A Disinhibitory Circuit Affects Drosophila Larval Light Avoidance

The innate behavior of living organisms plays an important role in the their survival and reproduction.Animals use environmental cues as decisive factors to guide them in making behavioral decisions.Therefore,the visual system is responsible for the transformation of light-dependent stimuli into encoded information.In recent years,there have been many studies in the neural process of visual information on larva.However,how the aversive/attractive sensory stimulus is transformed through central brain neurons into avoidance or approaching behavior is largely unclear.Our lab's work has found that light-avoidance of Drosophila larva may be regulated by a disinhibitory circuit according to calcium imaging data.In this circuit,a pair of GABAergic neurons(LRIN)can be suppressed by light,which exert tonic inhibition on a pair of downstream light-sensitive neurons(CLPN).This paper demonstrates the function of this disinhibitory circuit using a new behavioral method-light spot assay.We found that CLPN could control the turning behavior of larva.When a larva enters the light area,the upstream LRIN is inhibited,the downstream CLPN is disinhibited.The larva performs reorientation to avoid light.When larva exits the light area,LRIN is not inhibited,and its inhibition on CLPN is restored to repress reorientation,the larva can be avoided re-entering the light area.In this way,the circuit ensures that the larvae can avoid light when they are from dark to light,and then suppress the left larvae from re-entering the light area when they are from light to dark.We suggest that disinhibition can serve as a common neural mechanism for animal innate preference behavior.