A functional hallucination is a rare perceptual disorder where a hallucination is triggered by a real external stimulus in the same sensory modality and happens at the exact same time. [1, 2]
Key Characteristics
- Co-occurrence: The hallucination appears alongside a real sensory input and stops immediately when the real sound or stimulus stops. For example, a person might hear critical voices only while a rotating fan or running water is making noise. [1, 2]
- Same Modality: The trigger and the hallucination belong to the same sense (such as hearing a real sound and simultaneously hearing a hallucinated voice). [1, 2]
- Underlying Mechanism: Researchers believe the brain misinterprets or abnormally encodes the natural acoustic features of a real environmental sound in the auditory cortex. [1, 2]
- Context: They are most commonly reported in individuals with schizophrenia or other functional psychotic disorders.