“…In the literature, most of the studies related to the assessment of consciousness can be divided into two broad categories, namely, (a) sensory stimulation-based and (b) resting-state based analysis methods. As opposed to the sensory stimulation-based methods, resting-state analysis ( Martinez et al, 2015 ; Schorr et al, 2016 ; Naro et al, 2018 ; Stefan et al, 2018 ; van den Brink et al, 2018 ; Cacciola et al, 2019 ; Wang et al, 2019 ) does not require the subjects to perform any specific task and it can provide valuable information about the spontaneous neural activity relevant to the fundamental brain state ( Lv et al, 2018 ). On the other hand, sensory stimulation-based methods ( Kotchoubey et al, 2005 ; Boly et al, 2007 ; Cruse et al, 2011 ; Schorr et al, 2015 ; Guger et al, 2017 ; Luauté et al, 2018 ; Schneider et al, 2018 ; Xiao et al, 2018 ; Agoiz Badia et al, 2019 ; Cacciola et al, 2019 ; Formisano et al, 2019 ; Huang et al, 2019 ; Xu et al, 2019 ) employ various modalities of sensory stimuli such as auditory, visual, olfactory, tactile and mental-imagery ( Figure 1 ) and look for the expected cerebral response corresponding to the stimuli.…”