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A study by Fernández-Espejo et al1 in this issue of JAMA Neurology addresses the important question of what underlying brain mechanisms may account for the sharp dissociation of a retained but unrecognized (covert) cognitive capacity in some severely brain-injured patients with nonpurposeful or absent behavioral responses. During the past 10 years, several studies2- 8 have exposed the challenging problem of understanding the biological basis and meaning of such covert cognition measured by neuroimaging or electrophysiologic techniques in patients who have complex injuries involving the central nervous system. Across many different methods tested in the literature,8 those using motor imagery techniques provide a proxy for command-following behaviors2- 7 and unequivocal evidence, when identified, of higher-level cognitive capacities in patients otherwise fulfilling behavioral criteria for the vegetative state or low-level, minimally conscious state.8 Understanding of the possible mechanisms underlying this marked dissociation of motor and cognitive function is slowly emerging.3- 7
Schiff ND. Cognitive Motor Dissociation Following Severe Brain Injuries. JAMA Neurol. 2015;72(12):1413-1415. doi:10.1001/jamaneurol.2015.2899