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

PLoS One. 2018 Nov 7;13(11):e0205967. doi: 10.1371/journal.pone.0205967. eCollection 2018.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Consciousness Disorders / diagnostic imaging*
  • Consciousness Disorders / physiopathology
  • Electroencephalography
  • Humans
  • Microelectrodes
  • Neurons / physiology
  • Parietal Lobe / diagnostic imaging*
  • Parietal Lobe / physiopathology
  • Persistent Vegetative State / diagnostic imaging
  • Persistent Vegetative State / physiopathology
  • Thalamus / diagnostic imaging*
  • Thalamus / physiopathology

Grants and funding

This study was supported by a grant (ricerca corrente 08019701/08) to Roberto Imberti and Lorenzo Magrassi from the Fondazione I.R.C.C.S. Policlinico S. Matteo. The funding source had no role in the study design or implementation.