Adaptation of lower limb movement patterns when maintaining performance in the presence of muscle fatigue

Adaptations in lower limb movement patterns were examined when performance was maintained during a fatiguing repetitive loading task. Forty recreationally active male and female participants performed single-leg hopping to volitional exhaustion at 2.2 Hz to a submaximal height. Spatio-temporal characteristics, mechanical characteristics and variability of the knee-ankle and hip-knee joint couplings were determined at 20% increments during the duration of the hopping task. Variability of the knee-ankle and hip-knee couplings in the flexion/extension axis significantly increased during the loading and propulsion phases during the hopping task (p < 0.05). Performance (vertical stiffness, hopping frequency and height) did not change significantly during the task (p > 0.05), however foot contact time increased progressively during this task (p < 0.05) and maximum hop height significantly decreased after the task (p < 0.05). The observed increase in variability between adjoining lower limb segments demonstrated the ability of the neuromotor system to adapt and maintain performance even with the onset of fatigue. This finding highlights that during the performance of a rapid and repetitive loading activity, performance can be preserved when there is variability in the neuromotor system.     

Visual perceptual and handwriting skills in children with Developmental Coordination Disorder

ObjectiveChildren with Developmental Coordination Disorder demonstrate a lack of automaticity in handwriting as measured by pauses during writing. Deficits in visual perception have been proposed in the literature as underlying mechanisms of handwriting difficulties in children with DCD. The aim of this study was to examine whether correlations exist between measures of visual perception and visual motor integration with measures of the handwriting product and process in children with DCD.MethodThe performance of twenty-eight 8–14 year-old children who met the DSM-5 criteria for DCD was compared with 28 typically developing (TD) age and gender-matched controls. The children completed the Developmental Test of Visual Motor Integration (VMI) and the Test of Visual Perceptual Skills (TVPS). Group comparisons were made, correlations were conducted between the visual perceptual measures and handwriting measures and the sensitivity and specificity examined.ResultsThe DCD group performed below the TD group on the VMI and TVPS. There were no significant correlations between the VMI or TVPS and any of the handwriting measures in the DCD group. In addition, both tests demonstrated low sensitivity.ConclusionClinicians should execute caution in using visual perceptual measures to inform them about handwriting skill in children with DCD.     

Training compliance control yields improved drawing in 5–11 year old children with motor difficulties

There are a large number of children with motor difficulties including those that have difficulty producing movements qualitatively well enough to improve in perceptuo-motor learning without intervention. We have developed a training method that supports active movement generation to allow improvement in a 3D tracing task requiring good compliance control. Previously, we tested a limited age range of children and found that training improved performance on the 3D tracing task and that the training transferred to a 2D drawing test. In the present study, school children (5–11 years old) with motor difficulties were trained in the 3D tracing task and transfer to a 2D drawing task was tested. We used a cross-over design where half of the children received training on the 3D tracing task during the first training period and the other half of the children received training during the second training period. Given previous results, we predicted that younger children would initially show reduced performance relative to the older children, and that performance at all ages would improve with training. We also predicted that training would transfer to the 2D drawing task. However, the pre-training performance of both younger and older children was equally poor. Nevertheless, post-training performance on the 3D task was dramatically improved for both age groups and the training transferred to the 2D drawing task. Overall, this work contributes to a growing body of literature that demonstrates relatively preserved motor learning in children with motor difficulties and further demonstrates the importance of games in therapeutic interventions.     

Motor,affective and cognitive empathy in adolescence: Interrelations between facial electromyography and self-reported trait and state measures

This study examined interrelations of trait and state empathy in an adolescent sample. Self-reported affective trait empathy and cognitive trait empathy were assessed during a home visit. During a test session at the university, motor empathy (facial electromyography), and self-reported affective and cognitive state empathy were assessed in response to empathy-inducing film clips portraying happiness and sadness. Adolescents who responded with stronger motor empathy consistently reported higher affective state empathy. Adolescents' motor empathy was also positively related to cognitive state empathy, either directly or indirectly via affective state empathy. Whereas trait empathy was consistently, but modestly, related to state empathy with sadness, for state empathy with happiness few trait–state associations were found. Together, the findings provide support for the notion that empathy is a multi-faceted phenomenon. Motor, affective and cognitive empathy seem to be related processes, each playing a different role in the ability to understand and share others' feelings.     

Current knowledge on motor disorders in children with autism spectrum disorder (ASD)

Motor symptomatology in autism is currently poorly understood, and still not included in the autism spectrum disorder (ASD) diagnostic criteria, although some studies suggest the presence of motor disturbances in this syndrome. We provide here a literature review on early motor symptoms in autism, focusing on studies on psychomotor issues (tone, postural control, manual dexterity, handedness, praxis). The approach adopted in research to study altered motor behaviors is generally global and there is no detailed semiology of the motor or neuromotor disorders observed in people with ASD. This global approach does not enable understanding of the neuro-developmental mechanisms involved in ASD. Identification of clinical neuro-psychomotor profiles in reference to a standard would help to better understand the origin and the nature of the disorders encountered in ASD, and would thus give new directions for treatment.     

自闭症碎镜理论之迷思:缘起、问题与前景

自闭症患者在社会沟通和交往障碍上主要涉及社会情感互动缺陷、非语言行为交流缺陷、发展维持和理解人际关系的缺陷。该群体在社会认知过程中潜在自动的直觉成分受损被视为其独特的临床症状。鉴于镜像神经元系统在社会认知的直觉成分上扮演的重要角色,该系统的功能障碍假说(或称"碎镜"理论)被提出并用以解释自闭症的成因及其异常表现。然而,在经历了10年的发展与证据检验后,该理论潜在的问题逐渐暴露。当前的研究显示,迄今为止人类镜像神经元系统的研究存在内在缺陷,镜像神经元系统至多是社会认知的附带原因,该系统功能障碍也并非自闭症患者社会认知障碍的必要条件。碎镜理论面临来自临床行为研究与认知神经科学实验证据的广泛质疑。未来,伴随自闭症研究对象的变化,镜像神经元的社会响应学说的提出,双个体范式、第二人称神经科学范式与计算精神病学的兴起,镜像神经元与自闭症的真正关系将有望得以阐明。     

Spilling thoughts: configuring attentional resources in infants’ goal-directed actions

The focus and organization of attention in perception-action coupling is systematically examined in two studies involving 9 and 10 -month-old infants engaged in learning goal-directed behaviors. Experiment 1 (discrimination study) observed the influence of an attentionally demanding motor task on learning and cognition, while Experiment 2 (means-ends study) observed the influence of an attentionally demanding goal on motor planning and reaching performance. Taken together the results of these two experiments revealed that when mental processing resources were directed to thinking about movement, discrimination performance became compromised; conversely, when processing resources were directed to thinking about the goal-state, the motor planning and execution became compromised. These results suggest a “spilling forward” of thoughts onto actions and goal-states and thus an attention-driven cognition/action trade-off for infants’ goal-directed actions. Findings highlight the ultimate importance of emerging motor skills on cognition and are contextualized within the on-going dialogues and developmental debates surrounding perceptual-motor skill development and problem-solving strategies during the first year.     

Delayed imitation of complex behavioural sequences by 14- to 16-month olds

The present study was conducted to determine if children under the age of 18 months can exhibit delayed imitation of three-event sequences when they have no opportunity to practice. Twenty-three 14- to 16-month-old children underwent two different imitation conditions. In the practice condition the children could imitate the sequence immediately after modelling; then they were tested 1 or 7 days later. In the no practice condition the children had the chance to imitate only on the test day. Children were able to imitate the sequences under both conditions irrespective of the delay period. They produced significantly more target actions, and more target actions in the correct order, in the test phase and cued recall phase, compared with the baseline. There were no differences between the two conditions with a 1-day delay period, but after a 7-day delay, the number of target actions produced during the practice condition was significantly higher than those in the no practice condition. The results are discussed in terms of nonverbal mimetic representations. © 1998 John Wiley & Sons, Ltd.     

Neonatal imitation in a mother–infant setting

Imitation of tongue protrusions and mouth openings was investigated in 18 newborn infants using a procedure differing in three ways from previous laboratory studies: the mother presented the target gestures, she was permitted to adjust to the infant's reactions, and the infant's baseline response rate was assessed during face-to-face interaction. This procedure was assumed to facilitate infant imitation. Compared with baseline responses in face-to-face interaction, both tongue protrusions and mouth openings were imitated in the two conditions. No imitation, however, was found when the responses in the two imitation conditions were compared. These results are less convincing than those found in strictly controlled laboratory experiments. A less restrictive procedure did not, therefore, promote imitation. The mixed results could be explained by too short an exposure to the target gesture. If repeated and insistent gesturing is a crucial condition, neonatal imitation might be understood to be the result of instruction and teaching, rather than a means of mutual communication. © 1998 John Wiley & Sons, Ltd.     

Quadriceps-hamstrings intermuscular coherence during single-leg squatting 3–12 years following a youth sport-related knee injury

The purpose of this study was to determine the degree of co-contraction as per electromyographic gamma-band intermuscular coherence of the quadricep (Q) and hamstring (H) muscles during single-leg squatting (SLS), and to assess the influence of sex and self-reported knee complaints on the association between knee injury history and medial and lateral Q-H intermuscular coherence.Participants included 34 individuals who suffered a youth sport-related intra-articular knee injury 3–12 years previously, and 37 individuals with no knee injury history. Surface electromyographic signals were recorded from medial and lateral thigh muscles bilaterally to determine the gamma-band (30–60 Hz) intermuscular coherence between medial and lateral Q-H muscle pairs during SLS. Multivariable linear regression (α = 0.05) was performed to investigate the relationship between knee injury history (main exposure) and medial and lateral Q-H coherence (outcome) while accounting for the influence of sex and self-reported knee pain and symptoms (covariates).The median age of participants was 25 (range 18–30) and 67% were female. Q-H gamma-band coherence was present for 60–90% of legs. Medial and lateral Q-H coherence was higher in females compared to males. There was no evidence for an association between medial Q-H coherence, knee injury history, knee pain, or symptoms. There was evidence for an association between knee injury history and lateral Q-H coherence, which was modified by sex such that previously injured males demonstrated reduced Q-H coherence compared to uninjured males.These finding suggest that females demonstrate a more pronounced Q-H co-contraction strategy during a SLS than males regardless of knee injury history. Further, that male who suffered a youth sport-related knee injury 3–12 years previously demonstrate less Q-H co-contraction during a SLS than uninjured males. The mechanisms behind differences in neuromuscular control between males and females as well as previously injured and uninjured males require further investigation.