Abstract
Human intracranial recordings offer cellular-resolution access to the human brain, connecting mechanistic insights from animal electrophysiology to the representations underlying human cognition. In this talk, I will present work using recordings from thousands of human neurons to trace a path from sensory encoding to semantic abstraction and memory.
I will begin with olfaction, showing how neurons across the human olfactory network encode odour identity and link these representations to behaviour, with amygdala neurons tracking valence and hippocampal activity predicting odour identification. To capture olfactory coding dynamics, I will introduce a respiration-locked odour-stimulation paradigm that resolves when olfactory representations emerge and how they persist after stimulation. Moving from sensory coding to semantics, I will show that olfactory responses can engage abstract object representations, raising a broader question: how is semantic information organised in the human medial temporal lobe? Using closed-loop sampling of semantic object space, we show that neurons exhibit semantic tuning curves, revealing a structured neural code for abstract meaning. I will then explore how these semantic neuronal representations support memory. We find that neurons selective for later remembered items are preferentially reactivated during sleep ripples, linking ripple-mediated reinstatement of item-tuned representations to successful memory consolidation. Conversely, disrupting item-specific responses at encoding with low-dose propofol reveals that the degree of attenuation predicts later forgetting. Together, these findings outline neuronal coding principles from perception to meaning to memory, and set the stage for studying how cellular-resolution recordings in humans and animal models can jointly reveal mechanisms of flexible, adaptive cognition.
Biography
Marcel Kehl has a multidisciplinary background spanning physics, medicine, and human systems neuroscience. He trained in physics at the University of Toronto and the University of Bonn, earning MSc degrees in Physics and Astrophysics, and contributed to the first detection of gravitational waves. In addition, he earned a medical degree from the University of Bonn, with a focus on neurology and epilepsy. For his PhD, Marcel joined the Mormann Lab in Bonn, where he used human intracranial recordings to study the neuronal mechanisms of olfaction, semantic coding, and memory. During this time, he performed the first human single-neuron recordings in olfaction, uncovering how odour identity, valence, and semantic information are encoded across the human olfactory network. In 2023, Marcel joined the Staresina Lab at the University of Oxford, where he studies sleep-dependent memory consolidation across scales, from human single-neuron recordings to high-density scalp EEG and MEG.
Across his work, Marcel has recorded intracranial activity from large patient cohorts across multiple centres in the UK and Germany, combining technical development and hospital-based setup with patient-facing cognitive paradigms and advanced single-neuron and population-level analyses. He has established a platform for precise chemosensory stimulation during intracranial recordings and leads the technical development of the sleep laboratory in Oxford. By linking human intracranial electrophysiology with mechanistic insights from animal models, his work aims to establish a cellular-level understanding of how the human brain transforms experience into meaning and memory.