RESUMEN

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.

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RESUMEN

Mounting evidence suggests that information derived from environmental and behavioral sources is represented and maintained in the brain in a context-dependent manner. Here we investigate whether activity patterns underlying movements paced according to an internal temporal representation depend on how that representation is acquired during a previous pacing phase. We further investigate the degree to which context dependence is modulated by different time delays between pacing and continuation. BOLD activity was recorded while subjects moved at a rate established during a pacing interval involving either synchronized or syncopated coordination. Either no-delay or a 3, 6 or 9s delay was introduced prior to continuation. Context-dependent regions were identified when differences in neural activity generated during pacing continued to be observed during continuation despite the intervening delay. This pattern was observed in pre-SMA, bilateral lateral premotor cortex, bilateral declive and left inferior semi lunar lobule. These regions were more active when continuation followed from syncopation than from synchronization regardless of the delay length putatively revealing a context-dependent neural representation of the temporal interval. Alternatively, task related regions in which coordination-dependent differences did not persist following the delay, included bilateral putamen and supplementary-motor-area. This network may support the differential timing demands of coordination. A classic prefrontal-parietal-temporal working memory network was active only during continuation possibly providing mnemonic support for actively maintaining temporal information during the variable delay. This work provides support for the hypothesis that some timing information is represented in a task-dependent manner across broad cortical and subcortical networks.

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Much debate in the behavioral literature focuses on the relative contribution of motor and perceptual processes in mediating coordinative stability. To a large degree, such debate has proceeded independently of what is going on in the brain. Here, using blood oxygen level-dependent measures of neural activation, we compare physically executed and imagined rhythmic coordination in order to better assess the relative contribution of hypothesized neuromusculoskeletal mechanisms in modulating behavioral stability. The executed tasks were to coordinate index finger to thumb opposition movements of the right hand with an auditory metronome in either a synchronized (on the beat) or syncopated (off the beat) pattern. Imagination involved the same tasks, except without physical movement. Thus, the sensory stimulus and coordination constraints were the same in both physical and imagination tasks, but the motoric requirements were not. Results showed that neural differences between executed synchronization and syncopation found in premotor cortex, supplementary motor area, basal ganglia and lateral cerebellum persist even when the coordinative patterns were only imagined. Neural indices reflecting behavioral stability were not abolished by the absence of overt movement suggesting that coordination phenomena are not exclusively rooted in purely motoric constraints. On the other hand, activity in the superior temporal gyrus was modulated by both the presence of movement and the nature of the coordination, attesting to the intimacy between perceptual and motoric processes in coordination dynamics.

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