This paper focuses on the "higher-order representation (HOR)" of FOR, rather than the "primary representation (FOR)" that encodes the content or structure of the observer's environment. In particular, we study HOR, which addresses aspects of FOR such as intensity and uncertainty, and specifically, HOR for uncertainty. Research on how the brain represents expectations about uncertainty is lacking. This study develops and applies a "Reinforcement-Based Noise Estimation via Diffusion (NERD)" model using neural data obtained from a "decoded neurofeedback" task, in which subjects learn to intentionally generate target neural patterns. Through this, we characterize how the brain learns to respond to noise and demonstrate that the NERD model offers a high level of explanatory power for human behavior.