Attentional Reinforcement Learning in the Brain

Recently, attention mechanisms have significantly boosted the performance of natural language processing using deep learning. An attention mechanism can select the information to be used, such as by conducting a dictionary lookup; this information is then used, for example, to select the next utterance word in a sentence. In neuroscience, the basis of the function of sequentially selecting words is considered to be the cortico-basal ganglia-thalamocortical loop. Here, we first show that the attention mechanism used in deep learning corresponds to the mechanism in which the cerebral basal ganglia suppress thalamic relay cells in the brain. Next, we demonstrate that, in neuroscience, the output of the basal ganglia is associated with the action output in the actor of reinforcement learning. Based on these, we show that the aforementioned loop can be generalized as reinforcement learning that controls the transmission of the prediction signal so as to maximize the prediction reward. We call this attentional reinforcement learning (ARL). In ARL, the actor selects the information transmission route according to the attention, and the prediction signal changes according to the context detected by the information source of the route. Hence, ARL enables flexible action selection that depends on the situation, unlike traditional reinforcement learning, wherein the actor must directly select an action.