What We Don't Know

Consciousness

• Lana Howell • Season 1 • Episode 9

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What is consciousness? Who experiences it? Why? How?

In this episode, I will first offer a definition of consciousness and consider the aspects that make it up. Then I’ll summarise some of the main questions we can ask about consciousness, drawing a distinction between the philosophical and neuroscientific sides to the problem. I will look over different scientific models of how the brain produces consciousness, as incomplete and flawed as they may be, before finishing with the practical consequences that understanding consciousness would have. 

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Consciousnessness

Hello everyone, welcome to the ninth episode of ‘What We Don’t Know’, a podcast that explores the boundaries of human knowledge, investigating the unanswered questions and theories that unravel them at the frontiers of science. During this podcast I hope to get you interested in new areas of science, maths and technology, teaching you about existing concepts and igniting a curiosity for the things we have yet to know.

What is consciousness? Who experiences it? Why? How?

In one word, a multitude of mysterious coalesce. Our own consciousness is perhaps the one thing we can each be certain of. Right now, wherever you are, how can you truly be certain that there's a floor beneath your feet, other people in the world, that there exist stars in the sky and birdsong in the air? Because your senses tell you so? 

Perception is often deceptive, and many philosophical arguments consider the possibility of fundamental doubt in all of our knowledge. Yet we can feel ourselves thinking. We know what it is like to experience things. Herein lies Descartes’ famous ‘I think therefore I am’, an assurance in the existence of at least our own minds. But what actually is the mind?

In this episode, I will first offer a definition of consciousness and consider the aspects that make it up. Then I’ll summarise some of the main questions we can ask about consciousness, drawing a distinction between the philosophical and neuroscientific sides to the problem. I will look over different scientific models of how the brain produces consciousness, as incomplete and flawed as they may be, before finishing with the practical consequences that understanding consciousness would have. 

Anton-Babinski syndrome (ABS) is a rare form of anosognosia, itself a rare condition where someone cannot perceive their own illness1. Sufferers of ABS deny their own loss of vision. Damage to the occipital cortex in the brain results in blindness, but the patient seems completely unaware of this blindness2.

The condition of hemispatial neglect is another example of the distinction between information processing and experiencing that information. This syndrome involves reduced awareness of objects, or other stimuli, on one side of space3 despite the visual information processing that does occur, and can affect the patient’s behaviour, shown in recent studies4.

Consciousness is often defined as the awareness, or the experience, of the world around us, and the experience of ourselves as the centre of that world. You should instinctively know what it is like to be conscious. It is the continuous flow of perceptions, thoughts, feelings, each of which we can examine, or use to make decisions about our behaviour.

In 1995, Ned Block classified two types of consciousness. Phenomenal consciousness is the subjective experience of what it is like to be in a particular state, for example, afraid of a bear. Access-consciousness is what is used in rational thought 5. This distinction is often used by philosophers and scientists studying consciousness.

There are a lot of questions around consciousness. 

One famous one is the Problem of Other Minds. This philosophical problem asks about the evidence that others besides oneself have minds capable of experiencing the world like oneself 6. i.e. I have a consciousness, but how can I be sure that you do too? In fact, how can I be sure that anyone does? Perhaps I am the lone conscious being in a world populated by unconscious automatons. 

This may sound a bit self-absorbed, but it is a perfectly valid question to ask. Even more so when you look at other organisms. It may be easy to believe in the consciousness of your dog, but what about an earthworm, a comb jellyfish, a venus-fly trap, a bacterium, or a rock? 

If we cannot prove that other people have inner lives, how can we disprove that anything else doesn’t?

Another philosophical problem is David Chalmer’s hard problem of consciousness, defined in 1995. In essence, it asks why a given physical process generates the specific experience it does, as well as why physical processes are accompanied by experience at all. In contrast, ‘easy’ problems are specifically related to a brain’s purpose, e.g. integrating information, categorising environmental stimuli, and focusing attention7. In understanding the neurological mechanisms responsible for each of these processes, scientists should solve the ‘easy’ problems. But understanding the science behind every aspect of consciousness, may still leave Chalmer’s hard problem unanswered. 

It should be noted that philosophers dispute the existence of a hard problem 8.

So far, we have looked at the philosophical side of consciousness. Murky is the boundary between philosophy and neuroscience in the study of our subjective experience. 

At this boundary lies the group of higher-order-thought theories, which aim to explain the difference between unconscious and conscious mental states using a relation between the conscious state and a higher-order representation, either of that state, or of a thought about it. Higher-order perception theory states that humans not only have first-order non-conceptual perceptions of their environments and bodies e.g. vision, hearing, pain, but also ‘inner’ senses or ‘higher-order’ senses which scan the first-order senses to produce representations of these experiences. We experience these representations as consciousness9. This is but a simplified fraction of a complex and sophisticated class of philosophical theories delving into the equally sophisticated concept of consciousness.

Before going into detail about some of the models that aim to explain how consciousness arises - namely the global workspace model, the modular model and attention schema theory - let us consider the aspects of consciousness, as seen by Anil Seth at the University of Sussex. These are level, content and self. 

Measuring the level of consciousness allows neuroscientists to formally determine how conscious a being is. Intuitively, most of us believe that our waking state is more conscious than our sleeping state, which is more conscious than a brain under general anaesthesia. But how can this be measured?

Perhaps using causal density, neural complexity, or integrated information? Causal density measures the overall causal interactivity supported by a system10, i.e. how much parts of the brain influence each other.

Neural complexity ‘quantifies the strength of correlations across all scales in a neural system’ like the brain11. 

Finally, integrated information refers to Giulio Tononi’s Integrated Information Theory (IIT)12. In his theory, each neural system is given a number, phi, which represents integrated information. The better a system is at distributing information while processing it, the higher phi. For example, the human brain is both highly connected and processes a lot of information13.

All of these metrics have strengths and weaknesses. It is likely that a more accurate measure of consciousness will require taking all into account.

For more information on consciousness’ content and self, I would recommend the recording of Anil Seth’s lecture at The Royal Institution, called ‘The Neuroscience of Consciousness’.

Now I’ll look at theories about how consciousness is produced using the biology of the brain. 

Developments in technology in neuroscience have enabled more accurate brain-imaging, for example using EEG, MRI and fMRI scans, which image electrical activity14, anatomical structure and metabolic activity respectively15. Much work has been done to create a map of the neural activity most responsible for consciousness.

A collection of neuroscientists from the University of Turin, in Italy, defined the ‘neural correlates’ of consciousness as the ‘minimal neural mechanisms that are together necessary and sufficient for experiencing any conscious percept’ end quote. fMRI and lesion studies - which correlate cognitive problems with areas of brain damage - suggest there is a complex interplay between different neural networks, such as the ascending reticular activating system (ARAS) in the brainstem, and the posteromedial cortex16.

Their paper outlines two theoretical models for the production of consciousness. The first, called the ‘global workspace model’, involves a sequence of increasingly sophisticated steps, at which some content of consciousness (e.g. visual, tactile, somatosensory) is processed until it becomes a conscious experience. This model accounts well for access consciousness, but not the unification of different perceptions into the phenomenal consciousness. In the second model, called the ‘modular model’, the whole consciousness is created from a combination of macro-consciousnesses specific to senses or higher-order mental functions (like memory and language), and each of these are also combinations of micro-consciousnesses from specific brain nodes. This second model seems to have more clinical supporting evidence, but has the similar problem of phenomenal unification17.

Another model of consciousness is the attention schema theory, proposed by Michael Graziano of Princeton University. It states that attention is the process where signals in the brain compete for limited computing resources. Our brain cannot focus on every piece of information at once: it has to choose. This behaviour of focal attention is proposed to improve through the brain’s construction of a simplified, but imperfect, model of attention, which can be felt as subjective experience18. In this way, our consciousness is almost an illusion: we believe very strongly in our non-physical, subjective awareness, regardless of whether that actually exists in the brain. The perceived equivalence of attention schema and consciousness may be a starting point for developing artificial consciousness19. 

There are many more practical applications of a better understanding of consciousness. It may help treat people in comas or  people with consciousness-related diseases, like anosognosia. Understanding how we perceive the world and our bodies may encourage development of treatments for psychiatric disorders, like schizophrenia or anxiety.

This episode I offered a definition of consciousness and different classifications within it, including phenomenal versus access. I explained important philosophical problems such as The Problem of Other Minds and the Hard Problem of Consciousness. After a brief overview of higher-order-thought theories, and the potential ways of measuring level of consciousness, I considered three neuroscientific models of consciousness: global workspace, modular and attention schema. Finally, I mentioned the medical advances that would result from better understanding.

Consciousness, by definition, is how we experience the world. It transforms a universe full of particles, waves, molecules, objects, forces, sensory signals, into our own subjective reality. It is the filter through which we see everything, think about everything, feel everything. 

Consciousness raises so many questions. These questions can feel insurmountable. But then we remember how much of ourselves is defined by our subjective experience of life. How little would be left if we had no consciousness. 

And we continue the ancient pursuit of answers.

Thank you for listening.


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Lana Howell

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