State representation is fundamental to behavior. However, identifying the true state of the world is challenging when explicit cues are ambiguous. Here, Bradfield and colleagues show that the medial OFC is critical for using associative information to discriminate ambiguous states. State representation is fundamental to behavior. However, identifying the true state of the world is challenging when explicit cues are ambiguous. Here, Bradfield and colleagues show that the medial OFC is critical for using associative information to discriminate ambiguous states.