An emerging idea in theoretical neuroscience is that what really matters for consciousness in the brain are not so much activity levels, access to sensory inputs or neural synchronization per se,  but rather the ability of different areas of the thalamocortical system to interact causally with each other to form an integrated whole. In particular, the Information Integration Theory of Consciousness (IITC) argues that consciousness is integrated informationand that the brain should be able to generate consciousness to the extent that it has a large repertoire of available states (information), yet it cannot be decomposed into a collection of causally independent subsystems (integration). To evaluate the ability to integrate information among distributed cortical regions, it may not be sufficient to observe the brain in action. Instead, it is useful to employ a perturbational approach to measure effective connectivity and to examine to what extent different regions of the thalamocortical system can interact causally ( integration) and produce specific responses (information). Thanks to a recently developed technique, transcranial  magnetic stimulation and high-density electroencephalography (TMS/EEG), one can record the immediate reaction of the entire thalamocortical system to controlled perturbations of different cortical areas. During my talk I will show that TMS/EEG can detect clear-cut changes in the ability of the thalamocortical system to integrate information when the level of consciousness fluctuates across the sleep-wake cycle, when consciousness is reduced by the administration of different anaesthetics (midazolam and propofol) and when consciousness is impaired by pathological processes (in coma, vegetative state and minimally conscious patients). Based on these results, we discuss the potential applications of this novel technique to evaluate objectively the brain’s capacity for consciousness at the bedside of brain injured patients.

Video registration (1h40min)

Podcast interview (39min)