Deciphering Functional Hallucinations – Insights from Three Patients with Schizophrenia

Abstract Hallucinations may involve any of the sensory modalities – auditory, visual, tactile, olfactory, and gustatory and may present in mixed or complex perceptual hallucinations. Among the rarer forms of hallucinations are functional hallucinations. Functional hallucinations are a rare and understudied phenomenon in which hallucinations are consistently triggered by a specific real external stimulus, typically within the same sensory modality. We describe three cases of functional hallucinations in schizophrenia, involving auditory and visual modality. This unique phenomenology requires careful assessment to differentiate it from other types of perceptual abnormalities. Further research is needed to understand their neurobiological basis and long-term prognosis.