Brain States for Plasticity
The Brain States for Plasticity Group aims to understand how information is encoded and stored in the human brain and how different brain states shape this process.
Rapid Neocortical Memory Formation
Traditionally, it has been assumed that our memory for facts and events is supported by two dedicated memory systems, with distinct, complementary functions: The hippocampus, which rapidly encodes and temporarily stores large amounts of detailed information and the slow-learning neocortex, which requires frequent hippocampus-driven reactivation of the encoded information to store long-lasting generalized memories. Challenging these theories, we could show that reactivation in the form of repeated rehearsal can rapidly engender an independent, neocortically stored engram within hours after learning. Our lab aims to understand the conditions for rapid neocortical memory formation and its behavioral and neural implications. In addition to identifying the key cognitive and physiological factors that specifically benefit neocortical memory formation, we are interested in the quality of rapid neocortical memory representations in terms of their precision, longevity and semantic integration. On the neural level, we study the interaction between the neocortical and hippocampal memory systems as well as the distribution of information within the neocortical network. Here, we are especially interested in the relation between multi-modal association cortices such as the medial posterior parietal and medial prefrontal cortex and more upstream sensory areas, for which a genuine mnemonic function is still under debate. To answer these research questions, we combine novel behavioral paradigms with multivariate analysis of functional brain activity and microstructural tissue properties to assess online and offline memory representations, respectively.
Brain State Dependent Memory Formation and Consolidation
The beneficial effect of sleep for memory consolidation, and specifically neocortical memory consolidation, is assumed to be conveyed by two complementary processes: A global homeostatic process of synaptic downscaling and an active process of reactivation, which selectively strengthens the neural connections that code previously encountered information. Having shown that reactivation through repeated rehearsal likewise benefits neocortical memory consolidation, we investigate how memories that are reactivated in different brain states differ in quality and contributing brain networks and which neurobiological mechanisms convey these differences. In addition to the substates of sleep, also the transitional phases between wakefulness and sleep offer unique windows into the interplay between memory and other information processing components such as perception and behavioral responsiveness, as they can become uncoupled during these phases. Using this approach, we can elucidate the specific brain mechanisms that are responsible for successful memory encoding. For this line of research, we utilize mobile EEG technology to allow for natural sleeping conditions at home as well as combined EEG-fMRI during different brain states to infer regional brain activation.
Imaging Human Neuroplasticity
Functional MRI is a useful technique to image internal representations in the brain while they are activated. However, to infer the location in which mnemonic content is stored during offline phases, optimally we would like to assess learning-induced structural changes that indicate the generation or reorganization of neuronal connections. Our lab is exploring possibilities to image human neuroplasticity noninvasively and in vivo with the help of MR-based biomarkers. In a first step, we could already show that the combination of functional and diffusion MRI can detect learning-induced microstructural plasticity rapidly after learning in task-relevant brain regions, which correlates with subsequent memory performance. To gain insight into the neurobiological processes underlying these observed microstructural changes, we are elucidating their exact time course as well as their relation to functional activation and other structural MRI indices.