Contribution of hippocampal region CA3 to consciousness and schizophrenic hallucinations.

Recent advances in understanding hippocampal information processing offer new vistas on the mind-body and binding problems. Information encoded by the autoassociation network of cornu ammonis 3 (CA3) situates landmarks and objects within an allocentric framework of space and time. Guiding locomotion across the spatial environment, and generally organizing behaviour that transcends space and time, the hippocampus creates phenomenal space and time themselves, thus laying the foundations for conscious awareness. It is argued that conscious experience describes/symbolizes the informational content of self-organizing activity patterns in CA3. Imagery, conscious perception or hallucinations do not in themselves affect the physical trajectory of behaviour but are evidence for patterns of neuronal activity that, acting via the medial prefrontal cortex, modulate action dispositions and influence prefrontal top-down attentional control of sensory processing and thus subsequent event memory formation. Evidence for GABAergic deficit and pyramidal cell hyperexcitability in CA3 in patients with schizophrenia is consistent with the notion that binding, by the CA3 network, of cortical modules representing weakly related sensory representations underlies hallucinations in this disorder.