The supplementary motor area in motor and perceptual time processing: fMRI studies

The neural bases of timing mechanisms in the second-to-minute range are currently investigated using multidisciplinary approaches. This paper documents the involvement of the supplementary motor area (SMA) in the encoding of target durations by reporting convergent fMRI data from motor and perceptual timing tasks. Event-related fMRI was used in two temporal procedures, involving (1) the production of an accurate interval as compared to an accurate force, and (2) a dual-task of time and colour discrimination with parametric manipulation of the level of attention attributed to each parameter. The first study revealed greater activation of the SMA proper in skilful control of time compared to force. The second showed that increasing attentional allocation to time increased activity in a cortico-striatal network including the pre-SMA (in contrast with the occipital cortex for increasing attention to colour). Further, the SMA proper was sensitive to the attentional modulation cued prior to the time processing period. Taken together, these data and related literature suggest that the SMA plays a key role in time processing as part of the striato-cortical pathway previously identified by animal studies, human neuropsychology and neuroimaging.     

Evaluation of two methods of prompting drivers to use specific exits on conflicts between vehicles at the critical exit

The Florida Department of Transportation used a series of changeable-message signs that functioned as freeway guide signs to divert traffic to Universal Theme Park via one of two eastbound exits based on traffic congestion at the first of the two exits. An examination of crashes along the entire route indicated a statistically significant increase in crashes at the first eastbound exit following the actuation of the system. Furthermore, all of the crashes occurred in close proximity to the exit gore (the crosshatched area at exits that drivers are not supposed to enter or traverse) at the first exit. In Experiment 1, behavioral data were collected using an alternating treatments design. These data revealed that reassigning the exit signs was effective in producing a change in the percentage of drivers using each of the two exits. These data also showed that the reassignment of the theme park exit was associated with an increase in the percentage of motor vehicle conflicts that consisted of vehicles cutting across the exit gore. An analysis revealed that the method used for switching the designated or active theme park exit on the series of changeable-message signs led to the presentation of conflicting messages to some motorists, thus resulting in erratic driving behavior (cutting across the exit gore). In Experiment 2, the treatment evaluated the use of a phased method of switching the designated theme park exit to eliminate the delivery of conflicting messages. The new method for switching the designated theme park exit was not associated with an increase in motorists cutting across the exit gore.     

The Neural Basis of Motor-Skill Learning

Recent work indicates that motor-skill learning is supported by four processes: a strategic process that selects new goals of what to change in the environment, a perceptual-motor integration process that adjusts to new relationships between environmental stimuli and the appropriate motor response, a sequencing process that learns sequences of motor acts, and a dynamic process that learns new patterns of muscle activations. These four processes can operate in one of two modes: an unconscious mode, in which one is aware only of the goal of the movement, or a conscious mode, in which one consciously controls detailed aspects of the movement. This article provides an overview of these four processes and two modes, and describes their neural bases.     

Methylphenidate Does Not Modify the Impact of Response Frequency or Stimulus Sequence on Performance and Event-Related Potentials of Children with Attention Deficit Hyperactivity Disorder

Twenty-six children with attention deficit/hyperactivity disorder (ADHD) participated in a double-blind trial consisting of 2 consecutive weeks each of placebo and methylphenidate (M = 26.92 mg/day = 0.78 mg/kg/day). As expected, stimulant therapy resulted in moderate weight loss, increased somatic complaints, and teacher and parent reports of reduced inattentiveness, aggression, and oppositionality. In both phases of the trial, patients were tested in a choice reaction time task assessing two aspects of the task that presumably affect response selection: response frequency (ratio of targets/nontargets = 25/75 vs. 50/50) and stimulus sequence (alternations vs. repetitions). Both manipulations yielded expected results on performance and event-related potentials (ERPs). Stimulant treatment increased accuracy and speed among younger children and curtailed variability of reaction time for the sample as a whole. However, methylphenidate did not affect ERPs. In combination, the results imply that the enhancement of performance by methylphenidate does not involve the demands of response selection examined in this study.     

短时动作记忆的容量和精确度与动作学习的关系

该研究采用实验室实验法,被试自我报告分析及调查访问法,以三个年龄（１０岁、１４岁、１８岁）组学生及专项运动员为实验对象,揭示短时动作记忆的容量和精确度及其与动作学习指数的关系。结果表明：（１）被试的短时动作记忆容量为“５±２”,短时动作记忆的容量与动作学习的练习次数相联系;短时动作记忆的精确度与第一次动作练习的准确度相联系。（２）短时动作记忆的容量有随年龄增长而递增的趋势。（３）运动员与非运动员被试对于同类动作学习的练习次数存在显著性差异。     

Teacher rated problems and school ability tests in relation to preschool problems and parents'' health information at school start. A study of first-graders

The reliability of assessments at four and six years of age in identifying teacher rated problems in behaviour, concentration, motor skill and school achievement was investigated in a study of first-graders. Relationships between preschool data and school ability tests, and between parents' information at school start and teacher ratings were also studied. Problems noted in preschool and school were often present in more than one area. Multiple problems at four and six years were strong predictors of later school problems, but preschool assessments of separate areas could not in general predict problems in corresponding areas in school. However, cross situational concentration deficits at the age of six did reliably identify concentration problems in the first grade, at the age of seven.     

Another look at “tummy time” for primary plagiocephaly prevention and motor development

It is three decades since it was recommended that infants sleep on the back to reduce risk of sudden unexpected infant death (SUID). The SUID prevention program is known as “back to sleep” or “safe sleeping”, and this initiative is not questioned. Sleeping on the back is associated with, but not the cause of, the development of infant positional plagiocephaly, also known as deformational or a non-synostotic misshapen head when the skull sutures are open, not fused. This paper provides a synthesis of the history and impact of positional plagiocephaly. It includes a scoping review of plagiocephaly prevention facilitating motor development and reveals few articles on primary prevention which aims to prevent it developing in the first place. It is concerning that preschool-aged children with a history of infant plagiocephaly continued to receive lower developmental scores, particularly in motor development, than unaffected controls, and this may be a marker of developmental delay. Tummy-time (prone) for play is the mainstay of plagiocephaly prevention advice to minimize development of plagiocephaly and to facilitate infant motor development, particularly head control. While tummy-time has shown benefit for infant development, there is limited evidence of its effectiveness in preventing plagiocephaly and some evidence that it promotes only prone-specific motor skills. Most of the published literature is concerned with treatment post-diagnosis, in the form of reviews, or clinical notes. There is a plethora of opinion articles reinforcing tummy-time from birth for plagiocephaly prevention. The review shows that there are gaps in advice for early infant development of head control. An accepted test of head control in infants is “pull to sit” from supine which demonstrates antigravity strength of the neck flexors and coordination of the head and neck when the infant is drawn to sit from supine. This motor skill was cited as achievable by 4 months in the earliest paper on plagiocephaly in 1996. Physical therapists and others should revisit the mechanism of early infant head control development against gravity, particularly antigravity head, neck and trunk coordinated flexion movement in supine, as there has been little attention to early facilitation of this motor skill as a plagiocephaly prevention strategy. This may be achieved by considering “face time” as well as tummy time for primary prevention of plagiocephaly.     

Unweighting infants reveals hidden motor skills

We investigated the role of rate limiting factors in development using walking as a model system. The achievement of bipedal posture and locomotion are among the most significant achievements in an infant's first year, with poor balance and weak muscles long proposed as the rate limiting factors. Compensating for either may reveal upright motor skill that has not yet emerged in the infant's natural repertoire. To probe this question, we unweighted prewalking infants and measured their performance in various standing and walking behaviors while unweighted compared to baseline. Our secondary objective was to determine if the influence of unweighting was related to infants’ locomotor experience. Infants stood unsupported for longer durations with 20% or 40% unweighting. Infants took more independent steps and more steps with one hand held with 40% unweighting. No differences in transition to/from standing were observed. Locomotor experience was related to the influence of unweighting during cruising and walking with a push toy. This is the first report of more advanced motor skills—longer periods of unsupported standing and the emergence of independent walking—revealed by unweighting infants. We interpret our observations to suggest that the refinement of motor control needed to support bipedal posture and locomotion precedes the functional emergence of these skills in infants. In other words, the musculoskeletal components required for walking are slower to develop than the neurological factors – and consequently may be the rate limiters. We further suggest that training regimens including unweighting should be explored in infants with motor delays.     

The mediational role of motivation in the model of motor development in childhood: A longitudinal study

The aim of this study was twofold: first, to examine the stability of the hypothesized conceptual model of motor development (without and with including various types of motivation) when children are followed up one-year later, and second to examine longitudinally whether changes in one model variable predict changes in other variables, according to the hypothesized pathways in the model. A sample of 361 Spanish students (50.7% girls, 8–11 years old) voluntarily participated in this study. In relation to the first aim, structural equation modeling revealed the expected positive relationship between the model variables in both measurement times. That is: actual motor competence (MC) predicted physical activity (PA) (p < .001), perceived MC mediated the relationship between actual MC and PA (p < .001), and autonomous motivation mediated the relationship between perceived MC and PA (p < .05). Moreover, the comparison of the invariance analysis showed non-practical differences between the unconstrained model and the constrained model, supporting the stability of the model over time. In relation to the second aim, the hypothesized model in Time 2 controlling for Time 1 values showed that changes in children’s actual MC positively predicted changes in their perceived MC (p < .001), which in turn, predicted changes in their autonomous motivation (p < .001), and PA (p < .001) at Time 2. Based on these findings Physical Education teachers are recommended to foster children’s actual and perceived MC as well as their autonomous motivation over time in order to promote PA strategies for lifelong health.     

The co‐construction of joint action between mothers and 2–4‐month‐old infants: the mother's role

The purpose of this longitudinal study was to describe object‐centred interactions between mothers and their 2–4‐month‐old infants, before and during the emergence of reaching and grasping movements. We hypothesized that when reaching movements emerge at around 3 months, mothers alternate between attention stimulation and reaching stimulation, before joint actions between mother and infant develop around objects. Twelve dyads were recorded when infants were 2 months, 3 months and 4 months. The interactive sessions lasted 5 min. Three age‐appropriate toys the infant could handle were available to the mother. A principal component analysis (PCA) was performed on verbal and non‐verbal maternal behaviours, motor infant behaviours and co‐occurrences of those behaviours. The developmental course of prehension in infants when playing with their mother follows similar pathways, as was described when they are observed alone. Mothers appeared to early scaffold prehension skills by verbal and non‐verbal means. Moreover, maternal behaviours change according to the infant's behaviour, and conversely, infant's behaviours influence maternal behaviours: mother plays first an active part in joint action, while later on, the infant achieves joint action when motor skills develop. Copyright © 2000 John Wiley & Sons, Ltd.