Effects of single-modality sensory stimulation on brain function in patients with prolonged disorders of consciousness: a near-infrared spectroscopy-based study

Objective To explore the effects of four single-modality sensory stimulations on the brain functional networks in patients with prolonged disorders of consciousness (pDOC), and to clarify the correlation between different sensory stimulations and the improvement of patients’ consciousness level, so as to provide references for clinical treatment and rehabilitation of pDOC patients. Methods A prospective, multicenter, randomized controlled trial design was adopted. A total of 57 patients with pDOC were enrolled and divided into visual stimulation group, auditory stimulation group, olfactory-gustatory stimulation group, somatosensory-nocieptive stimulation group, and control group. The intervention duration of each group was 15 min. Behavioral assessments were performed using the Coma Recovery Scale-Revised (CRS-R) and Glasgow Coma Scale (GCS). Combined with functional near-infrared spectroscopy (fNIRS), hemodynamic parameters and brain functional connectivity were detected. Changes in brain function and consciousness level before and after different sensory stimulation interventions were evaluated. Results Visual, auditory and olfactory-gustatory stimulations induced significant and robust alterations in cerebral activity across most detected channels ( p < 0.001), while the cerebral response to somatosensory-nocieptive stimulation was relatively limited ( p < 0.05). At the channel activation level, viewing family photographs in visual stimulation, light music, personalized music and family voice calling in auditory stimulation, and acetic acid stimulation in olfactory-gustatory stimulation significantly activated the corresponding brain regions ( p < 0.05). At the brain functional connectivity level, viewing family photographs markedly enhanced functional connectivity within visual-related brain regions ( p < 0.05); ethanol stimulation improved functional connectivity of olfactory-gustatory brain regions ( p < 0.05). Conclusion Single-modality sensory stimulation elicits acute cerebral activation in pDOC patients, which is superior to conventional rehabilitation alone. Visual and auditory stimulations exert significantly better intervention effects than olfactory-gustatory and somatosensory-nocieptive stimulations. Among olfactory-gustatory interventions, acetic acid stimulation produces prominent brain region activation, and ethanol enhances functional connectivity of related brain regions. Both can serve as an effective supplementary intervention for pDOC patients with visual and auditory dysfunction, and possess important value for further research and clinical application in the management of pDOC.