The Curse of Consciousness – a Review
Posted by Science Oxford on October 19, 2011 | comments
Talk reviewed by Blanka Collis, a Science Oxford volunteer and postdoctoral scientist at the University of Oxford.
A Science Oxford talk by Dr Peter Naish, a lecturer in cognitive psychology who discussed the issues surrounding consciousness and its problems and benefits.
How are we, as humans, able to read, write, recognise voices, pictures and faces, and do all the other things that allow us to interact with the outside world? Well, all of this is facilitated by neurones, the 10 trillion (that’s 1 million million, a 1 followed by 12 zeros!) of which are found in our brains, each connected to another 1000 of these to provide an almost indefinite number of possible connections, at least for our purposes. Yet, things such as voice and face recognition can these days be achieved by a fairly simple computer (in which neuronal connections are replaced by logic decisions), but I suspect you and I would agree that a computer is not conscious. So what is it, Dr Naish asked, that makes us conscious?
First of all, he explained how all this transmission through the nervous system works – after all, without it, being conscious would be impossible. The nervous system, including the brain, is made up of the aforementioned nerve cells. Cells are the main building block of a living body and the nerve cells are unique and particularly suited for their function in transmitting signals by being particularly long. They look approximately like the one in the picture below.
(picture credit:mistrust.org.uk)
The cell body is invaginated at the edges, resulting in the formation of dendrites, which give the cell a large surface area which can receive signals from sense organs and other neurons. The cell body then extends with a long axon, which can be up to 2 metres long, carrying signals from the end of your leg all the way to the brain, and then ends in split hair-like extensions, which end in synapses that connect to other neurons. That’s how a nerve cell looks, but why does it transfer signals? Well, it is because it has a leaky membrane, which allows the passage of charged ions (mainly sodium Na+, and potassium K+), which results in a change in voltage across the membrane. If the change is large enough (and in this context, 0.1V, compared to your standard AA battery of 1.5V, is enough), this leads to a positive feedback loop and a pulse being fired which results in the voltage change moving gradually along the neuron from cell body towards the synapses (for more details, see for example this video by garlandscience ). In order for the impulse to travel faster, the neurone is mostly insulated by the fatty myelin sheath cells, with only small gaps, the nodes of Ranvier, between these insulating cells. Due to the relationships between capacitance, voltage change and the distance between two conducting nodes (voltage = (constant x number of ions transferred)/capacitance and capacitance = 1/distance), the presence of myelin insulators means that the neuron becomes less leaky to ions and the nerve impulse can travel at a much faster rate than it would in an unmyelinated neuron. In the end, a nerve impulse can travel at up to 100m/s, without the transfer (and subsequent need for return of) too many ions across the membrane.
This nicely brought Dr Naish to the issue that propagating a nerve impulse requires the constant pumping back of ions through the cell membrane, which consumes a lot of energy such that the brain, which makes up 2% of the body mass actually uses up 20% of its energy. So a large brain is certainly not a very energy efficient piece of machinery, and there must be a reason for why it has evolved. As Dr Naish explained, the early and basic uses of the nervous system are independent of the brain and include many reflexes that allow us and other animals to survive in our hostile environment. As an example, try moving your head from side to side as you read a newspaper, book or computer screen. You don’t have a problem keeping track of the text, do you? Now move the computer, book or newsprint from side to side with your hands, keeping your head still and you should find that the text becomes much more difficult to read. In the former case, you could keep on reading because your head contains a simple sensor-muscle connection, which detected movement of your head and resulted in your eye muscles being moved to compensate for the movement. This did not happen in the latter case, when hands were moved, because such a sensor does not exist in your hands/arms. Crucially, this reflex occurred without the intervention of the brain.
Another example is of the tongue pain sensor being connected to your jaw muscles – if you bite your tongue, you detect pain and the jaw muscle is immobilised. Should this require a nerve impulse journey to the brain, processing of the information and then a journey back, you would have probably bitten your tongue off many times already. Similarly, the famous kneejerk reflex stems from the fact that the patellar tendon in your knee is wired to the spinal cord such that when there is a sudden strike of the tendon, reflective of an imbalance and impending fall, the quadriceps muscle is activated to prevent you from falling. Again, if this message had to be relayed via the brain and required conscious thought instead of an involuntary reflex reaction, you’d be on the floor by the time you realised what was going on.
OK, so some functions of the human body do not require a large brain, but we have one. Why? A single synapse is OK for a simple reflex reaction where a pre-determined action leads to a single reaction. However, a complex brain allows us to process information from multiple synapses in parallel, allowing a range of reactions to more complicated stimuli instead of a reflex one. This is useful for more complex animals, including us humans. One of the important aspects of having a complex brain is to enable us to process information in parallel, taking in visual, auditory and other sensory information from the external world and processing it to lead to a reaction.
Parallel processing was demonstrated by Dr Naish in an experiment where he asked us to pick out an X or a red letter on the screen, which we all did very quickly. When it came to identifying a red X, the answer was slower to come. It turns out that the reason for this is that when we look for an X or a red letter, this is detected subconsciously in a parallel process (i.e. we look at all the letters at the same time), whereas looking for a red X required the one-by-one checking of each letter in a slow and serial process. (You can read more here about a similar experiment if you are interested). This is where consciousness comes in. When we process information in parallel, this is all done at subconscious level, but when we have to think about it (are conscious of it), we need to process it in series, which is slower. Where else was this noticeable in experiments? For example in the Stroop effect (http://en.wikipedia.org/wiki/Stroop_effect) where one of the audience members found reading out the colour of words denoting non-colour related objects very easy (but the words were not memorable afterwards), yet when the words were names of a colour, different to that in which they were written, the reading of these became significantly more difficult. This suggests that once we have learnt to read (are conscious of the words’ meaning), we cannot take in words simply as shapes, but will also read them for the meaning. In support of the conclusion, this problem isn’t encountered by very young children who have not learnt to read yet and are simply assessing the word for its colour. Other examples used by Dr Naish included our inherent ability to remember groups of letters more readily when they were grouped into recognisable words (well learned words are processed in parallel, single letters have to be processed in series), and the fact that people were much better at deciding on the right car for them when they didn’t think about the complex set of information given to them but simply picked the first choice that came into their head – based on this Dr Naish argued that parallel information processing is good for making complex decisions.
Interestingly, here Dr Naish explained that when people’s brains are scanned (using magnetoencephalography, or MEG) during a decision making process, such as when they are asked which product they would like to buy, the decision signature is visible long before the person actually consciously utters what they have decided. Arguably then, the conscious part of our decision making is tacked on at the end of the parallel information processing almost as an afterthought and our conscious self does not actually have any freewill at all. Is this a problem if our legal system is built upon us having a free will to make all our decision, if ‘my subconscious made me do it’ could be used as a defence, as discussed in the philosophical treatise on the Royal Society website? Perhaps, though, there is just enough time to stop the decision suggested by the unconscious self being made so in Dr Naish’s words, even if there is no free will there might be a free won’t…
How do we learn about the parallel decision making world then, if it all happens in our subconscious? Well, apparently we don’t, as we often don’t see the things that are obviously in front of our eyes, as demonstrated by Dr Naish showing us a picture of a plane and a queue of soldiers flicked to another similar image with one difference. A large proportion of the audience did not see that the different was a missing motor, taking some 5% of the photograph’s area. Similarly, when we don’t know something, the conscious part of the brain tries to extrapolate as happens for instance with time for an event which must have happened, but we don’t know when it did. Conscious awareness is made up of feedback loops in the brain – the local ones occur at sensory level and the more complex ones occur at a higher level and result from the activation of a number of related stimuli, which can be integrated and interpreted as resulting from one particular piece of input information. Conscious awareness is thought to be formed by integration of the information from these temporary loops in a part of the brain called the prefrontal cortex (see for instance this section of article on consciousness).
So far, we and Dr Naish in his talk have concentrated on the fact that consciousness is a bit of a burdensome thing that prevents us from processing information and making decisions quickly. Yet, there are benefits to being conscious, including:
- Making connections and seeing patterns very quickly.
- Being able to remember things (such as our position in the pecking order when we’re a herd-living mammal or our communication skills when speaking to others of our species).
- Making plans and asking ‘what if?’ questions, allowing us to be inventive and creative (interestingly, this is supported by the fact that the brain activity when thinking about doing a certain tasks is actually very similar to when we perform the same task).
On the other hand, Dr Naish said there were downsides to being conscious, including the fact that:
- Feedback can exacerbate depression because of the inherent preferential memory for sad things if one is sad.
- We have an inescapable awareness of the passage of time.
- We can develop phobias such as being afraid to leave the house due to social phobias that mean we are afraid of making a bad impression.
That is of course in the functioning and properly working brain, things can get even worse when disorders occur including for example in:
- Post-traumatic stress disorder (PTSD) when traumatic memories, often involving death and mayhem, can come back unbidden to haunt the sufferer. Interestingly, sometimes we can have PTSD for events that did not even happen, suggesting that false memories can be easily created, and linking back to the suggestion that the conscious mind fills in the gaps that ‘it thinks are missing’.
- Schizophrenia where inhibition of the brain when actions are carried out by oneself do not occur for some reason, which means that the sufferer ‘hears’ their own thoughts as voices.
So is it good that we are conscious or would it be better if we were still Neanderthals, blissfully unaware of our own world around us yet only able to use some very rudimentary tools, the repertoire of which has not expanded in 1000s of years? Dr Naish concluded in a positive vein, arguing that the vulnerability that results from consciousness is the cost for our creativity as a species and as individuals – after all, many of the most creative minds of the past (Virginia Woolf, Pablo Picasso, Da Vinci amongst many others) may have been borderline psychotic, yet without their psychoses some of the best art, literature and inventions may have never seen the light of day. On reflection, consciousness is an important aspect of human nature, even if it may uncover a number of small vulnerabilities.
It was certainly a stimulating (if you’ll excuse the pun) talk by Dr Peter Naish, who has previously talked at Science Oxford about the related topic of science behind hypnosis. You can find out more about his most recent talk by listening to the pre-talk interview and hearing his entire talk on the webcast.
What do you think?