Ventral tegmental area GABA neurons integrate positive and negative valence
The ventral tegmental area (VTA) is classically linked to reward learning and reinforcement via the actions of dopamine neurons. Intermingled VTA GABA neurons are positioned to regulate dopaminergic systems, but we lack detailed insight into how this population contributes to conditioned motivation across learning contexts. Here, recording population calcium activity in VTA dopamine and GABA neurons during different conditioning paradigms, we found that, while dopamine neurons were selectively responsive only to appetitive stimuli, GABA neurons actively encoded both appetitive and aversive cues and outcomes. GABA neurons also signalled errors in violation of expectations for associations of either valence. Critically, we found that GABA neurons selectively integrated events when both valences were simultaneously present, reflecting motivational state under cost. In a motivational conflict task, where rats must weigh decisions to avoid shock or seek reward, VTA GABA neuron activity scaled with escalating cost, and was predictive of reward seeking motivation. Optogenetic inhibition of VTA GABA neurons disrupted reward seeking specifically under conditions of motivational conflict. Together, our data show that VTA GABA neurons reflect a broader learning signal, compared to dopamine neurons, one that is particularly important for directing appropriate behavioral responses in complex, multivalent environments. Our results reveal new insights into the functional landscape of the VTA, where distinct populations of neurons act in parallel to signal different aspects of motivation under various behavioral conditions.