Memory Consolidation and Contextual Interference Effects with Computer Games

Perceptual and Motor Skills. Oct, 2003  |  Pubmed ID: 14620247

Some investigators of the contextual interference effect contend that there is a direct relation between the amount of practice and the contextual interference effect based on the prediction that the improvement in learning tasks in a random practice schedule, compared to a blocked practice schedule, increases in magnitude as the amount of practice during acquisition on the tasks increases. Research using computer games in contextual interference studies has yielded a large effect (f = .50) with a random practice schedule advantage during transfer. These investigations had a total of 36 and 72 acquisition trials, respectively. The present study tested this prediction by having 72 college students, who were randomly assigned to a blocked or random practice schedule, practice 102 trials of three computer-game tasks across three days. After a 24-hr. interval, 6 retention and 5 transfer trials were performed. Dependent variables were time to complete an event in seconds and number of errors. No significant differences were found for retention and transfer. These results are discussed in terms of how the amount of practice, task-related factors, and memory consolidation mediate the contextual interference effect.

Assessment of Wavelet Analysis of Gait in Children with Typical Development and Cerebral Palsy

Journal of Biomechanics. Jun, 2005  |  Pubmed ID: 15863120

The objective of this study was to examine the use of the continuous wavelet transform (CWT) on surface electromyographic (sEMG) signals acquired from the lower extremity muscles during gait in children with typical development (TD) and cerebral palsy (CP). This was done to explore the possibility of developing a quantitative assessment scale of motor function based on time-frequency information. An initial study was conducted on retrospective gait data from three children, matched in gender and in anthropometric variables but with differing levels of walking ability. EMG data were extracted from five lower extremity muscles to assess the degrees of differentiation. The data were processed using the CWT to derive an average scalogram, from which the instantaneous mean frequency (IMNF) was calculated. Principal component analysis was used to assess the differences between the curves. Preliminary results indicated that for select lower extremity muscles, there was a significant deviation in the IMNF curves in the child with CP as compared to the child with TD. Furthermore, as motor impairment increased, total percent explained variance to the TD curves decreased. This suggests that it might be possible to derive a physiologically based quantitative index for assessing motor function and for assessing clinical treatments in CP using the wavelet analysis.

Immediate Effect of Percutaneous Intramuscular Stimulation During Gait in Children with Cerebral Palsy: a Feasibility Study

Developmental Medicine and Child Neurology. Oct, 2005  |  Pubmed ID: 16174312

The feasibility of percutaneous intramuscular functional electrical stimulation (P-FES) in children with cerebral palsy (CP) for immediate improvement of ankle kinematics during gait has not previously been reported. Eight children with CP (six with diplegia, two with hemiplegia; mean age 9 years 1 month [SD 1 y 4 mo; range 7 y 11 mo to 11 y 10 mo]) had percutaneous intramuscular electrodes implanted into the gastrocnemius (GA) and tibialis anterior (TA) muscles of their involved limbs. Stimulation was provided during appropriate phases of the gait cycle in three conditions (GA only, TA only, and GA/TA). immediately after a week of practice for each stimulation condition, a gait analysis was performed with and without stimulation. A significant improvement in peak dorsiflexion in swing for the more affected extremity and dorsiflexion at initial contact for the less affected extremity were found in the GA/TA condition. Clinically meaningful trends were evident for improvements in dorsiflexion kinematics for the more and less affected extremities in the TA only and GA/TA conditions. The results suggest that P-FES might immediately improve ankle kinematics in children with CP.

Test-retest Reliability of Isokinetic Dynamometry for the Assessment of Spasticity of the Knee Flexors and Knee Extensors in Children with Cerebral Palsy

Archives of Physical Medicine and Rehabilitation. May, 2006  |  Pubmed ID: 16635633

To assess test-retest reliability of the peak resistance torque and slope of work methods of spasticity measurement of the knee flexors and extensors in children with cerebral palsy (CP).

Gait Initiation in Children with Cerebral Palsy

Gait & Posture. Jul, 2007  |  Pubmed ID: 17081756

The task of gait initiation (GI), or taking a first step from a static standing position requires the development of forward momentum while maintaining dynamic balance as the body's center of mass (COM) moves forward and outside the base of support. The dynamics of GI in children (aged 7-12 years) with hemiplegic cerebral palsy (CP), diplegic CP and children with typical development (TD) were compared to characterize the mechanics and control of this task. Ground reaction forces (GRFs) and muscle activity were collected during GI at three different self-selected speeds (slow, moderate and fast). Movement of a sacral marker was also tracked to estimate downward shifting of the body during the GI task. Results demonstrate the presence of a motor sequence characterized by increased forward momentum development with increased GI speed for all groups of children. Anticipatory movements of children with CP were different when compared to children with TD. Children with hemiplegic CP demonstrated decreased lateral shifting while children with diplegic CP demonstrated a trend of decreased downward shifting of the body compared to children of TD. Analysis of the GI motor sequence in children provides a means to characterize coordination and motor control of a functional ambulatory task in children with CP compared to children with TD.

A Time-frequency Based Electromyographic Analysis Technique for Use in Cerebral Palsy

Gait & Posture. Sep, 2007  |  Pubmed ID: 17161603

Surface electromyography (sEMG) is part of an instrumented gait assessment, however, the interpretation of the data in a clinically meaningful manner is often limited to the extraction of individual sEMG characteristics. The purpose of this study was to develop an assessment methodology using sEMG time and frequency characteristics extracted using wavelet analyses to provide clinically relevant information in children with cerebral palsy (CP). A retrospective study was conducted with 37 children (16 children with typical development (TD) and 21 children with spastic CP). sEMG signals were examined from selected musculature of the lower extremities during level ground walking. Wavelet analysis techniques, along with functional principal component analyses, were employed to calculate a sEMG index. The data indicated a grouping in the EMG index based on the level of motor impairment and the clinical diagnosis of spastic hemiplegia or diplegia. Further analyses of the index exhibited moderate to high (r=-0.43 to -0.74 and r=0.62-0.65) correlations with the existing gait kinetics, kinematics, and clinical measures of motor impairment, and was sensitive to walking ability according to the Gross Motor Functional Classification Scale (GMFCS). Overall, this methodology may have the potential to provide additional insight into the outcome of a clinical intervention that was not available previously, and may find use as a predictive tool that can be utilized for clinical decision making.

Time-frequency Changes in Electromyographic Signals After Hamstring Lengthening Surgery in Children with Cerebral Palsy

Journal of Biomechanics. , 2007  |  Pubmed ID: 17328900

Increased knee flexion during stance is a common gait deviation in the child with cerebral palsy (CP), with distal hamstring lengthening surgeries being an accepted course of treatment. Post-operatively, improvements in gait kinematics have been reported, however little change is noted in the patterns of muscle activity as portrayed by onset and offset timing in the surface electromyographic (sEMG) signals. Similar analysis based on the frequency content of the sEMG signals has seldom been applied, yet may provide additional insight into changes in muscle activity in response to surgery. The purpose of this study was to determine if changes in the time-frequency characteristics of the sEMG, extracted using wavelet analysis techniques, corresponded to improved gait kinematics observed post-surgical intervention, and whether there existed a relationship between frequency characteristics of the sEMG signals and the type of surgery required to correct gait kinematics. Data were collected from 16 children with typical development (TD) and 17 children with CP pre- and post-surgery. Muscle activity was recorded from the medial hamstring (MH) and vastus lateralis (VL) muscles, processed using the wavelet transform, and analyzed using functional principal component analyses (PCA). Results indicated that frequency differences were present pre-operatively depending if surgery was to be performed bilaterally or involved bone modification. Post-operatively, frequency characteristics of the VL more closely approximated those observed in children with TD, agreeing with the improved gait kinematics. MH characteristics, however, for the surgical groups demonstrated a deviation away for TD reflecting the altered muscle structure.

Co-contraction During Passive Movements of the Knee Joint in Children with Cerebral Palsy

Clinical Biomechanics (Bristol, Avon). Nov, 2007  |  Pubmed ID: 17870220

Co-contraction is an impairment commonly reported in children with cerebral palsy. However, co-contraction has not been investigated during passive movements which may be used to assess spasticity in children with cerebral palsy. The purpose of this study was to examine the frequency of co-contraction and the relationship between reflex activity and co-contraction during passive movements of the knee joint in children with cerebral palsy.

Muscle Tendon Unit Comparisons Between Infants Born Preterm and Infants Born Full Term: a Pilot Study

Pediatric Physical Therapy : the Official Publication of the Section on Pediatrics of the American Physical Therapy Association. , 2007  |  Pubmed ID: 18004199

This study assessed differences in measures of the muscle tendon unit between infants born preterm and infants born full-term.

Examination of Spasticity of the Knee Flexors and Knee Extensors Using Isokinetic Dynamometry with Electromyography and Clinical Scales in Children with Spinal Cord Injury

The Journal of Spinal Cord Medicine. , 2008  |  Pubmed ID: 18581670

To examine the role of reflex activity in spasticity and the relationship between peak passive torque, Ashworth Scale (AS), and Spasm Frequency Scale (SFS) of the knee flexors and extensors during the measurement of spasticity using an isokinetic dynamometer in children with spinal cord injury (SCI).

Roles of Reflex Activity and Co-contraction During Assessments of Spasticity of the Knee Flexor and Knee Extensor Muscles in Children with Cerebral Palsy and Different Functional Levels

Physical Therapy. Oct, 2008  |  Pubmed ID: 18703677

Spasticity is a common impairment in children with cerebral palsy (CP). The purpose of this study was to examine differences in passive resistive torque, reflex activity, coactivation, and reciprocal facilitation during assessments of the spasticity of knee flexor and knee extensor muscles in children with CP and different levels of functional ability.

Gastrocnemius-soleus Muscle Tendon Unit Changes over the First 12 Weeks of Adjusted Age in Infants Born Preterm

Physical Therapy. Feb, 2009  |  Pubmed ID: 19131398

Differences in the gastrocnemius-soleus muscle and tendon have been documented shortly after birth in infants born preterm compared with infants born at term. Knowledge of muscle tendon unit lengths at term age to 12 weeks of age in infants born preterm may be useful in understanding motor development.

Author Response to Invited Commentary by Heathcock

Physical Therapy. Feb, 2009  |  Pubmed ID: 19195075

Changes in Standing Postural Control During Acquisition of a Sequential Reaching Task

Gait & Posture. Feb, 2010  |  Pubmed ID: 19962316

Postural control acquired during learning functional reaching movements has not been well examined. Fourteen healthy adults practiced a serial reaching task 300 times. Task acquisition was examined considering two types of action-goals [1]: hand accuracy and consistency as the focal action-goals and control of equilibrium as the postural action-goal [2,3]. Hand accuracy and consistency were measured as absolute constant error and variable error. Postural control was measured by time to boundary (TtB). Improvements were expected in the focal goals and postural goal; however the timing of improvements might reflect explicit and implicit learning processes. Practice effects resulted in improvements for hand task accuracy, consistency and an increase in TtB values. Changes in postural control may reflect improved efficiency or improved perception-action coupling by the postural system within task performance.

Psychosocial Factors and Health Perceptions in Parents and Children Who Are Overweight or Obese

Obesity (Silver Spring, Md.). Aug, 2010  |  Pubmed ID: 20057378

This study examined the relationships among weight status (BMI), health perceptions, and psychosocial characteristics in children, parents, and parent-child dyads. A convenient sample of 114 parent-child dyads participated. All children were overweight or obese. Parents and children completed questionnaires by self-report or interview. Questionnaires included the Parenting Stress Index-Short Form (PSI), the Parents' Stage of Change (SOC) Questionnaire, and the Pediatric Quality of Life Inventory (PedsQL). Child's mean age was 10.34 years (s.d. = 1.87), mean BMI was 28.13 kg/m(2) (s.d. = 5.46), and mean BMI z-score was 2.17 (s.d. = 0.38). Parent mean age was 37.28 years (s.d. = 12.66) and mean BMI was 34.07 kg/m(2) (s.d. = 8.18). Most parents (68.5%) reported that they and their children (70.7%) were African American and many (44.3%) reported that they and their children were Hispanic. Significant correlations included: child health perceptions and child BMI (r = 0.309, P < 0.001) and parent perception of weight and parent BMI (r = 0.691, P < 0.001). For parent-child dyads, one correlation approached significance (child health perceptions and parent stage of change (r = -0.269, P < 0.01). Findings suggest that characteristics of parent-child dyads may be important considerations in the management of childhood obesity.

Hemodynamic Correlates of Visuomotor Motor Adaptation by Functional Near Infrared Spectroscopy

Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference. , 2010  |  Pubmed ID: 21095985

The development of rehabilitation engineering technologies such as the design of smart prosthetics necessitates a deep understanding of brain mechanisms engaged in ecological situations when human interact with new tools and/or environments. Thus, we aimed to investigate potential hemodynamic signatures reflecting the level of cognitive-motor performance and/or the internal or mental states of individuals when learning a novel tool with unknown properties. These markers were derived from functional Near Infrared Spectroscopy (fNIR) signals. Our results indicate an increased level of oxy-hemoglobin in prefrontal sensors associated with enhanced kinematics during early compared with late learning. This is consistent with previous neuroimaging studies that revealed a higher contribution of prefrontal areas during early compare to late adaptation learning. These non-invasive functional hemodynamic markers may play a role in bioengineering applications such as smart neuroprosthesis and brain monitoring where adaptive behavior is important.

Toward Improved Sensorimotor Integration and Learning Using Upper-limb Prosthetic Devices

Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference. , 2010  |  Pubmed ID: 21096030

To harness the increased dexterity and sensing capabilities in advanced prosthetic device designs, amputees will require interfaces supported by novel forms of sensory feedback and novel control paradigms. We are using a motorized elbow brace to feed back grasp forces to the user in the form of extension torques about the elbow. This force display complements myoelectric control of grip closure in which EMG signals are drawn from the biceps muscle. We expect that the action/reaction coupling experienced by the biceps muscle will produce an intuitive paradigm for object manipulation, and we hope to uncover neural correlates to support this hypothesis. In this paper we present results from an experiment in which 7 able-bodied persons attempted to distinguish three objects by stiffness while grasping them under myoelectric control and feeling reaction forces displayed to their elbow. In four conditions (with and without force display, and using biceps myoelectric signals ipsilateral and contralateral to the force display,) ability to correctly identify objects was significantly increased with sensory feedback.

Sliding-window Motion Artifact Rejection for Functional Near-Infrared Spectroscopy

Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference. , 2010  |  Pubmed ID: 21096508

Functional Near-Infrared Spectroscopy (fNIR) is an optical brain monitoring technology that tracks changes in hemodynamic responses within the cortex. fNIR uses specific wavelengths of light, introduced at the scalp, to enable the noninvasive measurement of changes in the relative ratios of deoxygenated hemoglobin (deoxy-Hb) and oxygenated hemoglobin (oxy-Hb) during brain activity. This technology allows the design of portable, safe, affordable, noninvasive, and minimally intrusive monitoring systems that can be used to measure brain activity in natural environments, ambulatory and field conditions. However, for such applications fNIR signals can get prone to noise due to motion of the head. Improving signal quality and reducing noise, can be especially challenging for real time applications. Here, we study motion artifact related noise especially due to poor and changing sensor coupling. We have developed a simple and iterative method that can be used to automate the preprocessing of data to identify segments with such noise for exclusion and this method is also suitable for real time applications.

An Optical Brain Computer Interface for Environmental Control

Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference. Aug, 2011  |  Pubmed ID: 22255785

A brain computer interface (BCI) is a system that translates neurophysiological signals detected from the brain to supply input to a computer or to control a device. Volitional control of neural activity and its real-time detection through neuroimaging modalities are key constituents of BCI systems. The purpose of this study was to develop and test a new BCI design that utilizes intention-related cognitive activity within the dorsolateral prefrontal cortex using functional near infrared (fNIR) spectroscopy. fNIR is a noninvasive, safe, portable and affordable optical technique with which to monitor hemodynamic changes, in the brain's cerebral cortex. Because of its portability and ease of use, fNIR is amenable to deployment in ecologically valid natural working environments. We integrated a control paradigm in a computerized 3D virtual environment to augment interactivity. Ten healthy participants volunteered for a two day study in which they navigated a virtual environment with keyboard inputs, but were required to use the fNIR-BCI for interaction with virtual objects. Results showed that participants consistently utilized the fNIR-BCI with an overall success rate of 84% and volitionally increased their cerebral oxygenation level to trigger actions within the virtual environment.

Optical Brain Monitoring for Operator Training and Mental Workload Assessment

NeuroImage. Jan, 2012  |  Pubmed ID: 21722738

An accurate measure of mental workload in human operators is a critical element of monitoring and adaptive aiding systems that are designed to improve the efficiency and safety of human-machine systems during critical tasks. Functional near infrared (fNIR) spectroscopy is a field-deployable non-invasive optical brain monitoring technology that provides a measure of cerebral hemodynamics within the prefrontal cortex in response to sensory, motor, or cognitive activation. In this paper, we provide evidence from two studies that fNIR can be used in ecologically valid environments to assess the: 1) mental workload of operators performing standardized (n-back) and complex cognitive tasks (air traffic control--ATC), and 2) development of expertise during practice of complex cognitive and visuomotor tasks (piloting unmanned air vehicles--UAV). Results indicate that fNIR measures are sensitive to mental task load and practice level, and provide evidence of the fNIR deployment in the field for its ability to monitor hemodynamic changes that are associated with relative cognitive workload changes of operators. The methods reported here provide guidance for the development of strategic requirements necessary for the design of complex human-machine interface systems and assist with assessments of human operator performance criteria.