What is Consciousness?
An arm reaching out with the hand holding a lightbulb in front of a faded pink sky.
The answer to what is consciousness is beyond what can be written in this blog post. Scientists, philosophers, and many individuals have attempted to answer this question and still continue. There is so much that we could talk about and many questions that have yet to be answered. While we cannot come to a definitive answer, we can begin the conversation in hopes of inspiring you to learn more on your own time. Ask questions! Explore! Get curious!
At this moment in time, I will say this about consciousness. Consciousness, to me, is everything that we experience - the beautiful sweet moments that life has to offer; the challenging, heart wrenching moments; and everything in between. It is our individual awareness of thoughts, memories, feelings, sensations, and environments. Consciousness I think is also subjective and unique to each person. I would also say that our conscious experiences are ever shifting, changing, and evolving. As mentioned above, one moment we can be experiencing a happy Christmas morning and the next mourning the loss of a loved one and the next thinking about how hard the chair is, etc. Before reading on, what do you think consciousness is at this moment in time? And, it is okay if what you write now changes in time. As we learn more about a topic our ideas and understanding grow and evolve!
States of Consciousness and Altered Levels of Consciousness
Changing directions just a little bit to what science says about what consciousness will help set the stage for the next part of the post which, you guessed it, is more about the neuroscience of consciousness.
There are a few different states of consciousness:
Dreams
Hallucinations
Hypnosis
Meditation
Sleep
States induced by psychoactive drugs
When a state of consciousness changes the result can be a change in perception, thinking, understanding, and interpretations of the world (Cherry, 2020). There are also altered levels of consciousness that arise from medical intervention or mental conditions that impair or change awareness. Examples include:
Coma
Confusion
Delirium
Disorientation
Lethargy
Stupor
Neurological Correlates
So, what does neuroscience have to say about consciousness? As mentioned above, we are going to look at the brain by diving back into the different parts that have been implicated in consciousness. Similar to previous weeks, if it helps, pull up the 3D brain by clicking the link and dive right in! And just a heads up, you are more than welcome to skip reading about each of the brain structures. It can get boring. If you like, simply look at the heading to learn more about the ones you find interesting or just even read the names of the structures. It is your choice.
One of the most popular understandings arises from what is called the neuronal correlate of consciousness, which says that consciousness arises as an emergent property of a large collection of neurons interacting (Libet 1995; Popper & Eccles 1981).
One of the other hypotheses is that there exists a special set of “consciousness” neurons distributed throughout the cortex systems, as well as associated systems and structures like the thalamus and basal ganglia that are representative of the ultimate neuronal correlate of consciousness (NCC), in the sense that activity of an appropriate subset of them is both necessary and sufficient to give rise to an appropriate conscious percept (Crick & Kock, 1995). For talking about specific brain structures below, we will use this hypothesis, the NCC.
Ascending reticular activating system (ARAS)
A group of specialized nodes in a complex network and pathways that controls arousal, this network includes the cholinergic nuclei in the upper brainstem and basal forebrain, the posterior hypothalamus histamine projection, and noradrenergic nuclei, especially the locus coeruleus. The pathways for dopamine and serotonin are also thought to be part of the ARAS. At the apex of the ARAS is the thalamus. The thalamic burst discharges are created through extensive inhibitory axon collaterals, produced by special thalamic and ARAS coordination. The discharges are responsible for gating specific reticular information which is then sent back to the cortex and this then reverts the information back to the brainstem (Abdulgader, 2021).
Amygdala
The amygdala, a structure that we have seen play a role in many processes, such as emotions and memory, is also at play here. There is a strong link between the amygdala with the orbital cortex which is associated with social interactions. The tight tripartite network from the amygdala with the thalamus in turn connects directly to the orbital cortex. This pathway provides strong evidence that emotions influence higher cortical areas involved in affective reasoning (Abdulgader, 2021).
Cerebellum
Involved in so much, like movement, posture, and balance, the cerebellum is also involved in regulatory functions involved in emotional processing, cognition, behavior, and collective consciousness experience. One of the important central afferent circuits is the corticopontocerebellar pathway which begins in the motor and sensory cortical areas. The pontocerebellar tracts connect with the pontine nuclei then connect with the contralateral cerebellar hemisphere in a somatotopic manner. All this denotes feeling or consciousness experience, of point to point correspondence of a body area to a specific cortex point. Looking at the efferent cerebellar pathways (cerebellothalamocortical) there are four and all connect to the following structures: pons, medulla oblongata, reticular formation, basal ganglia, corticospinal and reticulospinal pathways and limbic cortices. Through both the corticopontocerebellar and cerebellothalamocortical pathways, the cerebellum exerts complex regulatory action and integrate information to the cortical cerebral areas that are associated with cognition and conscious experience (Abdulgader, 2021).
Thalamus
Another structure that has come up over and over again throughout these posts, nearly all the information destined to reach the cortex first reaches the thalamus. Reciprocally, the thalamus receives an even greater number of connections back from the cerebral cortex, and it is for this reason that the thalamus is a big part of all forebrain functions like consciousness. The thalamus relays the context of consciousness, in addition to contributing to regulation of arousal level that are essential for selective attention. Breaking it down even further, the specific thalamic relay nuclei communicate with the cerebral cortex about each sensory and motor function which is why these nuclei are thought to be responsible for the individual contents of consciousness (Abdulgader, 2021).
Frontoparietal circuits
Along with visual perception from the activity in the ventral visual cortex, the parietal and prefrontal areas contributions seem to be important for awareness. The network nodes for correlates of conscious are thought to be divided into primary and secondary. The early activity in the occipital lobe correlates with the perceptual processes, and is detrimental for later processes like the activity in the frontoparietal areas. Access consciousness is the direct control of experience through reasoning, reporting, or action requires the involvement of the frontoparietal areas (Abdulgader, 2021).
Prefrontal cortex (PFC)
There exists a debate about, whether as an NCC this structure, the PFC plays a role in the prefrontal theories or the posterior theories of consciousness. There are five main areas of the PFC: the anterior prefrontal cortex, the caudal prefrontal cortex. the dorsolateral prefrontal cortex, the ventrolateral prefrontal cortex, and the medial prefrontal cortex. These areas are all extensively connected with sensory areas which suggests that the PFC is essential to the consciousness experience, though the mechanism is not well understood (Abdulgader, 2021).
Precunues, posteromedial parietal lobe
Precunes are the mesial extent of Brodmann’s area located in the posteromedial portion of the parietal lobe and have connections to bother cortical and subcortical structures. Recent imaging suggests that it plays a role in visuo-spatial imagery, episodic memory retrieval, and self-processing operations. The current thought is that precuneus is involved in interwoven networks of neural correlates of self-consciousness, engaged in self-related mental representations during rest (Abdulgader, 2021).
Yes, that is a lot of information with names and descriptions that are very much rooted in the way a biologist would write. My apologies for that! In the end, it is not so important that you memorize or even internalize all the different structures or processes. It is more important that you begin to develop your own ideas about consciousness with some knowledge of what research has given us. We do know a lot, but we do not know everything about consciousness. Consciousness is complicated and multifaceted. There is so much to learn and consider. For example, take the amygdala, cerebellum, and thalamus. These structures are involved in processes like emotions, movement, and memory. If consciousness is potentially correlated with these structures, when working with people that information becomes useful in understanding how and why they may view the world like they do. This is just one thought. Now it is your turn!
take action today moment:
What questions do you have about consciousness? How might you use knowledge about consciousness to help improve your life and/or impact the lives of others around you? Take some time to consider and then write down your thoughts.
Learn More About consciousness:
Human Consciousness: Where Is It From and What Is It for
References
Abdulgader, A. A. A. (2021). Human consciousness: The role of cerebral and cerebellar cortex, vagal afferents, and beyond. In S. J. Baloyannis (Ed.), Cerebral and cerebellar cortex interaction and dynamics in health and disease. IntechOpen. DOI: 10.5772/intechopen.95040
Bateman, D. E. (2001). Neurological assessment of coma. Journal of Neurology, Neurosurgery & Psychiatry, 71, i13-i17.
BrainFacts. (n.d.). Coma. http://www.brainfacts.org/Diseases-and-Disorders/Neurological-Disorders-AZ/Diseases-A-to-Z-from-NINDS/Coma
Cherry, K. (2020, May 13). What is consciousness?. VeryWellMinded. https://www.verywellmind.com/what-is-consciousness-2795922
Crick, F., & Koch, C. (1995). Are we aware of neural activity in primary visual cortex?. Nature, 375, 121–123.
Fischer, D. B., Boes, A. D., Demertzi, A., Evrard, H. C., Laureys, S., Edlow, B. L., Liu, H., Saper, C. B., Pascual-Leone, A., Fox, M. D., & Geerling, J. C. (2016). A human brain network derived from coma-causing brainstem lesions. Neurology, 87(23), 2427–2434. https://doi.org/10.1212/WNL.0000000000003404
Libet, B. (1995). Neurophysiology of consciousness: Selected papers and new essays. Birkhäuser.
Mayo Clinic. (n.d.). Coma. https://www.mayoclinic.org/diseases-conditions/coma/diagnosis-treatment/drc-20371103\
Popper, K. R., & Eccles, J. C. (1981). The self and its brain. Springer.