Run-and-tumble chemotaxis using reinforcement learning
This work addresses chemotaxis optimization for biological or robotic agents, but it is incremental as it applies existing RL methods to a known biological model.
The study tackled the problem of optimizing bacterial-like run-and-tumble chemotaxis using reinforcement learning, finding that an optimal balance between exploration and exploitation is necessary for efficient localization in favorable zones and environmental learning, depending on attractant profiles and initial conditions.
Bacterial cells use run-and-tumble motion to climb up attractant concentration gradient in their environment. By extending the uphill runs and shortening the downhill runs the cells migrate towards the higher attractant zones. Motivated by this, we formulate a reinforcement learning (RL) algorithm where an agent moves in one dimension in the presence of an attractant gradient. The agent can perform two actions: either persistent motion in the same direction or reversal of direction. We assign costs for these actions based on the recent history of the agent's trajectory. We ask the question: which RL strategy works best in different types of attractant environment. We quantify efficiency of the RL strategy by the ability of the agent (a) to localize in the favorable zones after large times, and (b) to learn about its complete environment. Depending on the attractant profile and the initial condition, we find an optimum balance is needed between exploration and exploitation to ensure the most efficient performance.