Yu and Dayan 2005

• NE > ACh / (0.5 + ACh)

• "The threshold for NE that determines whether or not the context should be assumed to have changed is set monotonically by the level of ACh. Intuitively, when the estimated cue invalidity is low, a single observation of a mismatch between cue and target could signal a context switch. But when the estimated cue invalidity is high, indicating low correlation between cue and target, then a single mismatch would be more likely to be treated as an invalid trial rather than a context switch."

[Yu and Dayan (2005) Uncertainty, Neuromodulation, and Attention]