Behavioral control by depolarized and hyperpolarized states of an integrating neuron

<p><span>Coordinated transitions between mutually exclusive motor states are central to behavioral decisions. During locomotion, the nematode <i>Caenorhabditis elegans</i> spontaneously cycles between forward runs, reversals, and turns with complex but predictable dynamics. Here we provide insight into these dynamics by demonstrating how<i> </i>RIM interneurons, which are active during reversals, </span>act in two modes to stabilize both forward runs and reversals. <span>By systematically quantifying the roles of RIM outputs during spontaneous behavior, we </span>show that RIM lengthens reversals when depolarized through glutamate and tyramine neurotransmitters and lengthens forward runs when hyperpolarized through its gap junctions. RIM is not merely silent upon hyperpolarization: RIM <span>gap junctions actively reinforce a hyperpolarized state of the reversal circuit. Additionally, the combined outputs of chemical synapses and gap junctions from RIM regulate forward-to-reversal transitions. Our results indicate that multiple classes of RIM synapses create behavioral inertia during spontaneous locomotion.</span></p>