Fig. 7

Model for feedback excitation by glutamate spillover inducing repetitive reversal behavior. Under normal conditions (WT) glutamate (indicated by the gray arrows) is rapidly cleared from the synaptic cleft by glia-expressed GLT-1. In glt-1 mutants, glutamate is allowed to diffuse away from the synapse, resulting in activation of presynaptic MGL-2 and the induction of cycles of presynaptic activations