Validation of New Consciousness Indicators in Conscious Participants

The assessment of the diagnosis and prognosis of patients with disorders of consciousness (DoC) represents a major clinical and ethical challenge, as it may influence therapeutic decision-making. Despite the use of standardized assessment tools such as the Coma Recovery Scale-Revised (CRS-R), diagnostic errors persist. In order to improve the identification of residual conscious activity, several research studies have focused on identifying and validating new clinical indicators of consciousness.

In addition to the items already included in the CRS-R to characterize a minimally conscious state, some behavioral manifestations that are not yet included in current assessment scales are being investigated for their diagnostic potential. Mat et al. (2022) proposed several behavioral indicators, including leg crossing, auditory localization, habituation to the auditory startle reflex, resistance to eye opening, spontaneous blink rate, certain motor behaviors, facial expressions in response to nociceptive stimulation, swallowing or oral intake, and responses to olfactory stimuli. To these indicators, we added other potentially relevant behavioral manifestations, including responses to tickling, anticipation of painful stimulation, and responses to pleasant touch.

These different items were grouped into an Additional Signs of Consciousness (ASC) Scale. This scale aims to investigate whether these behavioral manifestations may constitute reliable new indicators of consciousness and contribute to improving the diagnostic and prognostic assessment of patients with DoC.

To date, this scale has primarily been used in post-coma patients with DoC. However, it is essential to assess the validity of these indicators in healthy, fully conscious participants. Indeed, the relevance of these signs as indicators of residual consciousness in post-coma patients can only be properly interpreted if they are also observable in conscious individuals. Therefore, the aim of this study is to validate these new indicators of consciousness in conscious participants.