Development of stepping patterns in human infants: a dynamical systems perspective

Upright locomotion has been, perhaps, the most studied of all human motor behaviors. The acquisition of this motor milestone has been of major interest to developmentalists from the motor as well as the cognitive domains. Until recently, developmentalists have chosen a nonexperimental approach, opting instead to describe the motor behaviors that precede walking, assigning them precursor status, and attributing the sequence solely to maturation of the nervous system. In this paper, I will discuss evidence that suggests that we may better understand this and other aspects of motor development by viewing them from the theoretical perspective of nonlinear and complex dynamical systems. Focus will be on the availability of a coordinated and alternating stepping pattern throughout much of the first year of life. Factors that influence the expression of and variability in this movement pattern will also be discussed. In addition, I will address the need to understand the development of control of pattern formations as well as their coordination, and I will discuss one approach that may provide some insight; that is, to study the modulations and patterns of muscle and other forces underlying limb movements.     

Descending control to the nonparetic limb degrades the cyclic activity of paretic leg muscles

During anti-phased locomotor tasks such as cycling or walking, hemiparetic phasing of muscle activity is characterized by inappropriate early onset of activity for some paretic muscles and prolonged activity in others. Pedaling with the paretic limb alone reduces inappropriate prolonged activity, suggesting a combined influence of contralesional voluntary commands and movement-related sensory feedback. Five different non-target leg movement state conditions were performed by 15 subjects post-stroke and 15 nonimpaired controls while they pedaled with the target leg and EMG was recorded bilaterally. Voluntary engagement of the non-lesioned motor system increased prolonged paretic vastus medialis (VM) activity and increased phase-advanced rectus femoris (RF) activity. We suggest bilateral descending commands are primarily responsible for the inappropriate activity in the paretic VM during anti-phase pedaling, and contribute to the dysfunctional motor output in the paretic RF. Findings from controls suggest that even an undamaged motor system can contribute to this phenomenon.     

Think about it: Cognitive-motor dual-tasking affects sub-regional spine responses to unexpected trunk perturbations

Cognitive motor interference (CMI) is a psychomotor phenomenon characterized by alterations in kinematic spatial-temporal parameters during concurrent cognitive and motor tasks (i.e. dual-tasking). Previous literature has demonstrated that cognitive-motor dual-tasking induces alterations gait parameters; however, the influence of CMI on spine reflexive motion has yet to be researched. The purpose of this study was to assess the influence of cognitive-motor dual-tasking during unexpected spine loading, in particular focusing on paraspinal muscle responses and spine sub-regional kinematic responses. To do this, the spine was perturbed by unexpectedly dropping a 6.8 kg mass into the participants' hands during cognitive dual-task and control conditions. Intersegmental spine angles, paraspinal muscle onset latencies, baseline activations, and response magnitudes were measured. The results demonstrated that participants experienced greater spine flexion at all intersegmental levels during the cognitive dual-task condition compared to the control condition. Additionally, muscle onset latencies were significantly delayed in three of the four paraspinal muscles studied when performing the cognitive-motor dual-task. These results demonstrate that the additional cognitive load led to delayed muscle activation responses and subsequently greater intersegmental lumbar spine flexion in response to a sudden loading perturbation. This suggests that cognitive-motor dual-tasking may increase the risk of developing an acute spine injury under similar conditions.     

Motor and cognitive interference effects on unimanual tapping rates

Experiments conducted on both normal and disordered populations have led to the hypothesis that the left hemisphere's specialization for language results from its control over motor activities. This control is reflected in the lateralized disruption of manual activity during cerebral time-sharing tasks. Recent studies have challenged this hypothesis, stating that the interference effects reflect both cognitive and motor mechanisms in the left hemisphere. This experiment investigates whether the left hemisphere's control over speech involves both of these components or is purely motor. The question was examined by measuring the effect of concurrent hemispheric activity on single-finger tapping rates. Forty subjects tapped under two conditions: speaking and listening. The data show there may be both motor and cognitive mechanisms involved in left-hemisphere control.     

Driver performance effects of simultaneous visual and cognitive distraction and adaptation behavior

Driver distraction has become a major concern for transportation safety due to increasing use of infotainment systems in vehicles. To reduce safety risks, it is crucial to understand how fundamental aspects of distracting activities affect driver behavior at different levels of vehicle control. This study used a simulator-based experiment to assess the effects of visual, cognitive and simultaneous distraction on operational (braking, accelerating) and tactical (maneuvering) control of vehicles. Twenty drivers participated in the study and drove in lead-car following or passing scenarios under four distraction conditions: without distraction, with visual distraction, with cognitive distraction, and with simultaneous distraction. Results revealed higher perceived workload for passing than following. Simultaneous distraction was most demanding and also resulted in the greatest steering errors among distraction conditions during both driving tasks. During passing, drivers also appeared to slow down their responses to secondary distraction tasks as workload increased. Visual distraction was associated with more off-road glances (to an in-vehicle device) and resulted in high workload. Longer headway times were also observed under visual distraction, suggesting driver adaptation to the workload. Similarly, cognitive distraction also increased driver workload but this demand did not translate into steering errors as high as for visual distraction. In general, findings indicate that tactical control of a vehicle demands more workload than operational control. Visual and cognitive distractions both increase driver workload, but they influence vehicle control and gaze behavior in different ways.     

工作记忆负荷对无意注意的影响

通过探讨工作记忆负荷对无意注意的影响,考察工作记忆的认知控制功能对选择性注意的作用机制。为了避免工作记忆和选择注意的目标或者干扰子之间的知觉注意资源的竞争,采用言语工作记忆任务和视觉空间位置辨别任务,同时视觉干扰刺激采用被试无法识别的韩语。结果发现,在高负荷条件下,干扰效应显著;而在低和中负荷条件下,没有观察到干扰效应。说明在高负荷条件下,被试没有额外的资源来抑制干扰加工,从而出现了显著的干扰效应。由此,本研究支持负荷理论的观点：工作记忆在选择性注意中执行认知控制功能。     

Distraction intervention for preschoolers undergoing intramuscular injections and subcutaneous port access.

This study evaluated a distraction intervention designed to reduce the distress of preschool children undergoing repeated chemotherapy injections. Twenty-nine children aged 2-5 years were randomly assigned either to distraction by a developmentally appropriate electronic toy or to a wait-list control. Children who received the distraction intervention demonstrated lower overt behavioral distress and were rated by parents and nurses as less anxious than children in the control condition. The improvements were maintained over the 8-week intervention. The results suggest that a developmentally appropriate, multisensory, variable-distracting activity that requires active cognitive processing and active motor responses may be a viable cost-effective alternative to more time-intensive parent-training programs for preschool-age children.     

Can preference for background music mediate the irrelevant sound effect?

Research suggests that listening to background music prior to task performance increases cognitive processes, such as attention and memory, through the mechanism of increasing arousal and positive mood. However, music preference has not been explored with regard to a more common and realistic scenario of concurrent music and cognition, namely the ‘irrelevant sound effect’ (ISE). To examine this, serial recall was tested under quiet, liked and disliked music sound conditions as well as steady‐state (repetition of ‘3’) and changing‐state speech (random digits 1–9). Results revealed performance to be poorer for both music conditions and the changing‐state speech compared to quiet and steady‐state speech conditions. The lack of difference between both music conditions suggests that preference does not affect serial recall performance. These findings are discussed within the music and cognition and auditory distraction literatures. Copyright © 2010 JohnWiley & Sons, Ltd.     

The effect of visual and cognitive distraction on driver’s anticipation in a simulated car following scenario

Distraction is a common cause of accidents (e.g. NHTSA, 2009), and different distraction conditions influence the driving behaviour in a specific way. Despite a lot of research in this area, most studies concentrate on perception errors as a result of visual distraction. The effects of different distraction conditions on higher cognitive processes are still unclear. The fact that accidents happen even if the drivers perceive all relevant information implies that cognitive factors contribute to accidents, too. For this reason, this study was conducted to investigate how different distraction conditions influence the anticipation of events in a car–following scenario. Anticipation is required to know what will happen next, and to react adequately to the situation. In a driving simulator, scenarios with different manoeuvres of a preceding car were created to generate various anticipations and therefore a different adaptation of the driving behaviour. Additionally, a cognitive and a visual secondary task were introduced. The question was in which way either a cognitive or visual distraction influences the generation of anticipations and the construction of an appropriate situation model.The results indicate that in the phase when the preceding car showed braking manoeuvres, drivers prolonged their safety distance only when being visually distracted which is probably done to compensate for this visual distraction. This compensation ensued to some extent in the second phase where the preceding cars drove with a constant speed. Additionally, drivers who were visually distracted went somewhat slower when the car in front had braked in phase one. Thus, the drivers seemed to anticipate that the car might brake again and adapted their speed accordingly. This was not found in drivers with cognitive distraction. Thus, cognitive distraction seems to disturb this anticipation.Finally, at an intersection, drivers with visual distraction had a smaller TTC and a higher velocity when the car in front made an unexpected turn. Thus, the impairment of perception due to the visual distraction leads to a slower reaction as compared to a cognitive distraction. Overall, cognitive distraction influences the anticipation of possible future actions of other car drivers negatively while visual distraction deteriorates perception and thus the reaction to critical, sudden events. Thus, different intervention strategies are required to prevent these kinds of accidents.     

Classification of gait muscle activation patterns according to knee injury history using a support vector machine approach

Abnormal muscle activation patterns during gait following knee injury that persist past the acute injury and rehabilitation phase (>three years) are not well characterized but may be related to post-traumatic knee osteoarthritis. The aim was to characterize the abnormal muscle activity from electromyograms of five leg muscles that were recorded during treadmill walking for young adults with and without a previous knee injury 3–12 years prior. The wavelet transformed and amplitude normalized electromyograms yielded intensity patterns that reflect the muscle activity of these muscles resolved in time and frequency. Patterns belonging to the affected or unaffected leg in previously injured participants and patterns belonging to a previously injured vs. uninjured participant were grouped and then classified using a principal component analysis followed by a support vector machine. A leave-one-out cross-validation was used to test the model significance and generalization. The results showed that trained classifiers could successfully recognize whether muscle activation patterns belonged to the affected or unaffected leg of previously injured individuals. Classification rates of 83% were obtained for all subjects, 100% for females only, indicating sex-specific knee injury effects. In contrast, it was not possible to discriminate between patterns belonging to the previously injured legs or dominant legs of control subjects. For females, the injured leg showed a stronger muscle activity for hamstring muscles and a lower activity for the vastus lateralis. In conclusion, systematic knee injury effects on the neuromuscular control of the knee during gait were present 3–12 years later.     

How distraction affects pedestrian response: Evidence from behavior patterns and cortex oxyhemoglobin changes

ObjectivesDistracted walking is a major cause of pedestrian road traffic injuries, but little is known about how distraction affects pedestrian safety. The study was designed to explore how visual and auditory distraction might influence pedestrian safety.MethodsThree experiments were conducted to explore causal mechanisms from two theoretical perspectives, increased cognitive load from the distraction task and resource competition in the same sensory modality. Pedestrians’ behavior patterns and cortex oxyhemoglobin changes were recorded while they performed a series of dual tasks.ResultsFour primary results emerged: (a) participants responded more slowly to both visual and auditory stimuli in traffic, as well as walked more slowly, while talking on the phone or text messaging compared to when undistracted or listening to music; (b) when participants completed pedestrian response tasks while distracted with a high cognitive load, their response was significantly slower and poorer than when they carried out a lower cognitive load distraction task, (c) participants had higher levels of oxy-Hb change in cortices related to visual processing and executive function while distracted with a higher cognitive load; and (d) participants' responses to traffic lights were slower and resulted in a higher activation in prefrontal cortex and occipital areas when distracted by a visual distraction task compared to when distracted with an auditory task; similarly, brain activation increased significantly in temporal areas when participants responded to an auditory car horn task compared to when they responded to visual traffic lights.ConclusionsBoth distracting cognitive load demands and the type of distraction task significantly affect young adult pedestrian performance and threaten pedestrian safety. Pedestrian injury prevention efforts should consider the effects of the type of distracting task and its cognitive demands on pedestrian safety.     

Pupil Diameter May Reflect Motor Control and Learning

Non–luminance-mediated changes in pupil diameter have been used since the first studies by Darwin in 1872 as indicators of clinical, cognitive, and arousal states. However, the relation between processes involved in motor control and changes in pupil diameter remains largely unknown. Twenty participants attempted to compensate random walks of a cursor with a computer mouse to restrain its trajectory within a target circle while the authors recorded their pupil diameters. Two conditions allowed the authors to experimentally manipulate the motor and cognitive components of the task. First, the step size of the cursor's random walk was either large or small leading to 2 task difficulties (difficult or easy). Second, they instructed participants to imagine controlling the cursor by moving the mouse, but without actually moving it (task modality: imagined movement or real movement condition). Task difficulty and modality allowed the authors to show that pupil diameters reflect processes involved in motor control and in the processing of feedback, respectively. Furthermore, the authors also demonstrate that motor learning can be quantified by pupil size. This noninvasive approach provides a promising method for investigating not only motor control, but also motor imagery, a research field of growing importance in sports and rehabilitation.     

A virtual reality scenario for all seasons: the virtual classroom

Treatment and rehabilitation of the cognitive, psychological, and motor sequelae of central nervous system dysfunction often relies on assessment instruments to inform diagnosis and to track changes in clinical status. Typically, these assessments employ paper-and-pencil psychometrics, hands-on analog/computer tests, and rating of behavior within the context of real-world functional environments. Virtual reality offers the option to produce and distribute identical "standard" simulation environments in which performance can be measured and rehabilitated. Within such digital scenarios, normative data can be accumulated for performance comparisons needed for assessment/diagnosis and for treatment/rehabilitation purposes. In this manner, reusable archetypic virtual environments constructed for one purpose can also be applied for applications addressing other clinical targets. This article will provide a review of such a retooling approach using a virtual classroom simulation that was originally developed as a controlled stimulus environment in which attention processes could be systematically assessed in children with attention-deficit/hyperactivity disorder. This system is now being applied to other clinical targets including the development of tests that address other cognitive functions, eye movement under distraction conditions, social anxiety disorder, and the creation of an earthquake safety training application for children with developmental and learning disabilities.     

Performance costs when emotion tunes inappropriate cognitive abilities: implications for mental resources and behavior

Emotion tunes cognition, such that approach-motivated positive states promote verbal cognition, whereas withdrawal-motivated negative states promote spatial cognition (Gray, 2001). The current research examined whether self-control resources become depleted and influence subsequent behavior when emotion tunes an inappropriate cognitive tendency. In 2 experiments, either an approach-motivated positive state or a withdrawal-motivated negative state was induced, and then participants completed a verbal or a spatial working memory task creating conditions of emotion-cognition alignment (e.g., approach/verbal) or misalignment (e.g., approach/spatial). A control condition was also included. To examine behavioral costs due to depleted self-control resources, participants completed either a Stroop task (Stroop, 1935; Experiment 1) or a Black/White implicit association test (IAT; Greenwald, McGhee, & Schwartz, 1998; Experiment 2). Participants in the misalignment conditions performed worse on the Stroop task, and they were worse at controlling their implicit attitude biases on the IAT. Thus, when emotion tunes inappropriate cognitive tendencies for one's current environment, self-control resources become depleted, impairing behavioral control.     

The effects of unilateral grab rail assistance on the sit-to-stand performance of older aged adults

This study investigated the effects of unilateral grab rail assistance during the sit-to-stand transfer to develop an understanding of lower limb joint mechanics and whole body movement patterns. External reaction forces at the grab rail and floor interfaces were also investigated to understand the nature of the assistance provided by the introduction of unilateral upper body assistance. While 12 older aged adults performed the sit-to-stand, three-dimensional body segment kinematics were recorded to determine lower body joint motion and whole body centre of mass motion. Grab rail reaction forces and bilateral ground reaction forces were recorded to determine external reaction forces and lower body joint kinetics. Grab rail assisted conditions were compared with unassisted transfers. During grab rail assistance, a systematic asymmetry was introduced to lower limb joint kinetics, without noticeable alterations to peak lower body joint motion and whole body movement patterns. Ipsilateral net joint moments and powers decreased in the ankle and hip and increased in the knee, while the contralateral net joint moments and powers increased in the hip and decreased in the knee. Joint kinetic and kinematic responses suggest a motor control strategy that maintains symmetric sit-to-stand movement patterns by adjusting bilateral muscle control when a unilateral external reaction force is provided. Understanding the mechanical assistance that is generated during the sit-to-stand will facilitate optimal design of grab rails for older aged adults and may contribute to design for specific pathologies. Such design implementation will influence the ability of older aged adults to remain independent in the community.     

Pointing and the interference effect in obsessive‐compulsive disorder (OCD)

The interference effect in obsessive‐compulsive disorder (OCD) was investigated in order to analyze cognitive aspects of motor stereotypy in OCD‐related compulsions. So far, the domain of cognitive control in compulsive behavior has been under‐investigated. Twelve participants (OCD patients and healthy controls) completed a newly created computer‐based pointing task as well as standard clinical and psychological background measures. Findings showed that the patients displayed a larger visual interference effect compared to the controls and pointing paths were longer in time as well as distance when a distractor stimulus was present. It is concluded that, for compensation, patients would need to generate excessive amounts of attentional resources not available to overcome motor rigidity on the one side and visual distraction on the other side.     

Behavioral distraction by auditory novelty is not only about novelty: The role of the distracter’s informational value

Unexpected events often distract us. In the laboratory, novel auditory stimuli have been shown to capture attention away from a focal visual task and yield specific electrophysiological responses as well as a behavioral cost to performance. Distraction is thought to follow ineluctably from the sound’s low probability of occurrence or, put more simply, its unexpected occurrence. Our study challenges this view with respect to behavioral distraction and argues that past research failed to identify the informational value of sound as a mediator of novelty distraction. We report an experiment showing that (1) behavioral novelty distraction is only observed when the sound announces the occurrence and timing of an upcoming visual target (as is the case in all past research); (2) that no such distraction is observed for deviant sounds conveying no such information; and that (3) deviant sounds can actually facilitate performance when these, but not the standards, convey information. We conclude that behavioral novelty distraction, as observed in oddball tasks, is observed in the presence of novel sounds but only when the cognitive system can take advantage of the auditory distracters to optimize performance.     

The plausibility of using unmanned aerial vehicles as a serious game for dealing with attention deficit-hyperactivity disorder

Attention Deficit-Hyperactivity Disorder (ADHD) is considered a mental disease that affects an estimated 5% of the world’s youth population. Brain-Computer Interfaces (BCIs) such as Electroencephalograms (EEGs) and functional Magnetic Resonance Imaging (fMRI) have been used to study and treat this mental disease. This paper shows the plausibility of using Unmanned Aerial Vehicles (UAVs) as a serious game for therapeutic purposes through a systematic review of the current state of UAVs and how they have been coupled to BCIs in order to control them through mental commands. Also, challenges and research opportunities from a usability approach related to the game design, interaction design, and cognitive rehabilitation are identified and described. We hope that the research opportunities identified in this paper can be useful to guide future research and gain insight into how to solve challenges related to the use of Unmanned Aerial Vehicles in cognitive therapies.     

The management of unwanted pre-sleep thoughts in insomnia: distraction with imagery versus general distraction

Insomniacs commonly complain that they are unable to get to sleep at night due to unwanted thoughts, worries and concerns. The present study investigated whether brief training in identifying and elaborating an interesting and engaging imagery task for use during the pre-sleep period can reduce unwanted pre-sleep cognitive activity and sleep onset latency. Forty one people with insomnia were given one of three instructional sets to follow on the experimental night; instructions to distract using imagery, general instructions to distract, or no instructions. Based on previous findings reported by Salkovskis & Campbell (1994) 'Behaviour Research and Therapy 32 (1994) 1' and ironic control theory (Wegner, 1994) 'Psychological Review 101 (1994) 34', it was predicted that (1) "imagery distraction" would be associated with shorter sleep onset latency and less frequent and distressing pre-sleep cognitive activity compared to the "no instruction" group and that (2) "general distraction" would be associated with longer sleep onset latency and more frequent and distressing pre-sleep cognitive activity compared to the "no instruction" group. Support was found for the first but not the second prediction. The success of the "imagery distraction" task is attributed to it occupying sufficient "cognitive space" to keep the individual from re-engaging with thoughts, worries, and concerns during the pre-sleep period. In addition, "imagery distraction" involved a very specific alternative cognitive task hence the operating process was given a feature positive search, conditions where mental control is likely to be achieved.