Biology subjects

Baumann, T.

Publications and source records attributed to Baumann, T..

6 recordsLinked to original sources

bioRxiv2026

Hippocampus-reuniens beta coupling supports goal-directed spatial navigation

Prefrontal-hippocampal communication, supported by both direct and indirect anatomical pathways, is essential for a range of cognitive functions, including spatial navigation. The midline thalamic nucleus reuniens (RE) has been proposed as a key hub along this indirect pathway, coordinating bidirectional interactions between the hippocampus (HC) and prefrontal cortex (PFC). Here, we investigated functional dynamics within the HC-RE-PFC network as adult male rats learned to navigate a complex maze. Initial behavioral analyses revealed three distinct learning phases: exploration, goal-oriented learning, and efficient navigation. Aligning neural data with subject-specific transitions between these phases uncovered distinct neural signatures associated with each learning phase. Notably, the transition from exploratory to goal-directed behavior was accompanied by the emergence of persistent HC-RE beta-band (15-25Hz) interactions, including elevated beta coherence, theta-beta phase-amplitude coupling, and HC-to-RE Granger causality. The interactions further scaled with navigational efficiency, showing increased HC-RE beta coherence in trials without errors. Together, these findings provide new evidence for dynamic HC-RE interactions during goal-directed navigation and support an emerging view that RE functions as a working memory buffer for route-related information, revealing a potential network mechanism underlying flexible spatial behavior. HighlightsO_LIBeta-band hippocampus-reuniens coupling emerges during goal-directed navigation. C_LIO_LIPAC between HC theta and RE beta increased during goal learning. C_LIO_LIHC-RE coupling strength increases with navigational efficiency. C_LIO_LIDirectional hippocampus-to-reuniens communication emerges during learning C_LIO_LIReuniens supports hippocampal-prefrontal integration for flexible behavior C_LI Significance StatementFlexible spatial navigation requires coordinated communication between the hippocampus (HC) and the prefrontal cortex (PFC), yet the thalamic mechanisms coordinating HC-PFC interaction remain poorly understood. This study reveals that the nucleus reuniens (RE) of the midline thalamus plays a critical role in mediating HC-PFC communication during spatial learning. By combining detailed behavioral analysis with simultaneous multi-site electrophysiological recording, we identify beta-band HC-RE coupling as a neural signature of the transition from exploration to goal-directed navigation. The strength and directionality of this interaction tracked improvements in navigational efficiency, revealing a thalamic mechanism for integrating hippocampal output into prefrontal circuits. These findings highlight the RE as a working memory buffer for route-related information and advance our understanding of how thalamic hubs contribute to the circuit-level dynamics underlying flexible behavior.

neuroscience↗

bioRxiv2023

Mitochondrial CISD1 is a downstream target that mediates PINK1 and Parkin loss-of-function phenotypes

Parkinsons disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra of the midbrain. Familial cases of PD are often caused by mutations of PTEN-induced kinase 1 (PINK1) and the ubiquitin ligase Parkin, both pivotal in maintaining mitochondrial quality control. CISD1, a homodimeric mitochondrial iron-sulfur-binding protein, is a major target of Parkin-mediated ubiquitination. We here discovered a heightened propensity of CISD1 to form dimers in Pink1 mutant flies and in dopaminergic neurons from PINK1 mutation patients. The dimer consists of two monomers that are covalently linked by a disulfide bridge. In this conformation CISD1 cannot coordinate the iron-sulfur cofactor. Overexpressing Cisd, the Drosophila orthologue of CISD1, and a mutant Cisd incapable of binding the iron-sulfur cluster in Drosophila reduced climbing ability and lifespan. This was more pronounced with mutant Cisd and aggravated in Pink1 mutant flies. Complete loss of Cisd, in contrast, rescued all detrimental effects of Pink1 mutation on climbing ability, wing posture, dopamine levels, lifespan, and mitochondrial ultrastructure. Our results suggest that Cisd, probably iron-depleted Cisd, operates downstream of Pink1 shedding light on PD pathophysiology and implicating CISD1 as a potential therapeutic target.

neuroscience↗

bioRxiv2023

Metric information in cognitive maps: Euclidean embedding of non-Euclidean environments

The structure of the internal representation of surrounding space, the so-called cognitive map, has long been debated. A Euclidean metric map is the most straight-forward hypothesis, but human navigation has been shown to systematically deviate from the Euclidean ground truth. Vector navigation based on non-metric models can better explain the observed behavior, but also discards useful geometric properties such as fast shortcut estimation and cue integration. Here, we propose another alternative, a Euclidean metric map that is systematically distorted to account for the observed behavior. The map is found by embedding the non-metric model, a labeled graph, into 2D Euclidean coordinates. We compared these two models using human data from Warren et al. (2017), where participants had to navigate and learn a non-Euclidean maze (i.e., with Wormholes) and perform direct shortcuts between different locations. Even though the Euclidean embedding cannot correctly represent the non-Euclidean environment, both models predicted the data equally well. We argue that the so embedded graph naturally arises from integrating the local position information into a metric framework, which makes the model more powerful and robust than the non-metric alternative. It may therefore be a better model for the human cognitive map.

neuroscience↗

bioRxiv2023

PenTag, a Versatile Platform for Covalent Bioconjugation, Purification, and Tagging of Proteins Towards the Development of Novel Biohybrid Material Systems

The site-specific and covalent conjugation of proteins on solid supports and in hydrogels is the basis for the synthesis of biohybrid materials offering broad applications. Current methods for conjugating proteins to desired targets are often challenging due to unspecific binding, unstable (non-covalent) coupling, or expensive and difficult-to-synthesize ligand molecules. Here, we present PenTag, an approach for the biorthogonal, highly-specific and covalent conjugation of a protein to its ligand for various applications in materials sciences. We engineered penicillin- binding protein 3 (PBP3) and showed that this protein can be used for the stable and spontaneous conjugation of proteins to dyes, polymers, or solid supports. We applied PenTag as a crosslinking tool for synthesizing stimuli-responsive hydrogels or for the development of a biohybrid material system performing computational operations emulating a 4:2 encoder. Based on this broad applicability and the use of a small, cheap and easy-to-functionalize ligand and a stable, soluble recombinant protein, we see PenTag as a versatile approach towards biohybrid material synthesis.

synthetic biology↗

bioRxiv2022

Gateway Identity and Spatial Remapping in a Combined Grid and Place Cell Attractor.

The spatial specificities of hippocampal place cells, i.e., their firing fields, are subject to change if the rat enters a new compartment in the experimental maze. This effect is known as remapping. It cannot be explained from path integration (grid cell activity) and local sensory cues alone but requires additional knowledge of the different compartments in the form of context recognition at the gateways between them. Here we present a model for the hippocampalentorhinal interplay in which the activity of place and grid cells follows a joint attractor dynamic. Place cells depend on the current grid cell activity but can also reset the grid cell activity in the remapping process. Remapping is triggered by the passage through a gateway. When this happens, a previously stored pattern of place cell activity associated with the gateway is reactivated from a "gateway database". The joint attractor will then reinstate the grid cell pattern that was active when the gateway had first been learned and path integration can proceed from there. The model is tested with various mazes used in the experimental literature and reproduces the published results, and we make predictions for remapping in a new maze type. We propose the involvement of memory in the form of "gate cells" that drive the place cells and with them the joint hippocampal-entorhinal loop into the corresponding attractor whenever a compartment is entered.

neuroscience↗

bioRxiv2018

Microfluidic study of effects of flow velocity and nutrient concentration on biofilm accumulation and adhesive strength in microchannels

AbstractBiofilm accumulation in the porous media can cause plugging and change many physical properties of porous media. Up to now, applications of desired biofilm growth and its subsequent bioplugging have been attempted for various practices. A deeper understanding of the relative influences of hydrodynamic conditions including flow velocity and nutrient concentration, on biofilm growth and detachment is necessary to plan and analyze bioplugging experiments and field trials. The experimental results by means of microscopic imaging over a T-shape microchannel show that flow velocity and nutrient concentrations can have significant impacts on biofilm accumulation and adhesive strength in both flowing and stagnant microchannels. Increase in fluid velocity could facilitate biofilm growth, but that above a velocity threshold, biofilm detachment and inhibition of biofilm formation due to high shear stress were observed. High nutrient concentration prompts the biofilm growth, but was accompanied by a relatively weak adhesive strength. This research provides an overview of biofilm development in a hydrodynamic environment for better predicting and modelling the bioplugging associated with porous system in petroleum industry, hydrogeology, and water purification.\n\nIMPORTANCEIn the recent decade, the use of bacteria has become more and more important in many applications. Bioplugging caused by bacteria growth in porous media has been explored as a viable technique for some applications, such as bioremediation, water purification and microbial enhanced oil recovery (MEOR). In order to control biofilms/biomasses selectively/directionally plugging in desirable places, the role of hydrodynamic conditions on biofilm growth and detachment is essential to investigate. Herein, a T-shape microchannel was prepared to study effects of flow velocity and nutrient concentration on biofilm accumulation and adhesive strength at pore scale. Our results suggest that flow velocity and nutrient concentration could control biofilm accumulation in microchannels. The finding helps explain and predict the engineering bioplugging in porous media, especially for the selective plugging strategy of a MEOR field trial.

bioengineering↗