title: Single-trial decoding of auditory novelty responses facilitates the detection of residual consciousness.
abstract: Detecting residual consciousness in unresponsive patients is a major clinical concern and a challenge for theoretical neuroscience. To tackle this issue, we recently designed a paradigm that dissociates two electro-encephalographic (EEG) responses to auditory novelty. Whereas a local change in pitch automatically elicits a mismatch negativity (MMN), a change in global sound sequence leads to a late P300b response. The latter component is thought to be present only when subjects consciously perceive the global novelty. Unfortunately, it can be difficult to detect because individual variability is high, especially in clinical recordings. Here, we show that multivariate pattern classifiers can extract subject-specific EEG patterns and predict single-trial local or global novelty responses. We first validate our method with 38 high-density EEG, MEG and intracranial EEG recordings. We empirically demonstrate that our approach circumvents the issues associated with multiple comparisons and individual variability while improving the statistics. Moreover, we confirm in control subjects that local responses are robust to distraction whereas global responses depend on attention. We then investigate 104 vegetative state (VS), minimally conscious state (MCS) and conscious state (CS) patients recorded with high-density EEG. For the local response, the proportion of significant decoding scores (M=60%) does not vary with the state of consciousness. By contrast, for the global response, only 14% of the VS patients' EEG recordings presented a significant effect, compared to 31% in MCS patients' and 52% in CS patients'. In conclusion, single-trial multivariate decoding of novelty responses provides valuable information in non-communicating patients and paves the way towards real-time monitoring of the state of consciousness.
authors.affiliation: Cognitive Neuroimaging Unit, Institut National de la Santé et de la Recherche Médicale, U992, F-91191 Gif/Yvette, France; NeuroSpin Center, Institute of BioImaging Commissariat à l'Energie Atomique, F-91191 Gif/Yvette, France; Institut du Cerveau et de la Moelle Épinière Research Center, Institut National de la Santé et de la Recherche Médicale, U975 Paris, France. Electronic address: jeanremi.king@gmail.com.
authors.forename: J R
authors.initials: JR
authors.lastname: King
authors.forename: F
authors.initials: F
authors.lastname: Faugeras
authors.forename: A
authors.initials: A
authors.lastname: Gramfort
authors.forename: A
authors.initials: A
authors.lastname: Schurger
authors.forename: I
authors.initials: I
authors.lastname: El Karoui
authors.forename: J D
authors.initials: JD
authors.lastname: Sitt
authors.forename: B
authors.initials: B
authors.lastname: Rohaut
authors.forename: C
authors.initials: C
authors.lastname: Wacongne
authors.forename: E
authors.initials: E
authors.lastname: Labyt
authors.forename: T
authors.initials: T
authors.lastname: Bekinschtein
authors.forename: L
authors.initials: L
authors.lastname: Cohen
authors.forename: L
authors.initials: L
authors.lastname: Naccache
authors.forename: S
authors.initials: S
authors.lastname: Dehaene
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001921:Brain / Q000502:physiology; D003243:Consciousness / Q000502:physiology*; D003244:Consciousness Disorders / Q000503:physiopathology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult
keywords: Decoding; EEG; MEG; Minimally conscious state; Multivariate pattern classifier; Unresponsive wakefulness syndrome; Vegetative state