Motor Lateralization Research Articles

The complementary dominance hypothesis: a model for remediating the 'good' hand in stroke survivors.

The complementary dominance hypothesis is a novel model of motor lateralization substantiated by decades of research examining interlimb differences in the control of upper extremity movements in neurotypical adults and hemisphere-specific motor deficits in stroke survivors. In contrast to earlier ideas that attribute handedness to the specialization of one hemisphere, our model proposes complementary motor control specializations in each hemisphere. The dominant hemisphere mediates optimal control of limb dynamics as required for smooth and efficient movements, whereas the non-dominant hemisphere mediates impedance control, important for countering unexpected mechanical conditions and achieving steady-state limb positions. Importantly, this model proposes that each hemisphere contributes its specialization to both arms (though with greater influence from either arm's contralateral hemisphere) and thus predicts that lesions to one hemisphere should produce hemisphere-specific motor deficits in not only the contralesional arm, but also the ipsilesional arm of stroke survivors - a powerful prediction now supported by a growing body of evidence. Such ipsilesional arm motor deficits vary with contralesional arm impairment, and thus individuals with little to no functional use of the contralesional arm experience both the greatest impairments in the ipsilesional arm, as well as the greatest reliance on it to serve as the main or sole manipulator for activities of daily living. Accordingly, we have proposed and tested a novel intervention that reduces hemisphere-specific ipsilesional arm deficits and thereby improves functional independence in stroke survivors with severe contralesional impairment.

Structured Program for Developing the Psychomotor Skills of Institutionalized Children with Special Educational Needs.

Tailoring motor activities to the unique needs of children with special educational requirements has shown considerable efficacy. Our study aimed to develop a structured program specifically designed to enhance psychomotor abilities, focusing on balance and motor-cognitive skills among 28 students (aged 12-14) from two institutional centers in Romania. The program spanned 36 weeks, with biweekly 30 min sessions. Psychomotor skills were assessed through tests measuring balance, speed of movements, and upper limb motor laterality. Initial and final data were collected for evaluation. A statistical analysis, employing the Kolmogorov-Smirnov and Wilcoxon Z tests, compared the assessments. The results indicated significant improvements in movement speed, with a notable increase in stimulus identification (averaging from approximately 13 to 14) (p < 0.05) and reduced processing time (decreasing from about 28.7 to 28 s) (p < 0.05). However, while the structured program demonstrated substantial enhancements in specific motor and cognitive-motor skills, it did not yield significant changes in dynamic balance, maintaining values close to 0.9 (p > 0.05) for open-eyed balance and 0.88 (p > 0.05) for closed-eyed balance. Additionally, an analysis of the processing speed in pulses per second showcased a marginal decline, from approximately 0.46 to 0.45, revealing notable disparities between the initial and final measurements (p < 0.05).

Correlation between motor laterality, temperament and cortisol levels in dogs.

This study aimed to evaluate the correlation between motor lateralisation, temperament, and serum levels of cortisol. The study group consisted of 39 clinically healthy dogs: 21 females and 18 males. Lateralisation and temperament were assessed during periodic animal health checks using a standardised tape test and a proprietary assessment algorithm. The median cortisol level in the dogs was 4.6 ng/ml. The median cortisol level was 4.31 ng/ml in dogs under 3 years of age and 4.92 ng/ml in dogs over 3 years of age. The median cortisol level was 4.21 ng/ml in left-pawed dogs and 4.8 ng/ml in right-pawed dogs. Statistically significant differences were found between cortisol levels and temperament. The median cortisol level was 5.06 ng/ml in extrovert dogs and 4 ng/ml in introvert dogs.

Considerable effects of lateralization and aging in intracortical excitation and inhibition.

Findings based on the use of transcranial magnetic stimulation and electromyography (TMS-EMG) to determine the effects of motor lateralization and aging on intracortical excitation and inhibition in the primary motor cortex (M1) are inconsistent in the literature. TMS and electroencephalography (TMS-EEG) measures the excitability of excitatory and inhibitory circuits in the brain cortex without contamination from the spine and muscles. This study aimed to investigate the effects of motor lateralization (dominant and non-dominant hemispheres) and aging (young and older) and their interaction effects on intracortical excitation and inhibition within the M1 in healthy adults, measured using TMS-EMG and TMS-EEG. This study included 21 young (mean age = 28.1 ± 3.2 years) and 21 older healthy adults (mean age = 62.8 ± 4.2 years). A battery of TMS-EMG measurements and single-pulse TMS-EEG were recorded for the bilateral M1. Two-way repeated-measures analysis of variance was used to investigate lateralization and aging and the lateralization-by-aging interaction effect on neurophysiological outcomes. The non-dominant M1 presented a longer cortical silent period and larger amplitudes of P60, N100, and P180. Corticospinal excitability in older participants was significantly reduced, as supported by a larger resting motor threshold and lower motor-evoked potential amplitudes. N100 amplitudes were significantly reduced in older participants, and the N100 and P180 latencies were significantly later than those in young participants. There was no significant lateralization-by-aging interaction effect in any outcome. Lateralization and aging have independent and significant effects on intracortical excitation and inhibition in healthy adults. The functional decline of excitatory and inhibitory circuits in the M1 is associated with aging.

Perceived sidedness and correlation to vertical movement asymmetries in young warmblood horses.

The prevalence of vertical asymmetries is high in "owner-sound" warmblood riding horses, however the origin of these asymmetries is unknown. This study investigated correlations between vertical asymmetries and motor laterality. Young warmblood riding horses (N = 65), perceived as free from lameness were evaluated on three visits, each comprising objective gait analysis (inertial measurement units system) and a rider questionnaire on perceived sidedness of the horse. A subgroup (N = 40) of horses were also subjected to a forelimb protraction preference test intended as an assessment of motor laterality. We hypothesized associations between vertical asymmetry and motor laterality as well as rider-perceived sidedness. Vertical asymmetry was quantified as trial means of the stride-by-stride difference between the vertical displacement minima and maxima of the head (HDmin, HDmax) and pelvis (PDmin, PDmax). Laterality indexes, based on counts of which limb was protracted, and binomial tests were used to draw conclusions from the preference tests. In the three visits, 60-70% of horses exhibited vertical asymmetries exceeding clinically used thresholds for ≥1 parameter, and 22% of horses exhibited a side preference in the preference test as judged by binomial tests. Linear mixed models identified a weak but statistically significant correlation between perceived hindlimb weakness and higher PDmin values attributable to either of the hindlimbs (p = 0.023). No other statistically significant correlations to vertical asymmetry were seen for any of the questionnaire answers tested. Tests of correlation between the absolute values of laterality index and asymmetry parameters (HDmin, HDmax, PDmin, PDmax) identified a weak correlation (p = 0.049) with PDmax, but when accounting for the direction of asymmetry and motor laterality, no correlations were seen for either of the asymmetry parameters. No convincing evidence of associations between vertical asymmetries and motor laterality were seen and further studies investigating motor laterality and the origin of vertical asymmetries are needed.

Acute and chronic stress alter behavioral laterality in dogs

Dogs are one of the key animal species in investigating the biological mechanisms of behavioral laterality. Cerebral asymmetries are assumed to be influenced by stress, but this subject has not yet been studied in dogs. This study aims to investigate the effect of stress on laterality in dogs by using two different motor laterality tests: the Kong™ Test and a Food-Reaching Test (FRT). Motor laterality of chronically stressed (n = 28) and emotionally/physically healthy dogs (n = 32) were determined in two different environments, i.e., a home environment and a stressful open field test (OFT) environment. Physiological parameters including salivary cortisol, respiratory rate, and heart rate were measured for each dog, under both conditions. Cortisol results showed that acute stress induction by OFT was successful. A shift towards ambilaterality was detected in dogs after acute stress. Results also showed a significantly lower absolute laterality index in the chronically stressed dogs. Moreover, the direction of the first paw used in FRT was a good predictor of the general paw preference of an animal. Overall, these results provide evidence that both acute and chronic stress exposure can change behavioral asymmetries in dogs.

REPERCURSSÕES DO TREINO DE RESISTÊNCIA DO CORE SOBRE O DESEMPENHO DOS JOGADORES DE FUTEBOL

ABSTRACT Introduction: Soccer players are athletes who need to develop advanced characteristics of strength and speed. The resistance training of the muscles involved in the core is a new training theory applicable to modern sports that is gaining prominence due to its amazing results. It is of great value for researchers to integrate the strengths of core strengthening into soccer training, improve their protocols, and compensate for their limitations. Objective: This study aimed to analyze the relationship between core strength training and physical conditioning in soccer players. At the same time, this article discusses the influence of core muscle strength characteristics on athletes’ physical performance. Methods: This article selects advanced soccer players as research subjects. Volunteers were randomly divided into two groups (control and experimental groups). The experimental group received core muscle strength training, while the control group received daily training. This paper analyzed the muscle strength characteristics of the two groups of volunteers. Then, this paper conducts a statistical and mathematical analysis of the muscle strength level data in two groups of athletes. Results: The experimental group showed significant differences in bilateral hip and ankle joint flexors after core muscle strength training (P&lt;0.01). The relative peak moment of flexion and extension of the left hip was lower than that of the right hip, a factor justified by the predominant motor laterality principle on the players. The muscle strength of the left knee and ankle joints was greater than that of the right. Both experimental and control groups showed that the strength of the ankle flexors was better than the ankle extensors (knee toe flexors). The data were very significantly different (P&lt;0.01). Conclusion: Muscular endurance training can help improve the physical conditioning of soccer players. Athletes can reinforce core strength training in their daily training. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

Atrial Fibrillation Detected After Acute Ischemic Stroke

Atrial fibrillation (AF) increases 4-5 times incidence of cardiac embolic stroke. In contrast, as many as 70% of AF cases can be detected in stroke within three days of onset, and this can affect the patient's prognosis. This case report describes the causal pathophysiology of AF and acute stroke and identifies the associated risk factors. Case 1 is a 44-year-old woman, acute stroke with acute decrease level of consciousness. The patient came with status epilepticus and a hypertensive emergency. Obtained a history of stroke, uncontrolled hypertension, and myocardial infarction. Initial Score National Institutes of Health Stroke Scale (NIHSS) was 33 and CHA2DS2-VASc was 5. Investigation non-contrast head Computed Tomography (CT) scan showed no bleeding and echocardiography (ECG) showed AF with rapid ventricular response. The patient died after 3 days of treatment. Case 2 is an 83-year-old woman, acute stroke with acute decrease level of consciousness and right motor lateralization. There was a history of hypertension and stroke with left hemiparesis. The initial NIHSS was 28 and CHA2DS2-VASc was 6. Investigations non-contrast head CT scan showed no bleeding and ECG showed AF with normal ventricular response. The patient was discharged from the hospital after being treated for 22 days with NIHSS of 20. Several risk factors for post-stroke AF are elderly, hypertension, subtype of ischemic stroke, prior stroke, and comorbidities such as DM and hypertension. Post-stroke AF can occur because of changes in heart rhythm through autonomic disorders, increased plasma catecholamine levels, and inflammatory reactions. Early Recognition of risk factors, focusing on patients at higher risk of AF detected after stroke becomes important for comprehensive management of stroke with AF.&#x0D; Keywords: acute ischemic stroke, atrial fibrillation, CHA2DS2-VASc score, risk factors.

Testing the relationship between lateralization on sequence-based motor tasks and language laterality using an online battery

ABSTRACT Studies have highlighted an association between motor laterality and speech production laterality. It is thought that common demands for sequential processing may underlie this association. However, most studies in this area have relied on relatively small samples and have infrequently explored the reliability of the tools used to assess lateralization. We, therefore, established the validity and reliability of an online battery measuring sequence-based motor laterality and language laterality before exploring the associations between laterality indices on language and motor tasks. The online battery was completed by 621 participants, 52 of whom returned to complete the battery a second time. The three motor tasks included in the battery showed good between-session reliability (r ≥ .78) and were lateralized in concordance with hand preference. The novel measure of speech production laterality was left lateralized at population level as predicted, but reliability was less satisfactory (r = .62). We found no evidence of an association between sequence-based motor laterality and language laterality. Those with a left-hand preference were more strongly lateralized on motor tasks requiring midline crossing; this effect was not observed in right-handers. We conclude that there is little evidence of the co-lateralization of language and sequence-based motor skill on this battery.

Cooperative feeding and foraging lateralization by Eden's whales off southern China

AbstractWe investigated surface feeding behaviors of Eden's whales (Balaenoptera edeni edeni) in northern Beibu Gulf, southern China, between April 3, 2018, and April 26, 2021. During 122 days at sea, 1,065 individual feeding events were recorded, and eight feeding behaviors were identified: two nonlunging (tread‐water and/or trap‐feeding, 7.7%, and a novel behavior we call “pirouette feeding,” 15.3%) and six lunging (right lateral lunging, RLL, 10.9%; left lateral lunging, 0.2%; upright lunging, 6.3%, vertical lunging, 18.5%; inverted lunging, 0.3%; cooperative lateral lunging, COL, 40.9%). During COL, 2–8 whales swam clockwise around a fish school and simultaneously performed RLL on surfacing—the first cooperative feeding behavior recorded for a Balaenoptera whale. Five lateralized feeding behaviors (entailing either a left or right rotation on the long‐body axis) accounted for 65.8% of individual feeding events, with a strong right‐side bias (99.7%). Lateralized behavior is prevalent in many vertebrates, including several species of rorquals, and we suggest that the right‐biased foraging lateralization among rorquals specifically allows them to keep their right eye on their prey (i.e., a sensory versus motor lateralization), and that this shared asymmetry among conspecifics may have preadapted Eden's whale for cooperative foraging.

Lateralized behavior of jackal-dog hybrid

This paper examines the phenomenon of interhemispheric asymmetry, which underlies lateralization, using jackal-dog hybrid as an example. The aim of the work is to reveal the existence of a connection between the leading paw used and individual characteristics of dogs, such as sex, age, and percentage of jackal blood. The identification of such patterns can help to adjust or select a more effective method of training a working dog, which is the relevance of this work. Using the first-pitch method, it was found that of the 76 jackal-dog hybrid, 46 favored the right paw, 23 favored the left paw, and 7 used both paws equally. Among right-handed ones there are 31 females and 15 males, among left-handed ones there are 3 females and 20 males, and among ambidextrous ones, those who have not decided with the leading limb, there are 2 females and 5 males. In general, there is a correlation between the sex of the dog and severity of motor lateralization: females prefer the right limb more often than males, and males, in their turn, prefer the left limb more often than females. Among older dogs there are only jackal-dog hybrid with pronounced lateralization, i.e. only left- or right-handed dogs. As for the percentage of jackal blood and emotional functionality no regularities were found.

Investigating the influence of neuter status on paw preference in dogs and cats

ABSTRACT Motor lateralization is commonly observed through preferential paw use in dogs and cats. Previous studies have uncovered sex-related differences in paw preference, hypothesizing that these differences may be related to sex hormones. The current study aimed to compare neutered and entire individuals to further investigate whether paw preference is influenced by sex hormones. Dog and cat owners were required to fill in a questionnaire with demographic information such as sex and neuter status of their pets. They then carried out two simple paw preference tasks within their homes: a “reaching for food” task and a “reaching for a toy” task. This study revealed an overall preference among the 272 dogs and 137 cats tested to use their right paw in both tasks. In cats, the degree of paw preference (i.e., regardless of the direction) was significantly influenced by an interaction between neuter status and life stage. Also in dogs, both life stage and an interaction between neuter status and life stage tended to influence the degree of paw preference. Post-hoc power analysis revealed a lack of statistical power, suggesting that future studies using a larger sample size are needed to further investigate potential effects of neuter status on paw preference.

The Relationship Between the Motor Lateralization and the Concentration of Cortisol and Tyrosine in Dogs Exposed to Stress During Veterinary Activities

ABSTRACT The aim of the study was to assess the relationship between the motor lateralization in dogs and the concentration of cortisol and tyrosine in their plasma during a visit to a veterinary clinic. The research group consisted of 56 dogs. Motor lateralization was tested by of an adhesive tape test. The stress intensity was assessed basing on the levels of cortisol and ft4 in the serum blood. The statistical analysis revealed that in the group of 56 dogs there were 14 left-pawed dogs, 36 right-pawed dogs, and 6 dogs did not show particular paw preference. The average cortisol levels in particular groups were as follows: 7.94 ug/dl, 3.92 ug/dl and 3.7 ug/dl, whereas the level of tyrosine in the subjects that demonstrated left-sided lateralization (mean ± SE) (1.95 ± 0.46 ng/dl) for those with right-side lateralization (1.56 ± 0.23 ng/dl) and ambilateral dogs (1.01 ± 0.22 ng/dl). The statistical calculation of Pearson’s χ2 showed a significant relationship between the sex and the lateralization (χ2 = 6.238, df = 2, p = 0.0442).

Participation of Soccer Training Improves Lower Limb Coordination and Decreases Motor Lateralization.

Athletes, who display less lateralization, are considered to be more successful in their sports. Therefore, it is important to test the lateralization profiles of the athletes to determine future prospects. Soccer is one of the sports where lateralization plays an important role because performing the passes and kicks with either foot may increase the success rate. Improved lower limb coordination is also very essential to perform the soccer skills more efficiently. Thus, the purpose of this study was to investigate the motor lateralization profiles of youth soccer players and to compare the same lateralization to non-athletes. A total of 28 healthy youth (14 soccer players) aged between 14 and 16 years voluntarily participated in this study. All participants were right-footed and were asked to hit the targets with their either foot maintaining accuracy in a custom-made virtual reality interface. Final position error (FPE) and foot path deviation from linearity (FPDL) were calculated to test motor lateralization for each foot and group. Two-way Mixed Model ANOVA was conducted for each dependent variable. Results indicated significant differences for FPDL between groups, while there were no significant differences between groups and within feet for FPE. Nonathletes had significantly higher FPDL with their nondominant foot compared to their dominant foot, which was not observed among soccer players. Overall, nonathletes' movements were more curvature path compared to soccer players, thus, can be considered as less coordinated. As soccer players did not show a difference between their feet on FPDL and performed better than nonathletes, soccer participation can improve lower limb coordination as well as alter motor performance and lateralization.

Laterality in Horse Training: Psychological and Physical Balance and Coordination and Strength Rather Than Straightness.

Simple SummaryFor centuries, straightening a horse has been considered a key element in achieving its responsiveness and suppleness and has been a traditional goal in training. However, body asymmetry (natural crookedness), motor laterality (the preference for limbs on one side) and sensory laterality (the preference for sensory organs on one side) are naturally occurring phenomena. In humans, the forced correction of these imbalances, for example, forcing left-handed children to write with their right hands, has been shown to lead to psychological imbalance. In view of this, lateral asymmetries in horses should be accepted, and training should focus on psychological and physical balance, coordination and equal strength on both sides, instead of enforcing “straightness”. To explore this, we conducted a review of the literature on motor and sensory laterality in horses and found that the evidence suggests that enforcing straightness may be stressful and may even be counterproductive by causing psychological and physical imbalance relative to a horse, making it tense and uncooperative. In general, body asymmetry has been shown to have little impact on performance, but increases in motor and sensory laterality can indicate insufficiencies in housing, handling and training. We, therefore, propose that laterality should be recognized as a welfare indicator and that straightness in a horse should be achieved by conducting training focused on balance, coordination and equal strength on both sides.For centuries, a goal of training in many equestrian disciplines has been to straighten the horse, which is considered a key element in achieving its responsiveness and suppleness. However, laterality is a naturally occurring phenomenon in horses and encompasses body asymmetry, motor laterality and sensory laterality. Furthermore, forcibly counterbalancing motor laterality has been considered a cause of psychological imbalance in humans. Perhaps asymmetry and laterality should rather be accepted, with a focus on training psychological and physical balance, coordination and equal strength on both sides instead of enforcing “straightness”. To explore this, we conducted a review of the literature on the function and causes of motor and sensory laterality in horses, especially in horses when trained on the ground or under a rider. The literature reveals that body asymmetry is innate but does not prevent the horse from performing at a high level under a rider. Motor laterality is equally distributed in feral horses, while in domestic horses, age, breed, training and carrying a rider may cause left leg preferences. Most horses initially observe novel persons and potentially threatening objects or situations with their left sensory organs. Pronounced preferences for the use of left sensory organs or limbs indicate that the horse is experiencing increased emotionality or stress, and long-term insufficiencies in welfare, housing or training may result in left shifts in motor and sensory laterality and pessimistic mentalities. Therefore, increasing laterality can be regarded as an indicator for insufficiencies in housing, handling and training. We propose that laterality be recognized as a welfare indicator and that straightening the horse should be achieved by conducting training focused on balance, coordination and equal strength on both sides.

Does Carrying a Rider Change Motor and Sensory Laterality in Horses?

Simple SummaryLaterality, or one-sidedness, has been studied in many species, including horses, and has been linked to factors such as stress and emotionality. Today, although most horses are used for riding, the impact that carrying a rider has on their sensory (preferred side of sensory organs) and motor (preferred side of body usage) laterality has not been researched to date. In this study, 23 horses were tested to assess, firstly, motor laterality by observing which foreleg a horse would use to step over a pole and, secondly, sensory laterality by observing the preferred side of sensory organs when exposed to (a) an unknown person and (b) a novel object. All three experiments were conducted with and without a rider. The rider gave minimal aids and rode on a long rein to allow the horse free choice. The results of this preliminary study show that the strength of motor laterality (the number of times the preferred foreleg was used) increased when horses carried a rider but that sensory laterality did not change. This suggests that carrying a rider who is as passive as possible does not have an adverse effect on a horse’s stress levels and mental state.Laterality in horses has been studied in recent decades. Although most horses are kept for riding purposes, there has been almost no research on how laterality may be affected by carrying a rider. In this study, 23 horses were tested for lateral preferences, both with and without a rider, in three different experiments. The rider gave minimal aids and rode on a long rein to allow the horse free choice. Firstly, motor laterality was assessed by observing forelimb preference when stepping over a pole. Secondly, sensory laterality was assessed by observing perceptual side preferences when the horse was confronted with (a) an unfamiliar person or (b) a novel object. After applying a generalised linear model, this preliminary study found that a rider increased the strength of motor laterality (p = 0.01) but did not affect sensory laterality (p = 0.8). This suggests that carrying a rider who is as passive as possible does not have an adverse effect on a horse’s stress levels and mental state.

Ambidextrous Grazing Posture in the Catalan Pyrenean Horse

Motor laterality has been often studied in non-human animals, including ungulates, and it has been noted that adult animals tend to be ambidextrous. Therefore, the current study aimed to study the laterality of grazing posture when standing in a quadrupedal position. To this end, a total of 106 horses (24 foals, 8 yearlings, 14 subadults and 60 adults 53 females and 7 males) of Pyrenean horse from 11 grazing areas farms were observed and their forelimb preference when grazing was recorded (1-3 times for each animal). The obtained results revealed that approximately half of the horses were right-handed and half left-handed, and females were equally lateralized than males. Moreover, lateralization was not affected by age. Therefore, it seems that forelimb ambidexterity in Pyrenean horses is probably due to the lack of human contact. As the presentation of unevenness may be crucial to orthopaedic health and the compensatory mechanisms used by uneven footed horses are currently unknown, data presented here have a complementary crucial interest.

Ocean warming and acidification degrade shoaling performance and lateralization of novel tropical-temperate fish shoals.

Gregarious behaviours are common in animals and provide various benefits such as food acquisition and protection against predators. Many gregarious tropical species are shifting poleward under current ocean warming, creating novel species and social interactions with local temperate taxa. However, how the dynamics of these novel shoals might be altered by future ocean warming and acidification remains untested. Here we evaluate how novel species interactions, ocean acidification and warming affect shoaling dynamics, motor lateralization and boldness of range-extending tropical and co-shoaling temperate fishes under controlled laboratory conditions. Fishes were exposed to 1 of 12 treatments (combinations of three temperature levels, two pCO2 levels and two shoal type levels: mixed species or temperate only) for 38days. Lateralization (a measure of asymmetric expression of cognitive function in group coordination and predator escape) of tropical and temperate species was right-side biased under present-day conditions, but side bias significantly diminished in tropical and temperate fishes under ocean acidification. Ocean acidification also decreased shoal cohesion irrespective of shoaling type, with mixed-species shoals showing significantly lower cohesion than temperate-only shoals irrespective of climate stressors. Tropical fish became bolder under ocean acidification (after 4 weeks), and temperate fish became bolder with increasing temperature, while ocean acidification dampened temperate fish boldness. Our findings highlight the direct effect of climate stressors on fish behaviour and the interplay with the indirect effects of novel species interactions. Because strong shoal cohesion and lateralization are key determinants of species fitness, their degradation under ocean warming and acidification could adversely affect species performance in novel assemblages in a future ocean, and might slow down tropical species range extensions.

Glucocerebrosidase Mutations and Motor Reserve in Parkinson's Disease.

The concept of motor reserve explains the individual differences in motor deficits despite similar degrees of nigrostriatal dopamine depletion in Parkinson's disease (PD). To investigate glucocerebrosidase (GBA) variants as potential determinants of motor reserve for exploratory purposes. A total of 408 patients with drug-naïve PD were enrolled from the Parkinson's Progression Markers Initiative cohort database. All patients underwent SPECT dopamine transporter (DAT) scans and had results for Sanger sequencing of GBA. Parkinsonian motor deficits were assessed using the Movement Disorders Society Unified Parkinson's Disease Rating Scale Part III (MDS-UPDRS-III). We compared MDS-UPDRS-III scores while adjusting for DAT availability in the putamen (i.e., motor reserve) between the PD groups according to the presence of GBA mutations. Fifty-four (13.2%) patients carried GBA mutations. PD patients with GBA mutations were younger than those without mutations. There were no significant differences in sex, disease duration, years of education, and striatal DAT availability between the PD groups. PD patients with GBA mutations had higher MDS-UPDRS-III scores for the less affected side than those without mutations, despite similar levels of DAT availability in the contralateral putamen. The MDS-UPDRS-III sub-scores of the more affected side did not differ between the two PD groups. The results of this study demonstrated the detrimental effect of GBA variants on individual capacity to cope with PD-related pathologies, with different impacts depending on the motor laterality.

Laterality preferences at rest and predatory behaviour of the Gyrfalcon (Falco rusticolus): An alpha predator of the sky

ABSTRACT Brain lateralization is generally considered adaptive for an individual and it can be ascertained, for example, by measuring the preferential use of limbs. Avian models have been extensively used to investigate the evolution and the advantages of brain lateralization. Birds of prey are a good model to study motor laterality, however to date they have been studied almost exclusively in the context of predatory behaviour. In this study, we tested lateralization in Gyrfalcon (Falco rusticolus) across multiple contexts, and collected the following measures:(1) standing leg preference when sleeping, (2) wing preference to position the head while sleeping and (3) leg preference to grasp food. At the population level, we found left-leg lateralization while sleeping and no preference for placing the head under the left or the right wing. In the context of the predatory behaviour, we found a trend towards using the left leg to grasp food. Across the behaviours observed, we did not find evidence of lateralization at an individual level, as most of the subjects were ambidextrous. This study highlights the importance of the behavioural context when investigating side-bias and hemispheric laterality.