Synaptic Self: How Our Brains Become Who We Are


Joseph LeDoux








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Although the human brain is the most complex thing known to man, all brains are broadly similar, with the same areas performing the same tasks. How then is it that we all end up so different; with different personalities, attitudes and beliefs? This is the question that Joseph LeDoux sets out to answer in 'Synaptic Self'.

LeDoux begins with a short overview of the physiology of the brain - what neurons are, how synapses connect them and why these connections are key to the brain's many functions. He follows that with a discussion of brain development, explaining how nature and nurture work together to shape the synaptic organisation of the brain.

Much of the book, and for me the most interesting part, is LeDoux's explanation of how the brain modifies itself based on experience through the process of 'neural plasticity'. He explains how scientists have discovered that if a synaptic network within the brain is repeatedly stimulated with a mild electric current, then the electricity measured at the end of the circuit gradually increases in strength. In effect, the network is becoming stronger as the brain 'rewires' itself. Neural plasticity is therefore the means by which the brain 'learns' and it is how memories are formed.

Memories can broadly be divided into two types; those that we need to consciously recalled, such as a phone number or a person's name, and those that are innate, such as how to walk or ride a bike. It is interesting that the innate memories are mainly laid down while we are young and studies have demonstrated on several occasions that children learn more easily than adults. This is why if you want to be good at sport it is better to start young and why children are able to learn multiple languages if they are spoken in their home, yet adults have to study hard to learn an additional language.

The second type of memories are those that require cognitive processing to recall. It is thought that these types of memories require this processing because the executive functions of the brain need to collate the information from various different sources. For example, your memory of a meal in a restaurant may involve the simultaneous binding of memories of the people you were with, the food you ate and the general ambiance of the restaurant. LeDoux suggests that all these memories are stored in different parts of the brain such that there is no single part of the brain dedicated to memory per se. There are however specific parts of the brain that are responsible for pulling these separate elements of a memory together.

Many people have questioned why human brains are so advanced, as it appears that they have evolved beyond the level of capability that could be explained simply by a Darwinian process of natural selection. LeDoux however provides an explanation that differs from most conventional theories of evolution, namely that the process of learning simply enables the brain to do its job better. The more we learn the better we function and therefore the process of natural selection will inevitably lead to ever improving brains.

LeDoux, building on the work of people such as Antonio Damasio, points to the fact that much of the brains recent development has been in the cerebral cortex, but that the brain has not evolved to the point where the new systems that make complex thinking possible can easily control the older systems that give rise to our base needs, motives and emotional reactions. Hence, doing the right thing does not always flow naturally from knowing what the right thing to do is. But possibly it is this ability of even the cleverest people to make mistakes and get things wrong that makes us so human.

In conclusion, Synaptic Self provides an excellent insight into the development of individuality while also providing a very good overview of the functioning of the brain as a whole. It is not a book I would recommend to someone approaching the subject for the first time, but I would strongly recommend it to anyone else.