Biology subjects

Romanos, M.

Publications and source records attributed to Romanos, M..

6 recordsLinked to original sources

bioRxiv2026

A self without a "we": Individuals with Borderline personality disorder show signatures of disrupted social basis functions

A capacity to navigate social relationships is fundamental to human wellbeing. However, the cognitive mechanisms underlying social dysfunction in psychiatric conditions remain poorly understood. Using an abstract multi-person decision making task that isolates the relational structure of multi-person interactions, we compare non-clinical controls (NCC, n=51) and individuals with BPD symptoms (n=46), a condition characterized by disturbances in self-other boundaries and chronic feelings of loneliness. Generally, we found a pattern of less self-centered decision-making in BPD. More specifically, individuals with BPD showed signatures of perceiving opponents as a coherent group ("them"), but a markedly reduced tendency to represent themselves as part of their own team ("us"). This pattern of results points towards a disruption of a primary social basis function. Our laboratory findings extend to experienced loneliness in daily life as measured by ecological momentary assessments (EMA). Together, this suggests that BPD is characterized by an unbalanced representation of social structure, with an attenuated "we" alongside a heightened "they".

neuroscience↗

bioRxiv2025

Continuous theta-burst stimulation of the ventromedial prefrontal cortex reduces Pavlovian go-invigoration and enhances thalamo-striatal reward prediction error signals

The ventromedial prefrontal cortex (vmPFC) represents value, i.e. whether environmental cues are good or bad. Rewarding cue value is aligned with a tendency to act or to inhibit in case of potential punishment, a so-called Pavlovian Bias. Value-related vmPFC activation may therefore impact Pavlovian bias. However, it remains unknown how the activity in the vmPFC modulates the Pavlovian bias. Thus, we applied continuous theta-burst stimulation (cTBS), a non-invasive protocol that transiently reduces cortical excitability, over the vmPFC in a single-blinded, between-subject study. 90 healthy adults performed a motivational Go/NoGo learning task during fMRI after receiving cTBS (n=45) or sham (n=45) stimulation. Behaviourally, cTBS reduced overall Go response rates and slowed reaction times. Computational modelling showed a decrease in the learning rate, selectively for rewarding outcomes. Computational fMRI analysis showed stronger reward prediction error (RPE) signals in the vmPFC, mediodorsal thalamus, and left dorsal striatum after cTBS, without changes in neural signals at cue onset. These findings provide causal evidence that the vmPFC drives the action-invigoration component of the Pavlovian bias. Significance statementWe causally link ventromedial prefrontal cortex (vmPFC) function to motivated action in humans. In a single-blind cTBS-fMRI study (n=90), transient vmPFC inhibition reduced Go responding, slowed reaction times, and selectively lowered the positive learning rate early in learning. At the same time, reward-prediction-error signals increased in mediodorsal thalamus, dorsal striatum, and vmPFC, while cue-onset value/choice signals were unchanged. Together, the results indicate that vmPFC normally speeds value updating and invigorates actions; when inhibited, control shifts toward slower, subcortically supported learning under higher uncertainty.

neuroscience↗

bioRxiv2024

The mechanism of spatial pattern transition in motile bacterial collectives

Understanding how individual behaviours contribute to collective actions is key in biological systems. In Myxococcus xanthus, a bacterial predator, swarming shifts to rippling patterns due to changes in the local environment near prey colonies. Through high-resolution microscopy and theoretical analysis, we demonstrate that two key properties drive this shift: local cellular alignment guided by an extracellular matrix and the ability of cells to reverse to resolve congestion. A tunable refractory period in the reversal system enables collective adaptation, allowing cells to synchronise in rippling and resolve congestion in swarming. These transitions occur without changes in genetic regulation but create stable spatial domains that promote local differentiation, a mechanism of spatial sorting that may be widespread in biology.

microbiology↗

bioRxiv2024

Differential proliferation regulates multi-tissue morphogenesis during embryonic axial extension: Integrating viscous modeling and experimental approaches.

The study of how mechanical interactions and different cellular behaviors affect tissues and embryo shaping has been and remains an important challenge in biology. Axial extension is a morphogenetic process that results in the acquisition of the elongated shape of the vertebrate embryonic body. Several adjacent tissues are involved in the process, including the tissues that form the spinal cord and musculoskeletal system: the neural tube and the paraxial mesoderm, respectively. Although we have a growing understanding of how each of these tissues elongates, we still need to fully understand the morphogenetic consequences of their growth and mechanical interactions. In this study, we develop a 2D multi-tissue continuum-based mathematical model to simulate and study how differential growth, tissue biophysical properties, and mechanical interactions affect the morphogenesis of the embryonic body during axial extension. Our model captures the long-term dynamics of embryonic posterior tissues previously observed in vivo by time-lapse imaging of bird embryos. It reveals the underestimated influence of differential tissue proliferation rates in inter-tissue interaction and shaping by capturing the relative impact of this process on tissue dynamics. We verified the predictions of our model in quail embryos by showing that decreasing the rate of cell proliferation in the paraxial mesoderm affects long-term tissue dynamics and shaping of both the paraxial mesoderm and the neighboring neural tube. Overall, our work provides a new theoretical platform to consider the long-term consequences of tissue differential growth and mechanical interactions on morphogenesis.

developmental biology↗

bioRxiv2023

Reduced discrimination between signals of danger and safety but not overgeneralization is linked to exposure to childhood adversity in healthy adults

Childhood adversity is a strong predictor of developing psychopathological conditions. Multiple theories on the mechanisms underlying this association have been suggested which, however, differ in the operationalization of exposure. Altered (threat) learning mechanisms represent central mechanisms by which environmental inputs shape emotional and cognitive processes and ultimately behavior. 1402 healthy participants underwent a fear conditioning paradigm (acquisition training, generalization), while acquiring skin conductance responses (SCRs) and ratings (arousal, valence, and contingency). Childhood adversity was operationalized as (1) dichotomization, and following (2) the specificity model, (3) the cumulative risk model, and (4) the dimensional model. Individuals exposed to childhood adversity showed blunted physiological reactivity in SCRs, but not ratings, and reduced CS+/CS-discrimination during both phases, mainly driven by attenuated CS + responding. The latter was evident across different operationalizations of exposure following the different theories. None of the theories tested showed clear explanatory superiority. Notably, a remarkably different pattern of increased responding to the CS-is reported in the literature for anxiety patients, suggesting that individuals exposed to childhood adversity may represent a specific sub-sample. We highlight that theories linking childhood adversity to (vulnerability to) psychopathology need refinement.

neuroscience↗

bioRxiv2020

Cell-to-cell heterogeneity in Sox2 and Brachyury expression guides progenitor destiny by controllingtheir movements.

Although cell-to-cell heterogeneity in gene and protein expression within cell populations has been widely documented, we know little about its potential biological functions. We addressed this issue by studying progenitors that populate the posterior region of the vertebrate embryos, a cell population known for its capacity to self-renew or to contribute to the formation of the neural tube and paraxial mesoderm tissues. Posterior progenitors are characterized by the co-expression of Sox2 and Brachyury (Bra), two transcription factors related to neural and mesodermal lineages, respectively. In this study, we show that the respective levels of Sox2 and Bra proteins display a high degree of variability among posterior progenitors of the quail embryo. By developing forced expression and downregulation approaches, we further provide evidence that the value of the Sox2-to-Bra ratio in a given progenitor directs its choice of staying in place or exit the progenitor zone to generate neural or mesodermal cells. Time-lapse imaging together with mathematical modeling then reveal that variations of the Sox2-to-Bra ratio confer these cells heterogeneous motile behaviors. While high Bra levels display high motile properties that push cells to join the mesoderm, high levels of Sox2 tend to inhibit cell movement making cells get integrated into the neural tube. Our work thus provides evidence that the spatial heterogeneity of posterior progenitors, with regards to their relative contents of Sox2 and Bra and thus to their motile properties, is fundamental to maintain a pool of resident progenitors while others segregate to contribute to tissue formation. More broadly, our work reveals that heterogeneity among a population of progenitor cells is critical to ensure robust multi-tissue morphogenesis.

developmental biology↗