Dopamine D2 receptors mediate two-odor discrimination and reversal learning in C57BL/6 mice
Paul J Kruzich and David K Grandy
BMC Neuroscience (2004)
The conceptual gap or the scientific question: did D2-receptor mediated signaling contribute to goal-directed reward learning? If so, how?
How the authors proposed the question: their are two major types of dopamine receptors expressed in striatum: D1-like and D2-like receptors. It had been demonstrated that D1 receptor signaling was required for many goal-directed behaviors, so the authors tried to test the roles of D2 receptor mediated signaling.
This is a common logic in both the scientific and daily inquiring: you will naturally ask about the remaining one after knowing the first.
Brief summary: Kruzich and Grandy shown that D2 receptor deficient mice shown impairments in both the initial learning and reversal learning of odor-place association task.
The finding that D2 signaling was critical for initial learning is contradicted with that in the study shared yesterday. Normally, there are many potential causes can contribute to conflicting observations, such as difference in the techniques used, the behavioral paradigms, the training protocols, etc. So usually it is difficult to reconcile them in systems neuroscience research. It seems that the more caveats exist, the fewer chance for falsifiability and for the construction of the so-called ‘grand theory’. So in behavioral neuroscience study, or in a sub-field, if researchers could construct a ‘grand theory’ or ‘conceptual framework’ to interpret the many findings at both the behavioral and neuronal levels, it will be a big success, to both the individual and the field. The dopamine in reward-learning is such a field, but the basal ganglia field, the working memory field, the OFC field are not. They had awaited such a moment for a long time and they will come in the next few decades. The brain science is just at its shining time!
