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ARTICLES: C. Schnakers, F. Perrin, M. Schabus, S. Majerus, D. Ledoux, P. Damas, M. Boly, A. Vanhaudenhuyse, M. -A. Bruno, G. Moonen, and S. Laureys Voluntary brain processing in disorders of consciousness Neurology 2008; 71: 1614-1620 [Abstract] [Full text] [PDF]

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Voluntary brain processing in disorders of consciousness

Iraj Derakhshan   (1 April 2009)

Reply from the authors

Caroline Schnakers, S. Laureys   (1 April 2009)

Voluntary brain processing in disorders of consciousness 1 April 2009
Iraj Derakhshan, Private practice 415 Morris Street, Suite 401, Charleston, WV 25301 Send Correspondence to journal: Re: Voluntary brain processing in disorders of consciousness idneuro{at}hotmail.com Iraj Derakhshan	I congratulate Schnakers and colleagues for exploring event-related cortical potentials (ERPs) in ascertaining awareness in those with disorders of consciousness. [1] The method used by the authors may be further improved by employing the recently described concept of directionality in callosal traffic that underpins lateralities of motor and sensory control including speech. [2,3] This method would entail selecting signals from lateral frontal lobes (i.e., C3, C4) instead of the central leads. In this method, patients are requested to imagine moving their right and left hands. This would have enabled the authors to document earlier onset of signals from the major hemisphere. There is also occurrence of bi-hemispheric activity when patients imagine moving the non-dominant side as the signal appears first in the major and then minor hemisphere. This is because the commands traverse the corpus callosum for moving the non-dominant side. This modification would have confirmed the presence of conscious awareness in their patients. [4,5] References 1. Schnakers C, Perrin F, Schabus M, et al. Voluntary brain processing in disorders of consciousness. Neurology 2008;71:1614-1620. 2. Derakhshan I. Nonconvulsive status epilepticus with an unusual EEG: a fresh look at lateralities of motor control and awareness. Epilepsy Behav 2006; 9:204-210. 3.Derakhshan I. Laterality of Motor Control and its Robotic Applications: A Paper and Pencil Method for Lateralizing the Major (Action, Thought) Hemisphere. In: Proceedings of the 2008 international conference on bioinformatics and computational biology, Las Vegas Nevada, edited by Arabnia HR, Yang HQ, Yang JY, Las Vegas NV, CSREA Press, 2008, vol. 2, PP 775-786 [online]. Available at: www.mimickingman.com . Accessed February 24, 2009 4. Sabaté M, González B, Rodríguez M. Brain lateralization of motor imagery: motor planning asymmetry as a cause of movement lateralization. Neuropsychologia 2004;42:1041-1049. 5. Wisneski KJ, Anderson N, Schalk G, Smyth M, Moran D, Leuthardt EC. Unique cortical physiology associated with ipsilateral hand movements and neuroprosthetic implications. Stroke 2008;39:3351-3359. Disclosure: The author reports no disclosures.
Reply from the authors 1 April 2009
Caroline Schnakers, Centre de Recherches du Cyclotron Sart Tilman, B30, University of Liège, 4000 Liège, Belgium, S. Laureys Send Correspondence to journal: Re: Reply from the authors c.schnakers{at}hotmail.com Caroline Schnakers, et al.	We thank Dr. Derakhshan for his comments and concur that there is a need to develop sensitive techniques to detect signs of conscious brain activity in severely brain injured patients recovering from coma. In our paper, we described an active ERP paradigm which allowed us to detect voluntary brain activity even in minimally conscious patients with low behavioral responses. [1] Dr. Derakhshan suggests that, based on the concept of directionality in callosal traffic, [2,3] we could improve our methods using motor imagery. [4,5] A mental imagery paradigm has previously been developed [6] and administered to patients with disorders of consciousness using fMRI. This paradigm allowed detecting conscious brain activity in a patient diagnosed as being in a vegetative state. [7] In our article, we wanted to investigate the possibility of detecting signs of consciousness in severely brain injured patients by using an active ERP paradigm as this electrophysiological technique can be used at the patient’s bedside and is easier and less expensive to perform than fMRI. In addition, our goal was to assess remnant cognitive functioning existing in these patients. Our paradigm implies a series of cognitive components such as attention and working memory which are suggested to play key roles in consciousness. [8] However, these components in patients recovering from coma have not been investigated. This population is particularly useful to study the concept of consciousness via the progressive recovery of its most basic aspects. Our article does not suggest that this paradigm is the only one to detect conscious brain activity but proposes one active paradigm which can be used in a clinical setting. Moreover, our approach demonstrates the complex remnant cognitive activity existing in minimally conscious patients and even in patients who manifest few behavioral signs of consciousness. Our findings also confirm that ambiguous behavioral signs including visual fixation—considered by the Aspen workgroup/USA as a sign of consciousness [9] but not by the Royal College of Physicians/UK [10] — are truly reflecting non-reflex behavior. Finally, our study underlines the need for further investigation of residual cognition in these patients thereby improving our understanding of the cognitive components that are essential to be minimally conscious. References 6. Boly M, Coleman MR, Davis MH, et al. When thoughts become action: an fMRI paradigm to study volitional brain activity in non-communicative brain injured patients. Neuroimage 2007;36:979-992. 7. Owen A, Coleman M, Boly M, Davis MH, Laureys S, Pickard J. Detecting awareness in the vegetative state. Science 2006;313:1402. 8. Zeman A. What in the world is consciousness? Prog Brain Res 2005;150:1-10. 9. Giacino J, Ashwal S, Childs N, et al. The minimally conscious state: Definition and diagnostic criteria. Neurology 2002;58:349-353. 10. Working Party of the Royal College of Physicians. The vegetative state: guidance on diagnosis and management. Clin Med 2003;3:249-254. Disclosure: The authors report no disclosures.