Role of Downstream VTA GABA Neuron Projections in Associative Learning
Decision making based on past experiences and incentives is a key skill needed for survival and growth. One of the main brain regions involved in decision making is the ventral tegmental area which is responsible for cue-driven behavior and associative learning (van Zessen et al., 2012). Associative learning in the VTA depends on the activity patterns of two specific neuron subtypes: GABA and dopamine (DA). DA neurons in the VTA have been theorized to be involved in positive and negative reinforcement, as well as decisions making and incentive salience (Morales & Margolis, 2017). The other major neuronal subtype of the VTA are the GABA neurons. GABA neurons in the VTA synapse on DA neurons and inhibit them. Recent data suggest a reversed relationship between VTA DA and GABA neurons, in which VTA GABA stimulation increases reward seeking behavior. A key factor that makes the circuitry of the VTA unique is its heterogeneity. The VTA as mentioned earlier, contains several different cell types that, importantly, project to and synapse in many other brain regions (Breton et al., 2019). It has become clear that the VTA engages in parallel connectivity of GABA and DA neuron projections to different brain regions, and that complex connectivity is essential for motivation and reward behavior. Recent research has identified two important VTA projection locations to be the nucleus accumbens (NAc) and the ventral pallidum (VP), both of which are important players in the basal ganglia, the center for reward and motivation in the brain (Breton et al., 2019). The objective of this project is to investigate the role of distal projections of VTA GABA neurons (VP and NAc GABA neurons) in the reinforcing effect of VTA GABA stimulation on reward seeking behavior. It was found that stimulation of VP GABA neurons increased reward seeking behavior.