A recent study from the Waddell Group (DPAG) published in Nature, reveals how the strength of memory-directed behavior is either suppressed or maintained depending on whether a new experience opposes or fits a previously learned expectation.
Their paper "Re-evaluation of learned information in Drosophila" demonstrates that different dopaminergic neurons in the Drosophila brain work in support or opposition to a previous memory of food reward and so allow the fly to accumulate information from all experiences to optimise behaviour.
Read more (DPAG website)