Intrinsic and extrinsic factors of turning preferences in humans

Neuropsychological Evidence Underlying Counterclockwise Bias in Running: Electroencephalography and Functional Magnetic Resonance Imaging Studies of Motor Imagery

We aimed to answer the question "why do people run the track counterclockwise (CCW)?" by investigating the neurophysiological differences in clockwise (CW) versus CCW direction using motor imagery. Three experiments were conducted with healthy adults. Electroencephalography (EEG) was used to examine hemispheric asymmetries in the prefrontal, frontal, and central regions during CW and CCW running imagery (n = 40). We also evaluated event-related potential (ERP) N200 and P300 amplitudes and latencies (n = 66) and conducted another experiment using functional magnetic resonance imaging (fMRI) (n = 30). EEG data indicated greater left frontal cortical activation during CCW imagery, whereas right frontal activation was more dominant during CW imagery. The prefrontal and central asymmetries demonstrated greater left prefrontal activation during both CW and CCW imagery, with CCW rotation exhibiting higher, though statistically insignificant, asymmetry scores than CW rotation. As a result of the fMRI experiment, greater activation was found during CW than during CCW running imagery in the brain regions of the left insula, Brodmann area 18, right caudate nucleus, left dorsolateral prefrontal cortex, left superior parietal cortex, and supplementary motor area. In the ERP experiment, no significant differences were found depending on direction. These findings suggest that CCW rotation might be associated with the motivational approach system, behavioral activation, or positive affect. However, CW rotation reflects withdrawal motivation, behavioral inhibition, or negative affect. Furthermore, CW rotation is understood to be associated with neural inefficiency, increased task difficulty, or unfamiliarity.

A study of turn bias in people with idiopathic Parkinson's disease

The objective of the study is to explore whether people with Parkinson's disease (PwPD) display a preferential turn bias dependent upon disease asymmetry, and whether specific disease features predict turn bias. PwPD and age-matched controls were instructed to walk on an instrumented gait mat making "normal" turns. Trials were analyzed using Proto Kinetics Movement Analysis Software (PKMAS) and time-locked video recordings to obtain turn directionality and spatiotemporal turn measures. Turn bias was estimated using previously defined formulas. Seventy-two PwPD and 28 controls were included. One hundred percent of controls and 85% of PwPD had left turn bias. Turn bias was not significantly associated with age, gender, handedness, disease asymmetry, cognition, or disease severity. The Freezing of Gait Questionnaire (FOGQ) questions 5 and 6 showed linear-by-linear association with turn bias. In binary logistic and ordinal regression models, FOGQ question 6 (average duration of turn freezing) and turn width were predictive of turn bias. Rightward turns had greater frequency of freezing episodes. Turn bias in our PwPD cohort does not appear related to disease asymmetry or other disease features, except gait freezing. Whether freezing severity on turning leads to non-left turn bias or vice versa requires more focused studies. Physical therapy interventions targeting turning direction in PwPD could reduce freezing severity.

Spontaneous emergence of counterclockwise vortex motion in assemblies of pedestrians roaming within an enclosure

The emergence of coherent vortices has been observed in a wide variety of many-body systems such as animal flocks, bacteria, colloids, vibrated granular materials or human crowds. Here, we experimentally demonstrate that pedestrians roaming within an enclosure also form vortex-like patterns which, intriguingly, only rotate counterclockwise. By implementing simple numerical simulations, we evidence that the development of swirls in many-particle systems can be described as a phase transition in which both the density of agents and their dissipative interactions with the boundaries play a determinant role. Also, for the specific case of pedestrians, we show that the preference of right-handed people (the majority in our experiments) to turn leftwards when facing a wall is the symmetry breaking mechanism needed to trigger the global counterclockwise rotation observed.

Assessing a Sensory-Motor-Cognition Triad in Amnestic Mild Cognitive Impairment With Dichotic Listening While Walking: A Dual-Task Paradigm

A contemporary topic in aging research relates to the significance of cognitive changes proper to mild cognitive impairment (MCI) to higher risk of falls and gait deteriorations. The present study addresses this question in the amnestic type of MCI (aMCI) by examining a triad of interrelated comorbidities occurring in the MCI condition: attentional impairments, hearing loss and gait disturbances. To this end, we applied a dichotic listening (DL) test during over-ground walking. DL assesses spontaneous and lateralized auditory attention in three conditions (i.e., free report or Non-forced (NF), Forced-Right (FR) ear and Forced-Left (FL) ear). Earlier reports suggest that this dual-task paradigm evoke asymmetric gait effects on healthy controls, which are moderated by degree of hearing loss. Therefore, the aim of the present study was to evaluate the effects of DL on bilateral (data from both limbs) and lateralized (each limb separately) gait outcomes in a group of forty-three aMCI participants (mean = 71.19) and fifty-two healthy older controls (mean = 70.90) by using hearing loss as a covariate in all analyses. Results showed the aMCI group presented overall compromised gait parameters, especially higher gait variability in all DL conditions during lateralized attentional control. These findings were observed bilaterally, and no lateralized effects on gait were observed. Only after controlling for hearing acuity, gait asymmetries on step length variability emerged almost exclusively in healthy controls. It was concluded that hearing loss in the aMCI group together with higher attentional impairments preclude aMCI individuals to properly execute DL and therefore, they do not display gait asymmetries. The present data demonstrate that varied demands on attentional control dependent on hearing acuity affects gait negatively in healthy older adults and aMCI individuals in very different ways. The appearance of asymmetric effects seems to be a perturbation related to normal aging, while the lack of asymmetries but exaggerated gait variability characterizes aMCI. The present findings show the intricate interplay of sensory, cognitive, and motor deteriorations in different group of older adults, which stresses the need of addressing co-occurring comorbidities behind gait perturbations in individuals prone to develop a dementia state.

Do dolphins really have a rightward lateralization for action? The importance of behavior-specific and orientation-neutral coding

Because each side of the vertebrate body is controlled by a different side of the brain, studies of behavioral lateralization can provide insight into functional cerebral asymmetries in humans and other animals. The current study examined behavioral lateralization for a variety of behaviors in a group of 26 dolphins, in order to assess the claim that cetaceans show strong rightward action asymmetries indicative of a left-hemisphere specialization for action. We distinguished between side asymmetries and whole body turning actions, and devised a new coding system to counter the problem that previous studies of rolling behaviors (i.e., rotations around the long axis) have used contradictory coding systems depending on species' typical orientation. Our results did not support a generalized population-level rightward action asymmetry across multiple behaviors. Instead, we suggest that many dolphin behavioral asymmetries may be better explained as a result of perceptual processing asymmetries common across many vertebrates.

Four meta-analyses across 164 studies on atypical footedness prevalence and its relation to handedness

Human lateral preferences, such as handedness and footedness, have interested researchers for decades due to their pronounced asymmetries at the population level. While there are good estimates on the prevalence of handedness in the population, there is no large-scale estimation on the prevalence of footedness. Furthermore, the relationship between footedness and handedness still remains elusive. Here, we conducted meta-analyses with four different classification systems for footedness on 145,135 individuals across 164 studies including new data from the ALSPAC cohort. The study aimed to determine a reliable point estimate of footedness, to study the association between footedness and handedness, and to investigate moderating factors influencing footedness. We showed that the prevalence of atypical footedness ranges between 12.10% using the most conservative criterion of left-footedness to 23.7% including all left- and mixed-footers as a single non-right category. As many as 60.1% of left-handers were left-footed whereas only 3.2% of right-handers were left-footed. Males were 4.1% more often non-right-footed compared to females. Individuals with psychiatric and neurodevelopmental disorders exhibited a higher prevalence of non-right-footedness. Furthermore, the presence of mixed-footedness was higher in children compared to adults and left-footedness was increased in athletes compared to the general population. Finally, we showed that footedness is only marginally influenced by cultural and social factors, which play a crucial role in the determination of handedness. Overall, this study provides new and useful reference data for laterality research. Furthermore, the data suggest that footedness is a valuable phenotype for the study of lateral motor biases, its underlying genetics and neurodevelopment.

Effect of orienteering experience on walking and running in the absence of vision and hearing

Purpose

This study aimed to examine differences between track and field (T&F) runners and foot-orienteers (Foot-O) in the walking and running tests in the absence of vision and hearing. We attempted to determine whether experienced foot orienteers show better ability to maintain the indicated direction compared to track and field runners.

Methods

This study examined 11 Foot-O and 11 T&F runners. The study consisted of an interview, a field experiment of walking and running in a straight line in the absence of vision and hearing, and coordination skills tests.

Results

Participants moved straight min. 20 m and max. 40 m during the walking test and min. 20 m and max. 125 m during the running test and then they moved around in a circle. Significant differences between groups were found for the distance covered by walking. Differences between sexes were documented for the distance covered by running and angular deviations. Relationship between lateralization and tendencies to veer were not found. Differences were observed between Foot-O and T&F groups in terms of coordination abilities.

Conclusions

Participants moved in circles irrespective of the type of movement and experience in practicing the sport. Orienteers may use information about their tendencies to turning more often left or right to correct it during their races in dense forests with limited visibility or during night orienteering competition.

Movement variability emerges in gait as adaptation to task constraints in dynamic environments

BACKGROUND

Motor variability has been related to motor control playing a functional role in human adaptive behaviours. However, the direction of the relationship between variability and motor control can be unclear. The specific relations that exist between task constraints and movement (re)organization could explain some of this controversy.

RESEARCH QUESTION

This study sought to understand whether manipulation of task constraints result in changes in the magnitude or structure of motor system variability observed in a basic walking task. We also investigated the relationship between performance in achieving task goals and the structure of motor variability.

METHODS

Twenty volunteers walked around a circular track with binary combinations of 3 task constraints, providing 8 conditions. The manipulated task constraints were: 1) track width; 2) surface stiffness; and 3), walking direction. Performance was analysed using standard deviation (SD) of sacral displacement and its mean velocity (MV). Fuzzy Entropy (FE) and Detrended Fluctuation Analysis (DFA) were used to assess the kinematic variability structure.

RESULTS

Individuals showed lower SD and MV walking on the narrower track. These changes were also followed by higher DFA values, indicating a more auto-correlated structure of variability. The foam surface was also associated with an increase in amplitude, velocity and irregularity (FE) of movement.

SIGNIFICANCE

Results of this study describe how specific task constraints, such as the width of the walking track and the surface stiffness, shape emergent movement coordination patterns as participants search for functional information from the environment to regulate performance behaviors. Changes in variability structure could reveal the search for adaptive strategies during walking. Smaller movement fluctuations and higher velocity in gait patterns are related to greater irregularity and lower autocorrelation in the kinematic variability structure, demonstrating that a specific relationship emerges between system variability and movement performance, which is driven by task constraints.

Biomechanical Outcomes Due to Impact Loading in Runners While Looking Sideways

A stable gaze is necessary to optimize visual conditions during running. Head accelerations generally remain stable when looking in front; however, it is unclear if this response is similar when the head is turned sideways, and whether other adaptive strategies are present to maintain this stability. The purpose of this study, therefore, was to examine whether runners maintained stable head accelerations while gazing at fixed targets in front and to their sides. The authors collected biomechanical data from 13 runners as they directed their gaze to visual targets located in front, 45°, and 90° to the sides at a random sequence. Vertical head and tibial accelerations were the primary outcome measures, while vertical loading rate, footstrike angle, contact time, stride length, and stride rate were the secondary measures. A reduction in vertical head accelerations was found in the rightmost direction (P = .04), while an increase in vertical tibial accelerations was found on the same direction (P = .02). No other significant differences were observed for the other variables. The results of this study suggest that the tibia accommodated the increased shock to maintain head stability.

Arm swing asymmetry in overground walking

Treadmill experiments suggest that left-dominant arm swing is common in healthy walking adults and is modulated by cognitive dual-tasking. Little is known about arm swing asymmetry in overground walking. We report directional (dASI) and non-directional arm swing symmetry indices (ndASI) from 334 adults (mean age 68.6 ± 5.9 y) walking overground at comfortable (NW) and fast (FW) speeds and while completing a serial subtraction task (DT). dASI and ndASI were calculated from sagittal shoulder range of motion data generated by inertial measurement units affixed to the wrist. Most (91%) participants were right-handed. Group mean arm swing amplitude was significantly larger on the left in all walking conditions. During NW, ndASI was 39.5 ± 21.8, with a dASI of 21.9 ± 39.5. Distribution of dASI was bimodal with an approximately 2:1 ratio of left:right-dominant arm swing. There were no differences in ndASI between conditions but dASI was smaller during DT compared to FW (15.2 vs 24.6; p = 0.009). Handedness was unrelated to ndASI, dASI or the change in ASI metrics under DT. Left-dominant arm swing is the norm in healthy human walking irrespective of walking condition or handedness. As disease markers, ndASI and dASI may have different and complementary roles.

Observational Study of 180° Turning Strategies Using Inertial Measurement Units and Fall Risk in Poststroke Hemiparetic Patients

Objective

We analyzed spontaneous 180° turning strategies in poststroke hemiparetic patients by using inertial measurement units (IMUs) and the association of turning strategies with risk of falls.

Methods

We included right paretic (RP) and left paretic (LP) post-stroke patients, and healthy controls (HCs) from a physical and rehabilitation department in France between July 2015 and October 2015. All subjects were right-handed and right-footed for mobilization tasks. Participants were instructed to turn 180° in a self-selected direction after a 10-m walk while wearing three IMUs on their trunk and both feet. We defined three turning patterns based on the number of external steps (pattern I = 1; II = 2–4 steps; and III ≥ 5) and four turning strategies based on the side chosen to turn (healthy or paretic) and the stance limb used during the first step of the turn (healthy or paretic). Falls in the 6 months after measurement were investigated.

Results

We included 17 RP [mean (SD) age 57.5 (9.5) years (range 43–73)], 20 LP patients [mean age 60.7 (8.8) years (range 43–63)], and 15 HCs [mean age 56.7 (16.1) years (range 36–83)]. The LP and RP groups behaved similarly in turning patterns, but 90% of LP patients turned spontaneously to the paretic side versus 59% of RP patients. This difference increased with turning strategies: 85% of LP versus 29% of RP patients used strategy 4 (paretic turn side with paretic limb). Patients using strategy 4 had the highest rate of falls.

Conclusion

We propose to consider spontaneous turning strategies as new indicators to evaluate the risk of fall after stroke. IMU could be routinely used to identify this risk and guide balance rehabilitation programs.

Childrens' left-turning preference is not modulated by magical ideation

The literature on human turning preferences is inconsistent. While the few studies with children below 14 years of age uniformly describe an overall left-turning (counterclockwise) tendency, a recent Internet study with more than 1500 adults found a right-sided (clockwise) bias. We set out to investigate spontaneous turning behaviour in children age 5-3 years and, based on neuropsychiatric work in adults, also explored a potential association with magical thinking. Findings indicated a clear left-turning preference, independent of a participant's sex and handedness. Whether a child responded a question about the existence of extrasensory communication in the affirmative or not was unrelated to direction and size of turning bias and lateral preference. Our results are consistent with a left-sided turning preference reported for children, but in opposition to the clockwise bias recently described in a large-scale study with adults. Whether they point to a maturational gradient in the preferred direction of spontaneous whole-body rotation or rather to a lack of comparability between measures used in observational versus Internet-based studies remains to be further investigated. Regarding a purported association between body turns and magical thinking, our study is preliminary, as only one single question was used to probe the latter.

The effect of stopping before turning on the direct observational measure of whole body turning bias

Turning bias, the preferential tendency to turn toward a given direction has been reported in both rodents and human participants. The observational gait method of determining turning bias in humans requires a stop prior to turning. This study removed the stop and hypothesised that turning bias would remain the same between stop and non-stop conditions if bias was solely under the control of neurochemical asymmetries. The results showed that statistically turning bias remained the same (to the left) regardless of method used but there was no agreement between the methods thus rejecting the hypothesis. It is likely that when not stopping biomechanical factors related to gait when turning influence the direction of turn rather than solely neurochemical asymmetries.

Turning bias in virtual spatial navigation: age-related differences and neuroanatomical correlates

Rodents frequently exhibit rotational bias associated with asymmetry in lesions and neurotransmitters in the striatum. However, in humans, turning preference is inconsistent across studies, and its neural correlates are unclear. We examined turning bias in 140 right-handed healthy adults (18-77 years old), who navigated a virtual Morris Water Maze. On magnetic resonance images, we measured volumes of brain regions relevant to spatial navigation. We classified turns that occurred during virtual navigation as veering (less than 10°), true turns (between 10° and 90°) and course reversals (over 90°). The results showed that performance (time of platform search and distance traveled) was negatively related to age. The distance traveled was positively associated with volume of the orbito-frontal cortex but not with the volumes of the cerebellum, the hippocampus or the primary visual cortex. Examination of turning behavior showed that all participants veered to the right. In turns and reversals, although on average there was no consistent direction preference, we observed significant individual biases. Virtual turning preference correlated with volumetric asymmetry in the striatum, cerebellum, and hippocampus but not in the prefrontal cortex. Participants preferred to turn toward the hemisphere with larger putamen, cerebellum and (in younger adults only) hippocampus. Advanced age was associated with greater rightward turning preference. Men showed greater leftward preference whereas women exhibited stronger rightward bias.

Parkinson's disease and segmental coordination during turning: I. Standing turns

OBJECTIVE

Many of the falls among people with Parkinson's disease (PD) occur during sudden, on-the-spot turning which requires systematic reorientation of axial segments towards the new direction. We examined whether a disturbance in the coordination of segmental reorientation is an important cause of turning difficulty in individuals with PD and is altered by dopaminergic medication.

METHODS

The sequence and timing of segmental reorientation during 45° and 90° on-the-spot turns was examined in fourteen individuals with PD while "off" and "on" medication and nineteen healthy controls (HC).

RESULTS

Regardless of the magnitude of the turn, HC reoriented their head, shoulder, and pelvis simultaneously followed by mediolateral foot displacement. PD patients displayed temporal coordination patterns similar to the HC. PD however, reduced the velocity and early magnitude of reorientation of each body segment which were both slightly improved by dopaminergic medication.

CONCLUSION

Our finding that the HC and PD patients turn en bloc when the turn is predictable and there are no time constraints shows that the strategy of en bloc turning is not wrong if the movement parameters are unconstrained. However, in real life situations, which usually require quick and unpredictable turns, the en bloc strategy may be unsafe and more likely to result in falls. While in such situations HC are able to change the strategy from en bloc to sequential segmental turning, PD patients may not be able to do so and continue to turn en bloc.

Femoral neck-shaft angle in humans: variation relating to climate, clothing, lifestyle, sex, age and side

The femoral neck-shaft angle (NSA) varies among modern humans but measurement problems and sampling limitations have precluded the identification of factors contributing to its variation at the population level. Potential sources of variation include sex, age, side (left or right), regional differences in body shape due to climatic adaptation, and the effects of habitual activity patterns (e.g. mobile and sedentary lifestyles and foraging, agricultural, and urban economies). In this study we addressed these issues, using consistent methods to assemble a global NSA database comprising over 8000 femora representing 100 human groups. Results from the analyses show an average NSA for modern humans of 127° (markedly lower than the accepted value of 135°); there is no sex difference, no age-related change in adults, but possibly a small lateral difference which could be due to right leg dominance. Climatic trends consistent with principles based on Bergmann's rule are evident at the global and continental levels, with the NSA varying in relation to other body shape indices: median NSA, for instance, is higher in warmer regions, notably in the Pacific (130°), whereas lower values (associated with a more stocky body build) are found in regions where ancestral populations were exposed to colder conditions, in Europe (126°) and the Americas (125°). There is a modest trend towards increasing NSA with the economic transitions from forager to agricultural and urban lifestyles and, to a lesser extent, from a mobile to a sedentary existence. However, the main trend associated with these transitions is a progressive narrowing in the range of variation in the NSA, which may be attributable to thermal insulation provided by improved cultural buffering from climate, particularly clothing.

Coordination of segments reorientation during on-the-spot turns in healthy older adults in eyes-open and eyes-closed conditions

Turning has frequent occurrence in everyday activities. Despite the prevalence of turning in everyday life and the challenge it poses to older adults, there is far less known about the multisegmental control of turning than the control of standing and straight walking, especially in elderly individuals. The purpose of this study was to examine the timing and sequence of segments reorientation in healthy older adults during 90° on-the-spot turns. The role of vision on segments coordination was also examined by testing the participants in eyes-open and eyes-closed conditions. When turning on-the-spot, healthy elderly reoriented their head, shoulder and pelvis simultaneously, followed by foot displacement. This was a robust behavior not affected by visual condition. Axial segments turned slower and more synchronously when vision was not available. While all segments started to turn together in both visual conditions, head turned faster and reached its peak velocity earlier than shoulder and pelvis. However, the difference in segmental velocity and the time to reach the peak velocity was smaller in eyes-closed than eyes-open condition. Without vision, the functional importance of a faster head turn is diminished. Participants may have adopted a tighter control of segments to simplify the control of movement by reducing the degrees of freedom.

The influence of classical dance training on preferred supporting leg and whole body turning bias

A rightward turning bias has been more frequently noted during adult classical dance practice than during spontaneous rotations. Training could play a role in inducing a preferred direction. We observed the preferred direction for executing four spontaneous whole-body full turns (pirouettes), with eyes open or closed, in pre-pubertal untrained girls and classical dance students. Of untrained girls, 58% showed a leftward turning bias (LTB) and 42% a rightward turning bias (RTB), independently of vision, lateral preferences, and supporting leg. Only one dancer showed a consistent LTB while the majority showed a RTB, with a tendency to use the left leg to turn towards the right. These results suggest that the role of the vestibular and visual systems is minimal for untrained girls, and suggest a training influence for dancers. The dance students' choice of a supporting leg for turning may exploit some biomechanical properties facilitating the pirouette.

What are the factors responsible for the deviation in stepping on the spot?

Without vision, keeping a straight-ahead direction while stepping on the spot is almost impossible, everybody deviates more or less. Several explanations for this, such as laterality, vestibulo-spinal influence, dopamine system, have been proposed. The aims of the experiment presented here were (1) to quantify the lateral deviation when stepping using a modified Fukuda test apparatus, and (2) to determine the factors potentially underlying such deviation. Twenty-five young adults, blindfolded, performed the experiment which consisted in stepping while holding a rotating vertical roll bar fixed on the wall. Four experimental conditions (i.e., normal, with an imposed pace, dual-task, or with the neck bent) were tested. All participants deviated towards one side or the other in all conditions. Adding an attentional load or imposing a particular pace did not change the amount of deviation. For three conditions (normal, with an imposed pace and dual-task), the deviation towards one side was not significantly larger than towards the other side at the group level. In the bent-neck condition, the deviation was significantly larger than in the other conditions. Furthermore, in this condition the deviation towards the left was significantly larger than the deviation towards the right at the group level. We discussed the results regarding the role of vestibular information and proprioceptive feedback from neck muscles in correcting a spontaneous deviation. Our results, however, go against the idea that sensorimotor lateral preferences are among the factors underlying such deviations, since we found no relationship between lateral preferences (hand, foot, and eye) and the side of deviation.

Spontaneous whole body rotations and classical dance expertise: how shoulder-hip coordination influences supporting leg displacements

The link between supporting leg stability and individual trunk strategies used during spontaneous whole-body rotations was studied according to visual and kinesthetic imagery styles for classical dancers and untrained female participants. Shoulders-hip angles in the horizontal plane and supporting leg (SL) displacements were analyzed with three-dimensional kinematic at the beginning and end of the four turns, identified according to their SL (left vs. right) and turn direction (clockwise, CW vs. counterclockwise, CCW). To begin a turn in CCW on left SL, all the participants turned shoulders before hips (-25 degrees angle), p<0.01. Untrained participants yielded the reverse (+30 degrees angle) in CW - their non-preferred turn - whereas dancers maintained their trunk en bloc. In the turn slow down, in their preferred direction all the participants adopted en bloc behavior to avoid imbalance. Dancers kept this pattern in CCW but untrained participants separated shoulders and hips, p<0.01; on left SL (+20 degrees angle) hips finished before shoulders and on right SL (-25 degrees angle), shoulders finished before hips. Both mental imagery styles and spatial context link reduction of shoulder-hip angle and stability of SL. Daily expertise, not only dance training, facilitates the en bloc shoulder-hip coordination to maintain equilibrium.

Test–retest stability of an experimental measure of human turning behaviour in right-handers, mixed-handers, and left-handers

Animals turn away from the hemisphere with the more active dopamine (DA) system. For humans, a similar relationship has been assumed, albeit that side preferences obtained from different measures are inconsistent. Given the important role of DA on human behaviour and cognition, a stable human turning measure is of significant experimental value. We assessed the stability (test and retest 4 weeks apart) of veering behaviour (lateral deviations during blindfolded straight ahead walking) in 20 healthy right-handers, 20 mixed-handers, and 20 left-handers. Veering behaviour did not differ between groups, and did not reveal any particular side preference in any group. Relationships of side preferences between testing sessions for the different handedness groups was low for right-handers, and showed some minor consistency for the mixed-handed group. Neither handedness nor footedness was significantly related to preferred veering side. These findings, if not related meaningfully to DA-mediated conditions (e.g., clinical populations, pharmacological studies, personality) in the future, suggests that veering behaviour is an inappropriate alternative to the animal turning model. These findings challenge the reliability of human turning measures, and invite more broadly for a critical evaluation of turning measures as an indicator of hemispheric DA asymmetries in human populations.

Turning bias and lateral dominance in a sample of able-bodied and amputee participants

Turning bias is the tendency to turn towards a given direction. Conflicting results from previous studies suggest that a number of factors may influence turning direction. The aim of this study was to determine if biomechanical asymmetries influence turning bias. A total of 100 able-bodied participants, and 30 trans-tibial amputees who, by definition, possess a functional asymmetry, volunteered to participate in the study. The right hand and right foot were significantly dominant for the able-bodied sample. Able-bodied participants showed a significant turning preference towards the left, which was opposite to the dominant hand and foot. The amputees were significantly right-hand dominant and the side of the amputation influenced foot dominance. The amputee sample showed no preferred turning direction. Turning bias indices in the amputee sample were not significantly associated with handedness, footedness, side of amputation, or dominance prior to amputation. The lack of a preferred direction of turn in the amputee sample suggests that biomechanical asymmetries can influence turning bias.