Nir Gov's Lab

Motile cells often face microenvironmental constraints and obstacles that force them to extend multiple protrusions. However, the analysis of shape dynamics during directional decision-making has been restricted to single junctions. Here, we combined live-cell imaging and a coarse-grained model to study the migratory behavior of highly branched cells while simultaneously facing several junctions. The theoretical model predicts that the choice of a new direction is determined by the competition between the cellular protrusions in the form of seesaw oscillations. We found that macrophages and endothelial cells display different regimes moving on hexagonal networks, despite sharing a mesenchymal (i.e., adhesion-dependent) migratory strategy. The model describes the motility of both cell types and reveals a trade-off between branching and speed: Having many protrusions allows local microenvironmental exploration for directional cues, but long-range migration efficiency improves with fewer protrusions. Collectively, our data highlight the relevance and provide insights for the regulation of shape dynamics during cell navigation in complex geometries.

We study how simple eukaryotic organisms make decisions in response to competing stimuli in the context of phototaxis by the unicellular alga Chlamydomonas reinhardtii. While negatively phototactic cells swim directly away from a collimated light beam, when presented with two beams of adjustable intersection angle and intensities, we find that cells swim in a direction given by an intensity-weighted average of the two light propagation vectors. This geometrical law is a fixed point of an adaptive model of phototaxis and minimizes the average light intensity falling on the anterior pole of the cell. At large angular separations, subpopulations of cells swim away from one source or the other, or along the direction of the geometrical law, with some cells stochastically switching between the three directions. This behavior is shown to arise from a population-level distribution of photoreceptor locations that breaks front-back symmetry of photoreception.

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.