Introduction
Consciousness is the status that humans and animals can feel and detect
the environment, and are capable to make appropriate responses to
changed stimuli. In recent years, neuroscientists have taken difficult
experimental approaches to investigate the consciousness, or neuronal
correlates of consciousness (NCC). This is the minimal neuronal
mechanism that supports any specific consciousness experience (Kochet al. , 2016; Koch, 2018; Seth & Bayne, 2022). Different
experimental approaches have been used to investigate such neuronal
mechanisms, including brain imaging, and animal experiments with brain
injury or anesthesia. Pain and pleasure, are two major types of emotion
affecting the brain. Consciousness of pain is a key type of sensory
consciousness. It has been proposed to use to evaluate the level of
consciousness as well as the recovery of consciousness during
anesthesia.
The studies of consciousness have recently advanced by the use of modern
science and technology. Brain imaging has demonstrated that certain
central nervous system (CNS) areas that are activated or inactivated
during consciousness or during reappearance of consciousness. Animal
studies using optogenetic and selective brain stimulation revealed that
certain brain areas are critical for re-starting consciousness from
unconsciousness statues. It is believed that cortex and related
subcortical nuclei that form neuronal connections and feedback controls
with cortical neurons play important roles in consciousness (Kochet al. , 2016). It is no doubt that sensory sent through the
spinal cord, and motor-related neuronal activity contribute to
consciousness.
For our sensory experience, the more we learn, and more complex it
becomes. For many years, we treat all pain as one type of pain, or we
called it acute pain. Identification of capsaicin receptors and opioid
receptors has greatly helped us to understand pain. Recent progress in
synaptic plasticity leads to our understanding of chronic pain is
completely different from acute pain. How about consciousness? Are there
different forms of consciousness that are mediated by different chemical
proteins and receptors? Are there different types of consciousness, for
one, obedient consciousness that required minimal effort to brain
activity, and highly self-aware, and sustained consciousness? In this
review, I will first briefly review recent advances in the
thalamus-cortex investigation of consciousness, and discuss the possible
roles of the anterior cingulate cortex (ACC) in consciousness. Then,
from a pharmacological point of view, I will discuss several proteins,
receptors, and chemicals that interfere with consciousness, and their
possible synaptic functions that take place in the thalamus-cortex
network.