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Biomedical subjects

J A Kelso

Publications and source records attributed to J A Kelso.

At least 19 recordsLinked to original sources
PubMed1992

Evolution of behavioral attractors with learning: nonequilibrium phase transitions.

Learning a bimanual coordination task (synchronization to a visually specified phasing relation) was studied as a dynamical process over 5 days of practicing a required phasing pattern. Systematic probes of the attractor layout of the 5 Ss' coordination dynamics (expressed through a collective variable, relative phase) were conducted before, during, and after practice. Depending on the relationship between the initial coordination dynamics (so-called intrinsic dynamics) and the pattern to be learned (termed behavioral information, which acts as an attractor of the coordination dynamics toward the required phasing), qualitative changes in the phase diagram occurred with learning, accompanied by quantitative evidence for loss of stability (phase transitions). Such effects persisted beyond 1 week. The nature of change due to learning (e.g., abrupt vs. gradual) is shown to arise from the cooperative or competitive interplay between behavioral information and the intrinsic dynamics.

Adult↗
PubMed1992

Symmetry breaking dynamics of human multilimb coordination.

The dynamics of pattern formation and change are studied in a complex multicomponent system, specifically the arms and legs of human Ss. Among the novel features observed are differential stability of coordinative modes produced by limbs moving in the same versus different directions (Experiment 1); transitions between coordinative modes preceded by a slow drift in relative phase (Experiments 1 and 2); bifurcations or phase transitions from 1 four-limb pattern to another (Experiment 2); and spontaneous emergence of non-1:1-frequency- and phase-locked patterns, in addition to periods of relative coordination (Experiment 3). All observed relative phasing patterns and their dynamics (stability, loss of stability, intermittency) are shown to arise from the same underlying nonlinear dynamical structure, an important feature of which is broken symmetry.

Acceleration↗
PubMed1991

Modeling experimental time series with ordinary differential equations.

Recently some methods have been presented to extract ordinary differential equations (ODE) directly from an experimental time series. Here, we introduce a new method to find an ODE which models both the short time and the long time dynamics. The experimental data are represented in a state space and the corresponding flow vectors are approximated by polynomials of the state vector components. We apply these methods both to simulated data and experimental data from human limb movements, which like many other biological systems can exhibit limit cycle dynamics. In systems with only one oscillator there is excellent agreement between the limit cycling displayed by the experimental system and the reconstructed model, even if the data are very noisy. Furthermore, we study systems of two coupled limit cycle oscillators. There, a reconstruction was only successful for data with a sufficiently long transient trajectory and relatively low noise level.

Animals↗
PubMed1991

Multifrequency behavioral patterns and the phase attractive circle map.

With relative phase as a collective variable or order parameter, phase attractive dynamics can capture the temporally coherent behavior of a large number of different experimental systems. We present results from multifrequency coordination experiments in humans showing: a) that phase attraction persists especially for low order frequency ratios; b) that short-term jumps from one phase relation to another occur within a frequency ratio; c) that the most stable frequency-ratios are low order; and d) that transitions frequently occur from higher order (e.g. 5:2, 4:3) to lower order (2:1, 1:1) frequency ratios. We study a modified sine circle map with built-in phase attractive dynamics that qualitatively accounts for these results. In this phase-attractive map, patterns arise from competition between external driving and intrinsic phase attractive dynamics. The relative strength of extrinsic and intrinsic parameters determines the width of Arnol'd tongues, thereby influencing the delay or acceleration of irregular behavior. Behavioral complexity is inversely proportional to tongue width, thus accounting for the relative difficulty of performing different multifrequency behaviors and why "errors" in such behavior are often seen to occur.

Behavior↗
PubMed1991

Order parameters for the neural organization of single, multijoint limb movement patterns.

Subjects performed two patterns of coordination between the elbow and wrist joints of the right arm: 1) wrist flexion synchronized with elbow flexion and wrist extension with elbow extension (homologous muscle groups); and 2) wrist extension synchronized with elbow flexion and wrist flexion with elbow extension (nonhomologous muscle groups). As a parameter, cycling frequency, was increased, an abrupt switch in the phase relation between the elbow and wrist joints occurred. Similar effects were observed in underlying neuromuscular (EMG) timing patterns. Observed transitions depended on whether the forearm was prone or supine, not simply on the muscle pairing across the joints. With the forearm supine, transitions were from pattern (2) to pattern (1) above, and with the forearm prone the transitions were from pattern (1) to pattern (2). When subjects were initially prepared in pattern (1) with the forearm supine or in pattern (2) with the forearm prone, switching did not occur. En route to transitions, enhanced fluctuations in the phase relation occurred, indicating that loss of stability is at the origin of pattern change. Accompanying such changes in coordination were characteristic effects on end effector trajectories and velocity profiles. Possible neurophysiological mechanisms for context dependence in multijoint coordination are discussed.

Adult↗
PubMed1991

Steady-state and perturbed rhythmical movements: a dynamical analysis.

This study examined rhythmic finger movements in the steady state and when momentarily perturbed in order to derive their qualitative dynamical properties. Movement frequency, amplitude, and peak velocity were stable under perturbation, signaling the presence of an attractor, and the topological dimensionality of that attractor was approximately equal to one. The strength of the attractor was constant with increasing movement frequency, and the Fourier spectra of the steady-state trials showed an alternating harmonic pattern. These results are consistent with a previously derived nonlinear oscillator model. However, the oscillation was phase advanced by perturbation overall, and a consistent phase-dependent, phase-shift pattern occurred, which is inconsistent with the model. The overall phase advance also shows that any central pattern generator responsible for generating the rhythm must be nontrivially modulated by the limb being controlled.

Adult↗
PubMed1991

The production and perception of syllable structure.

Much research on speech over the years has focused on uncovering examples of the nonlinear relationship between acoustics and perception (e.g., so-called "categorical perception") and between articulation and acoustics [as described by Stevens's (1972) quantal theory]. In the present experiment we demonstrate that naturally occurring linear changes in articulation may also be perceived discontinuously. Specifically, linear changes in relative phase of glottal and oral movements are perceived as categorical changes in the location of syllable juncture. Thus, phase transitions observed during speech demarcate a change in syllabic organization.

Glottis↗
PubMed1990

A synergetic theory of quadrupedal gaits and gait transitions.

We present a theoretical analysis of the patterns of interlimb co-ordination in the gaits of quadrupedal locomotion. Introducing as collective variables a set of relative phases that describe the co-ordination patterns, we classify gaits by their symmetry properties, which can be expressed as invariances under groups of transformations. We define dynamics of the collective variables, on which we impose symmetry restrictions. The stable observable gait patterns correspond to atractors of these dynamics. A non-trivial consequence of this theoretical viewpoint is that gait transitions can take the form of non-equilibrium phase transitions that are accompanied by loss of stability. We show how various types of such phase transitions involving hysteresis, slowing down and fluctuation enhancement can occur. Also the difference between smooth and abrupt transitions is given theoretical foundation. While existing experimental evidence is consistent with the theory developed here, we propose new experimental measures that can serve to test the present theoretical framework. Finally, the influence of underlying symmetries of the dynamics on the nature of the gait patterns and their stability is analyzed. For example, breaking of a front-hind symmetry can lead to a change from absolute to relative co-ordination in the sense of von Holst (1939, Ergebnisse der Physiologie 42, 228). Also, differential stability of straight and reverse gaits results from thus lowering the symmetry.

Gait↗
PubMed1990

An evaluation of an alternating magnetic field device for monitoring tongue movements.

Alternating magnetic field devices hold much promise for tracking movements of multiple articulators, including the tongue, in the midsagittal plane. Here, the accuracy, repeatability, and linearity of one such device, the Articulograph AG-100 (Carstens Medizinelektronik GmbH, Göttingen, West Germany), are evaluated. The results indicate that with proper precautions in transducer calibration and placement, the Articulograph can be a useful tool in speech production research.

Adult↗
PubMed1989

Environmentally-specified patterns of movement coordination in normal and split-brain subjects.

Rhythmic movement patterns between the hands in response to environmental signals are studied in normal (musicians and nonmusicians) and split-brain subjects. Only two phase-locked states - in-phase and anti-phase - are shown to be stable for all subjects. Split-brain subjects show an even greater attraction to these patterns, thus providing no support for the notion that reduced cortical interaction between the hemispheres allows for independent visuomotor control of the hands in such tasks. Moreover, differences in trajectories produced by normal individuals and those without an intact corpus callosum are remarkable. The resultant patterns of coordination afford 1) a generalization of previous results on intrisincally generated rhythmic behavior to environmentally-specified movement patterns; and 2) a discussion of neural mechanisms underlying stable phase relations.

Adult↗
PubMed1988

Dynamic pattern generation in behavioral and neural systems.

In the search for principles of pattern generation in complex biological systems, an operational approach is presented that embraces both theory and experiment. The central mathematical concepts of self-organization in nonequilibrium systems (including order parameter dynamics, stability, fluctuations, and time scales) are used to show how a large number of empirically observed features of temporal patterns can be mapped onto simple low-dimensional (stochastic, nonlinear) dynamical laws that are derivable from lower levels of description. The theoretical framework provides a language and a strategy, accompanied by new observables, that may afford an understanding of dynamic patterns at several scales of analysis (including behavioral patterns, neural networks, and individual neurons) and the linkage among them.

Animals↗
PubMed1988

A synergetic theory of environmentally-specified and learned patterns of movement coordination. I. Relative phase dynamics.

This paper outlines and applies a synergetic strategy to the coordination of human rhythmical movement. It extends earlier empirical and theoretical work to include the influence of specific environmental information and of memory on the dynamics of the collective variables (order parameters) that characterize the coordination patterns. Key ideas concern cooperative and competitive influences on the collective dynamics. Recent experiments on environmentally specified and learned rhythmic movement patterns are modeled explicitly on the level of the collective variable, relative phase. New predictions are presented and research directions proposed that follow directly from the present theoretical approach.

Animals↗
PubMed1988

A synergetic theory of environmentally-specified and learned patterns of movement coordination. II. Component oscillator dynamics.

Rhythmic movement patterns have served as a model case for developing a synergetic theory of biological coordination. In part I of this work we extended the approach to environmentally-specified and learned movement patterns on the level of the collective variable relative phase. Here we show that an identical strategy may be applied to the same problem at the level of the component oscillators. Coordinative patterns and their dynamics are derived from the coupled component dynamics and their interaction with the environment. Thus, behavioral patterns are shown to arise in a purely self-organized fashion. New directions for further research (e.g. dynamics of action-perception systems) follow from the oscillator theory. Finally the relationship between our approach and other kinds of analyses of temporal order (e.g. phase resetting) is addressed.

Animals↗
PubMed1988

Patterns of interarticulator phasing and their relation to linguistic structure.

Work by Tuller and Kelso [J. Acoust. Soc. Am. 76, 1030-1036 (1984)] and Kelso et al. [J. Phon. 14, 29-59 (1986)] has demonstrated stable relations between jaw and lip movements in (bV#CVb) utterances across rate and stress conditions. Specifically, the onset of lip movement toward the intervocalic consonant was found to be constant with respect to the vowel-to-vowel jaw cycle in both time and relative phasing. An attempt was made to replicate and extend this work by investigating interarticulator phase relations for utterances having a broader range of linguistic organization: In addition to rate and stress, syllable structure (open versus closed syllables) and identity of the intervocalic consonant (/p/ vs /m/) were manipulated. Results showed that the upper lip's lowering onset varied systematically with respect to the jaw vowel cycle as a function of both rate and stress. In addition, syllable structure and consonant identity influenced the relation of lip and jaw gestures. There was a general tendency for any condition that shortened the first vowel to produce earlier onsets of the upper lip relative to the jaw. However, the within-condition jaw cycle duration variability did not correlate with the within-condition variability in phase. Thus it seems that stable interarticulator phase relations maintain not only the integrity of phonological structure, as suggested by Kelso et al., but structural integrity at other levels of linguistic organization as well.

Female↗
PubMed1987

Space-time behavior of single and bimanual rhythmical movements: data and limit cycle model.

How do space and time relate in rhythmical tasks that require the limbs to move singly or together in various modes of coordination? And what kind of minimal theoretical model could account for the observed data? Earlier findings for human cyclical movements were consistent with a nonlinear, limit cycle oscillator model (Kelso, Holt, Rubin, & Kugler, 1981) although no detailed modeling was performed at that time. In the present study, kinematic data were sampled at 200 samples/second, and a detailed analysis of movement amplitude, frequency, peak velocity, and relative phase (for the bimanual modes, in phase and antiphase) was performed. As frequency was scaled from 1 to 6 Hz (in steps of 1 Hz) using a pacing metronome, amplitude dropped inversely and peak velocity increased. Within a frequency condition, the movement's amplitude scaled directly with its peak velocity. These diverse kinematic behaviors were modeled explicitly in terms of low-dimensional (nonlinear) dissipative dynamics, with linear stiffness as the only control parameter. Data and model are shown to compare favorably. The abstract, dynamical model offers a unified treatment of a number of fundamental aspects of movement coordination and control.

Functional Laterality↗
PubMed1986

A stochastic theory of phase transitions in human hand movement.

The order parameter equation for the relative phase of correlated hand movements, derived in a previous paper by Haken et al. (1985), is extended to a time-dependent stochastic differential equation. Its solutions are determined close to stationary points and for the transition region. Remarkably good agreement between this theory and recent experiments done by Kelso and Scholz (1985) is found, and new predictions are offered.

Hand↗