Human goal-directed behavior results from the coordinated activity of widely distributed brain regions. Our central question is how neural circuits efficiently implement stable and consistent behaviors, but remain malleable to support cognitive flexibility. The overall goal is to understand how ever-changing brain activity supports cognitive processing.
To determine the importance of the temporal structure of large-scale brain activity, our lab explores how the human brain implements attention- and memory-guided actions, context-dependent decisions, and our ability to abstract and generalize rules. We further investigate sleep as a window to understand spontaneous neural activity in the absence of sensory input or immediate behavioral demands. The key aim is to bridge the gap between macroscale neural correlates of behavior and microscale circuit properties, ultimately uncovering the neural mechanisms that make us distinctly human.
Our approach combines detailed behavioral testing with intracranial and non-invasive neurophysiological recordings to study human cognition with high spatiotemporal resolution. This work includes an integrative approach that fosters cross-disciplinary collaboration to merge human, clinical and animal studies.
The functional architecture of human brain activity is inherently rhythmic, but we perceive the world as continuous and seamlessly connected and not in discrete snapshots. In our work, we explore how ever-changing supports continuous perception, action and goal-directed behavior. In our work, we probed covert attention on a fine-grained temporal scale, which unveiled that attention samples the environment rhythmically (Helfrich et al., 2018, Raposo et al., 2023). Building on this line of inquiry, we now explore the role of multiple temporal regularities (Raposo et al., 2025). A key focus is to determine how neural dynamics sample the environment across time and space, which might rely on the same temporal and spatial principles as overt exploration (Kienitz et al., 2024).
Key publications: Helfrich et al., (2018) Neuron; Raposo et al. (2023) Current Biology, Raposo et al. (2025) PLoS Biology; Kienitz et al. (2024) bioRxiv
We recently uncovered the relationship between oscillatory synchrony and low-dimensional population coding: Cognitive variables are reflected in low-dimensional population codes (Weber et al., 2023) where information transfer of ensuing action plans relies on communication subspaces and theta synchrony from prefrontal to motor cortex (Weber et al., 2024). We now address the mechanisms that define our mental space. What is the neural activity space that defines our mental experiences and how does brain activity shape and constrain our subjective perception of the world? We investigate how geometric representations enable cognitive abstraction. A central objective is to understand how latent cognitive variables as e.g., beliefs, are represented through modeling paired with neurophysiology (Iwama & Helfrich, 2024).
Key publications: Weber et al. (2023) PNAS; Weber et al. (2024) Nature Communications; Iwama & Helfrich (2024) bioRxiv
To understand the self-organization of large-scale circuits, we study the network mechanisms during sleep to understand how the human brain restores an optimal neural milieu for efficient and flexible next-day cognitive functioning. We demonstrated that the precise coupling of sleep oscillations indexes the integrity of memory pathways and predicts memory formation across the lifespan, which led to a novel framework on how sleep oscillations, in concert with desynchronized brain states, structure memory formation. In direct support, we demonstrated that desynchronized activity tracks neural excitability, which now enables studying neural plasticity and information processing at the whole-brain level.
Key publications: Helfrich et al. (2021) Trends in Cognitive Sciences; Lendner et al. (2023) Science Advances; van Schalkwijk et al. (2023) Progress in Neurobiology; Hahn et al. (2024) Progress in Neurobiology
In addition to the rhythmic structure of cognition, we explore arrhythmic temporal regularities, which dominate electrophysiological recordings. Critically, aperiodic temporal structure closely tracks the brain state during sleep (Lendner et al., 2020). We previously demonstrated that aperiodic activity provides new insights into REM sleep (Lendner et al., 2023) that goes beyond oscillation-centric models (Helfrich et al., 2021). We explore the temporal structure underlying cognition from multiple angles and employ multiple (causal) interventions to better understand how the brain integrates distinct snapshots into coherent concepts to guide goal-directed actions.
Key publications: Lendner et al. (2020) eLife; Lendner et al. (2023) Science Advances; Lendner et al. (2024) Journal of Neuroscience
Many tools we use in cognitive neuroscience are not routinely employed in the clinical world. We study different patient populations in many of our studies to better understand the underlying physiology. In addition, we have recently begun to also explore how our neuroscientific approaches can provide more detailed insights into the pathophysiology of various disorders, including epilepsy, post-stroke functional reorganization, emergence from coma and mechanisms of general anesthesia.
Key publications: Helfrich et al. (2019) Nature Communications; Lendner et al. (2020) eLife; Kopf et al. (2024) eNeuro