Postersession 1
Poster #: 13
Topic: Clinical applications (incl. consciousness)
Wednesday, Sep 9, 2015
1st floor

Improving the detection of voluntary processes in behaviorally unresponsive patients at bedside using an oddball paradigm

Dominique Morlet1, Perrine Ruby2, Nathalie André-Obadia3, & Catherine Fischer3

1Dycog Team, Lyon Neuroscience Research Center INSERM U1028, BRON cedex, France
2Dycog Team, INSERM U1028, BRON cedex, France
3Service de neurophysiologie et d’épileptologie, Hospices Civils de Lyon, Hôpital Neurologique, BRON cedex, France

In prolonged disorders of consciousness, patients show poor or non-existent interaction with the environment. Clinical assessment is powerless to assess the actual level of consciousness in these behaviorally unresponsive patients. Neuroimaging techniques have been recently used (fMRI or EEG) in an attempt to find evidence of brain signals reflecting covert consciousness, where the conscious modulation of brain signal was obtained using paradigms requiring voluntary participation of the subject (perform mental imagery or count targets).

We designed a new EEG paradigm for better detection of willful modulations of attention at the patient's bedside. A standard auditory oddball paradigm was used. First, the subjects passively heard the auditory stimuli. Then, subjects were required to focus their attention away from the stimuli using a mental imagery task (diverted attention) and finally the subjects were instructed to count auditory deviants (focused attention). Contrasting the condition of focused attention with a new condition of actively diverted attention, we expected an improved effect as compared with a classical active/passive contrast.

Indeed, in 20 healthy subjects, the contrast between diverted attention and focused attention was larger than between passive listening and focused attention. Event-related responses to auditory standard and deviant stimuli were significantly modulated by attention manipulation, not only at the group level but also at the individual level, thus providing clinically useful markers of voluntary processes.

Preliminary results show that this active paradigm can provide evidence of some conscious cooperation in unresponsive patients.