title: Assessing attention and cognitive function in completely locked-in state with event-related brain potentials and epidural electrocorticography.
abstract: OBJECTIVE
  Patients in the completely locked-in state (CLIS), due to, for example, amyotrophic lateral sclerosis (ALS), no longer possess voluntary muscle control. Assessing attention and cognitive function in these patients during the course of the disease is a challenging but essential task for both nursing staff and physicians.
  
  
  METHODS
  An electrophysiological cognition test battery, including auditory and semantic stimuli, was applied in a late-stage ALS patient at four different time points during a six-month epidural electrocorticography (ECoG) recording period. Event-related cortical potentials (ERP), together with changes in the ECoG signal spectrum, were recorded via 128 channels that partially covered the left frontal, temporal and parietal cortex.
  
  
  RESULTS
  Auditory but not semantic stimuli induced significant and reproducible ERP projecting to specific temporal and parietal cortical areas. N1/P2 responses could be detected throughout the whole study period. The highest P3 ERP was measured immediately after the patient's last communication through voluntary muscle control, which was paralleled by low theta and high gamma spectral power. Three months after the patient's last communication, i.e., in the CLIS, P3 responses could no longer be detected. At the same time, increased activity in low-frequency bands and a sharp drop of gamma spectral power were recorded.
  
  
  CONCLUSIONS
  Cortical electrophysiological measures indicate at least partially intact attention and cognitive function during sparse volitional motor control for communication. Although the P3 ERP and frequency-specific changes in the ECoG spectrum may serve as indicators for CLIS, a close-meshed monitoring will be required to define the exact time point of the transition.
authors.affiliation: Division of Functional and Restorative Neurosurgery & Division of Translational Neurosurgery, Department of Neurosurgery, Eberhard Karls University Tuebingen, Germany. Department of Computer Engineering, Wilhelm-Schickard Institute for Computer Science, Eberhard Karls University Tuebingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Bensch
authors.forename: Suzanne
authors.initials: S
authors.lastname: Martens
authors.forename: Sebastian
authors.initials: S
authors.lastname: Halder
authors.forename: Jeremy
authors.initials: J
authors.lastname: Hill
authors.forename: Femke
authors.initials: F
authors.lastname: Nijboer
authors.forename: Ander
authors.initials: A
authors.lastname: Ramos
authors.forename: Niels
authors.initials: N
authors.lastname: Birbaumer
authors.forename: Martin
authors.initials: M
authors.lastname: Bogdan
authors.forename: Boris
authors.initials: B
authors.lastname: Kotchoubey
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Rosenstiel
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schölkopf
authors.forename: Alireza
authors.initials: A
authors.lastname: Gharabaghi
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis / Q000503:physiopathology; D001288:Attention / Q000502:physiology*; D003071:Cognition / Q000502:physiology*; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000295:instrumentation / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D008297:Male; D011782:Quadriplegia / Q000175:diagnosis / Q000503:physiopathology*