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.