Pain and consciousness
Acute pain, which is a short-lasting stimulus, is known to increase the level of consciousness. It has been proposed that sensory pain-related consciousness may provide an excellent model for studying consciousness itself (Tiengo, 2003; Gu et al. , 2013; Ambron, 2023). In patients with DOC, it has been reported that there is a strong correlation between the responsiveness to nociceptive stimuli and the level of consciousness (Thibaut et al. , 2018). These findings suggest that there is a certain overlap in neuronal circuits for pain perception and consciousness such as ACC and IC. More interestingly, it has been reported that repetitive transcranial magnetic stimulation (rTMS) over ACC was able to increase pain perception in patients with DOC (Naro et al. , 2015). Consciousness can be a result of a network within the brain that is capable of storing and retrieving key self-information. A synaptic mechanism such as plasticity may play an important role in maintaining the status of consciousness by activating certain engram synapses that are previously learned. Disruption of such network or general reduction of network activity will lead to minimal consciousness statues or loss of consciousness. Two key components that are likely important for consciousness are the storage of key information about self; and sensory signaling that recalls the consciousness. Some of this sensory information can serve as a background activity that contributes to the maintenance of consciousness; and loss of such background activity, which can be caused by visual, auditory, somatosensory, motor position, etc., may lead to sub-consciousness statues such as sleep. Therefore, it is very easy to use such sensory information to recall consciousness back from sleep. Loss of one of such sensory background activities may lead to plasticity, and one may use other sensory information such as auditory to compensate for the loss of visual information (such as deaf man). A good dancer may use body position and muscle tones to gain a better level of consciousness, and a musician may be more use auditory signaling to do so. A thinker may use logical thinking to gain more consciousness. It is thus possible to propose that for those people who neither use a lot of sensory information nor inner brain activity, their consciousness level may be lower than those they use them.