Abstract
Estimating cognitive abilities in patients suffering from Disorders of Consciousness remains challenging. One cognitive task to address this issue is the so-called own name paradigm, in which subjects are presented with first names including the own name. In the active condition, a specific target name has to be silently counted. We recorded EEG during this task in 24 healthy controls, 8 patients suffering from Unresponsive Wakefulness Syndrome (UWS) and 7 minimally conscious (MCS) patients. EEG was analysed with respect to amplitude as well as phase modulations and connectivity. Results showed that general reactivity in the delta, theta and alpha frequency (event-related de-synchronisation, ERS/ERD, and phase locking between trials and electrodes) toward auditory stimulation was higher in controls than in patients. In controls, delta ERS and lower alpha ERD indexed the focus of attention in both conditions, late theta ERS only in the active condition. Additionally, phase locking between trials and delta phase connectivity was highest for own names in the passive and targets in the active condition. In patients, clear stimulus-specific differences could not be detected. However, MCS patients could reliably be differentiated from UWS patients based on their general event-related delta and theta increase independent of the type of stimulus. In conclusion, the EEG signature of the active own name paradigm revealed instruction-following in healthy participants. On the other hand, DOC patients did not show clear stimulus-specific processing. General reactivity toward any auditory input, however, allowed for a reliable differentiation between MCS and UWS patients.Electronic supplementary materialThe online version of this article (doi:10.1007/s00415-016-8150-z) contains supplementary material, which is available to authorized users.
Highlights
Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Laboratory for Sleep and Consciousness Research, Department of Psychology, University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, AustriaCentre for Cognitive Neuroscience (CCNS), University of Salzburg, Salzburg, AustriaApallic Care Unit, Neurological Division, Albert-SchweitzerKlinik, Graz, AustriaApallic Care Unit, Neurological Division, Sozialmedizinisches Zentrum Ost-Donauspital, Vienna, AustriaAfter severe brain injury, some patients do not or not fully regain consciousness
Results showed that general reactivity in the delta, theta and alpha frequency toward auditory stimulation was higher in controls than in patients
We only considered a target vs. other name difference a real effect, when it was present in the active condition, but not evident as a ‘‘target-to-be vs. other name effect’’ in the passive condition
Summary
Some patients do not or not fully regain consciousness The former are considered unresponsive, i.e., suffer from an Unresponsive Wakefulness Syndrome (UWS), meaning they open their eyes spontaneously but do not show any sign of consciousness of themselves or their environment. The latter group is diagnosed with Minimally Conscious State (MCS), which subsumes a broad range of patients who show weak behavioural signs of consciousness such as visual pursuit or the ability to follow simple commands. The clinical diagnosis is usually based on the evaluation of the
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