1231st OGM, AGM and public lecture

“Is the brain the right size?”

Paxinos and Hibbert  Scientia Professor George Paxinos AO

  School of Medical Sciences, UNSW

Wednesday 1 April 2015
Union, University and Schools Club, 25 Bent Street, Sydney

Scientia Professor George Paxinos described the outstanding body of research that he has conducted over many years on mapping the structure of the brain. His work is some of the most cited research in the scientific literature. Virtually every map of the human brain found in hospital operating theatres, doctors’ surgeries and medical practices is based on his work.

Descartes famously made the distinction between mind and brain but, Professor Paxinos argues, there is no ghost in the brain. The mind is a function of brain activity, nothing more. One of the primary differences between the brain and other organs is the extraordinary number of neurones that it contains. The human brain has many more neurones than the size of its body suggests.

Professor Paxinos described the approach taken to understand the structure of the brain. Mostly this revolves around looking at other animals, such as rats and research monkeys to determine the difference in brain structure and, from the differences conclude the function of various aspects of the human brain. One of the main techniques in studying brain tissue is histology. In this approach, tissue is cut it into very fine slices that are then stained to be observed under a microscope. About 40 years ago, a major breakthrough was made when it was realised that staining brain tissue using a variety of stains gave a much richer understanding of neurones structure – the stains were able to differentiate between different types of tissue.

More recently, magnetic resonance imaging (MRI) has been used to map brains, in particular mouse brains. This enables construction of three-dimensional images with different stains revealing different details. These can be then synthesised into many different types of image. Combining the histological approach with MRI has enabled highly detailed maps of brain structure to be synthesised using data from many sources.

Professor Paxinos’s group is now looking at the “ontology” of the brain (borrowing the term from philosophy) to better understand the way in which the structure of the brain relates to human thought. Of particular interest is the nature of thought processes, such as belief. All human belief derives from brain function.

So is the brain right size? If it was smaller it would not have allowed us to have achieved the quite extraordinary advances in human thought over the last several thousand years. We would not have been able to go to the moon or puzzle over challenges of quantum mechanics. But the brain is by no means infallible and indeed it may be the wrong size to enable us to come to terms with some of the highly complex issues such as climate change that challenge the very future of humanity.  

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