Visual hallucinations.

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Psychiatry

Background:

• Visual hallucinations are increasingly understood through complex multifactor models, moving beyond single-pathology explanations.
• Clinical studies link hallucinations in dementia, delirium, eye disease, and psychosis to dysfunction in the ventral object perception system.

Discussion:

• Dissociations suggest at least two distinct hallucinatory syndromes, requiring further clarification of boundaries.
• Neural models highlight the interplay of top-down (frontal) and bottom-up (occipital) systems, alongside regulatory brainstem and thalamic influences.
• Both qualitative and quantitative explanations fit current data on hallucination generation.

Key Insights:

• Hallucinations and veridical perceptions activate overlapping brain regions, indicating a critical role for top-down and bottom-up process negotiation.
• Hallucinations may occur when incorporating a hallucinatory element improves the prediction of sensory input.

Outlook:

• Translational research integrating clinical insights and basic vision science is crucial for developing effective treatments.
• Further research is needed to clarify the exact boundaries of different hallucinatory syndromes.