Spectral Parameters Modulation and Source Localization of Blink-Related Alpha and Low-Beta Oscillations Differentiate Minimally Conscious State from Vegetative State/Unresponsive Wakefulness Syndrome

• Published in: PloS one Vol. 9; no. 3; p. e93252
• Main Authors: Bonfiglio, Luca, Piarulli, Andrea, Olcese, Umberto, Andre, Paolo, Arrighi, Pieranna, Frisoli, Antonio, Rossi, Bruno, Bergamasco, Massimo, Carboncini, Maria Chiara
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 27.03.2014; Public Library of Science (PLoS)
• Subjects: Activation; Adult; Aged; Alpha Rhythm; Analysis; Analysis of Variance; Beta Rhythm; Biology and Life Sciences; Biomarkers; Blinking; Brain Mapping; Brain research; Case-Control Studies; Computer and Information Sciences; Consciousness; Cortex (cingulate); Cortex (occipital); Cortex (parietal); Cortex (temporal); Diagnosis; Diagnosis, Differential; Differential diagnosis; EEG; Electroencephalography; Environmental effects; Environmental monitoring; Female; Frequencies; Gyrus Cinguli - physiopathology; Humans; Laboratories; Localization; Male; Medical research; Medicine; Medicine and Health Sciences; Memory; Middle Aged; Neurosciences; Oscillations; Patients; Persistent vegetative state; Persistent Vegetative State - diagnosis; Persistent Vegetative State - etiology; Persistent Vegetative State - physiopathology; Rehabilitation; Research and Analysis Methods; Self awareness; Sleep and wakefulness; Surgery; Synchronism; Synchronization; Syndrome; Temporal lobe; Trends; Wakefulness; Windows (intervals); Young Adult
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0093252

Recently, the cortical source of blink-related delta oscillations (delta BROs) in resting healthy subjects has been localized in the posterior cingulate cortex/precuneus (PCC/PCu), one of the main core-hubs of the default-mode network. This has been interpreted as the electrophysiological signature of the automatic monitoring of the surrounding environment while subjects are immersed in self-reflecting mental activities. Although delta BROs were directly correlated to the degree of consciousness impairment in patients with disorders of consciousness, they failed to differentiate vegetative state/unresponsive wakefulness syndrome (VS/UWS) from minimally conscious state (MCS). In the present study, we have extended the analysis of BROs to frequency bands other than delta in the attempt to find a biological marker that could support the differential diagnosis between VS/UWS and MCS. Four patients with VS/UWS, 5 patients with MCS, and 12 healthy matched controls (CTRL) underwent standard 19-channels EEG recordings during resting conditions. Three-second-lasting EEG epochs centred on each blink instance were submitted to time-frequency analyses in order to extract the normalized Blink-Related Synchronization/Desynchronization (nBRS/BRD) of three bands of interest (low-alpha, high-alpha and low-beta) in the time-window of 50-550 ms after the blink-peak and to estimate the corresponding cortical sources of electrical activity. VS/UWS nBRS/BRD levels of all three bands were lower than those related to both CTRL and MCS, thus enabling the differential diagnosis between MCS and VS/UWS. Furthermore, MCS showed an intermediate signal intensity on PCC/PCu between CTRL and VS/UWS and a higher signal intensity on the left temporo-parieto-occipital junction and inferior occipito-temporal regions when compared to VS/UWS. This peculiar pattern of activation leads us to hypothesize that resting MCS patients have a bottom-up driven activation of the task positive network and thus are tendentially prone to respond to environmental stimuli, even though in an almost unintentional way.