Investigating the Extent to which Distributional Semantic Models Capture a Broad Range of Semantic Relations

Distributional semantic models (DSMs) are a primary method for distilling semantic information from corpora. However, a key question remains: What types of semantic relations among words do DSMs detect? Prior work typically has addressed this question using limited human data that are restricted to semantic similarity and/or general semantic relatedness. We tested eight DSMs that are popular in current cognitive and psycholinguistic research (positive pointwise mutual information; global vectors; and three variations each of Skip-gram and continuous bag of words (CBOW) using word, context, and mean embeddings) on a theoretically motivated, rich set of semantic relations involving words from multiple syntactic classes and spanning the abstract-concrete continuum (19 sets of ratings). We found that, overall, the DSMs are best at capturing overall semantic similarity and also can capture verb-noun thematic role relations and noun-noun event-based relations that play important roles in sentence comprehension. Interestingly, Skip-gram and CBOW performed the best in terms of capturing similarity, whereas GloVe dominated the thematic role and event-based relations. We discuss the theoretical and practical implications of our results, make recommendations for users of these models, and demonstrate significant differences in model performance on event-based relations.

Task dynamics define the contextual emergence of human corralling behaviors

Social animals have the remarkable ability to organize into collectives to achieve goals unobtainable to individual members. Equally striking is the observation that despite differences in perceptual-motor capabilities, different animals often exhibit qualitatively similar collective states of organization and coordination. Such qualitative similarities can be seen in corralling behaviors involving the encirclement of prey that are observed, for example, during collaborative hunting amongst several apex predator species living in disparate environments. Similar encirclement behaviors are also displayed by human participants in a collaborative problem-solving task involving the herding and containment of evasive artificial agents. Inspired by the functional similarities in this behavior across humans and non-human systems, this paper investigated whether the containment strategies displayed by humans emerge as a function of the task's underlying dynamics, which shape patterns of goal-directed corralling more generally. This hypothesis was tested by comparing the strategies naïve human dyads adopt during the containment of a set of evasive artificial agents across two disparate task contexts. Despite the different movement types (manual manipulation or locomotion) required in the different task contexts, the behaviors that humans display can be predicted as emergent properties of the same underlying task-dynamic model.

Human social motor solutions for human-machine interaction in dynamical task contexts

Multiagent activity is commonplace in everyday life and can improve the behavioral efficiency of task performance and learning. Thus, augmenting social contexts with the use of interactive virtual and robotic agents is of great interest across health, sport, and industry domains. However, the effectiveness of human-machine interaction (HMI) to effectively train humans for future social encounters depends on the ability of artificial agents to respond to human coactors in a natural, human-like manner. One way to achieve effective HMI is by developing dynamical models utilizing dynamical motor primitives (DMPs) of human multiagent coordination that not only capture the behavioral dynamics of successful human performance but also, provide a tractable control architecture for computerized agents. Previous research has demonstrated how DMPs can successfully capture human-like dynamics of simple nonsocial, single-actor movements. However, it is unclear whether DMPs can be used to model more complex multiagent task scenarios. This study tested this human-centered approach to HMI using a complex dyadic shepherding task, in which pairs of coacting agents had to work together to corral and contain small herds of virtual sheep. Human-human and human-artificial agent dyads were tested across two different task contexts. The results revealed (i) that the performance of human-human dyads was equivalent to those composed of a human and the artificial agent and (ii) that, using a "Turing-like" methodology, most participants in the HMI condition were unaware that they were working alongside an artificial agent, further validating the isomorphism of human and artificial agent behavior.

Universal Features in Phonological Neighbor Networks

Human speech perception involves transforming a countinuous acoustic signal into discrete linguistically meaningful units (phonemes) while simultaneously causing a listener to activate words that are similar to the spoken utterance and to each other. The Neighborhood Activation Model posits that phonological neighbors (two forms [words] that differ by one phoneme) compete significantly for recognition as a spoken word is heard. This definition of phonological similarity can be extended to an entire corpus of forms to produce a phonological neighbor network (PNN). We study PNNs for five languages: English, Spanish, French, Dutch, and German. Consistent with previous work, we find that the PNNs share a consistent set of topological features. Using an approach that generates random lexicons with increasing levels of phonological realism, we show that even random forms with minimal relationship to any real language, combined with only the empirical distribution of language-specific phonological form lengths, are sufficient to produce the topological properties observed in the real language PNNs. The resulting pseudo-PNNs are insensitive to the level of lingustic realism in the random lexicons but quite sensitive to the shape of the form length distribution. We therefore conclude that “universal” features seen across multiple languages are really string universals, not language universals, and arise primarily due to limitations in the kinds of networks generated by the one-step neighbor definition. Taken together, our results indicate that caution is warranted when linking the dynamics of human spoken word recognition to the topological properties of PNNs, and that the investigation of alternative similarity metrics for phonological forms should be a priority.

Herd Those Sheep: Emergent Multiagent Coordination and Behavioral-Mode Switching

Effectively coordinating one's behaviors with those of others is essential for successful multiagent activity. In recent years, increased attention has been given to understanding the dynamical principles that underlie such coordination because of a growing interest in behavioral synchrony and complex-systems phenomena. Here, we examined the behavioral dynamics of a novel, multiagent shepherding task, in which pairs of individuals had to corral small herds of virtual sheep in the center of a virtual game field. Initially, all pairs adopted a complementary, search-and-recover mode of behavioral coordination, in which both members corralled sheep predominantly on their own sides of the field. Over the course of game play, however, a significant number of pairs spontaneously discovered a more effective mode of behavior: coupled oscillatory containment, in which both members synchronously oscillated around the sheep. Analysis and modeling revealed that both modes were defined by the task's underlying dynamics and, moreover, reflected context-specific realizations of the lawful dynamics that define functional shepherding behavior more generally.

Is failed predictive control a risk factor for focal dystonia?

INTRODUCTION

Task-specific focal dystonia (TSFD) is a disorder marked by degraded coordination in complex and exacting psychomotor tasks, such as musical performance. Its development is associated with prolonged and intensive practice of these tasks, but the etiology of TSFD is still unknown. The prevailing hypothesis was informed by findings in primates following repetitive simple grasping actions. This model implies, however, that complex manual tasks that yield more intricate and subtly varying sensorimotor patterns, as found in musical performance and handwriting, should be unlikely to lead to focal dystonia.

HYPOTHESIS

We propose an alternative, "predictive-control" etiological hypothesis: When an overtaxed performer exhibits poorly controlled variability and errors in motor execution of a well-learned, high-precision task, predictive control processes deteriorate. This includes, in particular, those related to the formation or updating of a forward dynamic model that maps motor commands to predicted end-effector state, e.g. position and velocity of a key-pressing digit.

CONCLUSION

Based on a critical literature review we argue that this results in the characteristic signs of focal dystonia, such as freezing, halting and inappropriate co-contraction specific to the task. Directions for future research are briefly discussed. © 2016 International Parkinson and Movement Disorder Society.

Veering in hemi-Parkinson's disease: Primacy of visual over motor contributions

Veering while walking is often reported in individuals with Parkinson's disease (PD), with potential mechanisms being vision-based (asymmetrical perception of the visual environment) or motoric (asymmetry in stride length between relatively affected and non-affected body side). We examined these competing hypotheses by assessing veering in 13 normal control participants (NC) and 20 non-demented individuals with PD: 9 with left-side onset of motor symptoms (LPD) and 11 with right-side onset (RPD). Participants walked in a corridor under three conditions: eyes-open, egocentric reference point (ECRP; walk toward a subjectively perceived center of a target at the end of the corridor), and vision-occluded. The visual hypothesis predicted that LPD participants would veer rightward, in line with their rightward visual-field bias, whereas those with RPD would veer leftward. The motor hypothesis predicted the opposite pattern of results, with veering toward the side with shorter stride length. Results supported the visual hypothesis. Under visual guidance, RPD participants significantly differed from NC, veering leftward despite a shorter right- than left-stride length, whereas LPD veered rightward (not significantly different from NC), despite shorter left- than right-stride length. LPD participants showed significantly reduced rightward veering and stride asymmetry when they walked in the presence of a visual landmark (ECRP) than in the eyes-open condition without a target. There were no group differences in veering in the vision-occluded condition. The findings suggest that interventions to correct walking abnormalities such as veering in PD should incorporate vision-based strategies rather than solely addressing motor asymmetries, and should be tailored to the distinctive navigational profiles of LPD and RPD.

Musculoskeletal stiffness changes linearly in response to increasing load during walking gait

Development of biologically inspired exoskeletons to assist soldiers in carrying load is a rapidly expanding field. Understanding how the body modulates stiffness in response to changing loads may inform the development of these exoskeletons and is the purpose of the present study. Seventeen subjects walked on a treadmill at a constant preferred walking velocity while nine different backpack loading conditions ranging from 12.5% to 40% bodyweight (BW) were introduced in an ascending and then descending order. Kinematic data were collected using Optotrak, a 3D motion analysis system, and used to estimate the position of the center of mass (COM). Two different estimates of stiffness were computed for the stance phase of gait. Both measures of stiffness were positively and linearly related to load magnitudes, with the slopes of the relationships being larger for the descending than the ascending conditions. These results indicate that changes in mechanical stiffness brought about in the musculoskeletal system vary systematically during increases in load to ensure that critical kinematic variables measured in a previous publication remain invariant (Caron et al., 2013). Changes in stiffness and other kinematics measured at the 40% BW condition suggest a boundary in which gait stiffness control limit is reached and a new gait pattern is required. Since soldiers are now carrying up to 96% of body weight, the need for research with even heavier loads is warranted. These findings have implications on the development of exoskeletons to assist in carrying loads.

Self-organized complementary joint action: Behavioral dynamics of an interpersonal collision-avoidance task

Understanding stable patterns of interpersonal movement coordination is essential to understanding successful social interaction and activity (i.e., joint action). Previous research investigating such coordination has primarily focused on the synchronization of simple rhythmic movements (e.g., finger/forearm oscillations or pendulum swinging). Very few studies, however, have explored the stable patterns of coordination that emerge during task-directed complementary coordination tasks. Thus, the aim of the current study was to investigate and model the behavioral dynamics of a complementary collision-avoidance task. Participant pairs performed a repetitive targeting task in which they moved computer stimuli back and forth between sets of target locations without colliding into each other. The results revealed that pairs quickly converged onto a stable, asymmetric pattern of movement coordination that reflected differential control across participants, with 1 participant adopting a more straight-line movement trajectory between targets, and the other participant adopting a more elliptical trajectory between targets. This asymmetric movement pattern was also characterized by a phase lag between participants and was essential to task success. Coupling directionality analysis and dynamical modeling revealed that this dynamic regime was due to participant-specific differences in the coupling functions that defined the task-dynamics of participant pairs. Collectively, the current findings provide evidence that the dynamical coordination processes previously identified to underlie simple motor synchronization can also support more complex, goal-directed, joint action behavior, and can participate the spontaneous emergence of complementary joint action roles.

Forefoot angle at initial contact determines the amplitude of forefoot and rearfoot eversion during running

BACKGROUND

Clinically, foot structures are assessed intrinsically - relation of forefoot to rearfoot and rearfoot to leg. We have argued that, from a biomechanical perspective, the interaction of the foot with the ground may influence forces and torques that are propagated through the lower extremity. We proposed that a more appropriate measure is an extrinsic one that may predict the angle the foot makes with ground at contact. The purposes of this study were to determine if the proposed measure predicts contact angles of the forefoot and rearfoot and assess if the magnitude of those angles influences amplitude and duration of foot eversion during running.

METHODS

With the individual in prone, extrinsic clinical forefoot and rearfoot angles were measured relative to the caudal edge of the examination table. Participants ran over ground while frontal plane forefoot and rearfoot contact angles, forefoot and rearfoot eversion amplitude and duration were measured. Participants were grouped twice, once based on forefoot contact inversion angle (moderate<median and large>median) and once based on rearfoot contact inversion angle (moderate<median and large>median).

FINDINGS

The forefoot and rearfoot extrinsic clinical angles predicted, respectively, the forefoot and rearfoot angles at ground contact. Large forefoot contact angles were associated with greater amplitudes (but not durations) of forefoot and rearfoot eversion during stance. Rearfoot contact angles, however, were associated with neither amplitudes nor durations of forefoot and rearfoot eversion.

INTERPRETATION

Possible mechanisms for the increased risk of running injuries associated with large forefoot angles are discussed.

Movement Forms: A Graph-Dynamic Perspective

The focus of this paper is on characterizing the physical movement forms (e.g., walk, crawl, roll, etc.) that can be used to actualize abstract, functionally-specified behavioral goals (e.g., locomotion). Emphasis is placed on how such forms are distinguished from one another, in part, by the set of topological patterns of physical contact between agent and environment (i.e., the set of physical graphs associated with each form) and the transitions among these patterns displayed over the course of performance (i.e., the form's physical graph dynamics). Crucial in this regard is the creation and dissolution of loops in these graphs, which can be related to the distinction between open and closed kinematic chains. Formal similarities are described within the theoretical framework of task-dynamics between physically-closed kinematic chains (physical loops) that are created during various movement forms and functionally-closed kinematic chains (functional loops) that are associated with task-space control of end-effectors; it is argued that both types of loop must be flexibly incorporated into the coordinative structures that govern skilled action. Final speculation is focused on the role of graphs and their dynamics, not only in processes of coordination and control for individual agents, but also in processes of inter-agent coordination and the coupling of agents with (non-sentient) environmental objects.

The coarticulation/invariance scale: mutual information as a measure of coarticulation resistance, motor synergy, and articulatory invariance

Coarticulation and invariance are two topics at the center of theorizing about speech production and speech perception. In this paper, a quantitative scale is proposed that places coarticulation and invariance at the two ends of the scale. This scale is based on physical information flow in the articulatory signal, and uses Information Theory, especially the concept of mutual information, to quantify these central concepts of speech research. Mutual Information measures the amount of physical information shared across phonological units. In the proposed quantitative scale, coarticulation corresponds to greater and invariance to lesser information sharing. The measurement scale is tested by data from three languages: German, Catalan, and English. The relation between the proposed scale and several existing theories of coarticulation is discussed, and implications for existing theories of speech production and perception are presented.

Forefoot angle determines duration and amplitude of pronation during walking

The biomechanical mechanisms that link foot structure to injuries of the musculoskeletal system during gait are not well understood. This study had two parts. The purpose of part one was to determine the relation between clinical rearfoot and forefoot angles and foot angles as they make contact with the ground. The purpose of part two was to determine the effects of large vs. moderate values of both forefoot and rearfoot inversion angles at foot contact on foot kinematics. Clinical foot angle, the relationship between the foot and an axis extrinsically defined relative to the ground, was calculated from digital photographs taken in a prone position. During three speeds of over-ground walking, we measured frontal plane rearfoot and forefoot angle relative to the ground at foot contact, and the following stance phase kinematic measures: amplitude of rearfoot and forefoot eversion, duration of rearfoot and forefoot eversion, and duration between heel-off and onset of rearfoot and forefoot inversion. We found that the clinical forefoot angle predicted the forefoot angle at foot contact. Individuals with a large inversion forefoot angle at contact also had greater amplitude of forefoot eversion and everted longer during stance. We discuss the possible mechanisms for the increased risk of injury to the hip reported for individuals that have a large clinical forefoot angle in non-weight bearing. Equally important is the finding that rearfoot angle at contact did not predict the motions of the rearfoot or forefoot during stance.

A procedure for estimating gestural scores from speech acoustics

Speech can be represented as a constellation of constricting vocal tract actions called gestures, whose temporal patterning with respect to one another is expressed in a gestural score. Current speech datasets do not come with gestural annotation and no formal gestural annotation procedure exists at present. This paper describes an iterative analysis-by-synthesis landmark-based time-warping architecture to perform gestural annotation of natural speech. For a given utterance, the Haskins Laboratories Task Dynamics and Application (TADA) model is employed to generate a corresponding prototype gestural score. The gestural score is temporally optimized through an iterative timing-warping process such that the acoustic distance between the original and TADA-synthesized speech is minimized. This paper demonstrates that the proposed iterative approach is superior to conventional acoustically-referenced dynamic timing-warping procedures and provides reliable gestural annotation for speech datasets.

Bridging planning and execution: Temporal planning of syllables

This study compares the time to initiate words with varying syllable structures (V, VC, CV, CVC, CCV, CCVC). In order to test the hypothesis that different syllable structures require different amounts of time to prepare their temporal controls, or plans, two delayed naming experiments were carried out. In the first of these the initiation time was determined from acoustic recordings. The results confirmed the hypothesis but also showed an interaction with the initial segment (i.e., vowel-initial words were initiated later than words beginning with consonants, but this difference was much smaller for words starting stops compared to /l/ or /s/). Adding a coda did not affect the initiation time. In order to rule out effects of segment-specific articulatory to acoustic interval differences, a second experiment was performed in which speech movements of the tongue, the jaw and the lips were recorded by means of electromagnetic articulography. Results from initiation time, based on articulatory measurements, showed a significant syllable structure effect with VC words being initiated significantly later than CV(C) words. Only minor effects of the initial segment were found. These results can be partly explained by the amount of accumulated experience a speaker has in coordinating the relevant gesture combinations and triggering them appropriately in time.

Recognizing articulatory gestures from speech for robust speech recognition

Studies have shown that supplementary articulatory information can help to improve the recognition rate of automatic speech recognition systems. Unfortunately, articulatory information is not directly observable, necessitating its estimation from the speech signal. This study describes a system that recognizes articulatory gestures from speech, and uses the recognized gestures in a speech recognition system. Recognizing gestures for a given utterance involves recovering the set of underlying gestural activations and their associated dynamic parameters. This paper proposes a neural network architecture for recognizing articulatory gestures from speech and presents ways to incorporate articulatory gestures for a digit recognition task. The lack of natural speech database containing gestural information prompted us to use three stages of evaluation. First, the proposed gestural annotation architecture was tested on a synthetic speech dataset, which showed that the use of estimated tract-variable-time-functions improved gesture recognition performance. In the second stage, gesture-recognition models were applied to natural speech waveforms and word recognition experiments revealed that the recognized gestures can improve the noise-robustness of a word recognition system. In the final stage, a gesture-based Dynamic Bayesian Network was trained and the results indicate that incorporating gestural information can improve word recognition performance compared to acoustic-only systems.

A dynamic systems/constraints approach to rehabilitation

BACKGROUND

Classification systems (Nagi, International Classification for Function [ICF]) have become popular for categorizing the level of ability (ICF) or disability (Nagi) associated with movement disorders. Nevertheless, these classifications do not explore the ways in which one level may influence other levels. For example, how might the weakness and stiffness associated with some cases of cerebral palsy result in a stereotypical toe-gait? In this overview we describe a dynamic systems/constraints (DS/C) approach to understand relationships between levels, and how the approach can be used to rationalize a novel process for the evaluation and treatment of movement disorders.

OBJECTIVES

There are three specific aims in this paper: first to present a general systems approach to understanding behavior at different levels; second to present tools of, and the results of empirical work using the DS/C approach; third to discuss the clinical implications and results of clinical interventions motivated by DS/C analysis for children with cerebral palsy, and individuals with Parkinson disease.

Visuospatial perception and navigation in Parkinson's disease

A shifted field of view, an altered perception of optic flow speed, and gait asymmetries may influence heading direction in Parkinson's disease (PD). PD participants (left body-side onset, LPD, n=14; right body-side onset, RPD, n=9) and Healthy Control participants (n=17) walked a virtual hallway in which the optic flow speeds of the walls varied. Three-dimensional kinematics showed participants veered away from the faster moving wall. Although veering normally occurs toward the side with smaller step length, in both LPD and RPD this bias was overridden by a shifted field of view, which caused veering in the opposite direction, toward the side of the brain with more basal ganglia damage.

Retrieving Tract Variables From Acoustics: A Comparison of Different Machine Learning Strategies

Many different studies have claimed that articulatory information can be used to improve the performance of automatic speech recognition systems. Unfortunately, such articulatory information is not readily available in typical speaker-listener situations. Consequently, such information has to be estimated from the acoustic signal in a process which is usually termed "speech-inversion." This study aims to propose and compare various machine learning strategies for speech inversion: Trajectory mixture density networks (TMDNs), feedforward artificial neural networks (FF-ANN), support vector regression (SVR), autoregressive artificial neural network (AR-ANN), and distal supervised learning (DSL). Further, using a database generated by the Haskins Laboratories speech production model, we test the claim that information regarding constrictions produced by the distinct organs of the vocal tract (vocal tract variables) is superior to flesh-point information (articulatory pellet trajectories) for the inversion process.

Effects of optic flow speed and lateral flow asymmetry on locomotion in younger and older adults: a virtual reality study

The purpose of the study is to investigate whether there are age-related differences in locomotion due to changes in presence of vision, optic flow speed, and lateral flow asymmetry using virtual reality technology. Gait kinematics and heading direction were measured using a three-dimensional motion analysis system. Although older and younger adults were affected differentially by the availability of vision, a greater dependence on optic flow information in older adults during walking was not found. Linear relations were observed between walking performance and flow speed as well as heading direction and flow asymmetry. The findings suggest that the ability to integrate optic flow information into the multimodal system for assessment of walking speed and heading direction is comparable in older and younger adults.

Blood glucose and hormonal responses to small and large meals in healthy young and older women

Blood glucose regulation in the fasting and fed states has important implications for health. In addition, the ability to maintain normal blood glucose homeostasis may be an important determinant of an individual's capacity to regulate food intake. We tested the hypothesis that aging is associated with an impairment in the ability to maintain normal blood glucose homeostasis following the consumption of large meals but not small ones, a factor that could help to explain age-related impairments in the control of food intake and energy regulation. The subjects were eight healthy younger women (25 +/- 2 years, SD) and eight healthy older women (72 +/- 2 years) with normal body weight and glucose tolerance. Following a 36-h period when diet and physical activity were controlled, subjects consumed test meals containing 0, 1046, 2092, and 4184 kJ (simulating extended fasting, and consumption of a snack, a small meal, and a moderately large meal), with 35% of energy from fat, 48% from carbohydrate, and 17% from protein. Each subject consumed each of the test meals on a separate occasion. Serial blood samples were collected at baseline and during 5 h after consumption of the meals. Measurements were made of circulating glucose, insulin, glucagon, free fatty acids, and triglycerides. There was no significant difference between young and older women in their hormone and metabolite responses to fasting and consumption of the 1046-kJ meal. However, following consumption of 2092 and 4148 kJ, older individuals showed exaggerated responses and a delayed return to premeal values for glucose (p = .023), insulin (p = .010), triglycerides (p = .023), and the ratio of insulin to glucagon (p = .026). In conclusion, these results suggest an impairment in the hormonal and metabolite responses to large meals in older women.

Scaling of dynamics in the earliest stages of walking

BACKGROUND AND PURPOSE

Although the description of mature walking is fairly well established, less is known about what is being learned in the process. Such knowledge is critical to the physical therapist who wants to teach children with developmental delays. The purpose of this experiment was to test the notion that learning to walk efficiently involves fine-tuning the body's controllable stiffness (by co-contraction and isometric muscle contractions against gravity) to match (at a 1:1 scaling) the gravitational (pendular) stiffness of the swing leg.

SUBJECTS

The study participants were 7 children with typical development and the newly emerged ability to walk 6 steps without falling (ages 11 months to 1 year 5 months at the onset of walking).

METHODS

Pendular stiffness and spring stiffness were estimated from the equations of motion for a hybrid model with kinematic data as children walked over ground. Testing occurred once per month for the first 7 months of walking.

RESULTS

After the first month of walking, children walked with greater spring stiffness than would be predicted by the model. The ratio began to approach the predicted value (1:1) as the months progressed.

DISCUSSION AND CONCLUSION

The results of this and a previous study of the pendular dynamics of gait suggest that learning to walk is a 2-stage process. The first stage involves the child's discovery of how to conserve energy by inputting a particular muscular force at the correct moment in the cycle. The second stage involves the fine-tuning of the soft-tissue stiffness that takes advantage of the resonance characteristics of tissues. In order to address developmental delays, investigators must discover the dynamic resources used for the activity and attempt to foster their development. A number of interventions that probe this approach are discussed.

Food cravings and energy regulation: the characteristics of craved foods and their relationship with eating behaviors and weight change during 6 months of dietary energy restriction

OBJECTIVE

To examine characteristics of craved foods in relation to dietary energy restriction (ER) with high (HG) and low glycemic load (LG) diets.

DESIGN

Assessments of food cravings before and during a randomized controlled trial of HG and LG diets provided for 6 months.

SUBJECTS

Thirty-two healthy, overweight women aged 20-42 years.

MEASUREMENTS

Self-reported food cravings and dietary intake, body weight, weight history and measures of eating behaviors.

RESULTS

Foods craved at baseline were more than twice as high in energy density as the habitual diet (3.7+/-1.5 vs 1.7+/-0.3 kcal/g; P<0.001), and on average were lower in protein (P<0.001) and fiber (P<0.001) and higher in fat (P=0.002). There were no statistically significant changes in nutritional characteristics of craved foods after 6 months of ER. There was a significant relationship between reported portion size of craved food consumed at baseline and lifetime high body mass index (r=0.49, P=0.005). Additionally, there was a significant association between susceptibility to hunger and craving frequency at baseline, and there were significant relationships between hunger score, craving frequency, strength and percentage of time that cravings are given in to after 6 months of ER. In multiple regression models, subjects who lost a greater percentage of weight craved higher energy-dense foods at month 6 of ER, but also reported giving in to food cravings less frequently (adjusted R (2)=0.31, P=0.009).

CONCLUSION

High energy density and fat content, and low protein and fiber contents were identifying characteristics of craved foods. The relationships between craving variables and hunger score suggest that the relative influence of hunger susceptibility on cravings may be important before and especially after ER. Portion size of craved foods and frequency of giving in to food cravings appear to be important areas for focus in lifestyle modification programs for long-term weight loss.

Action representation of sound: audiomotor recognition network while listening to newly acquired actions

The discovery of audiovisual mirror neurons in monkeys gave rise to the hypothesis that premotor areas are inherently involved not only when observing actions but also when listening to action-related sound. However, the whole-brain functional formation underlying such "action-listening" is not fully understood. In addition, previous studies in humans have focused mostly on relatively simple and overexperienced everyday actions, such as hand clapping or door knocking. Here we used functional magnetic resonance imaging to ask whether the human action-recognition system responds to sounds found in a more complex sequence of newly acquired actions. To address this, we chose a piece of music as a model set of acoustically presentable actions and trained non-musicians to play it by ear. We then monitored brain activity in subjects while they listened to the newly acquired piece. Although subjects listened to the music without performing any movements, activation was found bilaterally in the frontoparietal motor-related network (including Broca's area, the premotor region, the intraparietal sulcus, and the inferior parietal region), consistent with neural circuits that have been associated with action observations, and may constitute the human mirror neuron system. Presentation of the practiced notes in a different order activated the network to a much lesser degree, whereas listening to an equally familiar but motorically unknown music did not activate this network. These findings support the hypothesis of a "hearing-doing" system that is highly dependent on the individual's motor repertoire, gets established rapidly, and consists of Broca's area as its hub.

The power of listening: auditory-motor interactions in musical training

We trained musically naive subjects to play a short piano melody by ear in a fully monitored computerized environment and tested their potential to acquire a functional linkage between actions and sounds. Individual notes that were simply acoustic pretraining signals became "physically meaningful" posttraining. In addition, we found preliminary evidence that passive listening to a newly learned musical piece can enhance motor performance in the absence of physical practice.

Dynamic action units slip in speech production errors

In the past, the nature of the compositional units proposed for spoken language has largely diverged from the types of control units pursued in the domains of other skilled motor tasks. A classic source of evidence as to the units structuring speech has been patterns observed in speech errors--"slips of the tongue". The present study reports, for the first time, on kinematic data from tongue and lip movements during speech errors elicited in the laboratory using a repetition task. Our data are consistent with the hypothesis that speech production results from the assembly of dynamically defined action units--gestures--in a linguistically structured environment. The experimental results support both the presence of gestural units and the dynamical properties of these units and their coordination. This study of speech articulation shows that it is possible to develop a principled account of spoken language within a more general theory of action.

Functional electrical stimulation changes dynamic resources in children with spastic cerebral palsy

BACKGROUND AND PURPOSE

Children with cerebral palsy (CP) often are faced with difficulty in walking. The purpose of this experiment was to determine the effects of functional electrical stimulation (FES) applied to the gastrocnemius-soleus muscle complex on the ability to produce appropriately timed force and reduce stiffness (elastic property of the body) and on stride length and stride frequency during walking.

SUBJECTS AND METHODS

Thirteen children with spastic CP (including 4 children who were dropped from the study due to their inability to cooperate) and 6 children who were developing typically participated in the study. A crossover study design was implemented. The children with spastic CP were randomly assigned to either a group that received FES for 15 trials followed by no FES for 15 trials or a group that received no FES for 15 trials followed by FES for 15 trials. The children who were having typical development walked without FES. Kinematic data were collected for the children with CP in each walking condition and for the children who were developing typically. Impulse (force-producing ability) and stiffness were estimated from an escapement-driven pendulum and spring system model of human walking. Stride length and stride frequency also were measured. To compare between walking conditions and between the children with CP and the children who were developing typically, dimensional analysis and speed normalization procedures were used.

RESULTS

Nonparametric statistics showed that there was no significant difference between the children with CP in the no-FES condition and the children who were developing typically on speed-normalized dimensionless impulse. In contrast, the children with CP in the FES condition had a significantly higher median value than the children who were developing typically. The FES significantly increased speed-normalized dimensionless impulse from 10.02 to 16.32 when comparing walking conditions for the children with CP. No significant differences were found between walking conditions for stiffness, stride length, and stride frequency.

DISCUSSION AND CONCLUSION

The results suggest that FES is effective in increasing impulse during walking but not in decreasing stiffness. The effect on increasing impulse does not result in more typical spatiotemporal gait parameters.

Discovery of the Pendulum and Spring Dynamics in the Early Stages of Walking

The authors investigated the self-selected, overground walking patterns of 7 children (aged 11 months to 1 year, 5 months) at the initiation of walking (brand-new walkers [BNWs]) and for the next 6 months at 1-month intervals. Walking speed, stride length, and stride frequency increased significantly between the first 2 visits without significant changes in height and weight. The authors calculated sagittal plane angular accelerations of the center of mass over the foot for each step as an indicator of the escapement pulse. Results for the acceleration profiles changed after the 1st visit to positive, single-peaked accelerations that occurred < 0.20 s after initial foot contact. Increases in sagittal plane hip angular displacement and decreases in frontal plane pelvic angular displacement were observed. The pattern changes suggest that children quickly discover appropriately timed and directed escapements that initiate and support the conservative sagittal plane pendulum and spring dynamics observed in older children.

Changes in axial stiffness of the trunk as a function of walking speed

Research suggests that abnormal coordination patterns between the thorax and pelvis in the transverse plane observed in patients with Parkinson's disease and the elderly might be due to alteration in axial trunk stiffness. The purpose of this study was to develop a tool to estimate axial trunk stiffness during walking and to investigate its functional role. Fourteen healthy young subjects participated in this study. They were instructed to walk on the treadmill and kinematic data was collected by 3D motion analysis system. Axial trunk stiffness was estimated from the angular displacement between trunk segments and the amount of torque around vertical axis of rotation. The torque due to arm swing cancelled out the torque due to the axial trunk stiffness during walking and the thoracic rotation was of low amplitude independent of changes in walking speeds within the range used in this study (0.85-1.52 m/s). Estimated axial trunk stiffness increased with increasing walking speed. Functionally, the suppression of axial rotation of thorax may have a positive influence on head stability as well as allowing recoil between trunk segments. Furthermore, the increased stiffness at increased walking speed would facilitate the higher frequency rotation of the trunk in the transverse plane required at the higher walking speeds.

Dietary phylloquinone depletion and repletion in postmenopausal women: effects on bone and mineral metabolism

INTRODUCTION

Vitamin K has been implicated in increased bone fracture risk. Despite a potential role of vitamin K in bone, little is known about the effects of altered dietary phylloquinone intake on the underlying components of bone and mineral metabolism.

METHODS

A 84-day in-house dietary phylloquinone (vitamin K) depletion-repletion study was undertaken in 21 postmenopausal women (mean age: 70 years) to assess the effects of altered vitamin K status on intestinal calcium (Ca) absorption, urinary and serum Ca and phosphorus (P), serum calcemic hormones, and serum biomarkers of bone turnover [osteocalcin and N-telopeptide type 1 collagen cross-links (NTx)] and the response to 1,25-dihydroxyvitamin D treatment (1 microg/dayx7 d).

RESULTS

The group receiving calcitriol treatment (n=11) had higher Ca absorption, urinary Ca, urinary and serum P and serum osteocalcin and lower serum parathyroid hormone (PTH). There were no significant effects of acute (4-week) phylloquinone depletion on response to 1,25-dihydroxyvitamin D treatment or on measures of bone formation or mineral metabolism. However, phylloquinone treatment had a significant effect (p<0.04) on serum NTx. Phylloquinone repletion, up to five times (450 microg phylloquinone per day) the currently recommended adequate intake level of dietary phylloquinone for women, significantly reduced serum NTx (16.8+/-0.9 nmol bone collagen equivalents (BCE) per liter following repletion vs 18.4+/-1.1 nmol BCE per liter following depletion; p<0.01).

CONCLUSIONS

These findings suggest that altering vitamin K status in postmenopausal women by manipulating phylloquinone intake does not have an acute affect on intestinal Ca absorption, renal mineral excretion, or bone formation, but high phylloquinone intake may modestly reduce bone resorption. The impact of high phylloquinone intake on bone mineral density and fracture risk needs to be ascertained in randomized clinical trials.

Biomechanical mechanism for transitions in phase and frequency of arm and leg swing during walking

As humans increase walking speed, there are concurrent transitions in the frequency ratio between arm and leg movements from 2:1 to 1:1 and in the phase relationship between the movements of the two arms from in-phase to out-of-phase. Superharmonic resonance of a pendulum with monofrequency excitation had been proposed as a potential model for this phenomenon. In this study, an alternative model of paired pendulums with multiple-frequency excitations is explored. It was predicted that the occurrence of the concurrent transitions was a function of (1) changes in the magnitude ratio of shoulder accelerations at step and stride frequencies that accompany changes in walking speed and (2) proximity of these frequencies to the natural resonance frequencies of the arms modeled as a pair of passive pendulums. Model predictions were compared with data collected from 14 healthy young subjects who were instructed to walk on a treadmill. Walking speeds were manipulated between 0.18 and 1.52 m/s in steps of 0.22 m/s. Kinematic data for the arms and shoulders were collected using a 3D motion analysis system, and simulations were conducted in which the movements of a double-pendulum system excited by the accelerations at the suspension point were analyzed to determine the extent to which the arms acted as passive pendulums. It was confirmed that the acceleration waveforms at the shoulder are composed primarily of stride and step frequency components. Between the shoulders, the stride frequency components were out-of-phase, while the step frequency components were in-phase. The amplitude ratio of the acceleration waveform components at the step and stride frequencies changed as a function of walking speed and were associated with the occurrence of the transitions. Simulation results using these summed components as excitatory inputs to the double-pendulum system were in agreement with actual transitions in 80% of the cases. The potential role of state-dependent active muscle contraction at shoulder joints on the occurrence of the transitions was discussed. Due to the tendency of arm movements to stay in the vicinity of their primary resonance frequency, these active muscle forces were hypothesized to function as escapements that created limit cycle oscillations at the shoulder's resonant frequency.

Dynamic resources used in ambulation by children with spastic hemiplegic cerebral palsy: relationship to kinematics, energetics, and asymmetries

BACKGROUND AND PURPOSE

The atypical walking pattern in children with spastic cerebral palsy is assumed to involve kinematic and morphological adaptations that allow them to move. The purpose of this study was to explore how the requirements of the task and the energy-generating and energy-conserving capabilities of children with cerebral palsy relate to kinematic and mechanical energy patterns of walking.

SUBJECTS

Six children with hemiplegic cerebral palsy and a matched group of typically developing children participated in the study.

METHODS

Kinematic data were collected at 5 different walking speeds. Vertical stiffness, mechanical energy parameters, and landing angle were measured during the stance phase.

RESULTS

The affected side of the children with cerebral palsy showed greater vertical stiffness, a greater ratio of kinetic forward energy to potential energy, and a smaller landing angle when compared with those of the nonaffected lower extremity and with those of typically developing children.

DISCUSSION AND CONCLUSION

Previous research has shown that children with cerebral palsy assumed a gait similar to an inverted pendulum on the nonaffected limb and a pogo stick on the affected limb. Our results indicate that asymmetries between lower extremities and differences from typically developing children in the landing angle of the lower extremity, vertical lower-extremity stiffness, and kinetic and potential energy profiles support the claim that walking patterns in children with spastic hemiplegic cerebral palsy emerge as a function of the resources available to them.

Binge eating disorder in extreme obesity

OBJECTIVE

To determine whether extremely obese binge eating disorder (BED) subjects (BED defined by the Eating Disorder Examination) differ from their extremely obese non-BED counterparts in terms of their eating disturbances, psychiatric morbidity and health status.

DESIGN

Prospective clinical comparison of BED and non-BED subjects undergoing gastric bypass surgery (GBP).

SUBJECTS

Thirty seven extremely obese (defined as BMI > or = 40 kg/m(2)) subjects (31 women, six men), aged 22-58 y.

MEASUREMENTS

Eating Disorder Examination 12th Edition (EDE), Three Factor Eating Questionnaire (TFEQ), Structured Clinical Interview for the Diagnostic and Statistical Manual-IV (SCID-IV), Short-Form Health Status Survey (SF-36), and 24 h Feeding Paradigm.

RESULTS

Twenty-five percent of subjects were classified as BED (11% met full and 14% partial BED criteria) and 75% of subjects were classified as non-BED. BED (full and partial) subjects had higher eating disturbance in terms of eating concern and shape concern (as found by the EDE), higher disinhibition (as found by the TFEQ), and they consumed more liquid meal during the 24 h feeding paradigm. No difference was found in psychiatric morbidity between BED and non-BED in terms of DSM-IV Axis I diagnosis. The health status scores of both BED and non-BED subjects were significantly lower than US norms on all subscales of the SF-36, particularly the BED group.

CONCLUSION

Our findings support the validity of the category of BED within a population of extremely obese individuals before undergoing GBP. BED subjects differed from their non-BED counterparts in that they had a greater disturbance in eating attitudes and behavior, a poorer physical and mental health status, and a suggestion of impaired hunger/satiety control. However, in this population of extremely obese subjects, the stability of BED warrants further study.

Effects of a hydrogenated form of vitamin K on bone formation and resorption

BACKGROUND

Hydrogenation of vegetable oils affects blood lipid and lipoprotein concentrations. However, little is known about the effects of hydrogenation on other components, such as vitamin K. Low phylloquinone (vitamin K1) intake is a potential risk factor for bone fracture, although the mechanisms of this are unknown.

OBJECTIVE

The objective was to compare the biological effects of phylloquinone and its hydrogenated form, dihydrophylloquinone, on vitamin K status and markers of bone formation and resorption.

DESIGN

In a randomized crossover study in a metabolic unit, 15 young adults were fed a phylloquinone-restricted diet (10 microg/d) for 15 d followed by 10 d of repletion (200 microg/d) with either phylloquinone or dihydrophylloquinone.

RESULTS

There was an increase and subsequent decrease in measures of bone formation (P = 0.002) and resorption (P = 0.08) after dietary phylloquinone restriction and repletion, respectively. In comparison with phylloquinone, dihydrophylloquinone was less absorbed and had no measurable biological effect on measures of bone formation and resorption.

CONCLUSION

Hydrogenation of plant oils appears to decrease the absorption and biological effect of vitamin K in bone.

A dynamical model of locomotion in spastic hemiplegic cerebral palsy: influence of walking speed

OBJECTIVE

The objective of this study was to assess the capability of an escapement-driven inverted pendulum with springs and damping model to estimate the effects of impairments (e.g. spasticity, muscle weakness) on the dynamics and patterns of locomotion of children with spastic cerebral palsy.

METHODS

Kinematic data of six children with spastic hemiplegic cerebral palsy and six matched, typically developing children were collected at five different self-selected overground walking speeds ('very slow' to 'very fast'). Changes in forcing, stiffness and gravitational potentials were estimated during the stance phase of each leg according to the model's equation of motion.

RESULTS

Significantly greater stiffness and decreased forcing was observed in the more affected limbs of children with spastic hemiplegic cerebral palsy and compared to typically developing peers. The forcing term of the non-affected limb was greater than that of the matched typically developing children.

CONCLUSIONS

Results support the claim that disabled individuals with losses in dynamic resources (stiffness, muscle forcing capability) exploit and develop the remaining resources in their adapted gait patterns. It was suggested that clinical interventions aimed at normalizing a gait pattern may be contraindicated, and that rehabilitation might be more effective if focused at the level of dynamics.

RELEVANCE

Pattern formation is seen as an optimal solution based on the individuals' action capabilities and dynamic properties under environmental and task demands. This perspective could lead to the development of interventions that address these dynamic variables with the objective of improving the functional capabilities of children with cerebral palsy.

An underfeeding study in healthy men and women provides further evidence of impaired regulation of energy expenditure in old age

The effect of aging on energy regulation remains controversial. We compared the effects of underfeeding on changes in energy expenditure and respiratory quotient in young normal weight men and women [YNW, age 25.7 +/- 3.2 y(SD), body mass index (BMI) 23.1 +/- 1.6 kg/m(2)], young overweight men and women (YOW, age 26.1 +/- 3.5 y, BMI 27.7 +/- 2.1 kg/m(2)) and older (OLD) men and women (age 68.4 +/- 3.3 y, BMI 27.4 +/- 3.4 kg/m(2)). The thermic effect of feeding (TEF) during weight maintenance, and changes in resting energy expenditure (REE) and respiratory quotient were determined in response to undereating by an average 3.75 MJ/d for 6 wk. In addition, body composition was measured. No significant differences among the groups were observed in TEF, fasting and postprandial respiratory quotient, or the change in fasting respiratory quotient with underfeeding. However, REE adjusted for fat-free mass and fat mass was significantly lower in OLD subjects compared with YNW and YOW subjects (P < 0.05). In addition, the REE response to weight change was significantly attenuated in the OLD subjects (P = 0.023). These data suggest that the responsiveness of energy expenditure to negative energy balance is attenuated in old age, and provide further support for the hypothesis that mechanisms of energy regulation are broadly disregulated in old age.

An oat-containing hypocaloric diet reduces systolic blood pressure and improves lipid profile beyond effects of weight loss in men and women

Hypertension, dyslipidemia and overweight contribute substantially to cardiovascular disease risk. One of the most effective methods for improving high blood pressure and lipid profiles is loss of excess weight. Other recommendations for reducing cardiovascular risk include changes in dietary micronutrient, macronutrient and fiber intakes. To better define a diet for reduction in cardiovascular risk, 43 adults (body mass index 26.4 +/- 3.3, range 20.5-33.9 kg/m(2)) participated in an 8-wk study to determine the effects of two diets on weight, blood pressure, lipids and insulin sensitivity. For 2 wk, weight was maintained and all subjects consumed a control diet. For the next 6 wk, subjects consumed one of two hypocaloric diets (maintenance energy minus 4.2 MJ/d): the control diet (n = 21) or a diet containing oats [45 g/(4.2 MJ dietary energy. d), n = 22]. There was no significant difference between groups in changes in weight loss (control -4.0 +/- 1.1 kg, oats -3.9 +/- 1.6 kg, P = 0.8). The oats diet resulted in greater decreases in mean systolic blood pressure (oats -6 +/- 7 mm Hg, control -1 +/- 10 mm Hg, P = 0.026), whereas diastolic blood pressure change did not differ between the two groups (oats -4 +/- 6 mm Hg, control -3 +/- 5 mm Hg, P = 0.8). The oat diet resulted in significantly greater decreases in total cholesterol (oats -0.87 +/- 0.47 mmol/L, control -0.34 +/- 0.5 mmol/L, P = 0.003) and LDL cholesterol (oats -0.6 +/- 0.41 mmol/L, control -0.2 +/- 0.41mmol/L, P = 0.008). In summary, a hypocaloric diet containing oats consumed over 6 wk resulted in greater improvements in systolic blood pressure and lipid profile than did a hypocaloric diet without oats.

Dietary fiber and weight regulation

The influence of dietary fiber on energy regulation remains controversial. This review summarizes published studies on the effects of dietary fiber on hunger, satiety, energy intake, and body composition in healthy individuals. Under conditions of fixed energy intake, the majority of studies indicate that an increase in either soluble or insoluble fiber intake increases postmeal satiety and decreases subsequent hunger. When energy intake is ad libitum, mean values for published studies indicate that consumption of an additional 14 g/day fiber for >2 days is associated with a 10% decrease in energy intake and body weight loss of 1.9 kg over 3.8 months. Furthermore, obese individuals may exhibit a greater suppression of energy intake and body weight loss (mean energy intake in all studies was reduced to 82% by higher fiber intake in overweight/obese people versus 94% in lean people; body weight loss was 2.4 kg versus 0.8 kg). These amounts are very similar to the mean changes in energy intake and body weight changes observed when dietary fat content is lowered from 38% to 24% of energy intake in controlled studies of nonobese and obese subjects. The observed changes in energy intake and body weight occur both when the fiber is from naturally high-fiber foods and when it is from a fiber supplement. In view of the fact that mean dietary fiber intake in the United States is currently only 15 g/day (i.e., approximately half the American Heart Association recommendation of 25-30 g/day), efforts to increase dietary fiber in individuals consuming <25 g/day may help to decrease the currently high national prevalence of obesity.