Background: Neuronal plasticity is the brain's ability to continuously adapt to experiences and learning of new skills. Although this affects multiple characteristics of the brain such as structure, function and metabolism, direct interactions between these aspects are largely missing.

Aim: Using recent advancements in neuroimaging we aim to identify novel relationships how neuronal plasticity is related across these characteristics.

Design: 40 healthy subjects will undergo two simultaneous PET/MR measurements at baseline and after 4 weeks. During the measurements a cognitively challenging task will be performed and the training group (20 subjects) will practice during the 4-week period.

Implications: We combine simultaneous PET/MR and novel task-specific PET imaging to study brain metabolism, structure and function in a single measurement session. This provides optimal sensitivity for assessment of multimodal neuroplasticity associations. Knowledge how cognitive training affects multiple characteristics of the brain will also increase our understanding of disorders like depression, dementia and brain injuries, since these are diagnosed with cognitive evaluations. Considering the vast usage of the applied imaging procedures in diagnosis and therapy monitoring, the thorough investigation of multimodal associations offers benefit for the interpretability of neuroimaging in clinical routine.

Methodological details: Each subject will undergo two PET/MR examinations. Imaging will include PET as well as acquisition of structural and functional MRI. Task-specific glucose metabolism will be quantified with the radioligand [18F]FDG. Gray matter volume and white matter microstructure will be assessed with T1-weighted and diffusion weighted MRI, respectively. Functional imaging will focus on functional connectivity during rest and task as well as cerebral blood flow as acquired with ASL.

Inclusion Criteria:

• Age range 21-30 years
• Right-handedness
• Willingness and competence to sign the informed consent form

Exclusion Criteria:

• History of or current physical, neurological or psychiatric disorder
• History of or current substance abuse or medication including antipsychotic, antidepressant and antianxiety agents
• Pregnancy or current breastfeeding
• Contraindications for MRI-scanning (e.g., metal implants, steel grafts, etc), including dental implants causing signal artifacts
• For subjects participating in earlier studies using ionizing radiation, the total radiation exposure of 30mSv over the last 10 years must not be exceeded, as specified in the Austrian legislation on radiation protection
• Regular players of the video game Tetris (3 years before scanning).
• Failure to comply with the study protocol or to follow the instructions of the investigating team