In this paper we describe how a theory of posture-based motion planning recently applied to human grasping may contribute to the understanding of grasping pathology. The theory is implemented as a computer model rendered as a stick-figure animation capable of generating realistic multi-joint grasping movements. As shown here, the model can also be used to simulate grasping movements whose kinematics resemble those of grasps performed by people with spastic hemiparesis. The simulations demonstrate effects of: (a) reduced ranges of motion of arm joints on the size of the reachable workspace, (b) awkward starting postures on me time course of the hand closing around an object, (c) increased costs of joint rotations on movement time, and (d) addition of noise to biphasic joint rotations on the low-velocity phase of wrist transport.
Ruud C.J. Meulenbroek, David A. Rosenbaum and Jonathan Vaughan
Tim McGarry and Ian M. Franks
The ability to inhibit an earlier intended action in a stop-signal task is commonly assessed using the measures of latency and probability. The usual findings from stop-signal trials of lower response probabilities and shorter reaction latencies at reduced stop-signal delays were reported, as described in previous studies in terms of an independent race between stochastic processes (see Logan & Cowan, 1984). In addition, using the less common measure of amplitude, a continuum of reductions in surface EMG onsets was reported. Weakened motor discharges have yet to be explained in terms of a mechanism of inhibitory control. Using computer simulations of neural functioning, the properties of independence and non-independence were examined for their effects on motor pool output in terms of probability, latency, and EMG onsets. The data provided support to question the requirement of independent processes for a theory of inhibitory control.
Senne Braem, Stephanie Supply, Sanne P. Roels and Wim Notebaert
Most cognitive control effects, although numerously reported in computer task studies, have rarely been tested outside the laboratory. The purpose of this study was twofold. First, we aimed to improve the ecological validity of a well-studied congruency effect. The Simon effect (Simon, 1969) is the observation that an irrelevant stimulus location can facilitate or impede task performance when it is congruent or incongruent with the response location. Secondly, we wanted to investigate the role of action experience on the Simon effect. In this study, experienced bowlers were asked to hit either the left- or rightmost pin, depending on the pitch of a tone. Irrelevant to the task, this tone could be presented in the congruent or incongruent ear. Our results demonstrate that the Simon effect can be observed outside the laboratory and that weekly training at bowling may help in shielding against irrelevant location stimuli.
Brian K.V. Maraj, Li Li, Rebecca Hillman, Jennifer J. Jeansonne and Shannon D. Ringenbach
This study examined motor learning in persons with Down syndrome (DS), persons with undifferentiated developmental disabilities (UnDD), and persons without disabilities (ND). Participants were instructed (either by verbal instruction or visual demonstration) to move a cursor to three items displayed on a computer screen. Results indicated that the ND group had superior performances to the other two groups for both instruction conditions. Participants with DS performed the task with both longer response and movement times when instructed verbally. In a transfer condition, results revealed the UnDD group displayed poor transfer, while participants with DS showed positive transfer from visual to verbal protocols. These results provide some evidence that persons with DS may be able to consolidate visual information to facilitate verbal-motor learning.
Richard N. Hinrichs
Ten male recreational runners ranging in age from 20 to 32 years were filmed using 3-D cinematography while running on a treadmill at 3.8 m/s, 4.5 m/ s, and 5.4 m/s. The 3-D segment endpoint data were entered into a computer program that computed the segmental contributions to the upward and forward propulsive impulses on the body (lift and drive, respectively) and to the vertical component of angular momentum (Hz). The results of two subjects who demonstrated asymmetrical arm action are discussed in detail and compared with the mean results computed over all subjects. The results revealed that the arms possess the potential to compensate for each other and for asymmetries elsewhere in the body.
Maurice R. Yeadon
At the 1988 Calgary Winter Olympics, six triple somersaults with three twists or four twists were filmed using two cameras. Angles describing body configuration and orientation were determined and were used as input into a computer simulation model of aerial movement. It was found that the twist angle of each simulation deviated from the corresponding angle obtained from film by less than 0.08 revolutions during the first somersault of each movement. Contributions to the tilt angle after one somersault were determined using simulations based on modifications of the film data. It was found that of the six competitors, two initiated the twist during the takeoff phase, two initiated the twist during the aerial phase, and two used a combination of both methods.
Maurice R. Yeadon, Sung-Cheol Lee and David G. Kerwin
At the 1988 Seoul Olympic Games, eight full twisting somersault dismounts from the high bar were filmed using two cameras during the compulsory exercises of the Men’s High Bar competition. Angles describing body configuration and orientation were determined and were input into a computer simulation model of aerial movement. The deviations between simulation and film were less than 2.5° for tilt angles and less than 0.07 revolutions for twist angles. The twisting techniques employed were quantified using the tilt angle as a measure of twisting potential. Contributions to the maximum tilt angle were determined using simulations based on modifications of the film data. Each of the eight competitors obtained most of the tilt using aerial rather than contact techniques. In general, the majority of the aerial contributions arose from asymmetrical arm and hip movements.
Rachael D. Seidler
Visuomotor adaptive processes were examined by testing transfer of adaptation between similar conditions. Participants made manual aiming movements with a joystick to hit targets on a computer screen, with real-time feedback display of their movement. They adapted to three different rotations of the display in a sequential fashion, with a return to baseline display conditions between rotations. Adaptation was better when participants had prior adaptive experiences. When performance was assessed using direction error (calculated at the time of peak velocity) and initial endpoint error (error before any overt corrective actions), transfer was greater when the final rotation reflected an addition of previously experienced rotations (adaptation order 30° rotation, 15°, 45°) than when it was a subtraction of previously experienced conditions (adaptation order 45° rotation, 15°, 30°). Transfer was equal regardless of adaptation order when performance was assessed with final endpoint error (error following any discrete, corrective actions). These results imply the existence of multiple independent processes in visuomotor adaptation.
Thomas Wandzilak, Ronald J. Bonnstetter and Lynn L. Mortensen
In order for university professors to become more effective at the practice of teaching, they must be provided with accurate, multidimensional feedback on what transpires in their own classes. The Teaching Feedback Model (TFM) is a process that combines the systematic observation of student and teacher behaviors with an analysis of student learning. Based on information provided by the coding of videotaped classroom episodes through a computer program and student learning data, a profile is constructed that informs the teacher whether continuity exists among what is supposed to occur (planning), what actually occurs (doing), and what the student has gained from the class (learning). The purpose of this paper is to present this model in detail and to demonstrate how it is currently being used in college-level physical education theory classes.
Rahman Davoodi and Gerald E. Loeb
Computer models of the neuromusculoskeletal systems can be used to study different aspects of movement and its control in humans and animals. SIMM with Dynamics Pipeline (Musculographics Inc., Chicago) and SD-Fast (Symbolic Dynamics Inc., Mountain View, CA) are software packages commonly used for graphic and dynamic simulation of movement in musculoskeletal systems. Building dynamic models with SIMM requires substantial C programming, however, which limits its use. We have developed Musculoskeletal Modeling in Simulink (MMS) software to convert the SIMM musculoskeletal and kinetics models to Simulink (Mathworks Inc., Natick, MA) blocks. In addition, MMS removes SIMM’s run-time constraints so that the resulting blocks can be used in simulations of closed-loop sensorimotor control systems.