abstract Steven Laureys

Steven Laureys (Coma Science Group, University and University Hospital of Liège, Belgium)

The neural correlate of consciousness: lessons from brain injury and coma.

The past 15years have provided an unprecedented collection of discoveries that bear upon our scientific understanding of recovery of consciousness in the human brain following severe brain damage. Highlighted among these discoveries are unique demonstrations that patients with little or no behavioral evidence of conscious awareness may retain critical cognitive capacities and the first scientific demonstrations that some patients, with severely injured brains and very longstanding conditions of limited behavioral responsiveness, may nonetheless harbor latent capacities for recovery. Included among such capacities are particularly human functions of language and higher-level cognition that either spontaneously or through direct interventions may reemerge even at long time intervals or remain unrecognized.

An improved assessment of brain function in coma and related states is not only changing nosology and medical care but also offers a better-documented diagnosis and prognosis and helps to further identify the neural correlates of human consciousness. Taken together, recent studies show that awareness is an emergent property of the collective behavior of frontoparietal top-down connectivity. Within this network, external (sensory) awareness depends on lateral prefrontal/parietal cortices while internal (self) awareness correlates with precuneal/mesiofrontal midline activity. Of clinical importance, this knowledge now permits to improve the diagnosis of patients with disorders of consciousness, which remains very challenging at the bedside. Current technology now also permits to show command-specific changes in EEG or fMRI signals providing motor-independent evidence of conscious thoughts and in come cases even of communication. We will conclude by discussing related ethical issues and the challenge of measuring and improving quality of life in these challenging patients with disorders of consciousness.