How did the chicken cross the road? With her striatal cholinergic interneurons, of course

Abstract

Recognizing when the world changes is fundamental for normal learning. In this issue of Neuron, Bradfield et al. (2013) show that cholinergic interneurons in dorsomedial striatum are critical to the process whereby new states of the world are appropriately registered and retrieved during associative learning.

Figure 1

Illustration of Bradfield et al.’s (2013) experimental design, results & interpretation. Rewards for the two actions were a food pellet or sucrose solution (Top). All tests were conducted without rewards, retraining was administered after tests as necessary, • denotes no action, and all conditions were counterbalanced (see Bradfield et al., 2013). Selective test responding only on the lever that had previously been mapped to the non-devalued/non-degraded/reinstated outcome in the control group suggests that each change in task contingencies was encoded by the rats as a new state (Middle). In contrast, disruption of cholinergic activity in pDMS resulted in nonspecific degradation, devaluation and reinstatement of both actions, but only after initial learning (Bottom). This could be ascribed to (A) a retrieval deficit that causes multiple states to be retrieved throughout, or (B) a deficit in creating new states when the identity but not the value of outcomes is changed, such that training in challenges I and II is combined with the initial training.