A long-standing open question is how brain circuits learn what information is behaviorally relevant and should be attended. We have a new key insight to this question published in the paper “Adaptive Reinforcement Learning is causally supported by Anterior Cingulate Cortex and Striatum” (Neuron, pdf). We found that brief 0.3 s electrical stimulation at the time subjects looked at visual objects causally changed how these objects became top-down attentional target objects. The stimulation enhanced learning the relevance of visual objects in the striatum and impaired this learning in the anterior cingulate cortex. The effect was most pronounced when there were many alternate features present that subjects needed to filter out from attention, i.e. when there was higher feature uncertainty and the need for feature-specific credit assignment during learning.

The paper is an experimental tour-de-force by stimulating in two brain areas, modeling the stimulation effects on behavior (to show the effects are strongest on adaptive reinforcement learning mechanisms) and recording from neurons in the brain areas (to show which neuronal task representations are likely affected). Kudos to Louis, Kia, Charlie and Adam to succeed with such a comprehensive study and to Prof. Paul Tiesinga for help with an advanced Triple Mechanisms Adaptive Reinforcement Learning model that critically helped understanding the mechanisms underlying the observed effects.