A much-debated question in the scientific study of consciousness is whether
prefrontal cortex actively determines what is consciously perceived, or rather serves cognitive functions that occur downstream of conscious experience, such as evaluating and acting on the contents of perception.

In the first part of the talk, I will present data from three experiments that investigated how prefrontal cortex contributes to the construction of unambiguous conscious experiences from ambiguous sensory information. Human participants reported periodic changes
in conscious experience that were induced by conflicting sensory information during bistable perception. Two functional magnetic resonance imaging experiments showed that prefrontal brain activity in inferior frontal cortex signals the conflict between conscious experience and available sensory information. In a third experiment, inhibitory transcranial magnetic stimulation revealed that disruption of neural activity in inferior frontal cortex leads to a decrease in conflict-driven changes in conscious experience. These results suggest that inferior frontal cortex plays a critical role in both the detection and the resolution of perceptual conflicts, pointing to a causal influence of prefrontal brain activity on the dynamic unfolding of conscious experience.

In the second part of the talk, I will present data from three studies that investigated the construction of unambiguous conscious experiences in healthy observers and patients suffering from paranoid schizophrenia. Two studies revealed ongoing changes in perception that lead to prolonged intervals of reduced and enhanced sensitivity to conflicting sensory information. A third case-control study suggested that patients suffering from paranoid schizophrenia were more sensitive to perceptual conflicts than healthy controls. Interestingly, the patients' sensitivity to perceptual conflict correlated positively with the severity of hallucinatory experiences.

I will conclude by discussing how model-based imaging and non-invasive brain stimulation of prefrontal cortex may advance the search for a therapeutic modulation of altered states of consciousness.