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1.
J Mot Behav ; 37(4): 295-309, 2005 Jul.
Article in English | MEDLINE | ID: mdl-15967755

ABSTRACT

Symmetry groups-rules that connect different configurations of a given set of components-represent a compact means of coding for effects, a feature that is desirable in both model- and theory-building. The present study was designed to compare the effects of spatial orientation differences with the various other asymmetries (e.g., timing differences, handedness preferences, the direction of attention) that are accommodated by current models of bimanual coordination. The authors used symmetry groups to predict specific patterns of results. In 2 experiments, participants (N = 13, Experiment 1; N = 9, Experiment 2) coordinated the movements of differently oriented (1 downward and 1 upward) pendulum pairs at a low (0.62 Hz) or high (0.82 Hz) movement frequency to establish an in-phase or antiphase pattern. Consistent with previous results (P. G. Amazeen, E. L. Amazeen, & M. T. Turvey, 1998a), the downward-oriented pendulum tended to lead slightly. In contrast to the effects of other bimanual asymmetries, the downward-oriented pendulum lead was amplified at low frequencies. Although the results contradicted the predictions of existing models of bimanual coordination, they were consistent with predictions from symmetry group theory. In the discussion, the authors focus on the application of symmetry groups to both bimanual coordination and other phenomena with more complex symmetric structures.


Subject(s)
Functional Laterality , Psychomotor Performance/physiology , Adult , Algorithms , Attention , Female , Humans , Male , Movement/physiology , Periodicity , Space Perception , Time Factors
2.
J Exp Psychol Hum Percept Perform ; 27(5): 1243-59, 2001 Oct.
Article in English | MEDLINE | ID: mdl-11642706

ABSTRACT

The hypothesis of this study was that stable coordination patterns may be found both within and between physiological subsystems. Many studies have been conducted on both monofrequency and multifrequency coordination, with a focus on both the frequency and phase relations among the limbs. In the present study, locomotor-respiratory coupling was observed in the maintenance of small-integer frequency ratios (2:1, 3:1, and 4:1) and in the consistent placement of the inspiratory phase just after the onset of the movement cycle during wheelchair propulsion. Level of experience and various motor and respiratory parameters were manipulated. Coupling was observed across levels of experience. Increases in movement frequency were accompanied by a shift to larger-integer ratios, suggesting that a single modeling strategy (e.g., the Farey tree; D. L. González & O. Piro, 1985) may be used for coordination both within the motor subsystem and between it and other physiological subsystems.


Subject(s)
Hand/physiology , Motion , Movement/physiology , Respiration , Wheelchairs , Adult , Female , Humans , Male
3.
Invest Radiol ; 35(5): 319-24, 2000 May.
Article in English | MEDLINE | ID: mdl-10803673

ABSTRACT

RATIONALE AND OBJECTIVES: To determine the relationship between the attenuation of backscatter intensity in B-scan images of the liver and diffuse liver disease in order to assess the usefulness of this method in providing quantitative objective characterization of diffuse liver diseases in general and in fatty liver in particular. METHODS: Twenty-four healthy volunteers and 28 patients with elevated liver enzyme levels who underwent liver biopsy were included in this study. An automatic far-field slope (FFS) algorithm that estimates the decrease in amplitude of the backscattered echo as a function of beam depth was implemented on the noncompensated image that was acquired on a commercial phased-array ultrasound system fitted to a custom-built interface card. The images were processed at a work-station. All scans were acquired repeatedly, read, and graded blindly by experienced ultrasound radiologists. Histology obtained via needle biopsy was reviewed without knowledge of the ultrasound findings. RESULTS: Analysis of the FFS data for fatty infiltration in all patient groups yielded a sensitivity of 67%, a specificity of 77%, a positive predictive value (PPV) of 77%, negative predictive value (NPV) of 67%, and an accuracy of 71%. The mean score of the ultrasound reviewers showed a sensitivity of 82%, a specificity of 66%, a PPV% of 68%, an NPV of 81%, and an accuracy of 72%. Normal FFS values (false-negative) were found in five patients with proved fatty infiltration. All of these patients had coexistent moderate to severe hepatic inflammation. However, FFS data in patients with uncomplicated (pure) fatty infiltration revealed a sensitivity of 100%, a specificity of 80%, a PPV of 89%, an NPV of 100%, and an accuracy of 92%. The best ultrasound score yielded a sensitivity of 100%, a specificity of 60%, a PPV of 80%, an NPV of 100%, and an accuracy of 85% in the same patients. CONCLUSIONS: The data demonstrate an excellent sensitivity (100%) of the FFS values in patients with uncomplicated fatty infiltration. This was also the only group of patients in whom the FFS score was superior to the radiologists' best score. The FFS method can be used as a tool to follow up the response to a clinical or research treatment and to obtain standardization of pattern interpretation independently of the individual reader.


Subject(s)
Image Processing, Computer-Assisted , Liver Diseases/diagnostic imaging , Adolescent , Adult , Aged , Algorithms , Analysis of Variance , Biopsy , Child , Fatty Liver/diagnostic imaging , Fatty Liver/pathology , Female , Humans , Liver Diseases/pathology , Male , Middle Aged , Predictive Value of Tests , Sensitivity and Specificity , Ultrasonography
4.
J Exp Psychol Hum Percept Perform ; 24(3): 884-900, 1998 Jun.
Article in English | MEDLINE | ID: mdl-9627423

ABSTRACT

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.


Subject(s)
Psychomotor Performance/physiology , Analysis of Variance , Female , Humans , Male
5.
J Mot Behav ; 30(3): 199-216, 1998 Sep.
Article in English | MEDLINE | ID: mdl-20037079

ABSTRACT

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.

6.
Biol Cybern ; 72(6): 511-8, 1995.
Article in English | MEDLINE | ID: mdl-7612722

ABSTRACT

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.


Subject(s)
Movement/physiology , Periodicity , Psychomotor Performance/physiology , Adult , Behavior/physiology , Female , Humans , Male
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