Block diagram of the symbiotic BMI controller.

The architecture contains two key components. The Actor is driven by the primary motor cortex (s_t) and its primary role is to select actions (a_i) in the environment. These actions are evaluated by the Critic, which is driven by the NAcc. At each instance in time, the Critic provides an error signal (ε_t) that is computed based on the gradient of reward expectation (v_t) and is used to adapt the parameters of the Actor for choosing actions that lead to reward. In this entire system, there is in intrinsic coupling between the motor system, reward system, and the environment.