Article

Improving our ability to detect conscious processing in non communicating
patients remains a major goal of clinical cognitive neurosciences. In this
perspective, several functional brain imaging tools are currently under
development. Bedside cognitive event-related potentials (ERPs) derived from the
EEG signal are a good candidate to explore consciousness in these patients
because: (1) they have an optimal time resolution within the millisecond range
able to monitor the stream of consciousness, (2) they are fully non-invasive and
relatively cheap, (3) they can be recorded continuously on dedicated individual
systems to monitor consciousness and to communicate with patients, (4) and they
can be used to enrich patients' autonomy through brain-computer interfaces. We
recently designed an original auditory rule extraction ERP test that evaluates
cerebral responses to violations of temporal regularities that are either local
in time or global across several seconds. Local violations led to an early
response in auditory cortex, independent of attention or the presence of a
concurrent visual task, while global violations led to a late and spatially
distributed response that was only present when subjects were attentive and aware
of the violations. In the present work, we report the results of this test in 65
successive recordings obtained at bedside from 49 non-communicating patients
affected with various acute or chronic neurological disorders. At the individual
level, we confirm the high specificity of the 'global effect': only conscious
patients presented this proposed neural signature of conscious processing. Here,
we also describe in details the respective neural responses elicited by
violations of local and global auditory regularities, and we report two
additional ERP effects related to stimuli expectancy and to task learning, and we
discuss their relations to consciousness.
CI - Copyright (c) 2012 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS