RESUMEN
The neural mechanisms conferring reduced motivation, as observed in depressed individuals, is poorly understood. Here, we examine in rodents if reduced motivation to exert effort is controlled by transmission from the lateral habenula (LHb), a nucleus overactive in depressed-like states, to the rostromedial tegmental nucleus (RMTg), a nucleus that inhibits dopaminergic neurons. In an aversive test wherein immobility indicates loss of effort, LHbâRMTg transmission increased during transitions into immobility, driving LHbâRMTg increased immobility, and inhibiting LHbâRMTg produced the opposite effects. In an appetitive test, driving LHbâRMTg reduced the effort exerted to receive a reward, without affecting the reward's hedonic property. Notably, LHbâRMTg stimulation only affected specific aspects of these motor tasks, did not affect all motor tasks, and promoted avoidance, indicating that LHbâRMTg activity does not generally reduce movement but appears to carry a negative valence that reduces effort. These results indicate that LHbâRMTg activity controls the motivation to exert effort and may contribute to the reduced motivation in depression.