A novel perspective on the role of nucleus accumbens neurons in encoding associative learning

The nucleus accumbens (NAc) has been considered a key brain region for encoding reward/aversion and cue–outcome associations. These processes are encoded by medium spiny neurons that express either dopamine receptor D1 (D1‐MSNs) or D2 (D2‐MSNs). Despite the well‐established role of NAc neurons in encoding reward/aversion, the underlying processing by D1‐/D2‐MSNs remains largely unknown. Recent electrophysiological, optogenetic and calcium imaging studies provided insight on the complex role of D1‐ and D2‐MSNs in these behaviours and helped to clarify their involvement in associative learning. Here, we critically discuss findings supporting an intricate and complementary role of NAc D1‐ and D2‐MSNs in associative learning, emphasizing the need for additional studies in order to fully understand the role of these neurons in behaviour. The nucleus accumbens is key for encoding reward/aversion and associative learning, being the limbic‐motor interface of the brain. This encoding occurs through activity of medium spiny neurons (MSNs) that express either dopamine receptor D1 or D2. Here, we discuss evidence supporting a complex and complementary role of D1‐ and D2‐MSNs in encoding both appetitive and aversive cue–outcome associative learning.