Polemnia G. Amazeen

A Comparison of Intra- and Interpersonal Interlimb Coordination: Coordination Breakdowns and Coupling Strength

Intra- and interpersonal interlimb coordination of pendulums swung from the wrist was investigated. For both kinds of coordination, the steady state and breakdown of bimanual rhythmic coordination as indexed by the time series of the relative phase angle phi were studied under the manipulation of coordination mode, frequency of oscillation, and the difference in the eigenfrequencies (preferred tempos) of the individual oscillating limbs. The properties observed for both intra- and interpersonal coordination were those predicted by a dynamical model of rhythmic coordination that considers the coordinated limbs coupled to be nonlinear oscillators. Using a regression method, the coupling strengths of the coupled system were recovered. As predicted by the dynamical model, the strength of the dynamic was generally greater for the in-phase than the anti-phase mode and decreased with increasing frequency. Further, the strength of the interpersonal interlimb coupling was weaker than that of intrapersonal interlimb coupling.

Frequency detuning of the phase entrainment dynamics of visually coupled rhythmic movements

An order parameter equation for correlated limb movements was applied to rhythmic coordination between the limbs of two people. The interlimb coordination was established and maintained through vision. Manipulations of frequency competition, coupled frequency, and intended mode (in-phase or anti-phase) produced equilibria and fluctuations in relative phase predicted by the order parameter equation and confirmed originally in within-person coordination. It was concluded that there is an elementary coordination dynamics governing the rhythmic coordination between organisms as well as between components of a single organism.

Attention and Handedness in Bimanual Coordination Dynamics

Predictions concerning the effects of handedness and attention on bimanual coordination were made from a dynamical model that incorporates the bodys lateral asymmetry. Both handedness and the direction of attention (to the left or right) were manipulated in an inphase 1:1 frequency locking task. Left-handed and right-handed participants had to coordinate the planar oscillations of 2 handheld pendulums while 1 pendulum oscillated between spatial targets positioned over either the left or right hand. Predictions from the model were that participants would show a phase lead with the preferred hand, and that, although the phase lead would be greater when attention was directed to the preferred hand, the variability of relative phase would be lower. Confirmation of these predictions suggests that the dynamical perspective offers the possibility of studying handedness and attention without compromising theoretical precision or experimental control.

Intermediate motor learning as decreasing active (dynamical) degrees of freedom

A classical view is that motor learning has distinguishable early, intermediate, and late phases. A recent view is that motor learning is the acquisition of an abstract equation of motion that specifies the time evolution of a pattern of coordination. The pattern is expressed by a collective variable that enslaves or orders component subsystems that, in turn, act on and generate the collective variable. In these latter terms, early learning resolves the collective variable and its motion equation, intermediate learning stabilizes and standardizes the subsystems or active degrees of freedom (DFs) producing the collective variable’s dynamics. The preceding ideas, and the phase-space reconstruction methods required to determine active DFs, are developed in tutorial fashion in the context of an experimental investigation of learning a bimanual rhythmic coordination. Results show that intermediate learning reduces the dimensionality of the learned coordination’s dynamics and renders those dynamics more deterministic. The tutorial development relates the preceding concepts, results and methods of analyses to (a) the contrast between PoincarCan and Newtonian dynamics, (b) contemporary interpretations of random processes, (c) definitions of DFs in respect to Bernstein’s problem, (d) the potential contribution of chaos to the adaptability of a learned coordination, and (e) possible links bctween active (dynamical) DFs and the control variables Y, c, and jr identified by the i hypothcsis. 0 1998 Elsevier Science B.V.

Breaking the Reflectional Symmetry of Interlimb Coordination Dynamics

Interlimb rhythmic coordination is reflectionally symmetric when the left and right limb segments are identical in uncoupled frequencies and spatial orientation. In the present studies (4 experiments, with a total of 31 participants), when reflectional symmetry was broken through differences in timing (frequency), the resulting stable states were related by reflection and were identical for paired identically oriented limb segments behaving either as inverted or as ordinary pendulums. When reflectional symmetry was broken both temporally and spatially (coordinating inverted and ordinary pendular motions), the resulting stable states were different from those produced by identically oriented pendulums but nevertheless were related by reflection. In the Discussion, the authors focus on (a) symmetry breaking as leading to one of a number of symmetrically related states and (b) extending coordination dynamics with reflectional symmetry so that temporal and spatial asymmetries can both be accommodated.

Timing the selection of information during rhythmic catching

Catching a ball requires that information be available close to the catch but early enough for prospective or corrective control. In the present experiment, 6 participants were asked to throw and catch a ball continuously for 1 min while wearing liquid-crystal goggles that restricted viewing to specific amounts of time at specific intervals. Participants were free to select the information by varying the frequency and phasing of throwing relative to the goggles. Video analysis revealed that they elected a frequency of throwing that matched the goggle frequency and chose to view the ball at or around its zenith. Earlier portions of the balls trajectory were viewed as the goggle frequency increased. Despite variations in the viewing location, participants elected to view the ball on average 365 ms before the catch. Analysis of the hands trajectory further revealed that the time interval (M = 82 ms) between the balls zenith and the initiation of the final motion of the hand toward the catch did not vary as a function of the frequency of throwing. The authors conclude that the timing constraints imposed by the hands movement are the basis for the selection of information for catching.

Eye movements and the selection of optical information for catching.

The direction of gaze during a single-ball throwing and catching task was analyzed to generate hypotheses regarding the optical information that participants used. Five intermediate and 5 expert jugglers threw and caught a single ball continuously with 1 hand while wearing a head-mounted eye tracker to monitor their direction of gaze. Participants were instructed to throw the ball at 3 self-paced frequencies: preferred, one half of preferred, and twice preferred. Analysis of the digital eye tracker data along with the video recording of the ball and hand revealed that all participants viewed the ball at or around the balls zenith. Intermediates varied only the mean phase of viewing across frequencies. Experts, however, varied the initiation of viewing, the point of minimum gaze to ball distance, the mean viewing phase, and the mean time between viewing and catching across frequencies. Both groups initiated the final downward movement of the hand toward the catch 89 msec after the balls zenith. The implications of these results for the optical information for catching and expertise in a perceptual-motor task are discussed.