Upright Condition Research Articles

Comparison of stochastic stability boundaries for parametrically forced systems with application to ship rolling motion

Numerous accidents caused by parametric rolling have been reported on container ships and pure car carriers (PCCs). Considering this dangerous phenomenon, the parametric rolling in irregular seas is examined in this paper based on the stability of the systems origin, which corresponds to the upright condition of the vessel. It provides a novel theoretical explanation of the instability mechanism for two cases: white-noise parametric excitation and colored-noise parametric excitation. Moreover, the authors confirm the usefulness of the previously provided formulae by Roberts and Dostal by means of numerical examples.

Numerical investigation on the effects of heel on the aerodynamic performance of wing sails

The utilization of wind-assisted propulsion technology could reduce ship fuel consumption and emission of pollutants. In the study, the effect of steady heel angles on the aerodynamic characteristics of wing sails was investigated. Full-scale three-dimensional simulations with the ship's superstructure were conducted at heel angles of 0°–15° in all apparent wind directions. The correctness of the numerical computations is verified by comparing them with the wind tunnel experimental data. Overall, the heel is detrimental to the capture of wind energy by the wing sails. The aerodynamic forces of the sail system decrease with increasing heel angles. Specifically, the average thrust performance is attenuated by 4.7%, 13.5% and 20.5%, respectively, at heel angles of 5°, 10°, and 15° compared to the upright condition. Due to changes in the airflow distribution around the sails, the aerodynamic force of sails in heeled to windward and heeled to leeward decreases by the reduced area of the low-pressure zone on the suction side and the high-pressure zone on the pressure side, respectively. Finally, a prediction scheme for assessing the effect of rolling motion on sail performance is proposed by steady heel results.

Effect of travel direction and wheelchair position on the ease of a caregiver getting an occupied wheelchair across a soft surface: a randomized crossover trial

Purpose To test the hypotheses that, in comparison with pushing an occupied upright manual wheelchair forward, pulling backward on the push-handles improves the objective and subjective ease with which a caregiver can get the wheelchair across a soft surface (e.g., grass, mud, sand, gravel); and the ease with which a caregiver can get the wheelchair across a soft surface improves if the wheelchair is tipped back into the wheelie position. Methods We used a randomized crossover trial with within-participant comparisons to study 32 able-bodied pairs of simulated caregivers and wheelchair occupants. The caregiving participants moved an occupied manual wheelchair 5 m across a soft surface (7.5-cm-thick gym mats) under four conditions (upright-forward, upright-backward, wheelie-forward and wheelie-backward) in random order. The main outcome measure was time (to the nearest 0.1 s) and the main secondary measure was the ease of performance (5-point Likert scale). Results The upright-backward condition was the fastest (p < 0.05) and had the highest ease-of-performance scores. In the forward direction, there was no statistically significant difference in the time required between the upright and wheelie positions, but the wheelie position was considered easier. Conclusions Although further study is needed, our findings suggest that caregivers should pull rather than push occupied wheelchairs across soft surfaces. In the forward direction, caregivers may find the wheelie position easier than the upright condition. These techniques have the potential to both improve the effectiveness of and reduce injuries to caregivers. Clinical Trial Registration Number: NCT 04998539

Predicting Time to Take-Off in a Countermovement Jump for Maximal Quickness From Upright and Squat Starting Positions

A countermovement jump (CMJ) is common in sport and often time-constrained. Little is known about contributors to quickness in jumps. This study examined effective predictors of time to take-off and effects of the starting position on reaction time and take-off time in a countermovement jump performed for quickness from upright and squat positions. Forty-nine collegiate athletes performed CMJs for quickness from upright and squatting starting positions to 75% of their maximal jump height. Several variables were calculated from the kinetic data related to jump performance. Correlation and multiple regression were used to determine variables related and predictive of time to take-off under both conditions. Paired t-tests evaluated differences in reaction and take-off times between conditions. In the upright condition, an increasing rate of force development and force, and decreasing time variables, impulses, and countermovement depth were associated with shorter time to take-off. The time to take-off prediction included rates of force development, force, time, and impulse. In the squat condition, shorter time to take-off was associated with lesser time variables, eccentric impulse, force at the end of the eccentric phase, and countermovement depth, and a greater rate of force development, concentric impulse, peak power, peak force, and reaction time. The time to take-off prediction equation included time to the bottom of the countermovement, time to peak force, and peak power. Reaction and take-off times were longer in the upright condition. Quick jump efficiency may be improved by strategies to increase maximum strength and the eccentric rate of force development while decreasing countermovement depth and time to bottom.

Comparison of trunk muscle exercises in supine position during short arm centrifugation with 1g at centre of mass and upright in 1g.

Spaceflight is associated with reduced antigravitational muscle activity, which results in trunk muscle atrophy and may contribute to post-flight postural and spinal instability. Exercise in artificial gravity (AG) performed via short-arm human centrifugation (SAHC) is a promising multi-organ countermeasure, especially to mitigate microgravity-induced postural muscle atrophy. Here, we compared trunk muscular activity (mm. rectus abdominis, ext. obliques and multifidi), cardiovascular response and tolerability of trunk muscle exercises performed during centrifugation with 1 g at individual center of mass on a SAHC against standard upright exercising. We recorded heart rate, blood pressure, surface trunk muscle activity, motion sickness and rating of perceived exertion (BORG) of 12 participants (8 male/4 female, 34 ± 7 years, 178.4 ± 8.2 cm, 72.1 ± 9.6 kg). Heart rate was significantly increased (p < 0.001) during exercises without differences in conditions. Systolic blood pressure was higher (p < 0.001) during centrifugation with a delayed rise during exercises in upright condition. Diastolic blood pressure was lower in upright (p = 0.018) compared to counter-clockwise but not to clockwise centrifugation. Target muscle activation were comparable between conditions, although activity of multifidi was lower (clockwise: p = 0.003, counter-clockwise: p < 0.001) and rectus abdominis were higher (clockwise: p = 0.0023, counter-clockwise: < 0.001) during centrifugation in one exercise type. No sessions were terminated, BORG scoring reflected a relevant training intensity and no significant increase in motion sickness was reported during centrifugation. Thus, exercising trunk muscles during centrifugation generates comparable targeted muscular and heart rate response and appears to be well tolerated. Differences in blood pressure were relatively minor and not indicative of haemodynamic challenge. SAHC-based muscle training is a candidate to reduce microgravity-induced inter-vertebral disc pathology and trunk muscle atrophy. However, further optimization is required prior to performance of a training study for individuals with trunk muscle atrophy/dysfunction.

The Left-Side Bias Is Reduced to Other-Race Faces in Caucasian Individuals.

One stable marker of face perception appears to be left-side bias, the tendency to rely more on information conveyed by the left side of the face than the right. Previous studies have shown that left-side bias is influenced by familiarity and prior experience with face stimuli. Since other-race facial recognition is characterized by reduced familiarity, in contrast to own-race facial recognition, the phenomenon of left-side bias is expected to be weaker for other-race faces. Among Chinese participants, face inversion has been found to eliminate the left-side bias associated with own-race faces. Therefore, it is of interest to know whether face inversion influences left-side bias for non-Chinese research participants and can be generalized across own- and other-race faces. This study assessed 65 Caucasian participants using upright and inverted chimeric Caucasian and Asian faces in an identity similarity-judgment task. Although a significant left-side bias was observed for upright own-race faces, this bias was eliminated by facial inversion, indicating that such a bias depends on the applicability of configural processing strategies. For other-race faces, there was no left-side bias in the upright condition. Interestingly, the inverted presentation yielded a right-side bias. These results show that while left-side bias is affected by familiarity differences between own- and other-race faces, it is a universal phenomenon for upright faces. Inverted presentation strongly reduces left-side bias and may even cause it to revert to right-side bias, suggesting that left-side bias depends on configural face processing.

Novel controller for the coupled surge-pitch problem by controlling the metacentric height of sandglass-type FDPSO

Compared with the conventional vessels and platforms, the water plane area of the sandglass-type FDPSO (floating, drilling, production, storage and offloading unit) under upright condition is smaller, which makes its longitudinal metacentric height lower and natural frequency of pitch motion smaller. As a result, coupled surge and pitch motion problem would be caused unexpectedly. In this paper, from the perspective of controlling the metacentric height, a novel dynamic positioning (DP) controller is proposed. The proposed controller can make the natural frequencies of surge and pitch motions away from each other. Consequently, both the surge and pitch motions satisfy the positioning accuracy. Besides, the coupled resonant and non-resonant zones with the control parameters are investigated. Considering the system stability, positioning accuracy and power consumption, a complete analysis process of optimal control parameter selection is proposed. By comparisons with two existing control laws, the novel controller is established with better performances on robustness, positioning accuracy and energy consumption.

PREDICTING MAXIMAL COUNTERMOVEMENT JUMP HEIGHT FROM UPRIGHT AND SQUAT POSITIONS HEAD TITLE: UPRIGHT AND SQUAT MAXIMUM JUMP HEIGHT PREDICTORS

Introduction. Countermovement jump is common in sport and testing and performed from various starting positions. Little is known about effective contributors to maximal countermovement jump height from various starting positions. Purpose and Objectives. Determine effective jump height predictors and effect of starting position on countermovement jump height. Applied Methodology. Forty-nine collegiate athletes performed maximal height countermovement jumps from upright and squatting positions with arm movement. Several variables were calculated from kinetic data. Correlation and regression determined variables related to and predictive of jump height in both conditions. Paired t-tests evaluated differences in jump height. Achieved Major Results. Upright condition jump height positively correlated with peak force and power, eccentric and concentric impulses, and countermovement depth. Jump height prediction included peak force and power, and eccentric and concentric impulses. Squat condition jump height positively correlated with peak force and power, mean rate of force development, force generated at the beginning of propulsion, and concentric impulse. Jump height prediction equation included mean rate of force development, force at the beginning of propulsion, and peak power. Jump height was higher in the upright condition. Conclusions. Higher jumps are achieved from the upright position. Peak force, peak power, and concentric and eccentric impulses best contribute to upright jump height. Mean rate of force development, force at the beginning of propulsion, and peak power best predicted squat jump height. Limitations. We did not restrict arm movement, to encourage natural motion. Depth was not controlled, rather advising a comfortable depth. Subjects were recruited from various collegiate sports. Practical implications. Maximal jump height from various positions may be achieved through efforts to maximize jump peak power and increase musculotendinous loading in sport-specific starting positions. Originality/Value. This is the first study to explore the predictors of upright and squat countermovement jumps. These results can guide jump performance training.

The effects of a simulated fMRI environment on voice intensity in individuals with Parkinson's disease hypophonia and older healthy adults

PurposeFunctional magnetic resonance imaging (fMRI) has promise for understanding neural mechanisms of neurogenic speech and voice disorders. However, performing vocal tasks within the fMRI environment may not always be analogous to performance outside of the scanner. Using a mock MRI scanner, this study examines the effects of a simulated scanning environment on vowel intensity in individuals with Parkinson's disease (PD) and hypophonia and older healthy control (OHC) participants. MethodThirty participants (15 PD, 15 OHC) performed a sustained /ɑ/ vowel production task in three conditions: 1) Upright, 2) Mock Scanner + No Noise, and 3) Mock Scanner + MRI noise. We used a linear mixed-effects (multi-level) model to evaluate the contributions of group and recording environment to vowel intensity. A second linear mixed-effects model was also used to evaluate the contributions of PD medication state (On vs. Off) to voice intensity. ResultsVowel intensity was significantly lower for PD compared to the OHC group. The intensity of vowels produced in the Upright condition was significantly lower compared to the Mock Scanner + No Noise condition, while vowel intensity in the Mock Scanner + MRI Noise condition was significantly higher compared to the Mock Scanner + No Noise condition. A group by condition interaction also indicated that the addition of scanner noise had a greater impact on the PD group. A second analysis conducted within the PD group showed no effects of medication state on vowel intensity. ConclusionOur findings demonstrate that performance on voice production tasks is altered for PD and OHC groups when translated into the fMRI environment, even in the absence of acoustic scanner noise. For fMRI studies of voice in PD hypophonia, careful thought should be given to how the presence of acoustic noise may differentially affect PD and OHC, for both group and task comparisons.

Suppression of Coupled Pitch-Roll Motions using Quasi-Sliding Mode Control

This paper addressed the problems of controlling the coupled pitch-roll motions in a marine vessel exposed to the regular waves in the longitudinal and transversal directions. Stabilization of the pitch and roll motions can be regarded as the essential task to ensure the safety of a ship’s navigation. One of the important features in the pitch-roll motions is the resonance phenomena, which result in unexpected large responses in terms of pitch and roll modes in some specific conditions. Besides, owing to its inherent characteristics of coupled combination and nonlinearity of restoring terms, the vessel shows various dynamical behaviors according to the system parameters, especially in the pitch responses. Above all, it can be seen that suppression of pitch rate remains the most significant challenge to overcome for ship maneuvering safety studies. To secure the stable upright condition, a quasi-sliding mode control scheme is employed to reduce the undesirable pitch and roll responses as well as chattering elimination. The Lyapunov theory is adopted to guarantee the closed stability of the pitch-roll system. Numerical simulations demonstrate the effectiveness of the control scheme. Finally, the control goals of state convergences and chattering reduction are effectively realized through the proposed control synthesis.

Beyond Hammersley’s Last-Passage Percolation: a discussion on possible local and global constraints

Hammersley’s Last-Passage Percolation (LPP), also known as Ulam’s problem, is a well-studied model that can be described as follows: let m points be chosen uniformly and independently in [0,1] ^2 , then what is the maximal number \mathcal L_m of points that can be collected by an up-right path? We introduce here a generalization of this LPP, allowing for more general constraints than the up-right condition: the constraints may be either local or global . We give the correct order of \mathcal L_m in a general manner, and we illustrate the interest and usefulness of this generalized LPP with examples and simulations.

Medical Staff’s Posture on Airflow Distribution and Particle Concentration in an Operating Room

During a surgical procedure, each of the medical staffs would have different postures. Supporting medical staff such as anaesthesiologist would stand in upright condition with straighten-forearm, while medical staff that is performing surgical procedures is in bent-forearm posture. The positioning of forearm might interrupt the air supplies from the ceiling-mounted diffuser, that serves to remove the airborne particles from the surgical zone. Consequently, the movement of particles in the surgical zone is affected, and the tendency of particles to fall onto the patient’s wound is increased. This situation could elevate the chances of a patient contracting surgical site infections and could increase the risk of death. The present study aims to examine the effects of medical staff’s forearm posture on the number of particles falling onto the patient. A simplified computational fluid dynamics (CFD) model of the operating room was developed and validated based on the published data. An RNG k-ε turbulence model based on the Reynolds-Averaged Navier-Stokes (RANS) equations was used to simulate the airflow, while a discrete phase model was used to simulate the movement of the airborne particles. Results show that bent-forearm of medical staff obstructed the downward airflow to remove the particles released by the medical staff. Approximately 37 particles/m3 accumulated in the chest region of the medical staff. A high particle accumulation is also observed at the gap between the staff’s legs due to the stagnant airflow.

Categorization of Emotional Faces in Insomnia Disorder.

It has been proved that emotionally positive facial expressions are categorized much faster than emotionally negative facial expressions, the positive classification advantage (PCA). In the present study, we investigated the PCA in primary insomnia patients. In comparison with controls, insomnia patients categorized emotional faces more slowly but there was no significant reduction in accuracy. In normal controls, happy faces were categorized faster than sad faces (i.e., PCA), which disappeared in the inverted condition. Insomnia patients did not show evident PCA except for the overall delayed response for the inverted compared to the upright condition. These data suggest the dysfunction of categorization of emotional faces in insomnia patients.

Modulation of alpha waves in sensorimotor cortical networks during self-motion perception evoked by different visual-vestibular conflicts.

Visually induced illusion of self-motion (vection) has been used as a tool to address neural correlates of visual-vestibular interaction. The extent to which vestibular cortical areas are deactivated during vection varies from one study to another. The main question in this study is whether such deactivation depends on the visual-vestibular conflict induced by visual motion. A visual motion about the line of sight (roll motion) induces a visual-canal conflict in upright and supine observers. An additional visual-otolith conflict arises in the upright position only, with the graviceptive inputs indicating that the head is stationary. A 96-channel electroencephalogram (EEG) was recorded in 21 participants exposed to roll motion in seated and supine positions. Meanwhile, perceptual state of self-motion was recorded. Results showed a transient decrease in the cortical sensorimotor networks' alpha activity at the onset of vection whatever the participant's position, and therefore the visual-vestibular conflict. During vection, an increase in alpha activity over parieto-occipital areas was observed in the upright condition, that is, in a condition of visual-otolith conflict. The modulation of alpha activity may be predictive of the illusion of self-motion but also may reflect the level of inhibition in the sensorimotor networks needed to reduce potential interference from vestibular conflicting inputs.NEW & NOTEWORTHY For the first time, we explored the neural correlates of different visuo-vestibular conflicts induced by visual motion using EEG. Our study highlighted a neuronal signature for illusory self-motion (vection) in the sensorimotor networks. Strong alpha activity may predict successful vection but also reflects the level of inhibition of sensorimotor networks needed to reduce potential interfering vestibular inputs. These findings would be of prime importance for simulator and virtual reality systems that induce vection.

The early stage of face detection in patients with major depressive disorder: an ERP study.

To investigate whether perceptual processes involved in early stages of face processing are influenced by depressive disorder, the face detection and configural analysis were assessed by recording the N170 component elicited by faces and objects (tables) presented under upright and inverted conditions. The N170 component elicited at occipital-temporal sites by faces was larger and peaked later than that elicited by tables, and inverted faces significantly enhanced and delayed the N170. The N170 in response to faces was enhanced in patients with major depressive disorder and the N170 face effect for upright condition was significantly larger in major depressive disorder patients than that in controls. However, the N170 inversion effect did not differ between two groups. These data indicate that, compared with normal controls, there is abnormal face perception at the early stage of processing faces in major depressive disorder patients but the major depressive disorder patients may have intact configural processing of faces.

Повышение эффективности и безопасности контроля посадки навалочного судна с использованием жидкостных манометров

The article discusses the practical use of liquid manometers method for bulk carrier vessels draught control. The scientific novelty is the first time performed generalization of author’s practical experience of liquid manometers method use on bulk carrier ships and its theoretical basis. Control of the ship’s draught, heel, and trim, is a constant duty of the responsible ship's personnel. Especially this control is important during ship’s operations with bulk cargo at the port, where the draught parameters changes rapidly, due to the high rate of loading and unloading on the modern dry bulk terminals. The vessel is required to be in strict compliance with the restrictions imposed by local conditions of navigation in the ports and approaching roadways, as well as the requirements of the International Convention on Load Lines, to the whole vessel’s voyage. The violation of those restrictions may cause the vessel arrest by port authority. It is important for the vessel to be in upright condition, without excessive trim, for the correct determination of onboard bulk cargo amount.The draught marks reading is the most time-consuming element of the vessel’s draught, heel and trim control. In addition, the draught readings on the "facing to the sea" vessel side are unsafe. Known tragic cases among crew members, occurred when they tried to read the draught marks with traditional rope ladders hanged overboard.The practical value of the liquid manometers method is the possibility to define vessel’s draught with greater precision then other known methods. Also, it gives the opportunity to facilitate and make safe the vessel’s draught, heel and trim managing by ship’s cargo mates and shore surveyors during the operations with bulk cargo.

A Comparison of Squatting Exercise on a Centrifuge and With Earth Gravity.

Purpose: Long-duration space missions require countermeasures against the muscular wasting and cardiovascular deconditioning associated with microgravity. Replacing gravitational acceleration by means of centrifugation is a promising alternative as it challenges all physiological systems at once. The aim of this study is to examine the metabolic energy costs of squatting on a centrifuge in comparison with squatting in an upright standing posture under natural gravity.Methods: 24 subjects (11 male, 13 female) performed continuous squatting exercise for 9 min with increasing cadence (10, 12, and 15 squats min-1). This was done under three conditions: Upright under natural gravity and lying supine on a centrifuge at two radii (2.5 and 3.5 m) at 1 g of centrifugal acceleration at the subject’s average center of mass during the exercise.Results: Generally, subjects did not suffer from motion sickness. Exercise under natural gravity led to a higher Δ V’O2/body mass (7.1 ± 2.0, ml min-1 kg-1, mean ± SD) compared with exercise on the centrifuge (6.1 ± 1.6, ml min-1 kg-1, mean ± SD). Exercise efficiency was also reduced under natural 1 g at 28.2 ± 1.0% compared to 40.4 ± 1.5% on the centrifuge. As expected, oxygen consumption increased with increasing cadences. The Coriolis effect had a negligible impact as there was no significant difference in V’O2 between the two radii. However, during centrifugation and upward movement the right leg was more loaded than the leg left and vice versa during downward movement (centrifuge running clockwise looking down, so to the subjects’ right).Conclusion: The lower V’O2 on the centrifuge may be attributed to the unloading of trunk muscles while subjects were lying on the sled, which in the upright condition leaning against the sled were still working to stabilize the torso. Subjects tolerated high rotational rates combined with exercise very well.

The influences of age, gender and geometric pattern of visual image on the verticality perception: A subjective visual vertical (SVV) study among Malaysian adults.

Subjective visual vertical (SVV) is a simple, quick and reliable test for measuring utricular function. The literature on the effects of fundamental demographic variables such as age and gender on SVV is inconclusive and should be supported by research with larger samples. The aim of the present study was to determine the influences of age, gender and geometric pattern of visual image on SVV among healthy adults. This study employed a repeated measures design. Otorhinolaryngology Clinic, Hospital Universiti Sains Malaysia, Malaysia. Eligible Malaysian adults (N=187, aged 21-75years) were recruited and categorised into young (N=60), middle-aged (N=66) and older (N=61) groups. Most of them were Malay, and 51.3% were men. Subjective visual vertical angles (in degrees) were determined from each participant in a static upright condition using a computerised SVV device. They were asked to indicate their verticality perception for three types of visual images (solid line, dotted line and arrow pattern). Three-way mixed ANOVA revealed insignificant influences of age and gender on SVV results (P>0.05). In contrast, mean SVV angles were significantly higher for the arrow pattern than for other visual images (P=0.004). While the insignificant influences of age and gender on static SVV are further ascertained with larger samples, the perception of verticality is less accurate when aligning a more geometrically complex visual image (ie, arrow pattern). Further SVV research on vestibular-disordered patients is beneficial, particularly to verify the normative data obtained with this complex visual image.

The neutral posture of the cervical spine is not unique in human subjects

Cervical spine injuries often happen in dynamic environments (e.g., sports and motor vehicle crashes) where individuals may be moving their head and neck immediately prior to impact. This motion may reposition the cervical vertebrae in a way that is dissimilar to the upright resting posture that is often used as the initial position in cadaveric studies of catastrophic neck injury. Therefore our aim was to compare the “neutral” cervical alignment measured using fluoroscopy of 11 human subjects while resting in a neutral posture and as their neck passed through neutral during the four combinations of active flexion and extension movements in both an upright and inverted posture. Muscle activation patterns were also measured unilaterally using surface and indwelling electromyography in 8 muscles and then compared between the different conditions. Overall, the head posture, cervical spine alignment and muscle activation levels were significantly different while moving compared to resting upright. Compared to the resting upright condition, average head postures were 6–13° more extended, average vertebral angles varied from 11° more extended to 10° more flexed, and average muscle activation levels varied from unchanged to 10% MVC more active, although the exact differences varied with both direction of motion and orientation. These findings are important for ex vivo testing where the head and neck are statically positioned prior to impact – often in an upright neutral posture with negligible muscle forces – and suggest that current cadaveric head-first impact tests may not reflect many dynamic injury environments.

Body-relative horizontal\u2013vertical anisotropy in human representations of traveled distances

A growing number of studies investigated anisotropies in representations of horizontal and vertical spaces. In humans, compelling evidence for such anisotropies exists for representations of multi-floor buildings. In contrast, evidence regarding open spaces is indecisive. Our study aimed at further enhancing the understanding of horizontal and vertical spatial representations in open spaces utilizing a simple traveled distance estimation paradigm. Blindfolded participants were moved along various directions in the sagittal plane. Subsequently, participants passively reproduced the traveled distance from memory. Participants performed this task in an upright and in a 30° backward-pitch orientation. The accuracy of distance estimates in the upright orientation showed a horizontal–vertical anisotropy, with higher accuracy along the horizontal axis compared with the vertical axis. The backward-pitch orientation enabled us to investigate whether this anisotropy was body or earth-centered. The accuracy patterns of the upright condition were positively correlated with the body-relative (not the earth-relative) coordinate mapping of the backward-pitch condition, suggesting a body-centered anisotropy. Overall, this is consistent with findings on motion perception. It suggests that the distance estimation sub-process of path integration is subject to horizontal–vertical anisotropy. Based on the previous studies that showed isotropy in open spaces, we speculate that real physical self-movements or categorical versus isometric encoding are crucial factors for (an)isotropies in spatial representations.