Lecture 4 - The seven ages of the brain
Our life starts with fertilisation of the mother's egg; however, only thirty days later the foetus already has a primitive recognisable brain which continues to bend around itself and swell. So how is a brain made from an egg? As the cells divide, some differentiate to become future neurons. After intense proliferation they move along a kind of 'monorail' made up of another type of cell, into different zones. These zones then gradually constitute the different regions of the brain, where the neurons finally become committed to a certain shape and size, as well as to using particular chemicals for transmitting signals to other cells. The establishment of connections between brain cells occurs not only in the womb, but also after birth. These connections can be modified, or even abolished, in accordance with certain changes in the environment. Hence the development of the brain is a little like sculpting, where a pattern is formed by removing the unwanted parts. During early life, particular connections between neurons are established in accordance with whether those neurons are going to be used in the lifestyle of that particular individual. Often neurons will compete for a target, such that the most active neurons make a contact, whereas the remaining neurons die. It is critical for neurons to be active, to be passing on signals in order to maintain connections. The more a particular limb is moved, or the more the sensory systems are stimulated by 'enriched' environments, the more connections there will be between neurons in the respective part of the brain. It is thus patterns of connections between brain cells that are all-important. These connections are, to a lesser extent, constantly changing throughout our lives, right up to old age.
About the 1994 CHRISTMAS LECTURES
Then Dr Susan, now Baroness Greenfield (b.1950), presented the 1994 CHRISTMAS LECTURES as a five-part series, entitled 'Journey to the Centres of the Brain'. Our brains are ourselves. Every emotion, prejudice and hope is grounded in a molecular scenario somehow and somewhere in the secretive, silent organ between the ears. These lectures will explore what we know, and what still mystifies us, about the workings of the brain. Starting with no prior knowledge, we shall see what the brain looks like, how it generates electricity, and how it uses chemicals to process information. We shall be left with the thought that we know a great deal about how different brain regions function, but how such regions work together to generate a cohesive, individual individual consciousness, remains a tantalising puzzle.