Biology subjects

Brouwer, T.

Publications and source records attributed to Brouwer, T..

3 recordsLinked to original sources

bioRxiv2026

Theta phase-locked memory reactivation during REM sleep reduces memories emotional tone

REM sleep appears to be involved in emotional memory processing, yet the nature and neural underpinnings of this involvement remain largely unclear. Recent findings suggest REM-related theta activity may play a central role. To test this, we developed an automated protocol to target non-arousing acoustic memory cues to specific phases of REM sleep theta oscillations. During sleep, participants who had undergone a fear conditioning procedure combined with a memory recollection and emotional evaluation task, were re-exposed to conditioned stimuli, timed to either the upswing or downswing of theta waves. Both up- and down-targeted memory cues significantly enhanced the theta dynamic. Moreover, theta phase-locked memory reactivation significantly reduced the emotional tone of conditioned memories compared to sham reactivation (no acoustic memory cue), without affecting recognition performance or dream qualities. This constitutes the first evidence that REM sleep theta oscillations are causally involved in emotional memory processing, specifically in attenuating memories emotional charge. These findings have important implications for understanding emotional memory consolidation and may lead to therapeutic applications in disorders featuring maladaptive emotional memories.

neuroscience↗

bioRxiv2025

Highly Correlated Activity across Higher-Order Thalamic Nuclei in Awake and Anesthetized States

The thalamus is an egg-shaped structure deep inside the brain and is of central importance for our cognitive functions. The thalamus can be divided into first- and higher-order (HO) nuclei. Unlike first-order thalamic regions which are known to primarily relay sensory signals to the neocortex, the functions of HO thalamic nuclei remain far less clear. Although previous studies indicate HO thalamic nuclei influence cortical processing and consciousness, most studies examined single thalamic nuclei in isolation. To investigate the relation between distinct HO thalamic nuclei, we recorded local field potentials (LFP) and multi-unit activity (MUA) across multiple thalamic nuclei simultaneously in awake and anesthetized mice with sensory stimulation. The effect of voluntary locomotion was also studied in the awake state. Surprisingly, we found that both LFP and MUA were strongly correlated across HO nuclei in both states, which cannot be explained by volume conduction alone but suggests the existence of shared synaptic inputs. Furthermore, in the awake state locomotion and sensory stimuli activated many HO nuclei, including those that have not classically been regarded as sensory or motor. These findings challenge the classical view of the thalamus being the aggregate of isolated, independent nuclei and suggest that the thalamus serves as an ideal bottleneck whose coordination resulted in effective orchestration of the entire brain.

neuroscience↗

bioRxiv2019

Multiplexed Nanometric 3D Tracking of Microbeads using a FFT-Phasor Algorithm

Many single-molecule biophysical techniques rely on nanometric tracking of microbeads to obtain quantitative information about the mechanical properties of biomolecules such as chromatin fibers. Their three-dimensional position can be resolved by holographic analysis of the diffraction pattern in wide-field imaging. Fitting this diffraction pattern to Lorentz Mie scattering theory yields the bead position with nanometer accuracy in three dimensions but is computationally expensive. Real-time multiplexed bead tracking therefore requires a more efficient tracking method. Here, we introduce 3D phasor tracking, a fast and robust bead tracking algorithm with nanometric localization accuracy in a z-range of over 10 {micro}m. The algorithm is based on a 2D cross-correlation using Fast Fourier Transforms with computer-generated reference images, yielding a processing rate of up to 10.000 regions of interest per second. We implemented the technique in magnetic tweezers and tracked the 3D position of over 100 beads in real-time on a generic CPU. Its easy implementation, efficiency, and robustness can improve multiplexed biophysical bead tracking applications, especially where high throughput is required.\n\nSignificanceMicrobeads are often used in biophysical single-molecule manipulation experiments and accurately tracking their position in 3 dimensions is key for quantitative analysis. Holographic imaging of these beads allows for multiplexing bead tracking but image analysis can be a limiting factor. Here we present a 3D tracking algorithm based on Fast Fourier Transforms that is fast, has nanometric precision, is robust against common artifacts and is accurate over 10s of micrometers. We show its real-time application for magnetic tweezers based force spectroscopy on more than 100 chromatin fibers in parallel, but we anticipate that many other bead-based biophysical essays can benefit from this simple and robust 3 phasor algorithm.

biophysics↗