open-field behavior is a common tool in studying exploration and navigation, as well as emotions and motivations. However, it has been suggested that this behavior might be parsimoniously interpreted as directed to optimize security, with no need to interpret the animal's mental state. This latter view was challenged here by providing voles with presumably sense of optimal security. For this, voles were introduced into a dark open-field inside a familiar shelter in which they previously lived in their home cage. Voles then emerged either to locomote only in the vicinity of the shelter, or to travel further out to explore the entire arena and only later to return to the shelter. While their staying near the shelter confirms the notion of optimizing security, their traveling further out along the perimeter negates this notion. This divergence of behavior under the same security conditions illustrates that open-field behavior, which is a multi-faceted and dynamic process, is also affected by an emotional component. That is, safety is a subjective emotional state dictated by various inputs and, therefore, the resulting dynamic behavior, which is the ultimate output of the central nervous system, may vary beyond the possibility of being parsimoniously interpreted by only one factor. In a similar vein, we show that the impact of the start point on the paths of locomotion is not an intrinsic property of that point, but depends on its physical location.
Pharmacology, Biochemistry and Behavior, Aug 1, 1990
EILAM, D. AND H. SZECHTMAN. Dosing regimen differentiates sensitization of locomotion and mouthin... more EILAM, D. AND H. SZECHTMAN. Dosing regimen differentiates sensitization of locomotion and mouthing to D2 agonist quinpirole. PHARMACOL BIOCHEM BEHAV 36(4) 989-991, 1990.-The study examines whether the order of administering 2
Mole rats were videotaped while locomoting in a Plexiglas tube to evaluate the effects of inclina... more Mole rats were videotaped while locomoting in a Plexiglas tube to evaluate the effects of inclination on locomotion. Animals moving uphill preferred to go backward using plantigrade foot postures, presumably to prevent sliding. Uphill backward locomotion also allowed animals to cope with changes in weight distribution between the hind and forelimbs without modifying footfall pattern relative to the direction of progression. When the animals did use uphill forward strides, they switched to asymmetrical gaits, which are associated with increased propulsive forces. These and prior results suggest that weight distribution and direction of progression can modify the natural pattern of stepping in mammalian quadrupeds. Walking Running Backward locomotion Symmetrical gaits Asymmetrical gaits Footfall patterns Stride Fossorial mammals Rodents Plantigrade Digitigrade
We sought to uncover the impact of the social environment on the spatial behavior of rats. Food-d... more We sought to uncover the impact of the social environment on the spatial behavior of rats. Food-deprived rats were trained in a spatial task of collecting food items from 16 equispaced objects. Following training, they were tested, first alone and then with a similarlytrained cage-mate. It was found that the presence of another rat substantially altered the rats' spatial behavior. Lone rats collected the food items faster while traveling a shorter distance, reflecting a higher efficiency of task completion. When accompanied by a partner, however, the rats traveled together, visiting the same set of objects in each trip with one of them leading. Whether alone or with a partner, rats continued to revisit the same objects; however, more such revisits occurred with a partner. We argue that revisiting objects is not necessarily an error, since returning to past places is an important aspect of rats' natural behavior. Revisiting an object following food depletion implies that searching for food was not the main driving force in the rats' spatial behavior. Specifically, despite food deprivation, rats were more attentive to one another than to the food. This could be adaptive, since foraging and feeding in groups is a way of poison avoidance in wild rats. Finally, the addition of a social component added complexity to the environment since the rats organized their spatial behavior in reference to one another in addition to their organization in the physical surrounding. Consequently, when tested with a partner, spatial behavior was less structured, less predictable and more chaotic.
Chronic intermittent injection of quinpirole (0.5mg/kg) to rats in a large non-standard open fiel... more Chronic intermittent injection of quinpirole (0.5mg/kg) to rats in a large non-standard open field (mirrored glass table without walls, 160 x 160cm and 60cm high) induces pronounced behavioral sensitization characterized by a 6-fold increase in locomotor distance and increased rigidity of travel along the same routes (path stereotype). Experiment 1 showed that equivalent treatment in the home cage induces much less sensitization of locomotor distance and no sensitization of path stereotypy, as evidenced by a test in the open field. In Experiment 2, transferring rats sensitized in one open field to a novel open field resulted in a 50% loss of sensitized locomotor distance and a virtual loss of sensitized path stereotypy. In Experiment 3, rotating the open field in relation to room cues did not affect sensitized responding, suggesting that the behavior is organized in relation to distal rather than local (open field) cues. Finally, an injection of saline in the sensitized environment failed to elicit conditioned locomotion (Experiment 4). These results are taken to indicate that the control of sensitization to quinpirole has components that are environment independent, behavior specific, and context dependent, each having a relatively different contribution and mechanism. It is suggested that under the experimental conditions of this study, the relative contributions to quinpirole sensitization were 50% for the context-dependent component, 30% for the behavior-specific component, and 20% for the environment-independent contribution. The mechanism for the context-dependent component may be related to development of path stereotypy and involve spatial learning.
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