Mechanisms and Sequential Progression of Plasticity
We define plasticity as the capacity of organisms to form lasting but reversible structural and related functional changes of neural connections in response to interactions with the environment. We seek to test a theory of structural brain plasticity across skill domains, developmental stages, and species.
According to an influential distinction introduced by Greenough and colleagues, plasticity comes in two ontogenetically distinct forms. One is experience-expectant, and enables organisms to meet affordances that allow for species-typical behavior, such as visual perception. The close link between maturation and plasticity is evident in this form of plasticity. The other form is experience-dependent, and enables individuals to respond and adapt to individualized challenges throughout ontogeny, such as the acquisition of a specialized skill. The latter form of plasticity acts as a source and promoter of individuality (Freund et al., 2013).
In our view, the distinction between experience expectancy and experience dependency is likely to reflect gradual differences in the scope and developmental timing of plastic episodes, rather than a fundamental contraposition. The experience-dependent ability to acquire skills that are idiosyncratic to the environmental niche of a given individual is itself an adaptation that has resulted from natural selection, and hence can be considered as a broader form of experience expectancy: Evolution “expects” (i.e. allows) individuals to develop in idiosyncratic ways. Hence, the mechanisms implementing either form of plasticity might be similar, with reinforcement learning likely to play a critical role in both.
Based on these general considerations, this project has three major goals. First, our work is informed by a theoretical model of experience-dependent plasticity, and we seek to test this model whenever the data allow us. Second, we probe plasticity across a range of age groups and a wide array of skill types to explore both general and domain-specific features of plastic change across the lifespan. Third, in order to arrive at a mechanistic account of plasticity, we seek to bridge the long-standing gap between animal models and research on human plasticity (Hille et al., 2024). A fourth line of research, which investigates plasticity as a source of individuality, is being pursued in the ATLAS project (PI: Sarah Power).
In the following, we present our theoretical model and report on our empirical work in three different skill domains.
The expansion, exploration, selection, and refinement (EESR) theory of plastic change
In 2020, Lövdén et al. proposed the expansion, exploration, selection, and refinement (EESR) theory of plastic change during skill acquisition (Lövdén et al., 2020; for an update, see Hille et al., 2024; for an extended discussion of related work, see Lindenberger & Lövdén, 2019). The point of departure is a situation in which the available neural resources are insufficient to meet the demands of the to-be-learned task (Lövdén et al., 2010). Driven by this mismatch, new synapses are formed in task-relevant cortical areas, and the resulting greater connectivity space is subsequently explored for neural circuits that can approximate the execution of the goal-relevant behavior. Eventually, the best-performing microcircuit is selected through a process of reinforcement learning that is partly mediated by the neurotransmitter dopamine, and neural and behavioral variability starts to decrease (read more).
Cognitive Skills
Research in this domain follows three strands. First, we have been analyzing data from the FLEX study, a large training study on task-set switching in childhood planned and conducted in collaboration with Silvia Bunge and Yana Fandakova. Second, following up on the results of the FLEX study, we are currently investigating the ontogeny of hierarchical control in childhood. Third, we investigated how brain maturation shapes learning in the context of sequence learning (read more).
Musical Skills
This branch of the project investigates plastic changes in brain structure and associated functions that accompany the acquisition and mastery of musical skills. Numerous findings from studies of trained musicians and musical training interventions demonstrate that musical practice across skill levels induces changes in both gray and white matter, along with alterations in functional activation and connectivity patterns. While some changes map onto well-defined neural substrates like the auditory and motor cortices, others tend to be more distributed across brain networks. Research in this domain has three foci. First, we have examined plasticity in prospective professional musicians. Second, our current emphasis is on assessing singing-induced plasticity in childhood. Third, in collaboration with colleagues from the MPI for Empirical Aesthetics, we are planning to delineate the neural representation of pitch and timbre in expert musicians (read more).
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, downhill mogul skiing and combat sports (read more).