Eight distinct models of complex visual hallucinations have been proposed since 2000, each based on different views of brain organization. Researchers from each model group have now agreed on an integrated Visual Hallucination Framework that aligns with current theories of both real and hallucinatory vision. The Framework identifies cognitive systems involved in hallucinations and enables systematic investigation of how hallucination experiences relate to changes in underlying cognitive structures. The episodic nature of hallucinations points to separate factors for their onset, persistence, and end, suggesting a complex relationship between temporary states and long-term traits of hallucination risk. The Framework also suggests new research directions and potential treatments for distressing hallucinations.
Coloured hearing synaesthetes experience colors when hearing words, and some also experience the 'alien colour effect' (ACE), where color names trigger a different color than the one named. The ACE slows color naming in a Stroop task, reflecting cognitive interference from consciously experienced synaesthetic colors. Functional magnetic resonance imaging shows that hippocampal activation distinguishes synaesthetes with the ACE from those without it and from non-synaesthetes. These findings challenge reductive functionalism, which identifies mental states with causal roles. In synaesthesia, color qualia arise from both hearing words and seeing surfaces, and in the ACE these functions oppose each other, providing empirical grounds to argue that reductive functionalism cannot account for conscious experiences.