Everybody Loves Dopamine

This study showed that rats who like to “gamble” on getting a larger sucrose reward have a weaker neural response after “losing.” In this case, losing means choosing the risky lever, which dispenses a low amount of sucrose 75% of the time (but a high amount 25%), and getting a tiny reward. The gambling rats will continue to choose the risky lever after losing. Other rats are risk-averse, and will choose the “safe” lever with a constant reward after losing.This paper was a technical tour de force with 14 multi-panel figures.1 For starters, cells in the nucleus accumbens (a VTA target) expressing the D2 receptor (NAc D2R+ cells) were modified to express a calcium indicator that allowed the imaging of neural activity (via fiber photometry). Activity in NAc D2R+ cells was greater after loss, and during the decision phase of post-loss trials. And these two types of signals were dissociable.2 Then optogenetic methods were used to activate NAc D2R+ cells on post-loss trials in the risky rats. This manipulation caused them to choose the safer option.- click to enlarge -Noted science writer Ed Yong wrote an excellent piece about these findings in The Atlantic (Scientists Can Now Watch the Brain Evaluate Risk).Now, there's a boatload of data on the role of dopamine in reinforcement learning and computational models of reward prediction error (Schultz et al., 1997) and discussion about potential weaknesses in the DA and RPE model. So while a very impressive addition to the ...
Source: The Neurocritic - Category: Neuroscience Authors: Source Type: blogs