Hallucinations may not be fundamentally different from normal conscious experiences; both arise from the same neural processes. Conscious experience reflects the formation of event (episodic) memories, linking hallucinations to the hippocampus. Perceptions and misperceptions are manifestations of activity patterns that recurrently emerge in the CA3 network of the hippocampus, which forms allocentric representations of objects in context. The hippocampus integrates sensory information, emotional context, and guides decision-making via the medial prefrontal cortex. Disruptions in relational memory processing in the hippocampus can give rise to hallucinations. Neurobiological and neuroimaging findings in schizophrenia research support this framework.
Unitary conscious experience can be defined as a symbolic representation of the pattern of hippocampal neuronal firing that encodes an event memory. At each cycle of the θ rhythm, the hippocampus rapidly forms event codes that integrate object information from the ventral visual stream and orbitofrontal cortex, contextual emotional information from the anterior insula, and spatial environmental information from the dorsal visual stream. These event codes, formed in the CA3-dentate network for memorization, are allocentric representations, similar to conscious experiences of events in a seemingly objective framework of phenomenal space and time. Conscious perception is evolutionarily related to autobiographical memory recall, mental imagery, dreaming, and hallucinations, and evidence for hippocampal contributions to these phenomena is reviewed.