Franz Mechsner

Representation of motor skills in human long-term memory

This study uses the example of the tennis serve to investigate the nature and role of long-term memory in skilled athletic performance. Information processing linked with complex movements has always been notoriously difficult to investigate. However, a new experimental method revealed that athletic expertise was characterized by well-integrated networks of so-called basic action concepts (BACs) that each corresponded to functionally meaningful submovements. In high-level experts, these representational frameworks were organized in a distinctive hierarchical tree-like structure, were remarkably similar between individuals and were well matched with the functional and biomechanical demands of the task. In comparison, action representations in low-level players and nonplayers were organized less hierarchically, were more variable between persons and were less well matched with functional and biomechanical demands. It is concluded that, in concert with situational goals and constraints, movement representations of this kind in long-term memory might provide the basis for action control in skilled voluntary movements in the form of suitably organized perceptual-cognitive reference structures.

Do muscles matter for coordinated action

This article investigates coordination stability when 2 fingers of each hand periodically tap together. The main question concerns the functional origin of the symmetry tendency, which has widely been conceived as a bias toward coactivation of homologous fingers and homologous muscular portions. In Experiment 1, the symmetry tendency was independent of finger combination. In Experiment 2, virtually identical stability characteristics were revealed under full vision and no vision. In Experiment 3, symmetrical and parallel visual labels on the fingers neither stabilized nor destabilized symmetrical and parallel tapping patterns. In Experiment 4, in which the relative position of the hands was varied, it revealed that the observed stability characteristics are to be defined in a hand-centered reference frame. Because the symmetry tendency was always independent of finger combination, the authors suggest that it is not a bias toward coactivation of homologous muscle portions but instead originates on a more abstract, functional level.

A psychological approach to human voluntary movements

Abstract The author argues that movements are planned, executed, and stored in memory as perceptible events, without regard to efferent patterns. Spontaneous bimanual coordination phenomena are hypothesized to originate on a perceptual-cognitive level, with the muscles automatically tuned in service to preferred perceptible movement properties. The perceptual-cognitive system is hypothesized to control skilled complex movements as well. In perceptual-cognitive control, the full potential of the perceptual-cognitive system could be exploited. Thus, movements could be enormously flexible, with a strong potential for improvisation and creativity. An effective representation might be organized in a surprisingly sparse and economic way. In sum, the author argues that a psychological approach is most promising as a possible unifying perspective for understanding human voluntary movements.

Motor execution affects action prediction

Previous studies provided evidence of the claim that the prediction of occluded action involves real-time simulation. We report two experiments that aimed to study how real-time simulation is affected by simultaneous action execution under conditions of full, partial or no overlap between observed and executed actions. This overlap was analysed by comparing the body sides and the movement kinematics involved in the observed and the executed action. While performing actions, participants observed point-light (PL) actions that were interrupted by an occluder, followed by a test pose. The task was to judge whether the test pose depicted a continuation of the occluded action in the same depth angle. Using a paradigm proposed by Graf et al., we independently manipulated the duration of the occluder and the temporal advance of the test pose relative to occlusion onset (occluder time and pose time, respectively). This paradigm allows the assessment of real-time simulation, based on prediction performance across different occluder time/pose time combinations (i.e., improved task performance with decreasing time distance between occluder time and pose time is taken to reflect real-time simulation). The PL actor could be perceived as from the front or back, as indicated by task instructions. In Experiment 1 (front view instructions), evidence of action simulation was obtained for partial overlap (i.e., observed and performed action corresponded either in body side or movement kinematics), but not for full or no overlap conditions. The same pattern was obtained in Experiment 2 (back view instructions), ruling out a spatial compatibility explanation for the real-time pattern observed. Our results suggest that motor processes affect action prediction and real-time simulation. The strength of their impact varies as a function of the overlap between observed and executed actions.

Reply to commentaries: Actions as perceptual-conceptual gestalts

The author clarifies the objective and essence of the psychological, or perceptual-cognitive, approach to voluntary movement. According to that approach, voluntary movements are organized and performed as meaningful, perceptible events with bodily and environmental aspects. Body-oriented control is thus not neglected in the perceptual-cognitive approach but is actually an important issue. He further clarifies how material and psychological factors relate to each other in motor control and why they are not considered a coalition of constraints. The central importance of the sparse coding principle for the perceptual-cognitive approach is underlined. Finally, the author argues that the psychological information format is particularly suitable for motion control and stresses the power of the perceptual-cognitive approach to possibly provide a unifying framework for understanding human voluntary movements.

A perceptual-cognitive approach to bimanual coordination

It is a matter of much debate whether voluntary movement performance and learning takes place in a perceptual-cognitive medium only or relies on an additional level of coordinative processes in the motor system. Here, I will argue in favor of the “perception and cognition only” working hypothesis, which says that there is no level or stage in human motor control where coherent muscular activity patterns are organized as such. Instead I propose that human movements are planned, executed, and stored in memory by addressing their anticipated perceptual consequences. Many factors including physical, biomechanical and neuro-muscular ones influence these consequences. However, the criteria ruling the coordinative action are those of the perceptual-cognitive system, in the first place. I present some experiments on bimanual interference whose outcome suggest that these phenomena are perceptual-conceptual in nature.

Perceptual influence on bimanual coordination: an fMRI study

In bimanual coordination subjects typically show a spontaneous preference for movement symmetry. While there is experimental evidence for the principle of muscle homology, recent evidence suggested that bimanual coordination may be mediated as perceptual goals ( Mechsner et al., 2001 ). To explore this controversy we performed a fMRI study in 11 healthy, right‐handed subjects using bimanual index finger abductions and adductions in a congruous condition, i.e. both palms down, and incongruous conditions with either the left or right palm up. Our fMRI data showed a widespread bihemispheric network mediating proprioceptive coordination of the two hands with significant differences mainly for a perceptual dissociation: in the incongruous conditions with the one palm up there was a BOLD signal increase in a bilateral frontoparietal network involving the motor and premotor cortical areas, particularly in the right palm‐up condition. These results accord with the notion that perceptual cues play an important role in the control of bilateral hand movements.

Bimanual circling in deafferented patients: Evidence for a role of visual forward models

The present study investigated the role of ideation and visual feedback, and their interaction in movement control in the absence of somatosensory feedback, with the hypothesis that visual imagery and internal visual models may play a crucial role in performance even without feedback. Two chronically deafferented participants, GL and IW, circled bimanually two occluded cranks first without vision and then with hand-congruent and hand-incongruent visual feedback provided by visible flags. Without vision, GL was unable to circle the cranks. In contrast, IW performed spontaneously a symmetric pattern. Again without feedback, IW performed an instructed symmetric crank pattern well, but was unable to perform anti-phase cranking. With hand-congruent visual feedback, GL and IW were able to perform both symmetric and anti-phase movements, with symmetry being more accurate. Visual feedback during preceding trials made possible trials without visual feedback in GL and improved anti-phase trials in IW. Frequency-transformed incongruent visual feedback resulted in poor performance in part due to unsuitable hand-related strategies. However, IW improved in the latter task after detailed explanations of the condition. In conclusion, we suggest that both participants use visual imagery and visual forward models to control their hand movements. Visual updating of the forward model also improves performance with no vision. In addition, IW seemed to have been able to move from a focus on hand position to one on the transformed visual feedback to improve movement control in the incongruent feedback/movement condition.

Perceptual‐cognitive control of bimanual coordination

Abstract The author proposes and investigates the hypothesis that spontaneous bimanual coordination phenomena arise at a perceptual‐cognitive level, with the relevant muscles automatically, flexibly, and effortlessly tuned in service to perceptible movement properties. It has often been held that the powerful symmetry tendency in bimanual coordination originates at a motor command level. New evidence suggests that, at least in some paradigms, the symmetry tendency is actually a bias towards perceptible symmetry and seems thus directly and solely to be governed by a purely perceptual‐cognitive control principle. It is argued that this proposal extends to spontaneous bimanual coordination phenomena in general, whether that symmetry is the guiding principle, or whether a powerful role of perceptual and conceptual grouping principles other than symmetry are plausible. Neuronal wiring and biomechanical factors may influence the preferred coordination mode by way of their perceptible consequences. Interestingly, bodily bimanual interference can virtually vanish if the movement goal is suitably defined. In this case, interference is defined with regard to these movement targets or objects to‐be‐manipulated. The organizational costs of a given movement seem to be independent of the bodily action as such, but rather dependent on how the whole movement is strategically conceived and represented as a perceptible event in its environment. An effective representation can often be organized in a surprisingly sparse and economic way. In particular, a detailed and complete parameterization of the bodily movement is not necessary. Even bodily movements that are impossible to perform when instructed as such may be performed with ease if a simple perceptual cognitive reference structure for control can be conceived. In conclusion, I propose the hypothesis that simple bimanual coordination is entirely guided and controlled by the perceptual‐cognitive system. Moreover, a perceptual‐cognitive approach seems most promising as a unifying perspective for understanding voluntary movements of all kinds at all levels of organization.

A Test of Order-Constrained Hypotheses for Circular Data With Applications to Human Movement Science

ABSTRACT Researchers studying the movements of the human body often encounter data measured in angles (e.g., angular displacements of joints). The evaluation of these circular data requires special statistical methods. The authors introduce a new test for the analysis of order-constrained hypotheses for circular data. Through this test, researchers can evaluate their expectations regarding the outcome of an experiment directly by representing their ideas in the form of a hypothesis containing inequality constraints. The resulting data analysis is generally more powerful than one using standard null hypothesis testing. Two examples of circular data from human movement science are presented to illustrate the use of the test. Results from a simulation study show that the test performs well.