The following is a summary of “Pupil dilation response elicited by violations of auditory regularities is a promising but challenging approach to probe consciousness at the bedside,” published in the November 2023 issue of Neurology by Sangare et al.

The pupil dilation response (PDR) has been suggested as a potential indicator of conscious awareness towards sensory stimuli, notably their novelty. In a previous study involving healthy participants, their research adapted an auditory paradigm known as the “local-global” paradigm, revealing that deviations from global regularity elicited a noticeable PDR. Interestingly, this effect was observed solely in participants who could consciously recognize these deviations without specific instructions. 

In this recent study, researchers applied a similar approach to 24 non-communicative patients affected by a Disorder of Consciousness (DoC). The study group aimed to compare PDR against Event-Related Potentials (ERPs) concerning their diagnostic and prognostic accuracy. At a collective level, the global effect of PDR was not identifiable among DoC patients. However, on an individual level, the sole patient exhibiting a PDR global effect was diagnosed in a Minimally Conscious State (MCS) and later regained consciousness within six months. Distinguishing between regular and irregular trials notably enhanced DoC patients’ PDR diagnostic and prognostic capabilities. While pupillometry holds promise as a tool for probing consciousness and cognition, it necessitates methodological enhancements to increase signal clarity and reliability when evaluating consciousness in individuals with DoC.

The pupil dilation response (PDR) shows potential as a measure of conscious access to stimuli. In a study involving non-communicating patients with a Disorder of Consciousness (DoC), the investigators explored PDR compared to Event-Related Potentials (ERPs) for diagnostic and prognostic insights. While PDR did not exhibit a group-level global effect in DoC patients, an individual patient who showed a PDR global effect was diagnosed in a Minimally Conscious State (MCS) and regained consciousness within six months. Comparing the most regular and irregular trials notably amplified the diagnostic and prognostic capabilities of PDR among DoC patients. However, further methodological improvements in pupillometry are crucial to increasing signal-to-noise ratio and robustness when investigating consciousness and cognition in DoC patients.

Source: nature.com/articles/s41598-023-47806-1