2.2 fMRI demonstrates covert consciousness despite fluctuations in responsiveness
In the following period (weeks 9-10-11) the patient continued to show significant variations in behavioral responsiveness (CRS-R total score ranging from 5 to 9) corresponding to transitions between a VS/UWS and a MCS- diagnosis. However, the clinical evolution and the consistently high values of brain complexity, suggested the possibility of an underlying state of covert consciousness amidst large fluctuations in behavioral responsiveness. To test this hypothesis, we evaluated the patient during a period of unresponsiveness (week 6, CRS-R=6; diagnosis VS/UWS) employing a fMRI paradigm whereby covert consciousness can be demonstrated with high specificity based on the patient’s ability to modulate brain activity in response to verbal commands (Owen et al. , 2006; Monti et al. , 2010; Owen, 2013). In particular, the fMRI paradigm (ABAB block design) consisted of a simple command-following task (Bekinschtein et al. , 2011; Curleyet al. , 2018) that prompted the patient to actually perform the motoric action of opening and closing the left or the right hand, even if incapable of doing so. The fMRI EPI* sequence was acquired on the same 3T Siemens Prisma scanner (resolution:3x3x3mm3; matrix:80x80; TR/TE: 2000ms/30ms). As shown in Figure 5, when comparing right-hand commands vs rest, a consistent blood-oxygen-level-dependent (BOLD) activation of left superior temporal and premotor cortices was revealed.