The Neural Signatures of Consciousness
By Sukanya Chakraborty
“A human being is a part of the whole called by us universe, a part limited in time and space. He experiences himself, his thoughts and feelings as something separated from the rest, a kind of optical delusion of his consciousness. This delusion is a kind of prison for us, restricting us to our personal desires and to affection for a few persons nearest to us. Our task must be to free ourselves from this prison by widening our circle of compassion to embrace all living creatures and the whole of nature in its beauty.”
– Albert Einstein
Be it the power to travel to outer space, battle deadly diseases, construct machines that can accomplish amazing feats or explore the world at the mesmerising level of subatomic particles, human beings have mastered it all. And yet, some intriguing questions continue to persist. Among these inexplicable questions that science still strives to answer, is the mystery of how consciousness arises and what it involves. There have been groundbreaking developments in furthering our understanding of this aspect through the advances in Neuroscience and Psychology. Yet the struggle to decipher its true meaning is still in its infancy.
Being one of the ‘final frontiers’ of modern science, many scientists regard the Holy Grail of scientific advances to be the elucidation of the concepts underlying consciousness. Philosophers have predominantly used the term ‘consciousness’ for explaining knowledge in general, intentionality, introspection (and the knowledge it specifically generates) and phenomenal experience, termed as ‘qualia’. John Locke, a British philosopher, in the 17th century, proposed that consciousness is the “the perception of what passes in a man’s own mind”. The earliest English language usage of the words “conscious” and “consciousness” date back, however, to as early as the early 16th century. Though the roots of the problem of understanding the conscious state of mind seem to be quite old, there is still a significant deal of controversy in the matter of finding an exhaustive definition of the same.
On a more scientific note, consciousness has been defined as the function of the human mind that receives and processes information, crystallizes it and then stores it or rejects it with the help of the five senses, the reasoning ability of the mind, imagination, emotion and memory (Vithoulkas et.al., 2013). The exact parts of the human brain where those functions take place are attempted to be explained by neurophysiology. An important observation is that the more information one is able to gather and process, the more “aware” and the more “conscious” one becomes regarding one’s internal and external world. Awareness and wakefulness represent the two main components of consciousness. In other words, all that we experience comprises our consciousness. But, is it really that simple?
In 1994 David Chalmers explained why consciousness is such a challenging phenomenon to understand. He categorised the challenges into “easy” problems and the “hard” problem. How the mind integrates information and develops focus and attention fall under the realm of easy problems. Easy, because solving them demands us to explore the mechanisms to explain these behaviours, often accomplished by cognitive science, psychology and neuroscience. The hard problem, on the other hand is regarded to be quite unsolvable. Specifically, the hard problem is determining why or how consciousness occurs given the right arrangement of brain matter. What makes it hard is that we cannot just point to some physical mechanism to solve it, for that would be the solution to the easy problem. Instead, we would like to find out why certain physical mechanisms give rise to consciousness instead of something else or nothing at all.
Through modern research techniques such as Functional Magnetic Resonance Imaging (fMRI), which gives a measure of brain activity due to increased blood flow, using Blood-Oxygen-level-dependent contrast (BOLD), electroencephalograms (EEG), where electrodes placed on the scalp measure gross neuronal activity and so on, it has been concluded that complex brain areas including the prefrontal cortex, which are responsible for a range of higher cognitive functions, are typically involved in conscious thought. A plausible reason as to why it is so difficult to study conscious experiences is that they are entirely internal and cannot be accessed by others. However, these techniques for measuring brain activity are enabling scientists to refine their theories about what consciousness is, how it forms in the brain and where the boundaries lie between being conscious and unconscious.
A notable breakthrough that deserves mention in this regard is the case of a 23-year-old woman who sustained a severe brain injury in a car accident in July 2005, leaving her in a non-responsive state. She could open her eyes and exhibited cycles of sleep and wakefulness, but did not respond to verbal commands or show signs of voluntary movement. Five months later, when she was still in this state, Adrian Owen, a neuroscientist, then at the University of Cambridge, UK, and his colleagues observed the subject using fMRI while giving her a series of verbal commands such as asking her to imagine playing tennis. They observed activity in a part of her brain called the supplementary motor area (SMA). When they asked her to imagine walking through her home, activity ramped up instead in three areas of the brain that are associated with movement and memory. The researchers observed the same patterns in healthy volunteers who were given identical instructions. This finding was a great leap for neuroscience. The work suggested that some people could understand speech and possibly communicate, even when they seemed not to respond to doctors and family members.
One recent yet widely accepted approach is to find the neuronal correlates of consciousness (NCC), defined as the minimal neuronal mechanisms jointly sufficient for any specific conscious experience. To put it simply, when we experience something, be it pain or hunger or happiness, what must happen in the brain? Is it possible that some enigmatic ‘consciousness neurons’ should be activated? If so, where in the brain are these neurons located?
Some philosophers, however, argue that finding the NCC will never solve the ‘hard problem’. Neural processes may explain functions, such as how a particular sensory input is mapped onto a motor output or even explain abstract ideas like motivation, intelligence or love. But why these functions are accompanied by conscious experiences, instead of simply being ‘carried out in the dark’, is something that NCC may fail to explain.
Victor A. Lamme, professor of cognitive neuroscience at the University of Amsterdam, Netherlands proposes a radically different approach. In this forward approach, conscious reports, states or actions are not taken as the starting point of which the NCC is sought. Instead, neural functions form the foundation, and with those a new ‘psychology’ is defined.
With the improvement in comprehending conscious processes, some researchers are beginning to build strategies for its manipulation, with the possibility of treating brain injuries, phobias and mental-health conditions such as post-traumatic stress disorder (PTSD) and schizophrenia. But even as research progresses, and ideas from science and philosophy continue to meld, essential questions remain unanswered. In the words of Dr. Anil Seth, a cognitive and computational neuroscientist and co-director of the Sackler Centre for Consciousness Science at the University of Sussex in Brighton, UK, “It’s still just fundamentally mysterious how consciousness happens”.
“Consciousness is the last and latest development of the organic and hence what is most unfinished and unstrong.”
– Friedrich Nietzsche
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2] Koch C. 2018. ‘What is Consciousness?’. Scientific American. 318, 6, 60-64 (June 2018) doi:10.1038/scientificamerican0618-60
3] Lamme V. ‘Can Neuroscience reveal the true nature of Consciousness?’
4] Nielsen N. June 2, 2018. ‘Must a Philosophy of Mind be a Philosophy of Consciousness?’ Medium
5] Sohn E. 25 July 2019. ‘Decoding Consciousness’. Nature. Vol 571. S2-S5 (2019) doi: 10.1038/d41586-019-02207-1