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)?
Kelly J. Cole
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.
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.
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
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.
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.
Mark L. Latash
Motor control is a relatively young field under the broad umbrella of kinesiology, younger than athletic training, biomechanics, exercise physiology, motor behavior, motor learning, sport psychology, and other established areas. Forty years ago, the seminal book edited by George Brooks had only one
Jack R. Engsberg, Richard E. A. Van Emmerik, Sandy A. Ross, and David R. Collins
This investigation developed a measure of motor control at the ankle for persons with CP using relative phase. Twenty-nine subjects, 14 with spastic diplegia cerebral palsy (CP group) and 15 without disability (WD group) were tested once. Video data were collected as a seated subject performed four full range of ankle plantar and dorsiflexion movement tasks (right ankle, left ankle, ankles in-phase with each other, and ankles antiphase to each other) at four different frequencies (self-paced, 0.5, 0.75, 1.0 Hz). The relative phase measure was able to discern the differences between the two groups of children. The CP group had poorer motor control than the WD group, based upon the measure. Both groups had more difficulty performing the antiphase than the in-phase movements. The investigation adds to the body of knowledge in that the concept of relative phase was used as a measure of motor control at the ankle in persons with CP. Results indicated that the measure was adequately sensitive to quantify differences between a group with CP and a group without disability. Clinically the measure could eventually be used as both an assessment and outcome tool.
Cheryl M. Glazebrook
Questions about how humans develop, learn, and control a wide range of motor skills are relevant not only to researchers in motor control and learning but also to teachers, parents, coaches, engineers, and health care practitioners from a variety of fields. An entire community of motor behavior
Jenya Iuzzini-Seigel, Tiffany P. Hogan, Panying Rong, and Jordan R. Green
Lip shape in adult talkers is primarily driven by vertical opening; however, little is known about how children converge on this highly organized and efficient lip shape pattern. This longitudinal study investigated the development of lip shape control and its relation to speech and vocabulary acquisition in 28 typically developing children between 3 months and 5 years of age. Results suggested that during infancy lip shape was characterized by horizontal spreading of the lips, but that the contribution of vertical opening increased nonmonotonically over time. This change co-occurred with gains in expressive communication. These data suggest that lip shape may represent an important marker of normal oromotor development. Future work is required to determine the functional significance of the observed changes in lip shape control for identifying children at risk for speech and language impairments.