[Interpersonal sensorimotor coordination dynamics in schizophrenic patients: introducing a new experimental paradigm]. / Dynamique des coordinations sensorimotrices interpersonnelles chez les patients schizophrènes: introduction d'un nouveau paradigme.

Compared to healthy individuals, schizophrenic patients suffer from sensorimotor disorders including problems when tracking moving targets and perceiving biological motion. Recent advances in embodied cognition and social coordination dynamics have emphasized the important role played by bodily information exchange (e.g. facial expressions, posture, and movements) in the way people interact with and mutually influence each other. These experimental studies on healthy participants provide data on sensorimotor performances of a patient that are recorded at high temporal and spatial resolutions. They should therefore be considered in studies on schizophrenic patients. These functional, quantitive and dynamic aspects of sensorimotor coordination abilities, may offer promising perspectives and could lead to a better understanding of sensorimotor disorders in schizophrenia. The purpose of this article is to introduce a new experimental paradigm in schizophrenia inspired by the field of coordination dynamics, a theoretical and experimental approach born more than 30 years ago that has recently expanded to interpersonal interactions, the so-called social coordination dynamics. In our study, we hypothesize that the sensorimotor deficits associated with schizophrenia in social interaction may be, at least partially, due to a failure to properly pick up information about the movements of other people. We therefore designed a study where healthy individuals and schizophrenic patients were asked to intentionally track the oscillations of visual targets of various social relevance using hand movements. Four different rhythmic visual stimuli varying in degree of biological relevance (form and motion) are used: [1] an oscillating dot; [2] a computer generated hand moving up and down continuously driven by a sine function; [3] pre-recorded oscillatory movements of a real hand; and [4] the hand of a real individual (behind a curtain that occluded vision of the rest of the body). Two distinct dependent variables are computed to quantify the coordination between the movements of the participants and the visual stimuli: the relative phase and the power spectrum overlap between their own movements. In this preliminary study, analyses of kinematic data revealed that schizophrenic patients had trouble synchronizing to (the more) "biological" target unlike control healthy individuals. These results suggest that patients with schizophrenia may suffer from sensorimotor coordination disabilities with socially relevant visual stimuli. The novel paradigm we introduce in research on schizophrenia should allow for a better understanding of the troubles these patients encounter when interacting with other people thanks to an approach rooted and building on social coordination dynamics as well as motor and social cognition.

Neuroimaging coordination dynamics in the sport sciences.

Key methodological issues for designing, analyzing, and interpreting neuroimaging experiments are presented from the perspective of the framework of Coordination Dynamics. To this end, a brief overview of Coordination Dynamics is introduced, including the main concepts of control parameters and collective variables, theoretical modeling, novel experimental paradigms, and cardinal empirical findings. Basic conceptual and methodological issues for the design and implementation of coordination experiments in the context of neuroimaging are discussed. The paper concludes with a presentation of neuroimaging findings central to understanding the neural basis of coordination and addresses their relevance for the sport sciences. The latter include but are not restricted to learning and practice-related issues, the role of mental imagery, and the recovery of function following brain injury.

Planning and efferent components in the coding of movement.

Two experiments were carried out to assess the cognitive contribution of a movement plan and its relationship to efferent-command information in explaining the superior accuracy of preselected movement. Subjects performed under conditions which differed with regard to efferent information (active versus passive) and the availability of a movement plan (preselected, subject defined vs. constrained, experimenter defined). In both experiments active preselection had significantly smaller reproduction errors than any other combination, indicating that the planning process in itself was insufficient to facilitate movement coding. The findings were interpreted in terms of the sometimes-synonymously viewed concepts of central monitoring of efference, efference copy, and corollary discharge. The latter notion, that a central signal occurs prior to movement which acts to facilitate the processing of information, seemed to provide the most appropriate account of the present data. The experiments reported here are a portion of a Ph.D. dissertation submitted to the University of Wisconsin-Madison under the supervision of George E. Stelmach, to whom appreciation is extended. Support for the research was provided by Grant MH 22081-01 from the National Institute of Mental Health and by Grant NE-G-3-0009 from the National Institute of Education. However, the opinions expressed herein do not necessarily reflect the position or policies of the above granting agencies and no official endorsement of them should be inferred. The author would like to thank Shelley Smith who assisted with data collection in these experiments.

The continuing saga of the nerve compression block technique.

In response to Bairstow and Laszlo (1976) the present paper points out the inconsistencies of their arguments relative to Laszlo's previous work and that of Kelso, Stelmach, and Wanamaker (1974). Data are presented indicating that the nerve compression block, as a tool, fails to meet the stringent requirements necessary for examining motor performance in the absence of kinesthetic information. Some possibilities for the discrepancy between Laszlo's performance data and those from Kelso et al. are discussed. These hinge on the availability of sensory information rather than any artifact in the Kelso et al. nerve conduction procedures as Bairstow and Laszlo (1976) suggest.

Behavioral and neurological parameters of the nerve compression block.

The nerve-compression block has been used to investigate movement control in the absence of kinesthetic information. Implicit is the assumption that tactile and kinesthetic sensation are eliminated 5 to 10 min. prior to motor function. Motor fibers in the ulnar and median nerves of the upper preferred limb were tested at systematic intervals throughout the duration of the block application. When kinesthetic cut-off was assigned, Ss performed three tapping trials with vision and audition eliminated. Progressive reduction in nerve-conduction parameters (motor nerve conduction velocity and amplitude of the muscle action potential) occurred across and below the block, with significant decrements occurring as early as 15 min. Results indicated that motor impairment was a confounding factor in the use of the nerve block technique.

Patterns of human interlimb coordination emerge from the properties of non-linear, limit cycle oscillatory processes.

The present article represents an initial attempt to offer a principled solution to a fundamental problem of movement identified by Bernstein (1967), namely, how the degrees of freedom of the motor system are regulated. Conventional views of movement control focus on motor programs or closed-loop devices and have little or nothing to say on this matter. As an appropriate conceptual framework we offer Iberall and his colleagues' physical theory of homeokinetics first elaborated for movement by Kugler, Kelso, and Turvey (1980). Homeokinetic theory characterizes biological systems as ensembles of non-linear, limit cycle oscillatory processes coupled and mutually entrained at all levels of organization. Patterns of interlimb coordination may be predicted from the properties of non-linear, limit cycle oscillators. In a set of experiments and formal demonstrations we show that cyclical, two-handed movements maintain fixed amplitude and frequency (a stable limit cycle organization) under the following conditions: (a) when brief and constantly applied load perturbations are imposed on one hand or the other, (b) regardless of the presence or absence of fixed mechanical constraints, and (c) in the face of a range of external driving frequencies from a visual source. In addition, we observe a tight phasic relationship between the hands before and after perturbations (quantified by cross-correlation techniques), a tendency of one limb to entrain the other (mutual entrainment) and that limbs cycling at different frequencies reveal non-arbitrary, sub-harmonic relationships (small integer, subharmonic entrainment). In short, all the above patterns of interlimb coordination fall out of a non-linear oscillatory design. Discussion focuses on the compatibility of these results with past and present neurobiological work, and the theoretical insights into problems of movement offered by homeokinetic physics. Among these are, we think, the beginnings of a principled solution to the degrees of freedom problem, and the tentative claim that coordination and control are emergent consequences of dynamical interactions among non-linear, limit cycle oscillatory processes.

Detection of correlated sources in EEG using combination of beamforming and surface Laplacian methods.

Beamforming offers a way to estimate the solution to the inverse problem in EEG and MEG but is also known to perform poorly in the presence of highly correlated sources, e.g. during binaural auditory stimulation, when both left and right primary auditory cortices are activated simultaneously. Surface Laplacian, or the second spatial derivative calculated from the electric potential, allows for deblurring of EEG potential recordings reducing the effects of low skull conductivity and is independent of the reference electrode location. We show that anatomically constrained beamforming in conjunction with the surface Laplacian allows for detection of both locations and dynamics of temporally correlated sources in EEG. Whole-head 122 channel binaural stimulus EEG data were simulated using a boundary element method (BEM) and realistic geometry forward model. We demonstrate that in contrast to conventional potential-based EEG beamforming, Laplacian beamforming allows to determine locations of correlated source dipoles without any a priori assumption about the number of sources. We also show (by providing simulations of auditory evoked potentials) that the dynamics at the detected source locations can be derived from subsets of electrodes. Deblurring auditory evoked potential maps subdivides EEG signals from each hemisphere and allows for the beamformer to be applied separately for left and right hemispheres.

Fechner-Benham subjective colors do not induce McCollough after-effects.

Fechner-Benham subjective color is widely believed to be governed by local interactions in early (probably retinal) mechanisms. Here we report three lines of phenomenological evidence that suggest otherwise: subjective colors seen in spatially extended stimuli (a) are dependent on global aspects of the stimuli; (b) can become multistable in position; and (c) even after being stabilized do not support the creation of McCollough's colored after-effects--a cortically based phenomenon generally thought to be more central than Fechner-Benham color. These phenomena suggest a central locus that controls perception of subjective color, characterized by pattern dependent interactions among cortical mechanisms that draw their inputs from peripheral units.

Memory trace strength and response biasing in short-term motor memory.

Two experiments, which attempted to create differential memory trace strengths in a response biasing paradigm, were performed. After the presentation of the criterion location, an interpolated target was presented which was either ±40 deg from the criterion. The S's task was to attend to both targets and recall each when instructed. The first experiment involved strengthening the criterion trace via repetition (0, 5, or 14 rep.) while the second involved providing additional feedback via visual, auditory, and heightened kinesthetic cues. In the initial experiment, a Repetition by Response Biasing interaction revealed that repetition systematically reduced error shifts at recall. The second experiment found that, in the combined feedback and visual conditions, response biasing was reduced. It seems feasible to suggest that both studies successfully manipulated memory trace strength which appears to be one determiner of error shifts at recall.