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Domestic chicks (Gallus gallus domesticus) have been widely used as a model to study the motion cues that allow visually naïve organisms to detect animate agents shortly after hatching/birth. Our previous work has shown that chicks prefer to approach agents whose main body axis and motion direction are aligned (a feature typical of creatures whose motion is constrained by a bilaterally symmetric body plan). However, it has never been investigated whether chicks are also sensitive to the fact that an agent maintains a stable front–back body orientation in motion (i.e. consistency in which end is leading and which trailing). This is another feature typical of bilateria, which is also associated with the detection of animate agents in humans. The aim of the present study was to fill this gap. Contrary to our initial expectations, after testing 300 chicks across 3 experimental conditions, we found a recurrent preference for the agent which did not maintain a stable front–back body orientation. Since this preference was limited to female chicks, the results are discussed also in relation to sex differences in the social behaviour of this model. Overall, we show for the first time that chicks can discriminate agents based on the stability of their front–back orientation. The unexpected direction of the effect could reflect a preference for agents' whose behaviour is less predictable. Chicks may prefer agents with greater behavioural variability, a trait which has been associated with animate agents, or have a tendency to explore agents performing "odd behaviours". [ABSTRACT FROM AUTHOR]

Purpose: Spontaneous postural sway during quiet standing has been considered a simple output error of postural control. However, as postural sway and inherent body orientation evoke compensatory activity of the plantar flexors, they might contribute to blood circulation under gravitational stress via the muscle pump. Hence, the present study employed an external support device to attenuate the plantar flexor activity in supported standing (SS), to experimentally identify its physiological impact on blood circulation. Methods: Eight healthy young subjects performed two 5-min quiet standing trials (i.e., normal standing (NS) and SS), and the beat-to-beat interval (RRI) and blood pressure (BP) were compared between trials. We confirmed that postural sway and corresponding plantar flexor activity, quantified by the anteroposterior displacement of the foot center of pressure and lower back position with respect to the wall, and by the amplitude of electromyography and mechanomyography, respectively, were attenuated in SS, while mean body orientation angle and relative position of the BP sensor were comparable to NS. Results: The 5-min averages of diastolic BP and mean arterial pressure during SS were significantly higher than during NS, while RRI and systolic BP did not change. These could be interpreted as an increase in peripheral vascular resistance; meanwhile, in NS, this effect was replaced by the muscle pump of the plantar flexors. Conclusion: The muscle contractions related to spontaneous postural sway and body orientation produce substantial physiological impact on blood circulation during quiet standing. [ABSTRACT FROM AUTHOR]

In supermarkets or grocery, a shopping cart is a necessary tool for shopping. In this paper, we have developed an intelligent shopping support robot that can carry a shopping cart while following its owners and provide the shopping support by observing the customer's head orientation, body orientation and recognizing different shopping behaviors. Recognizing shopping behavior or the intensity of such action is important for understanding the best way to support the customer without disturbing him or her. This system also liberates elderly and disabled people from the burden of pushing shopping carts, because our proposed shopping cart is essentially a type of autonomous mobile robots that recognizes its owner and following him or her. The proposed system discretizes the head and body orientation of customer into 8 directions to estimate whether the customer is looking or turning towards a merchandise shelf. From the robot's video stream, a DNN-based human pose estimator called OpenPose is used to extract the skeleton of 18 joints for each detected body. Using this extracted body joints information, we built a dataset and developed a novel Gated Recurrent Neural Network (GRU) topology to classify different actions that are typically performed in front of shelves: reach to shelf, retract from shelf, hand in shelf, inspect product, inspect shelf. Our GRU network model takes series of 32 frames skeleton data then gives the prediction. Using cross-validation tests, our model achieves an overall accuracy of 82%, which is a significant result. Finally, from the customer's head orientation, body orientation and shopping behavior recognition we develop a complete system for our shopping support robot. [ABSTRACT FROM AUTHOR]

The analysis of customer pose is one of the most important topics for marketing. Using the customer pose information, the retailers can evaluate the customer interest level to the merchandise. However, the pose estimation is not easy because of the problems of occlusion and left-right similarity. To address these two problems, we propose an Integral Pose Network (IntePoseNet) which incorporates the body orientation and visibility mask. Firstly, benefiting from the simple gaits in retail store, the body orientation can give the global information of pose configuration. For example, if a person is facing to right, the body orientation indicates the occlusion of his or her left body. Similarly, if a person is facing to the camera, his or her right shoulder is probably at the left side of image. The body orientation is fused with local joint connections by a set of novel Orientational Message Passing (OMP) layers in Deep Neural Network. Secondly, the visibility mask models the occlusion state of each joint. It is tightly related to the body orientation because the body orientation is the main reason of self-occlusion. In addition, occluding object (e.g. shopping basket in retail store environment) detection can also give the clues of visibility mask prediction. Furthermore, the system models the temporal consistency by introducing the optical flow and Bi-directional Recurrent Neural Network. Therefore, the global body orientation, local joint connections, customer motion, occluding objects and temporal consistency are integrally considered in our system. At last, we conduct a series of comparison experiments to show the effectiveness of our system. [ABSTRACT FROM AUTHOR]

The analysis of customer pose draws more and more attention of retailers and researchers, because this information can reveal the customer habits and the customer interest level to the merchandise. In the retail store environment, customers’ poses are highly related to their body orientations. For example, when a customer is picking an item from merchandise shelf, he or she must face to the shelf. On the other hand, if the customer body orientation is parallel to the shelf, this customer is probably just walking through. Considering this fact, we propose a customer pose estimation system using orientational spatio-temporal deep neural network from surveillance camera. This system first generates the initial joint heatmaps using a fully convolutional network. Based on these heatmaps, we propose a set of novel orientational message-passing layers to fine-tune joint heatmaps by introducing the body orientation information into the conventional message-passing layers. In addition, we apply a bi-directional recurrent neural network on top of the system to improve the estimation accuracy by considering both forward and backward image sequences. Therefore, in this system, the global body orientation, local joint connections, and temporal pose continuity are integrally considered. At last, we conduct a series of comparison experiments to show the effectiveness of our system. [ABSTRACT FROM AUTHOR]

Orientation of human body is an important feature that can be used for behavioral analysis in surveillance systems. This cue contains useful information such as the direction of movement or attention. Difficulties such as low quality images, cluttered background and partial occlusion harden orientation estimation. In this paper, we propose a novel approach for determining body orientation using the ensemble of logistic regression classifiers.The logistic regression is a discriminative model that is very efficient in time and space complexities. In addition to these desirable properties, we show that this classifier provides a good classification performance in our problem. These classifiers are trained using Histogram of Oriented Gradient (HOG) descriptors which are extracted from four regions in the bounding box of the subjects. Two types of regions are considered in our method: static and dynamic regions. Static regions include: the whole body, upper half and the lower half of the body. Dynamic region includes the region of head and shoulder, which is located dynamically in various images and should be localized for each instance. To enhance the output of each classifier, we propose a weighting scheme based on the inherent characteristics of the orientation estimation problem and finally combine these outputs in an ensemble method to improve the accuracy. Experimental results show the superiority of the proposed method in accuracy and time complexity as compared to the state-of-the-art methods. [ABSTRACT FROM AUTHOR]

After a period of stepping on a rotating platform, blindfolded subjects demonstrate a tendency to unconsciously turn when stepping in place, an after-effect known as podokinetic after-rotation (PKAR). Recent studies have also reported a change in postural orientation following the adaptive period and have suggested that this is causally related to PKAR. Here, we assess changes in trunk orientation following platform adaptation and determine their relationship to PKAR. Specifically, we determine whether a reorganized standing posture causes PKAR. Ten subjects stepped on a platform rotating at 60°/s for 10 min, with a cadence of 100 steps/min. Following adaptation, a significant PKAR response was seen, with a mean yaw rotation velocity of 6.0 ± 2.2°/s. In addition to this dynamic after-effect, there was a significant twist of the trunk with respect to the feet when standing still (6.9° ± 4.5°; mean ± SD), confirming the presence of a postural reorientation after-effect. However, the magnitudes of the two after-effects did not correlate ( r = 0.06, p = 0.87). Furthermore, in a second experiment, a prolonged passive twist of the trunk was used to induce postural reorientation. However, in this case, PKAR was not induced. These results demonstrate that PKAR is not an automatic consequence of reorganized standing posture. [ABSTRACT FROM AUTHOR]

Elephant seals are one of the most proficient diving mammals in the world and are also one of the most studied. However, their long periods at sea and pelagic habits make research into their foraging ecology particularly challenging. Most current understanding comes from the use of time-depth recorders (TDRs). We used TDRs that additionally recorded body pitch and roll on four juvenile southern elephant seals ( Mirounga leonina) foraging over the Patagonian Shelf to describe their diving behaviour and compared them with those of adults, using standard descriptions of elephant seal dive profile types provided by the literature. Over 280 days of diving data showed that dive types were similar to those of adults (types: A, B, C, D, E and E) but that dive types A and C differed slightly, probably because our animals were constrained by bottom topography. Steep dive and return-to-surface angles in all dive types except type B indicate that animals generally attempt to maximize vertical displacement. Horizontal displacement was much greater in type B dives, which indicates a travelling function. Pitching and rolling behaviour lends support to the functions ascribed to the dive types already described for adult elephant seals, although type E dives are unusual in that the animals appear to be taking prey by up-ending in the benthos. [ABSTRACT FROM AUTHOR]

We investigated the influence of gaze elevation on judging the possibility of passing under high obstacles during pitch body tilts, while stationary, in absence of allocentric cues. Specifically, we aimed at studying the influence of egocentric references upon geocentric judgements. Seated subjects, orientated at various body orientations, were asked to perceptually estimate the possibility of passing under a projected horizontal line while keeping their gaze on a fixation target and imagining a horizontal body displacement. The results showed a global overestimation of the possibility of passing under the line, and confirmed the influence of body orientation reported by Bringoux et al. (Exp Brain Res 185(4):673–680, ). More strikingly, a linear influence of gaze elevation was found on perceptual estimates. Precisely, downward eye elevation yielded increased overestimations, and conversely upward gaze elevation yielded decreased overestimations. Furthermore, body and gaze orientation effects were independent and combined additively to yield a global egocentric influence with a weight of 45 and 54%, respectively. Overall, our data suggest that multiple egocentric references can jointly affect the estimated possibility of passing under high obstacles. These results are discussed in terms of “interpenetrability” between geocentric and egocentric reference frames and clearly demonstrate that gaze elevation is involved, as body orientation, in geocentric spatial localization. [ABSTRACT FROM AUTHOR]

Previous studies have shown that the perception of the earth-based visual horizon, also named Gravity Referenced Eye Level (GREL), is modified by body tilt around a trans-ocular axis. Here, we investigated whether estimates of the elevation of a luminous horizontal line presented on a screen in otherwise darkness and estimates of the possibility of passing under are identically related to body tilt in absence of motion. Results showed that subjects overestimated the elevation of the projected line, whatever their body orientation. In the same way, subjects also overestimated their capacity of passing under the line. Both estimates appeared as a linear function of body tilt, that is, forward body tilt yielded increased overestimations, and backward body tilt yielded decreased overestimations. More strikingly, the linear effect of body tilt upon these estimates is comparable to that previously observed for direct GREL judgements. Overall, these data strongly suggest that the perception of the elevation of a visible obstacle and the perception of the ability of passing under in otherwise darkness shared common processes which are intimately linked to the GREL perception. The effect of body tilt upon these perceptions may illustrate an egocentric influence upon the semi-geocentric frame of reference required to perform the task. Possible interactions between egocentric and geocentric frames of reference are discussed. [ABSTRACT FROM AUTHOR]

The representation of the vertical can be assessed by measuring the visual, tactile or perception of the postural vertical (PV). It is well accepted that visceral graviceptors and Golgi tendon receptors contribute to perception of the PV, whereas the role of muscular proprioception (Ia muscle spindles) remains to be clarified. The objective of this study was to analyze whether or not muscular proprioception contributes to the representation of verticality. We hypothesized that the modulation of proprioception by appropriate tendinomuscular vibration may tilt the PV. We present two experiments that explore this hypothesis. PV was firstly measured in the pitch plane in twelve healthy subjects in two conditions: baseline and vibration of both Achilles tendons during six minutes, according to a counterbalanced presentation. PV orientation (mean) and dispersion (standard deviation) were calculated on the six measurements per condition. Vibration of the Achilles tendons induced a systematic backward tilt of PV (2.7° ± 0.8° on average; P < 10−3), and no significant changes regarding PV dispersion. A clear post-effect was found for PV orientation in subjects who started the experiment with the condition vibration on. The possibility that PV could also be modulated by a much shorter duration of vibration (less than 8 s of vibration) was analyzed in a second experiment using a similar general procedure but a simplified experimental plane in other subjects. Again a backward PV tilt was induced by the vibration, but with a magnitude lower than that found in the first experiment, and with no post-effect. Since body geometry was unchanged, these two studies mean that proprioception contributes to the representation of the vertical. In conclusion, this study brings new insights to our understanding of the sense of verticality and contributes to the interpretation of backward falls induced by vibration. The induced backward fall is partly due to alignment of the erect posture with a backward-tilted referential of verticality. [ABSTRACT FROM AUTHOR]

The otoliths are stimulated in the same fashion by gravitational and inertial forces, so otolith signals are ambiguous indicators of self-orientation. The ambiguity can be resolved with added visual information indicating orientation and acceleration with respect to the earth. Here we present a Bayesian model of the statistically optimal combination of noisy vestibular and visual signals. Likelihoods associated with sensory measurements are represented in an orientation/acceleration space. The likelihood function associated with the otolith signal illustrates the ambiguity; there is no unique solution for self-orientation or acceleration. Likelihood functions associated with other sensory signals can resolve this ambiguity. In addition, we propose two priors, each acting on a dimension in the orientation/acceleration space: the idiotropic prior and the no-acceleration prior. We conducted experiments using a motion platform and attached visual display to examine the influence of visual signals on the interpretation of the otolith signal. Subjects made pitch and acceleration judgments as the vestibular and visual signals were manipulated independently. Predictions of the model were confirmed: (1) visual signals affected the interpretation of the otolith signal, (2) less variable signals had more influence on perceived orientation and acceleration than more variable ones, and (3) combined estimates were more precise than single-cue estimates. We also show that the model can explain some well-known phenomena including the perception of upright in zero gravity, the Aubert effect, and the somatogravic illusion. [ABSTRACT FROM AUTHOR]

We investigated the effects of whole body tilt and lifting the arm against gravity on perceptual estimates of the Gravity-Referenced Eye Level (GREL), which corresponds to the subjective earth-referenced horizon. The results showed that the perceived GREL was influenced by body tilt, that is, lowered with forward tilt and elevated with backward tilt of the body. GREL estimates obtained by arm movements without vision were more biased by whole-body tilt than purely visual estimates. Strikingly, visual GREL estimates became more dependent on whole-body tilt when the indication of level was obtained by arm lifting. These findings indicate that active motor involvement and/or the addition of kinesthetic information increases the body tilt-induced bias when making GREL judgements. The introduction of motor/kinaesthetic cues may induce a switch from a semi-geocentric to a more egocentric frame of reference. This result challenges the assumption that combining non-conflicting multiple sensory inputs and/or using intermodal information provided during action should improve perceptual performance. [ABSTRACT FROM AUTHOR]

Steering is an integral component of adaptive locomotor behavior. Along with reorientation of gaze and body in the direction of intended travel, body center of mass must be controlled in the mediolateral plane. In this study we examine how these subtasks are sequenced when steering is planned early or initiated under time constraints. Whole body kinematics were monitored as individuals were required to change their direction of travel by varying amounts when visually cued either at the beginning of the walk or one stride before. The analyses focused on the transition stride from one travel direction to another. Timing of changes (with respect to first right foot contact) in trunk roll angle, head and trunk yaw angle, and right foot displacement in the mediolateral plane were analyzed. The magnitude of these measures along with right and left foot placement at the beginning and right foot placement at the end of the transition stride were also analyzed. The results show the CNS uses two mechanisms, foot placement and trunk roll motion (piking action about the hip joint in the frontal plane), to move the center of mass towards the new direction of travel in the transition stride, preferring to use the first option when planning can be done early. Control of body center of mass precedes all other changes and is followed by initiation of head reorientation. Only then is the rest of the body reorientation initiated. [ABSTRACT FROM AUTHOR]

Abstract: In vertebrates, brain lateralization has been described as a left hemispheric specialization for information processing and decision-making and a right hemispheric specialization for intense emotional reactions and fear responses. Accordingly, we may expect that ungulates will instinctively orientate their body in order to use their left eye for the detection of threats and social information. In this study, we investigate the factors influencing the body orientation of individuals during feeding activities in 55 captive common elands in two socially stable captive herds. Do lateralized postures differ while individuals perform activities with different vulnerability risks, and what are the factors affecting lateral exposure preferences? We recorded a large number of observations of the activity of the elands, the number of animals on each side, the positions and distances of the closest neighbour, the dominant individual and the closest visual barrier. Statistical analyses determined the positioning preferences of the animal according to these factors, including the influence of age, sex and ranking (own and that of the closest). At herd and individual levels, common elands have a left bias in lateral exposure preference to herdmates, dominant and closest individuals. Body orientation choice seems to be based on a trade-off between the perceived threat a nearby animal represents and the distance between them. Situations of higher vulnerability, like grazing, are characterized by a more intense lateralized pattern. This supports the theory that the animal would use its left side senses to more quickly and accurately detect and process danger and social stimuli.Significance statement: Common elands exhibit a left bias in lateral exposure preference to close surrounding individuals in order to process that information more efficiently with the right brain hemisphere. Body orientation choice is also based on a trade-off between the threat an animal in close proximity represents and the distance to it. Both tendencies are amplified when the dominant individual is present in the paddock. In the same way, situations of higher vulnerability degree, like grazing, are characterized by a more intense left bias in lateral exposure preference compared with other cognitive non-demanding activities like standing or ruminating. [ABSTRACT FROM AUTHOR]