The Controllosphere: The Neural Origin of Cognitive Effort

Why do some mental activities feel harder than others? The answer to this question is surprisingly controversial. Current theories propose that cognitive effort affords a computational benefit, such as instigating a switch from an activity with low reward value to a different activity with higher reward value. By contrast, in this article, I relate cognitive effort to the fact that brain neuroanatomy and neurophysiology render some neural states more energy-efficient than others. I introduce the concept of the "controllosphere," an energy-inefficient region of neural state space associated with high control, which surrounds the better known "intrinsic manifold," an energy-efficient subspace associated with low control. Integration of control-theoretic principles with classic neurocomputational models of cognitive control suggests that dorsolateral prefrontal cortex (DLPFC) implements a controller that can drive the system state into the controllosphere, anterior cingulate cortex (ACC) implements an observer that monitors changes of state of the controlled system, and cognitive effort reflects a mismatch between DLPFC and ACC energies for control and observation. On this account, cognitive effort scales with the energetic demands of the DLPFC control signal, especially when the consequences of the control are unobservable by ACC. Further, I propose that neural transitions through the controllosphere lead to a buildup of neural waste. Cognitive effort therefore prevents against neural damage by discouraging extended periods of high control.