Biology subjects

Schwimmbeck, F.

Publications and source records attributed to Schwimmbeck, F..

4 recordsLinked to original sources

bioRxiv2026

Non-invasive tracking of ripple-like activity during human sleep using MEG

Hippocampal ripples are considered a key mechanism of sleep-dependent memory consolidation. In humans, however, their direct investigation has relied on invasive recordings from patients with epilepsy, because EEG provides limited access to fast activity from deep medial temporal structures. Here, we tested whether source-resolved magnetoencephalography can reveal physiologically meaningful ripple-like activity during NREM sleep in healthy humans. These events showed hallmarks expected of sleep ripples: they were most prominent in medial temporal regions and embedded within slow oscillation (SO)-spindle dynamics, occurring preferentially during SO up-states and spindle centers. To test mnemonic relevance, we combined sleep MEG with targeted memory reactivation, in which learning cues were replayed during sleep. TMR improved memory performance, and later remembered cues preferentially recruited medial temporal ripple-like events alongside cortical spindles. Ripple-like events also coincided with enhanced item-specific reactivation during successful TMR. Together, these findings establish MEG as a non-invasive window onto hippocampo-cortical memory dynamics during sleep.

neuroscience↗

bioRxiv2026

Sequential coupling of sleep oscillations enables concept-neuron reactivation and supports information flow across the human hippocampal-cortical circuit

Effective memory consolidation during sleep is thought to rely on the transfer of reactivated memory traces from the hippocampus to the cortex. However, the mechanisms supporting this essential dialogue across brain areas remain poorly understood. Here, we recorded single-neuron activity (n = 1097) in the medial temporal lobe (MTL) of 10 epilepsy patients across 21 nights of sleep. Before sleep, patients engaged in a memory task with stimuli eliciting concept-neuron responses. During non-rapid eye movement (NREM) sleep, neuronal firing locked to sharp wave-ripples (SWR) revealed a directed flow of information from the hippocampus to cortical targets. Notably, within SWR-driven activity, experience-dependent concept neurons exhibited elevated co-activation both within and across MTL regions, indicating selective reactivation of behaviorally relevant information. Cross-regional co-activation of concept cells was markedly enhanced when hippocampal SWRs coincided with cortical slow oscillation-spindle complexes, suggesting an active role of the cortex in shaping interregional communication. These findings provide evidence that SWRs in humans selectively reactivate experience-related neural ensembles across the hippocampal-cortical network, while synergistic interactions with cortical slow oscillation-spindle events might facilitate effective memory consolidation.

neuroscience↗

bioRxiv2026

Episodic memory consolidation by reactivation of human concept neurons during sleep reflects contents, not sequence of events

How do our brains manage to store our everyday experiences into memory? Neurons in the human temporal lobe that respond to the concept of an individual person or object have been shown to provide the semantic building blocks for episodic memory. Recording from 1433 neurons in neurosurgical patients who learned a story involving specific concepts, we found reactivation of neurons representing these concepts during slow-wave sleep after learning. Concept neurons were conjointly reactivated, particularly during sharp-wave ripples, with time lags suitable for synaptic modification. However, the temporal sequence of reactivation did not reflect the sequence of concepts in the learned story. Unlike rodent place cells, which can acquire preferred firing locations during exploration of new environments according to their pre-existing preferred sequence of activation, human concept neurons are tuned to specific semantic contents before learning starts. Consequently, pre-existing firing sequences correlate with consecutive place fields in rodents, but not with sequences of events in human experience. Thus, in contrast to reactivation of rodent place cells, reactivation of human concept cells does not reflect sequences of events in human experience.

neuroscience↗

bioRxiv2025

Respiration shapes the neural dynamics of successful remembering in humans.

Respiration has been shown to impact memory retrieval, yet the neural dynamics underlying this effect remain unclear. Here, we investigated how respiration shapes both behavioral and neural expressions of memory retrieval by re-analyzing an existing dataset where scalp electroencephalography and respiration recordings were acquired while participants (N = 18) performed an episodic memory task. Our results unveil that respiration influences retrieval-related power fluctuations in the /{beta} band and concomitant memory reactivation. Specifically, we found that both key neural signatures of successful remembering were co-modulated during exhalation, with the strength of the interaction between respiration and reactivation processes being associated with memory performance. Together, these findings suggest that respiration may act as a scaffold for episodic memory retrieval in humans by coordinating the neural conditions that support effective remembering. Significance statementRecent evidence suggests that respiration may shape neural dynamics underlying various cognitive processes. In this study, we identify respiration as a potential pacemaker for memory retrieval by showing that key neural signatures of effective remembering--namely, decreases in /{beta} power and the reactivation of previously encoded neural representations--are tightly synchronized with the respiratory cycle. Notably, the strength of this respiration-brain coupling is associated with individual memory performance, underscoring the critical role and functional significance of brain-body interactions in supporting cognitive functions.

neuroscience↗