You don't have to be a neuroscientist to realise that this is an exciting time to be studying the brain.
Yet the brain remains one of the greatest areas of ignorance in contemporary science. The scale of the problem is immense. There are 100,000 million nerve cells or more in the human brain, with 10,000 times as many connections between them. That means that, on average, the brain makes a million connections every second for the whole of our lifetime.
Many of those connections are laid down before birth, guided by a blueprint contained in our genes. Half or more of all the genes in human chromosomes are switched on in brain cells, at one stage or another in life. But that's still only 12,000 or so genes.
One of the challenges to neuroscience is to understand how such a modest set of instructions can build a brain. We can now pinpoint where and when genes are turned on, and can modify genes in laboratory mice to define what they do. Genes don't only construct the brain. They run the internal machinery that keeps nerve cells functioning throughout life.
Just as in every area of medical science, the unravelling of the human genome is paying off in knowledge about genetic problems responsible for so many brain diseases.
And with that comes the possibility of developing treatments to correct the chemical deficiencies that underpin disease.
But the genetic revolution has also revealed the extent to which the organisation of the brain transcends the information contained in our genes. Your genes couldn't possibly know about bicycles or foreign languages or mobile phones, yet your brain deals with each of these challenges. One of the most significant changes of scientific attitude in my lifetime has been recognition that the brain is constantly adapting – modifying itself in response to the information flowing through it – remembering and learning.
Computers are also learning devices, with pre-programmed hardware and specialised software. The science of artificial intelligence promised not only to create computer systems that could rival human intelligence but also to provide better understanding of how our brains work. Fifty years on, the latter of these objectives remains unfulfilled but many still have faith in the computer analogy.
The brain poses huge challenges to science. But we simply have to solve them. The majority of presently incurable diseases affect the nervous system. Paradoxically, the spectacular success of medical science in prolonging the function of the rest of the body is amplifying the burden of brain disease.
The author is professor of neuroscience at the universities of Oxford and Warwick
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