Since time immemorial, one important question has perplexed the greatest minds: what is consciousness? It was once a question that only philosophers would dare try to answer, but scientific advances – specifically in the field of cognitive neuroscience – are allowing us to take a scientific look inside the ‘black box’ of consciousness.
Modern techniques such as functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) now let us examine our brain as we process and interact with our surroundings. Each event triggers a cascade of electrical and chemical processes, but much of what goes on in our brain we are unaware of. For example, when you look at a picture of a landscape, are you aware of the computations being performed by your brain to determine where the horizon is, what the shapes represent and how you identify birds, trees and sky?
We have both conscious and unconscious awareness, but in reality only a tiny proportion of the brain’s processes reach our conscious awareness. One line of evidence suggests that conscious and unconscious thoughts are actually very similar, but at different volumes. We may hear something, for example, and there is activity in the region of the brain responsible for processing sound. We may become aware of that sound, and the activity in that region becomes stronger. It is a bit like the brightness of a light with a dimmer switch – the light is on for both unconscious and consciously detected items, but on a low setting for the former, and turned up to a brighter setting with the latter.
Other research suggests that different brain regions, or different groups of brain cells are responsible for unconscious and conscious processing. One team of researchers have shown that in the first 275 milliseconds of being shown an image, only brain cells in the visual cortex are activated (at the back of the brain). The visual cortex must then send the information to the front of the brain to the ‘thinking’ regions (the prefrontal cortex) before the image enters conscious thoughts.
But if so many processes can continue unconsciously, why do we even need consciousness? Conscious thoughts are costly. They demand a lot of the brain’s processing resources and are slow. ‘Zombie systems’ exist that typically operate with very stereotyped, fixed and simple responses – such as removing your hand from a hot element on the stove. The answer is that consciousness offers us much more: a repertoire of responses that allow us to learn from our experiences and adapt to what comes our way.
We receive a huge amount of sensory information at any given moment. If we were to process every piece of information, our brain’s processing resources would be so clogged up that by the time we had conscious thoughts about the tiger running towards us, it would have eaten us! Despite this, we have the illusion of perceiving everything around us in a completely unified way. Different pieces of information from a single sense – such as colour, shape, and location – are combined. The information from each sense is then combined to form a ‘multisensory representation’ that we are conscious of.
Uncertainty over how these multisensory representations are formed into a coherent ‘consciousness’ is called the ‘binding problem’. Many cognitive scientists believe that specific sets of neurones exist that ‘bind’ all these different sensations into one. However, the identity and existence of these sets of neurones is a topic of great speculation. For example, Edelman and Tononi claim to have identified a ‘dynamic core’ consisting of neurons connecting the thalamus (the brain’s relay station for perceptual information) and the primary sensory cortices (the main cerebral regions that receive input from the thalamus) as the main ‘binding’ substance. Lamme, on the other hand, suggests that binding occurs when different regions of the cortex ‘fire’ at the same time (i.e. they become ‘synchronously active’). Whatever the exact process, it is widely accepted that cross-talk between different parts of the brain is vital for binding to occur and consciousness to emerge. Or as Lamme paraphrases Descartes: “I bind, therefore I am.”
By Stephanie Baines
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Edelman, G. and Tononi, G. (2000). Consciousness: How Matter Becomes Imagination. New York: Basic Books.