Table 1 Selected neuroimaging studies in which patients were enrolled

Naci and Owen [25]

fMRI

To determine whether fMRI can detect selective attention command following and communication

Three patients with PDoC were capable of selective attention command following. Two of these patients also responded correctly to yes/no questions

Beukema et al. [4]

EEG

To determine whether event-related potentials can detect preserved auditory processing

All enrolled patients with PDoC (N = 16) showed preserved auditory processing. Seven showed differentiated speech from noise

Gibson et al. [26]

EEG and fMRI

To determine whether somatosensory functions can serve as proxies for covert consciousness as compared to fMRI or clinical evaluation

Only those patients with PDoC who were capable of fMRI or behavioral command following also demonstrated relevant somatosensory functions

Naci et al. (27)

fMRI

To determine whether fMRI can detect covert consciousness with naturalistic stimuli (e.g., viewing a movie)

A model of cognitive changes during movie viewing was developed in healthy participants. Cognitive changes in one patient with PDoC were identical to those in the model while viewing the movie