Bettina Bläsing

Mechanisms of stick insect locomotion in a gap-crossing paradigm.

Locomotion of stick insects climbing over gaps of more than twice their step length has proved to be a useful paradigm to investigate how locomotor behaviour is adapted to external conditions. In this study, swing amplitudes and extreme positions of single steps from gap-crossing sequences have been analysed and compared to corresponding parameters of undisturbed walking. We show that adaptations of the basic mechanisms concern movements of single legs as well as the coordination between the legs. Slowing down of stance velocity, searching movements of legs in protraction and the generation of short steps are crucial prerequisites in the gap-crossing task. The rules of leg coordination described for stick insect walking seem to be modified, and load on the supporting legs is assumed to have a major effect on coordination especially in slow walking. Stepping into the gap with a front leg and antennal contact with the far edge of the gap provide information, as both events influence the following leg movements, whereas antennal “non-contact” seems not to contain information. Integration of these results into the model of the walking controller can improve our understanding of insect locomotion in highly irregular environments.

From action representation to action execution: exploring the links between cognitive and biomechanical levels of motor control

Along with superior performance, research indicates that expertise is associated with a number of mediating cognitive adaptations. To this extent, extensive practice is associated with the development of general and task-specific mental representations, which play an important role in the organization and control of action. Recently, new experimental methods have been developed, which allow for investigating the organization and structure of these representations, along with the functional structure of the movement kinematics. In the current article, we present a new approach for examining the overlap between skill representations and motor output. In doing so, we first present an architecture model, which addresses links between biomechanical and cognitive levels of motor control. Next, we review the state of the art in assessing memory structures underlying complex action. Following we present a new spatio-temporal decomposition method for illuminating the functional structure of movement kinematics, and finally, we apply these methods to investigate the overlap between the structure of motor representations in memory and their corresponding kinematic structures. Our aim is to understand the extent to which the output at a kinematic level is governed by representations at a cognitive level of motor control.

The functional architecture of the human body: assessing body representation by sorting body parts and activities

We investigated mental representations of body parts and body-related activities in two subjects with congenitally absent limbs (one with, the other without phantom sensations), a wheelchair sports group of paraplegic participants, and two groups of participants with intact limbs. To analyse mental representation structures, we applied Structure Dimensional Analysis. Verbal labels indicating body parts and related activities were presented in randomized lists that had to be sorted according to a hierarchical splitting paradigm. Participants were required to group the items according to whether or not they were considered related, based on their own body perception. Results of the groups of physically intact and paraplegic participants revealed separate clusters for the lower body, upper body, fingers and head. The participant with congenital phantom limbs also showed a clear separation between upper and lower body (but not between fingers and hands). In the participant without phantom sensations of the absent arms, no such modularity emerged, but the specific practice of his right foot in communication and daily routines was reflected. Sorting verbal labels of body parts and activities appears a useful method to assess body representation in individuals with special body anatomy or function and leads to conclusions largely compatible with other assessment procedures.

Direct Control of an Active Tactile Sensor Using Echo State Networks

Tactile sensors (antennae) play an important role in the animal kingdom. They are also very useful as sensors in robotic scenarios, where vision systems may fail. Active tactile movements increase the sampling performance. Here we directly control movements of the antenna of a simulated hexapod using an echo state network (ESN). ESNs can store multiple motor patterns as attractors in a single network and generate novel patterns by combining and blending already learned patterns using bifurcation inputs.

WalkNet — a Decentralized Architecture for the Control of Walking Behaviour Based on Insect Studies

A network model for controlling a six-legged, insect-like walking system is described, which is based as far as possible on data obtained from biological experiments. The network contains internal recurrent connections, but important recurrent connections utilize the loop through the environment. This approach leads to a modular structure, WalkNet, consisting of several subnets. One subnet controls the three joints of a leg during its swing which is arguably the simplest possible solution. The task for the stance subnet appears more difficult because the movements of a larger and varying number of joints have to be controlled such that each leg contributes efficiently to support and propulsion and legs do not work at cross purposes, i.e. do not produce interaction forces. This task appears to require some kind of “motor intelligence”. We show that an extremely decentralized, simple controller, based on a combination of negative and positive feedback at the joint level, copes with all these problems by exploiting the physical properties of the system.

Segmentation of dance movement: effects of expertise, visual familiarity, motor experience and music.

According to event segmentation theory, action perception depends on sensory cues and prior knowledge, and the segmentation of observed actions is crucial for understanding and memorizing these actions. While most activities in everyday life are characterized by external goals and interaction with objects or persons, this does not necessarily apply to dance-like actions. We investigated to what extent visual familiarity of the observed movement and accompanying music influence the segmentation of a dance phrase in dancers of different skill level and non-dancers. In Experiment 1, dancers and non-dancers repeatedly watched a video clip showing a dancer performing a choreographed dance phrase and indicated segment boundaries by key press. Dancers generally defined less segment boundaries than non-dancers, specifically in the first trials in which visual familiarity with the phrase was low. Music increased the number of segment boundaries in the non-dancers and decreased it in the dancers. The results suggest that dance expertise reduces the number of perceived segment boundaries in an observed dance phrase, and that the ways visual familiarity and music affect movement segmentation are modulated by dance expertise. In a second experiment, motor experience was added as factor, based on empirical evidence suggesting that action perception is modified by visual and motor expertise in different ways. In Experiment 2, the same task as in Experiment 1 was performed by dance amateurs, and was repeated by the same participants after they had learned to dance the presented dance phrase. Less segment boundaries were defined in the middle trials after participants had learned to dance the phrase, and music reduced the number of segment boundaries before learning. The results suggest that specific motor experience of the observed movement influences its perception and anticipation and makes segmentation broader, but not to the same degree as dance expertise on a professional level.

Doing Duo - a case study of entrainment in William Forsythe's choreography "Duo".

Entrainment theory focuses on processes in which interacting (i.e., coupled) rhythmic systems stabilize, producing synchronization in the ideal sense, and forms of phase related rhythmic coordination in complex cases. In human action, entrainment involves spatiotemporal and social aspects, characterizing the meaningful activities of music, dance, and communication. How can the phenomenon of human entrainment be meaningfully studied in complex situations such as dance? We present an in-progress case study of entrainment in William Forsythe’s choreography Duo, a duet in which coordinated rhythmic activity is achieved without an external musical beat and without touch-based interaction. Using concepts of entrainment from different disciplines as well as insight from Duo performer Riley Watts, we question definitions of entrainment in the context of dance. The functions of chorusing, turn-taking, complementary action, cues, and alignments are discussed and linked to supporting annotated video material. While Duo challenges the definition of entrainment in dance as coordinated response to an external musical or rhythmic signal, it supports the definition of entrainment as coordinated interplay of motion and sound production by active agents (i.e., dancers) in the field. Agreeing that human entrainment should be studied on multiple levels, we suggest that entrainment between the dancers in Duo is elastic in time and propose how to test this hypothesis empirically. We do not claim that our proposed model of elasticity is applicable to all forms of human entrainment nor to all examples of entrainment in dance. Rather, we suggest studying higher order phase correction (the stabilizing tendency of entrainment) as a potential aspect to be incorporated into other models.

Recognizing fencing attacks from auditory and visual information: A comparison between expert fencers and novices

Objective The present study investigated the impact of audible and visual information for the prediction of attack movements in fencing, the raddoppio and the fleche. Method A temporal occlusion paradigm with visually (i.e. soundless videos), auditory (i.e. the audio track of the videos), and audio‐visually (i.e. video with audio track) presented attack movements was used to investigate 15 experts’ (5 women; M age = 17.2 years, age range = 15–21) and 17 novices’ (15 women; M age = 23.4 years, age range = 19–30) performance in predicting fencing attacks. Results Results showed that the number of correct answers for all stimulus conditions increased for both groups the later a video was occluded. Moreover, experts outperformed novices in all stimulus conditions. Regarding auditory information, results indicated that neither group efficiently integrated the sounds of fencing steps with the visually provided information, however, experts were better able than novices to make use of auditory information if no visual information was provided and to filter out auditory information otherwise. Conclusion Future research might address the issue to what extent athletes might benefit from training interventions focusing on the use of auditory information. HighlightsTemporal occlusion with visual, acoustic and audiovisual stimuli is applied.Fencers and non‐fencers recognize fencing attacks from acoustic information.Fencers outperform non‐fencers in all three stimulus conditions.All participants recognize attacks better from visual than acoustic information.Non‐fencers perform better with visual than audiovisual information.

Spatio-temporal analysis of kinematic signals in classical ballet

Abstract Motions of markers arranged on a dancers body can be approximated by the sum of a minimal set of linear trajectories with given accuracy. The composition of approximating linear trajectories features the movement traits and discloses the level of movement expertise in the dancers. We suggest the computationally simple methods for the analysis of trajectories and body shape changes attested directly from the motion capture data. We have tested our approach for 6 figures from the classical ballet repertoire performed by 24 dancers varying in expertise. The methods allow to estimate the level of movement expertise, to draw the detailed structure of movements, and to classify movements into a given repertoire automatically.

Mental rotation of primate hands: human-likeness and thumb saliency

Mental rotation of human hands has been found to differ essentially from mental rotation of objects in such a way that reaction times and error rates of handedness judgements are influenced by the comfort and familiarity of the presented hand postures. To investigate the role of the similarity of the presented hands to the participant’s own hand, we used different primates’ hands as stimuli in a mental rotation task. Five out of 24 primate hands were chosen for their ratings in human-likeness and saliency of the thumb according to a questionnaire study and presented in two mental rotation experiments; in the second experiment, they were modified in such a way that all hands appeared thumbless. Results of both experiments revealed effects of species and orientation on reaction times, and an interaction between species and hand side occurred in the second experiment. In the first experiment, the thumbless Colobus hand differed from all other hands, showing the highest reaction times and error rates and failing to show the expected medial-over-lateral advantage. In the second experiment, the eccentricity of the Colobus hand was decreased and the facilitating effect of human-likeness was slightly increased. We conclude that motor strategies were applied that relied less on the asymmetry of the stimuli but rather on their similarity to the human hand. We argue that motor simulation might facilitate the processing of incomplete stimuli by mentally completing them, especially if all stimuli can be processed in a consistent manner.