Insights into effortful adaptation during speech perception: The role of dopamine, norepinephrine, and prediction error.

In a highly variable world, listeners must be able to rapidly adjust to changing circumstances to prioritize comprehension. The neurobiological underpinnings of this ability are largely unspecified. This review combines insights from reinforcement learning, predictive coding, and the function of dopamine and norepinephrine to explore the viability of an effortful and error-driven system of adaptation during speech perception. Iteration, internal monitoring, error generation, and prediction are shared across multiple models of adaptation, leading to the possibility of a common mechanism. In search of this mechanism, I consider the role of error signaling within a domain-general account of perceptual adaptation. Drawing heavily from work in the neurobiology of reinforcement learning and effort, I theorize that adaptation during speech perception may be mediated by reward prediction errors wherein successful comprehension may act as its own reward. However, reward prediction error alone is likely insufficient to capture the full dynamics of rapid adaptation. I further propose that the system also leverages norepinephrine signaling to push the listener into an arousal state that allows for rapid perceptual fine-tuning. Ultimately, I argue that complementary, and parallel, error signals originating from multiple subcortical nuclei may direct effortful adaptation during challenges to speech perception.