Identification of Exploration and Exploitation Balance in the Silkmoth Olfactory Search Behavior by Information-Theoretic Modeling.

Cesar A Hernandez-Reyes,Hideki Sezutsu,Takeshi Sakurai,Daisuke Kurabayashi,Ryohei Kanzaki,Shumpei Fukushima,Shunsuke Shigaki

doi:10.3389/fncom.2021.629380

Abstract

Insects search for and find odor sources as their basic behaviors, such as when looking for food or a mate. This has motivated research to describe how they achieve such behavior under turbulent odor plumes with a small number of neurons. Among different insects, the silk moth has been studied owing to its clear motor response to olfactory input. In past studies, the “programmed behavior” of the silk moth has been modeled as the average duration of a sequence of maneuvers based on the duration of periods without odor hits. However, this model does not fully represent the fine variations in their behavior. In this study, we used silk moth olfactory search trajectories from an experimental virtual reality device. We achieved an accurate input by using optogenetic silk moths that react to blue light. We then modeled such trajectories as a probabilistic learning agent with a belief of possible source locations. We found that maneuvers mismatching the programmed behavior are related to larger entropy decrease, that is, they are more likely to increase the certainty of the belief. This implies that silkmoths include some stochasticity in their search policy to balance the exploration and exploitation of olfactory information by matching or mismatching the programmed behavior model. We believe that this information-theoretic representation of insect behavior is important for the future implementation of olfactory searches in artificial agents such as robots.

Highlights

Odor source localization is a search problem that requires fast decision-making based on sporadic and stochastic detection of chemical particles
We considered as odor hits only those that occurred when the moth was facing upwind, that is, when cos(π − θ + θsrc) > 0, where θ and θsrc are the angle of the moth and the plume’s centerline, respectively
We conducted 20 trials in which the moth searched for a pheromone source in a 350 mm long by 200 mm wide virtual environment where the wind was blowing in the positive x-direction at a mean speed of 0.1 m/s

Summary

Introduction

Odor source localization is a search problem that requires fast decision-making based on sporadic and stochastic detection of chemical particles. Information-Theoretic Modeling of Silkmoth despite their simple brain motivates researchers to further analyze and understand the decision processes that these insects execute when conducting olfactory searches (Baker et al, 2018) With this motivation, our research group has analyzed the olfactory behavior of the male silk moth Bombyx mori (lepidoptera: bombycidae). Our research group has analyzed the olfactory behavior of the male silk moth Bombyx mori (lepidoptera: bombycidae) Despite having wings, this insect is unable to fly, and has a body that is on average 30 mm long and 10 mm wide. It has two antennae of approximately 6 mm in length on its head This insect has been widely employed to analyze olfactory behavior because it exhibits only one action: It walks only when it detects a pheromone (Bombykol) released by its female counterpart (Obara, 1979). Such behavior consists of a series of maneuvers called a “surge,” “zigzag,” and “loop.” This sequence of maneuvers has been approximated to a meanresponse model denoted as “programmed behavior” (Kanzaki et al, 1992)

Methods

Results

Discussion

Conclusion