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.