Motor history influences behavioral strategy more than response outcome in Drosophila melanogaster

In an ever-changing environment, animals continuously implement decision-making processes. This mechanism primarily relies on gathering sensory information through evidence accumulation, which enables the optimization of strategies in uncertain conditions. According to this scheme, the higher the evidence level, the greater the level of accuracy. However, it is not yet clear which, apart from direct sensory inputs, are the other factors that potentially impact strategy selection and their corresponding temporal operating windows in invertebrates. Moreover, it is not guaranteed that maximal accuracy could be the only parameter dictating the decision-making process. To address these questions, we employed a visual stimulation paradigm based on the random dot motion kinetogram (RDMk) with varying coherence levels, applied to tethered Drosophila melanogaster. In this scenario, flies tend to turn their heads according to the optic flows strength and direction. We observed stereotyped head saccadic-like movements across all the RDMk coherence levels, with greater coherence leading to a higher total saccade number and an increased proportion of correct turns. Importantly, logistic regression analysis revealed that, besides sensory inputs, the behavioral outcome and, consequently, the maximal accuracy, are influenced by other factors, in particular the past motor activity. In conclusion, our data support a scenario where accuracy and reaction time are balanced to reach an optimal response condition.