Single unit activities recorded in the thalamus and the overlying parietal cortex of subjects affected by disorders of consciousness

• Published in: PloS one Vol. 13; no. 11; p. e0205967
• Main Authors: Magrassi, Lorenzo, Zippo, Antonio G., Azzalin, Alberto, Bastianello, Stefano, Imberti, Roberto, Biella, Gabriele E. M.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 07.11.2018; Public Library of Science (PLoS)
• Subjects: Biology and Life Sciences; Brain; Bursting; Consciousness; Cortex (parietal); Coupling; Deep brain stimulation; EEG; Electroencephalography; Engineering and Technology; Firing pattern; Implantation; Medicine and Health Sciences; Microelectrodes; Neurons; Neurophysiology; NMR; Nuclear magnetic resonance; Patients; Pharmacology; Research and Analysis Methods; Sleep; Sleep and wakefulness; Studies; Surgery; Thalamus; Unconsciousness; Wakefulness; Italy
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0205967

The lack of direct neurophysiological recordings from the thalamus and the cortex hampers our understanding of vegetative state/unresponsive wakefulness syndrome and minimally conscious state in humans. We obtained microelectrode recordings from the thalami and the homolateral parietal cortex of two vegetative state/unresponsive wakefulness syndrome and one minimally conscious state patients during surgery for implantation of electrodes in both thalami for chronic deep brain stimulation. We found that activity of the thalamo-cortical networks differed among the two conditions. There were half the number of active neurons in the thalami of patients in vegetative state/unresponsive wakefulness syndrome than in minimally conscious state. Coupling of thalamic neuron discharge with EEG phases also differed in the two conditions and thalamo-cortical cross-frequency coupling was limited to the minimally conscious state patient. When consciousness is physiologically or pharmacologically reversibly suspended there is a significant increase in bursting activity of the thalamic neurons. By contrast, in the thalami of our patients in both conditions fewer than 17% of the recorded neurons showed bursting activity. This indicates that these conditions differ from physiological suspension of consciousness and that increased thalamic inhibition is not prominent. Our findings, albeit obtained in a limited number of patients, unveil the neurophysiology of these conditions at single unit resolution and might be relevant for inspiring novel therapeutic options.