Martin M Monti1, Matthew Rosenberg2, Paola Finoia2, Evelyn Kamau2, John D Pickard2, Adrian M Owen2. 1. From the Department of Psychology (M.M.M., M.R.), University of California Los Angeles; the Department of Neurosurgery (M.M.M.), Brain Injury Research Center (BIRC), Geffen School of Medicine at UCLA, Los Angeles; the Cognition and Brain Sciences Unit (P.F.), Medical Research Council, Cambridge; the Division of Neurosurgery (P.F., E.K., J.D.P.), University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; and the Natural Science Building (A.M.O.), Brain & Mind Institute, The University of Western Ontario, London, Canada. monti@psych.ucla.edu. 2. From the Department of Psychology (M.M.M., M.R.), University of California Los Angeles; the Department of Neurosurgery (M.M.M.), Brain Injury Research Center (BIRC), Geffen School of Medicine at UCLA, Los Angeles; the Cognition and Brain Sciences Unit (P.F.), Medical Research Council, Cambridge; the Division of Neurosurgery (P.F., E.K., J.D.P.), University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; and the Natural Science Building (A.M.O.), Brain & Mind Institute, The University of Western Ontario, London, Canada.
Abstract
OBJECTIVE: We employed functional MRI (fMRI) to assess whether (1) patients with disorders of consciousness (DOC) retain the ability to willfully engage in top-down processing and (2) what neurophysiologic factors distinguish patients who can demonstrate this ability from patients who cannot. METHODS: Sixteen volunteers, 8 patients in vegetative state (VS), 16 minimally conscious patients (MCS), and 4 exit from MCS (eMCS) patients were enrolled in a prospective cross-sectional fMRI study. Participants performed a target detection task in which they counted the number of times a (changing) target word was presented amidst a set of distractors. RESULTS: Three of 8 patients diagnosed as being in a VS exhibited significant activations in response to the task, thereby demonstrating a state of consciousness. Differential activations across tasks were also observed in 6 MCS patients and 1 eMCS patient. A psycho-physiologic interaction analysis revealed that the main factor distinguishing patients who responded to the task from those who did not was a greater connectivity between the anterior section of thalamus and prefrontal cortex. CONCLUSIONS: In our sample of patients, the dissociation between overt behavior observable in clinical assessments and residual cognitive faculties is prevalent among DOC patients (37%). A substantial number of patients, including some diagnosed with VS, can demonstrate willful engagement in top-down cognition. While neuroimaging data are not the same as observable behavior, this suggests that the mental status of some VS patients exceeds what can be appreciated clinically. Furthermore, thalamo-frontal circuits might be crucial to sustaining top-down functions.
OBJECTIVE: We employed functional MRI (fMRI) to assess whether (1) patients with disorders of consciousness (DOC) retain the ability to willfully engage in top-down processing and (2) what neurophysiologic factors distinguish patients who can demonstrate this ability from patients who cannot. METHODS: Sixteen volunteers, 8 patients in vegetative state (VS), 16 minimally conscious patients (MCS), and 4 exit from MCS (eMCS) patients were enrolled in a prospective cross-sectional fMRI study. Participants performed a target detection task in which they counted the number of times a (changing) target word was presented amidst a set of distractors. RESULTS: Three of 8 patients diagnosed as being in a VS exhibited significant activations in response to the task, thereby demonstrating a state of consciousness. Differential activations across tasks were also observed in 6 MCS patients and 1 eMCS patient. A psycho-physiologic interaction analysis revealed that the main factor distinguishing patients who responded to the task from those who did not was a greater connectivity between the anterior section of thalamus and prefrontal cortex. CONCLUSIONS: In our sample of patients, the dissociation between overt behavior observable in clinical assessments and residual cognitive faculties is prevalent among DOC patients (37%). A substantial number of patients, including some diagnosed with VS, can demonstrate willful engagement in top-down cognition. While neuroimaging data are not the same as observable behavior, this suggests that the mental status of some VS patients exceeds what can be appreciated clinically. Furthermore, thalamo-frontal circuits might be crucial to sustaining top-down functions.
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