Nir Gov's Lab

Humans and other organisms make decisions choosing between different options, with the aim of maximizing the reward and minimizing the cost. The main theoretical framework for modeling the decision-making process has been based on the highly successful drift-diffusion model, which is a simple tool for explaining many aspects of this process. However, recent observations challenge this model. It was found that inhibitory tone increases during situations of difficult discrimination tasks, but the origin of this phenomenon is not understood. Motivated by this observation, we extend a recently developed model for directional decision-making of animals moving in real space. We introduce an integrated Ising-type model that includes global inhibition and use it to describe two-choice decision-making. This model can explain how the brain may utilize inhibition to improve its decision-making accuracy. Compared to experimental results, this model suggests that the regime of the brains decision-making activity is in proximity to a critical transition line between the ordered and disordered phases. Within the model, this observation can be explained by noting that this critical region has unique dynamics that give rise to advantageous properties for the decision-making process.

This study theoretically investigates how anisotropic curved membrane components (CMCs) control vesicle morphology through curvature sensing, nematic alignment, topological defects and volume constraints. By comparing arc- and saddle-shaped CMCs, we identify a rich spectrum of steady-state phases. For fully CMC-covered vesicles, arc-shaped components drive a pearling-to-cylinder transition as nematic interactions strengthen, while on partially CMC-covered vesicles the saddle-shaped CMCs stabilize necks between the convex regions of bare membrane. We map the steady-state shapes of vesicles partially covered by arc- and saddle-shaped CMCs, exposing how different vesicle shapes depend on the interplay between nematic interactions and volume constraints, revealing several novel phases. By investigating the in-plane nematic field, we find that topological defects consistently localize to high-curvature regions, revealing how intrinsic and deviatoric curvature effects cooperate in membrane remodeling. These findings establish a unified framework for understanding how proteins and lipid domains with anisotropic intrinsic curvature shape cellular structures-from organelle morphogenesis to global cell shape.

Directed migration of single cells is central to a large number of processes in development and adult life. Corrections to the migration path of cells are often characterized by periodic loss of polarity that is followed by the generation of a new leading edge in response to guidance cues, a behavior termed \u201crun and tumble.\u201d While this phenomenon is essential for accurate arrival at migration targets, the precise molecular mechanisms responsible for the periodic changes in cell polarity are unknown. To investigate this issue, we employ germ cells in live zebrafish embryos as an in vivo model and show that a tunable molecular network controls periodic pulsations of Rac1 activity and actin polymerization. This process, which we term \u201cpolar pulsations,\u201d is responsible for the transitions between the run and tumble phases. In addition, we provide evidence for the role of apolar blebbing activity during tumble phases in erasing the memory of the previous front-back polarity of the migrating cell. To understand how the molecular components give rise to this distinct behavior, we develop a minimal mathematical model of the biochemical network that accounts for the observed cell behavior. Together, our in vivo findings and the mathematical model suggest that a pulsatory signaling network regulates the accuracy of individual cell migration.