Executive functions in the absence of behavior: functional imaging of the minimally conscious state
Section snippets
Participants
Twenty healthy volunteers (12 female) with no history of neurological disorder and one MCS patient participated in the experiment. Healthy volunteers signed informed consent prior to the experimental session. For the patient, assent was obtained from the next of kin. This study was approved by the Cambridge Local Research Ethics Committee.
Patient history
The patient was first hospitalized on October 28, 2007 after suffering a cardio-respiratory arrest, and was resuscitated in ITU (defibrillated/intubated and
Healthy volunteers
Averaging across all healthy volunteers, the target detection versus passive listening contrast revealed activations spanning frontal, temporal, and parietal cortex, along with regions of the cerebellum (see Table 1 and Fig. 2). Frontal cortex was activated bilaterally in the sub-lobar sections of the inferior frontal gyrus (BA 47), and in the middle frontal gyrus (BA 10). Activation was also observed in the right superior frontal (BA 10) and cingulate gyri (BA 32), left precentral gyrus (BA
Discussion
Compared to simple listening, the counting task elicited, in all healthy volunteers, a pattern of activation similar to that reported in previous studies of executive function, including target detection and working memory (see Naghavi and Nyberg, 2005). The very fact that the two (perceptually identical) tasks elicited different patterns of activation confirms that our paradigm does elicit the expected cognitive processes including maintenance of information through time and willful adoption
Conclusions
Detecting consciousness in brain injury survivors is critical for appropriate diagnosis and patient management (Bernat, 2006). Objective assessment on the basis of observed and elicited behavior, however, can be extremely challenging in patients with little ability for behavioral output. Use of noninvasive neuroimaging techniques to detect residual cognitive abilities and awareness may thus be crucial to reducing diagnostic error (Owen and Coleman, 2008). While there is at present limited
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2016, Progress in Brain ResearchCitation Excerpt :In one approach involving similar word stimuli as in Chennu et al. (2013), each patient was asked to select and maintain an arbitrary target word in mind throughout an experimental block (Monti et al., 2009). One patient diagnosed as in an MCS generated activation in the frontoparietal network during this task, which implied that the patient had both working memory and target detection abilities (Monti et al., 2009). Similar evidence that some patients with DoC can sustain their attention was reported by Naci and colleagues in two other fMRI studies (Naci and Owen, 2013; Naci et al., 2013).
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