In the target article Mark Latash has argued that there is but a single bona-fide theory for hand motor control (referent configuration theory). If this is true, and research is often phenomenological, then we must admit that the science of hand motor control is immature. While describing observations under varying conditions is a crucial (but early) stage of the science of any field, it is also true that the key to maturing any science is to vigorously subject extant theories and budding laws to critical experimentation. If competing theories are absent at the present time is it time for scientists to focus their efforts on maturing the science of hand motor control through critical testing of this long-standing theory (and related collections of knowledge such as the uncontrolled manifold)?
Hand Motor Control: Maturing an Immature Science
Kelly J. Cole
Limb versus Speech Motor Control: A Conceptual Review
Britta Grimme, Susanne Fuchs, Pascal Perrier, and Gregor Schöner
This paper presents a comparative conceptual review of speech and limb motor control. Speech is essentially cognitive in nature and constrained by the rules of language, while limb movement is often oriented to physical objects. We discuss the issue of intrinsic vs. extrinsic variables underlying the representations of motor goals as well as whether motor goals specify terminal postures or entire trajectories. Timing and coordination is recognized as an area of strong interchange between the two domains. Although coordination among different motor acts within a sequence and coarticulation are central to speech motor control, they have received only limited attention in manipulatory movements. The biomechanics of speech production is characterized by the presence of soft tissue, a variable number of degrees of freedom, and the challenges of high rates of production, while limb movements deal more typically with inertial constraints from manipulated objects. This comparative review thus leads us to identify many strands of thinking that are shared across the two domains, but also points us to issues on which approaches in the two domains differ. We conclude that conceptual interchange between the fields of limb and speech motor control has been useful in the past and promises continued benefit.
On Primitives in Motor Control
Mark L. Latash
slower or faster, stronger or weaker, actions. In this study, the author would like to review the history of the concept of primitives in the field of motor control, make explicit some of the basic assumptions underlying this concept, assess these assumptions critically, and then offer an interpretation
Motor Control Strategies in a Continuous Task Space
Christoph Schütz, Matthias Weigelt, Dennis Odekerken, Timo Klein-Soetebier, and Thomas Schack
Previous studies on sequential effects of human grasping behavior were restricted to binary grasp type selection. We asked whether two established motor control strategies, the end-state comfort effect and the hysteresis effect, would hold for sequential motor tasks with continuous solutions. To this end, participants were tested in a sequential (predictable) and a randomized (nonpredictable) perceptual-motor task, which offered a continuous range of posture solutions for each movement trial. Both the end-state comfort effect and the hysteresis effect were reproduced under predictable, continuous conditions, but only the end-state comfort effect was present under nonpredictable conditions. Experimental results further revealed a work range restriction effect, which was reproduced for the dominant and the nondominant hand.
Motor Control: A Conceptual Framework for Rehabilitation
Mindy F. Levin and Daniele Piscitelli
misunderstanding among rehabilitation clinicians and neuroscience researchers about motor control theoretical frameworks and terminology. Clinicians prescribe and apply treatment interventions based on hypotheses about the effectiveness of interventions. Assessment of effectiveness follows from the process of
Cognitive Models of Apraxia and Motor Control: Linking Theories and Methods across Two Complementary Research Domains
Robynne M. Gravenhorst and Charles B. Walter
Apraxia is a complex movement disorder that frequently occurs following left hemisphere stroke. Studies on patients with apraxia constitute an especially interesting body of literature for motor control researchers who seek to understand the cognitive mechanisms involved in the voluntary control of movement. Reciprocally, among apraxia researchers, great interest exists concerning the ways in which methods and theory from the field of motor control can be brought to bear in the clinical and empirical evaluation of this disorder. Here we will review representative evidence on the etiology, frequency, and assessment of apraxia, and suggest how research methods and theories from the field of motor control can be applied to, and also benefit from, a deeper understanding of apraxia. Parallels are proposed between the major cognitive models of apraxia and motor control to facilitate translation of terminology and concepts, and to enrich the emerging dialogue between these two complementary research domains.
Dynamic Characteristic Analysis of Spinal Motor Control Between 11- and 15-Year-Old Children
Daniel H.K. Chow and Newman M.L. Lau
Spinal motor control can provide substantial insight for the causes of spinal musculoskeletal disorders. Its dynamic characteristics however, have not been fully investigated. The objective of this study is to explore the dynamic characteristics of spinal motor control via the fractional Brownian motion mathematical technique. Spinal curvatures and repositioning errors of different spinal regions in 64 children age 11- or 15-years old during upright stance were measured and compared for the effects of age and gender. With the application of the fractional Brownian motion analytical technique to the changes of spinal curvatures, distinct persistent movement behaviors could be determined, which could be interpreted physiologically as open-loop behaviors. Moreover, it was found that the spinal motor control of 15-year-old children was better than that of 11-year-old children with smaller repositioning error and less curvature variability as well as shorter response time and smaller curvature deformation.
Coarticulation as an Indicator of Speech Motor Control Development in Children: An Ultrasound Study
Natalia Zharkova, Nigel Hewlett, and William J. Hardcastle
There are still crucial gaps in our knowledge about developmental paths taken by children to adult-like speech motor control. Mature control of articulators during speaking is manifested in the appropriate extent of coarticulation (the articulatory overlap of speech sounds). This study compared lingual coarticulatory properties of child and adult speech, using ultrasound tongue imaging. The participants were speakers of Standard Scottish English, ten adults and ten children aged 6–9 years. Consonant-vowel syllables were presented in a carrier phrase. Distances between tongue curves were used to quantify coarticulation. In both adults and children, vowel pairs /a/-/i/ and /a/-/u/ significantly affected the consonant, and the vowel pair /i/-/u/ did not. Extent of coarticulation was significantly greater in the children than in the adults, providing support for the notion that children’s speech production operates with larger units than adults’. More within-speaker variability was found in the children than in the adults.
Measuring Prospective Motor Control in Action Development
Janna M. Gottwald
This article critically reviews kinematic measures of prospective motor control. Prospective motor control, the ability to anticipatorily adjust movements with respect to task demands and action goals, is an important process involved in action planning. In manual object manipulation tasks, prospective motor control has been studied in various ways, mainly using motion tracking. For this matter, it is crucial to pinpoint the early part of the movement that purely reflects prospective (feed-forward) processes, but not feedback influences from the unfolding movement. One way of defining this period is to rely on a fixed time criterion; another is to base it flexibly on the inherent structure of each movement itself. Velocity—as one key characteristic of human movement—offers such a possibility and describes the structure of movements in a meaningful way. Here, I argue for the latter way of investigating prospective motor control by applying the measure of peak velocity of the first movement unit. I further discuss movement units and their significance in motor development of infants and contrast the introduced measure with other measures related to peak velocity and duration.