A small step for rats alters spatial behavior: rats on a bi-level arena explore each level separately.

We tested rats on a 'bi-level open-field' whose two halves were separated vertically by an 8-cm step that the rats could easily ascend/descend. We sought to determine what might be the factors that shape traveling in three-dimensional environments; what makes an environment perceived as multileveled; and how are multileveled environments explored compared to two-dimensional environments? We found that rats on the bi-level open-field traveled a greater distance on the lower level compared to the upper one. They also spent a long time at the foot of the step before ascending to the upper level. They established a home-base on one level and a local base on the other one, and explored each level separately. We could not find a particular factor that accounted for the preference for the lower level. We suggest that the momentary egocentric sensation of moving vertically, together with an overall area large enough for exploration, result in perceiving an environment as multilevel. Exploration of such environments is fragmented, and each level is explored relatively independently, as has also been shown in other studies. Regarding the unanswered question of earlier studies concerning what integrates fragmented representations, this is the first study that suggests that in rats, and perhaps also in other rodent species, such integration is achieved by means of home-base behavior, resulting in the establishment of a single comprehensive representation of the multilevel environment.

Can rats and ants exchange information between the horizontal and vertical domains?

Since traveling in nature involves encountering various vertical structures, integration of horizontal and vertical spatial information is required. One form of such integration is to use information acquired in one plane for spatial navigation in another plane. Here we tested whether rats and ants that learned a reward location in a horizontal maze could utilize this information when the maze was rotated to a vertical orientation and vice versa. Rats that were trained in a horizontal Y-maze required more time to reach the reward when the maze was vertically rotated, but they were more accurate in choosing the correct arm. In contrast, rats tested in a horizontal maze after being trained in a vertical maze were less accurate but reached the reward faster. Changes after maze rotation were moderate and non-significant in ants, perhaps since the number of ants arriving at the reward increased over trials, diminishing the effect of maze rotation in ants compared to rats. According to the notion that horizontal spatial information is encoded in more detail than vertical information, the slow performance of rats in the vertical domain could be due to a more physically demanding task whereas their accuracy was due to a preceding detailed horizontal encoding. In contrast, rats in the vertical maze could gather less detailed information and therefore were less accurate in subsequent horizontal trials, where the lower energy cost enabled them to swiftly correct wrong choices. Altogether, the present results provide an indication for transferring spatial information between horizontal and vertical dimensions.

Social spatial cognition: social distance dynamics as an identifier of social interactions.

We suggest that socio-spatial behavior, which is an interaction between social and spatial cognition, can be viewed as a set of excursions that originate and end in close proximity to another individual(s). We present an extension of earlier studies that perceived spatial behavior in individual animals as a series of excursions originating from a particular location. We measured here the momentary distance between two individuals (social distance) to differentiate among eight possible types of social excursion originating in a state of proximity between excursion-participants. The defined excursion types are based on whether or not the excursion initiator also concludes the excursion, whether or not the excursion starts and ends at the same location, and the dynamics of the distance between excursion participants. We validated this approach to socio-spatial behavior as a set of excursions using it to analyze the behavior of the two sexes in rodents, of normal vs. stereotyped rats, as well as of different rodent species. Each of these groups displays a prevalent excursion type that reflects a distinct social dynamics. Our approach offers a useful and comprehensive tool for studying socio-spatial cognition, and can also be applied to distinguish among different social situations in rodents and other animals.

"It's all in their head": hierarchical exploration of a three-dimensional layered pyramid in rats.

Wayfinding in a three-dimensional (3D) environment is intricate, and surface-bounded animals may overcome this complexity by breaking it down into horizontal layers along with the vertical location of each layer. Here, we examined how rats explored a layered pyramid placed in a large open field. We found that exploration presented a hierarchical (or fractal) shape of three types of roundtrips: (1) from the primary home-base to the open-field floor; (2) from the floor up and down the pyramid levels; and (3) from local home-base on each pyramid level. Ascent was slow and interrupted, whereas descent was fast. This difference was a result of level altitude, remaining after data were normalized proportionally to level area. In contrast, the time spent and the distance traveled on each level were dependent on level area, not on level altitude. This structure of spatial behavior accords with multilevel exploration, presenting a relatively independent exploration of each level. The vertical dimension in this experiment thus did not alter the typical spatiotemporal behavior, and the 3D environment was explored by application of the same spatiotemporal approach as that of a horizontal open field. We suggest that this lack of alteration is due to the horizontal posture of the animal's head and trunk during progression on the pyramid. This behavior also seems to fit the bicoding hypothesis, in which the vertical information is virtually contextual (non-metric), and so, when the rat progresses to a new level, it explores it as a newly accessed horizontal floor area.

Spatio-temporal organization during group formation in rats.

In the present study, the dynamic process of group formation in eight unfamiliar rats was followed in order to reveal how the group becomes oriented together in time and space, in light of the complexity that accompanies grouping. The focus was on who, where, and when joined together. We found that rats preferred to be in companionship over remaining alone, with all the rats gradually shifting to share the same location as a resting place. Group formation can be viewed as a tri-phasic process, with some rats gradually becoming more social than others, and thus playing a key role in group formation. Starting with seemingly independent traveling, the rats gradually converged to share the same location as a terminal (home base) for roundtrips in the arena. Because such a terminal is considered as the organizer of an individual's spatial behavior, the shared home-base location may be viewed as the organizer of spatial behavior of the entire group. Despite huddling together, the rats continued to travel alone or in duos throughout the 3 h of testing. We suggest that resting together and traveling alone or in duos enabled the maintenance of communal relationship while reducing the complexity involved in traveling in relatively large groups. Taken together, the present results demonstrate the dynamic process during which unfamiliar rats shift from independent to group spatial behavior.

Social spatial cognition in rat tetrads: how they select their partners and their gathering places.

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.

"Shall two walk together except they be agreed?" Spatial behavior in rat dyads.

When animals explore an unfamiliar environment, they gather information that enables them to form a cognitive representation of that environment and to use it subsequently in traveling there. In the present study, rats were tested in a large arena as singles, then in dyads, and finally, again as singles, in order to examine the effect of the social environment on exploration. Traveling in dyads facilitated exploration compared to the behavior of the same rats when they explored alone. Specifically, each rat in a dyad traveled a greater distance with higher velocity and took wider turns compared to its lone traveling. Moreover, rats in dyads spent a long time together, shared a home base, and when traveling in the same direction, one rat was leading the other. In addition to exploring the same locations, leaders explored more "private" locations, not visited by the other rat. Features of the dyad behavior were carried over to the behavior of the same rats when tested as individuals, after the dyad trial. Compared to singles, dyads represent the first step toward grouping, and it is suggested that the conspicuous change between the behavior of a rat as single compared to its behavior when in a dyad should be greater than any further changes that may occur in spatial cognitive behavior of triads, quartets, or larger groups. In other words, while the present changes in spatial cognition observed in dyads represent a small step toward grouping, they are a giant leap for the individual.

Spatial behavior reflects the mental disorder in OCD patients with and without comorbid schizophrenia.

OBJECTIVE: Resolving the entangled nosological dilemma of whether obsessive-compulsive disorder (OCD) with and without schizophrenia (schizo-OCD and OCD, respectively) are two independent entities or whether schizo-OCD is a combined product of its parent disorders. METHODS: Studying motor activity in OCD and in schizo-OCD patients. Performance of the patients was compared with the performance of the same motor task by a matching control individual. RESULTS: Behavior in both schizo-OCD and OCD patients differed from controls in the excessive repetition and addition of acts, thus validating an identical OC facet. However, there was a significant difference in spatial behavior. Schizo-OCD patients traveled over a greater area with less focused activity as typical to schizophrenia patients and in contrast to OCD patients, who were more focused and traveled less in a confined area. While schizo-OCD and OCD patients share most of the OC ritualistic attributes, they differ in the greater spread of activity in schizo-OCD, which is related to schizophrenia disorder. DISCUSSION: It is suggested that the finding on difference in spatial behavior is a reflection of the mental differences between OCD and schizophrenia. In other words, this could be an overt and observable manifestation of the mental state, and therefore may facilitate the nosology of OC spectrum disorders and OCD. CONCLUSION: It seems as if both the OCD patients' focus on specific thoughts, and the contrasting wandering thoughts of schizophrenia patients, are reflected in the focused activity of the former and wandering from one place to the next of the latter.

Tactile cues compensate for unbalanced vestibular cues during progression on inclined surfaces.

A previous study demonstrated that rodents on an inclined square platform traveled straight vertically or horizontally and avoided diagonal travel. Through behavior they aligned their head with the horizontal plane, acquiring similar bilateral vestibular cues - a basic requirement for spatial orientation and a salient feature of animals in motion. This behavior had previously been shown to be conspicuous in Tristram's jirds. Here, therefore jirds were challenged by testing their travel behavior on a circular arena inclined at 0°-75°. Our hypothesis was that if, as typical to rodents, the jirds would follow the curved arena wall, they would need to display a compensating mechanism to enable traveling in such a path shape, which involves a tilted frontal head axis and unbalanced bilateral vestibular cues. We found that with the increase in inclination, the jirds remained more in the lower section of the arena (geotaxis). When tested on the steep inclinations, however, their travel away from the arena wall was strictly straight up or down, in contrast to the curved paths that followed the circular arena wall. We suggest that traveling along a circular path while maintaining contact with the wall (thigmotaxis), provided tactile information that compensated for the unbalanced bilateral vestibular cues present when traveling along such curved inclined paths. In the latter case, the frontal plane of the head was in a diagonal posture in relation to gravity, a posture that was avoided when traveling away from the wall.

Metabolically Healthy Obesity Is a Misnomer: Components of the Metabolic Syndrome Linearly Increase with BMI as a Function of Age and Gender.

OBJECTIVES: We aimed to examine the relationships between body mass index (BMI) and metabolic syndrome (MS) components as a function of age and gender across weight categories. METHODS: This cross-sectional study included 19,328 subjects who participated in a health-screening program. We analyzed 14,093 apparently healthy subjects with a BMI ≥ 18.5 kg/m2 (ranging from 18.5 to 46 kg/m2). RESULTS: At a BMI of 18.5 kg/m2, 16% of subjects had one or more MS components (MS ≥ 1). The number of MS components increased linearly with BMI. The most prevalent components for MS1-4 were hypertension (in men) and increased waist circumference (in women). Among 6391 non-obese subjects with MS = 0, there was a linear increase in blood pressure, glucose, and triglycerides, as well as a decline in high-density lipoprotein cholesterol, as BMI increased. In 2087 subjects with a BMI ≥ 30 kg/m2, a true normometabolic state (MS = 0) was observed in only 7.5%, declining to less than 1% at a BMI ≥ 36 kg/m2 (ATP criteria). Women were metabolically protected relative to men between the ages of 30 and 50 years. CONCLUSIONS: (A) MS components increase linearly with BMI from the lowest normal BMI and continue to increase with age and BMI; (B) metabolically healthy obesity is rare in subjects with a high BMI and declines with age; (C) hypertension is the most common component in men; and (D) in women, MS components are seen at older ages than in men for the same BMI. Metabolic health declines with age and BMI in nearly all subjects with obesity.

On heights and plains: How rodents from different habitats cope with three-dimensional environments?

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.

Keep a level head to know the way ahead: How rodents travel on inclined surfaces?

Animals traveling on a horizontal surface stabilize their head in relation to the substrate in order to gather spatial information and orient. What, however, do they do when traveling on an incline? We examined how three rodent species differing in motor abilities and habitats explore a platform tilted at 0-90°, hypothesizing that they would attempt to maintain bilateral vestibular cues. We found that traveling up or down was mainly straight vertically rather than diagonally, which results in identical bilateral vestibular cues. This was also achieved when traveling horizontally through rotating the head to parallel the horizontal plane. Traveling diagonally up or down was avoided, perhaps due to different bilateral vestibular cues that could hinder orientation. Accordingly, we suggest that maintaining identical bilateral cues is an orientational necessity that overrides differences in motor abilities and habitats, and that this necessity is a general characteristic of animals in motion.

Rodents Prefer Going Downhill All the Way (Gravitaxis) Instead of Taking an Uphill Task.

We directly tested whether, when given the choice to ascend or descend, rodents would favor traveling downwards or upwards. The test incorporated different rodent species that dwell in different habitats and display different life and motor styles. Testing was performed in a three-dimensional Y-maze in which the basis was horizontal and, by rotating it, one arm of the maze could be pointing upwards at a certain angle and the other arm pointed downwards at the same angle. All the tested species displayed a general preference for descent, with rodents from complex habitats being less affected by inclination compared with rodents from flatlands. Unlike laboratory rats, wild species traveled greater distances along the lower compared to the upper maze arm. All the rodents initially tended to travel the entire length of the inclined maze arms, but such complete trips decreased with the increase in inclination. When introduced into the maze from top or bottom, flatland dwellers traveled mainly in the entry arm. Overall, when given the choice to ascend or descend, all the tested species displayed a preference to descend, perhaps as attraction to the ground, where they usually have their burrows.

Decision making at a crossroad: why to go straight ahead, retrace a path, or turn sideways?

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.

Spatial behavior: the impact of global and local geometry.

Humans and other animals use the global geometry of the surrounding environment in order to orient and determine which direction they are facing. Accordingly, the impact of environment geometry on spatial behavior is reflected in the paths of progression in the environment. When the perception of the global geometry is limited, such as in large or dark environments, the global geometry of the environment has to be constructed gradually as the accumulated geometry of locales. In the present study, we progressively altered the form of a dark square test arena by means of local alterations to its corners and walls, in order to differentiate the impact of the global arena geometry from that of the local arena geometry sectors on spatial behavior in rats. We found that as long as the local alterations did not distort the global square geometry of the dark environment, the rats' behavior did not significantly change. In contrast, distortion of the square shape of the arena resulted in significant changes in the spatial distribution of the rats' activity. Accordingly, we suggest that the perceived global geometry affects spatial behavior, overriding the impact of the local geometry.

City rats: insight from rat spatial behavior into human cognition in urban environments.

The structure and shape of the urban environment influence our ability to find our way about in the city. Understanding how the physical properties of the environment affect spatial behavior and cognition is therefore a necessity. However, there are inherent difficulties in empirically studying complex and large-scale urban environments. These include the need to isolate the impact of specific urban features and to acquire data on the physical activity of individuals. In the present study, we attempted to overcome the above obstacles and examine the relation between urban environments and spatial cognition by testing the spatial behavior of rats. This idea originated from the resemblance in the operative brain functions and in the mechanisms and strategies employed by humans and other animals when acquiring spatial information and establishing an internal representation, as revealed in past studies. Accordingly, we tested rats in arenas that simulated a grid urban layout (e.g. Manhattan streets) and an irregular urban layout (e.g. Jerusalem streets). We found that in the grid layout, rat movement was more structured and extended over a greater area compared with their restricted movement in the irregular layout. These movement patterns recall those of humans in respective urban environments, illustrating that the structure and shape of the environment affect spatial behavior similarly in humans and rats. Overall, testing rats in environments that simulate facets of urban environments can provide new insights into human spatial cognition in urban environments.

Social spatial cognition.

Social spatial cognition refers to the interaction between self, place, and partners, with emphasis on the impact of the social environment on spatial behavior and on how individual spatial representations converge to form collective spatial behavior - i.e., common places and routes. Recent studies suggest that in addition to their mental representation (cognitive map) of the physical environment, humans and other animals also have a social cognitive map. We suggest that while social spatial cognition relies on knowledge of both the physical and the social environments, it is the latter hat predominates. This dominance is illustrated here in the modulation of spatial behavior according to dynamic social interactions, ranging from group formation to an attenuation of drug-induced stereotypy through the mere presence of a normal subject. Consequently we suggest that the numerous studies on the biobehavioral controlling mechanisms of spatial behavior (i.e. - the hippocampal formation, animal models for mental disorders) should also consider the social environment rather than solely focusing on the spatial behavior of lone animals.

Are there between-country differences in motor behavior of obsessive-compulsive disorder patients?

BACKGROUND: Cross-cultural factors attributed to obsessive-compulsive disorder (OCD) that are widely investigated around the world are mostly epidemiological, with no respect to the impact of culture on the structure of OCD behavior itself. METHODS: Nine Israeli and nine British OCD patients with respective non-OCD individuals were compared. To determine whether OCD symptoms are consistent across cultures, similarities in behavior were analyzed, as well as differences due to a country effect. In each country, nine OCD patients and nine non-OCD individuals were videotaped while performing the task that the patients attributed to their behavior. RESULTS: Except for a significantly higher rate of repetition and higher performance of idiosyncratic acts, patients from both Israel and the United Kingdom showed high levels of similarities in 22 out of 24 parameters. Compared with Israeli subjects, British OCD patients had significantly longer chains of idiosyncratic acts, and a twice-higher prevalence of brief (1-2 second) idiosyncratic acts. Between-country differences were mild, possibly overridden by the conspicuous impact of OCD pathology, resulting in a similar OCD phenotype. CONCLUSION: These results qualitatively and quantitatively emphasize the universal appearance of the compulsions in OCD symptoms.

How do rodents explore a three-dimensional environment? Habitat-dependent and direction-dependent differences.

Many animals are surface-bounded, traveling mostly in two-dimensional (2D) environments. However, those that inhabit structured habitats might also require wayfinding in three-dimensional (3D) environments. Here we forced rodents to ascend or descend when traveling. We tested three species: laboratory rats (a common experimental subject); fat sand rats, which forage while climbing shrubs (representing those used to 3D travel); and Tristram's jirds, which forage in plains (not used to climbing). We examined differences between individuals initially placed on top of the apparatus compared with those placed on its bottom, assuming that this, in addition to the above difference in habitats and motor habits, would influence their spatial behavior. Exploratory activity of top-starting rats and sand rats, but not jirds, differed from bottom starters. Nevertheless, despite the need to continuously ascend or descend, both top- and bottom-starters of the three species displayed the spatio-temporal structure of open-field exploration as previously revealed in a horizontal arena. Specifically, exploration constituted a set of round-trips to a home-base. It is suggested that the preservation of a regular structure of spatial behavior was due to the ability of the tested rodents to mostly maintain a horizontal posture of their head when ascending and descending.

Social interaction modulates the intensity of compulsive checking in a rat model of obsessive-compulsive disorder (OCD).

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.