Amir Jahanian Najafabadi

• In our daily life, we are continuously required to learn new motor skills and adapt these skills to new situations, such as during tool-use. Tool-use as one of the hallmark skills in humans serves to functionally extend our body to overcome physical limitations to interact or manipulate other objects or organisms in an environment. In the present dissertation, I used behavioral and neural oscillation correlates of body schema plasticity during virtual tool-use in young and older adults to investigate the embodiment of virtual tools into the body schema, body image and the association between body ownership and agency as well as their mutual dependency on action-related sensory feedback. To do so, an arm-shaped virtual tool-use paradigm was employed in order to study forearm sensorimotor body schema, and its level of plasticity in young and older individuals during a sequential motor learning task. Overall, our findings suggest that virtual tools can be incorporated into the existing body schema of the forearm in younger adults but not in older adults, while showcasing how future work may further disambiguate the contributions of tactile and visual feedback. Additionally, resting-state beta power and task-related theta, alpha and beta power predicts stronger practice effect during virtual tool-use in younger adults compared to older adults. All together, I conclude that a sense of agency may strongly relate to improvement in tool-use in older adults dependent on practice effect but independent of alterations in the body schema, while ownership did not emerge due to a lack of body schema plasticity. Additionally, I concluded that the stronger practice effect during virtual tool-use training is positively related with resting-state relative beta power, higher task-related relative theta power and lower task-related alpha across frontal, parietal and occipital regions in younger adults but not in older adults.