Sensorimotor Skills
The skills studied in the sensorimotor domain vary widely in complexity. To probe the EESR theory as directly as possible, we have developed a grasping paradigm in humans that is meant to closely correspond to single-paw grasping behavior in rodents (Hille et al., 2024). To study plastic changes in more complex contexts, we have selected two sports, combat sports and mogul downhill skiing.
Plasticity of grasping behavior in humans and rodents
This line of research directly addresses the EESR theory. Hence, its main goal is to enhance the interpretability of macroscopic methods used in human research by complementing molecular and fine-structural measures used in animals with such macroscopic methods, and to create macroscopic metrics common to both examined species (see Figure 1).This requires an explicit effort to develop analogous experimental paradigms and comparable behavioral tasks that can be used to elicit structural brain plasticity on either side (Hille et al., 2024). To this end, we need to devise human analogues of well-researched animal models. Arguably, this strategy works best when studying the experience-dependent acquisition of specific skills that are relatively similar and meaningful in both examined species. Examples are grasping food items, encoding episodic memories, navigating new spaces, and various forms of perceptual learning. With these considerations in mind, we are currently conducting a series of collaborative studies in which both mice and humans learn a fine motor skill (Dissertation Maike Hille).
Over several days mice are trained in the single-pellet reaching task, in which they learn to grasp a small food item through a narrow slit in an acrylic glass wall, using their preferred paw. In the corresponding human task, the participants undergo a daily training regime with an adapted reaching task using chopsticks (see Figure 2). Thus, both mice and humans learn to reach for and grasp a little food object that is then transported over a short distance. Our expectation is that the use of such corresponding motor tasks will result in analogous learning curves and will induce similar mechanisms promoting plasticity in the motor cortices of either species. Both humans and mice undergo multiple structural magnetic resonance imaging (sMRI) measurements to acquire macroscopic anatomical measures (e.g., gray-matter volume estimates) at different timepoints during the time course of training. In mice, different cellular measures such as the number and morphology of dendritic spines, number and morphology of astrocytes, length of myelin sheaths, and diameter and density of blood vessels are additionally recorded and quantified. In addition, the motor cortices of the mice are examined histologically post mortem. Assessing plasticity-related changes at macroscopic and microscopic levels in the same animals will allow us to directly relate these measures and their variation over time to each other.
This line of research is carried out in close collaboration with the MPI for Biological Intelligence in Martinsried (Tobias Bonhoeffer), the University of Gothenburg (Martin Lövdén), and the Technical University of Munich (Franz Schilling). The work with rodents is carried out in Martinsried and Munich, whereas the work with human participants is carried out in Berlin and Gothenburg. In Gothenburg, PET imaging is used to examine whether synaptic density in skill-relevant brain areas is increasing during early phases of skill acquisition.
Complex motor skill acquisition and execution: Combat sports
Combat sports offer a rich context for studying plasticity in the context of acquiring a complex sensorimotor skill. Across disciplines such as Judo and wrestling, expert athletes seem to develop individualized and consistent patterns of technical-tactical actions, or fighting styles, that reflect adaptations to idiosyncratic biomechanical constraints and expertise in goal-directed behavior. Affordance theory further frames combat behavior as a perception-action loop, where athletes must detect and exploit fleeting opportunities for action based on their own and their opponent’s physical characteristics. Our goal in the line of work is to study adaptive actions as behavioral markers of enhanced perceptual-cognitive functions such as body representation, decision making, and action planning (Dissertation Phuc Thu Uyen Nguyen). Drawing on models of motor skill acquisition and EESR theory, we are investigating how cognitive and behavioral adaptations evolve across learning stages, and how these changes are supported by neural plasticity. This work is being carried out in collaboration with Klaus Gramann (Technical University of Berlin) and Patrick Haggard (University College London).
Complex motor skill acquisition and execution: Downhill skiing
When downhill skiers find themselves in difficult terrain, such as moguls, they need to constantly coordinate the planning and execution of behavior. Attention to planning is needed to decide on the skiing line and prepare the next turns; attention to execution is needed for keeping balance in the presence of environmental uncertainties. Hence, mogul skiing captures essential aspects of goal-oriented behavior in a manner that is accessible to observation. We assume that eye movements offer privileged access to the relative allocation and coordination of attentional resources. At the same time, we also aim at assessing body posture and force dynamics as well as detailed aspects of the terrain itself. We are currently piloting our equipment, which may inform related attempts at observing complex behaviors in real-life settings. This work is being carried out in close collaboration with Petr Janata (University of California at Davis) and Motion Metrics Limited.