Serious cerebrum wounds or head injuries in people can prompt different phases of purported problems of cognizance (DoC). Consciousness is either partially or completely absent in these states, such as a coma, a condition known as unresponsive wakefulness syndrome or a vegetative state, and a state of minimal awareness.
Because it enables medical professionals to determine which treatments to administer and how to facilitate the re-emergence of consciousness, accurately evaluating patients who have lost consciousness is of the utmost significance. When conducting a clinical evaluation of consciousness, doctors typically observe how patients respond to sensory stimuli like sounds or images.
Patients with MCS, on the other hand, exhibit some behaviors that indicate that they are conscious, whereas patients in a vegetative state are awake but continue to be unresponsive to external stimuli. The majority of current approaches to determining a patient’s level of consciousness are based on visual or auditory cues, but olfactory cues may also be useful.
Scientists at Southern Clinical College in China have recently done a review of the reactions of patients in a state of insensibility or vegetative state to smells to comprehend whether they could be utilized to assess cognizance. The potential of olfactory stimuli for assessing consciousness in clinical settings appears to be highlighted by their findings, which were published in Frontiers in Neuroscience.
“The purpose of this study was to see if olfactory response can be a sign of consciousness and represent higher cognitive processing in patients with disorders of consciousness (DoC) using clinical and electroencephalogram data.”
Wanchun Wu, Chengwei Xu, and their colleagues wrote in their paper.
Wanchun Wu, Chengwei Xu, and their colleagues wrote in their paper, “This study aimed to explore whether olfactory response can be a sign of consciousness and represent higher cognitive processing in patients with disorders of consciousness (DoC) using clinical and electroencephalogram data.”
The researchers looked at how 28 patients at various stages of DoC responded to olfactory stimuli as part of their study. Thirteen of these patients were in a vegetative state (UMS), while fifteen were in MCS. Based on whether or not they responded to olfactory stimuli, the study participants were divided into two groups.
Wu, Xu, and their colleagues wrote, “We recorded an olfactory task-related electroencephalogram (EEG) and analyzed the relative power and functional connectivity at the whole-brain level in the patients with DoC and healthy controls (HCs). “The coma recovery scale-revised (CRS-R)” [a standard assessment used to measure DoC in clinical settings] was used to monitor the outcomes of DoC patients after three months.
When Wu, Xu, and their colleagues looked over the data they had gathered, they discovered that the patients’ levels of consciousness were related to their olfactory responses. After being exposed to the vanillin scent, patients in the no-olfactory response group displayed higher theta functional connectivity than those in the olfactory response group, as well as lower alpha and beta relative powers than healthy participants who had no DoC. Three months later, follow-up data revealed that 10 out of 16 of the patients who responded to olfactory stimuli during the study had recovered consciousness, whereas only 2 out of the 12 participants who did not respond to olfactory stimuli This suggests that a brain response to olfactory stimuli typically indicates that DoC patients are gradually regaining consciousness.
This team’s research could help develop new methods for determining the level of consciousness of patients with varying DoC in the future, as well as other studies looking into the connection between consciousness and brain responses to smells.
In their paper, Wu, Xu, and their colleagues explained that “olfactory responses should be considered signs of consciousness.” The neural correlates of olfactory consciousness in DoC patients could be investigated by comparing the differences in olfactory processing between patients with and without olfactory responses. The olfactory response may aid in consciousness evaluation and aid in therapeutic orientation.”
More information: Wanchun Wu et al, Olfactory response is a potential sign of consciousness: electroencephalogram findings, Frontiers in Neuroscience (2023). DOI: 10.3389/fnins.2023.1187471.
