Brain Diaries: In conversation with Professor Zoltan Molnar
If you’ve ever wondered how the human brain grows, how it deteriorates, or why teenagers are tired and grumpy in the mornings, then from the 10th March the Museum of Natural History are opening an exhibition and series of events on the mysteries of neurological development, from the first moments after conception, until very old age.
Zoltan Molar is one of the figureheads and main contributors to the exhibition, and not just that – as a professor of developmental neuroscience at St John’s College, Zoltan conducts pioneering research on the brain, as well as teaching anatomy, molecular medicine and stem cell biology. OX spoke to this preposterously intelligent man to find out more.
Hi Zoltan, let’s talk about your contribution to the Brian Diaries exhibition.
The reason why I really love this exhibition is because it covers the entire life of the brain, all the way from the earliest developmental steps to the brain ageing and losing some of its processes. I think it’s a really unique idea, and I haven’t seen anything like it before. This really reflects the strength of neuroscience at Oxford, and Professor Chris Kennard should really get a lot of credit for that – he mobilised all of the neuroscientists to get involved in this exhibition.
When you talk about the development of the brain, are you focusing on the physical growth of the organ, or the psychology of what your brain learns to do over time?
Everything. Also, by looking at the developing brain, you can get an insight into conserved evolutionary mechanisms, which can be quite frightening because our brains have a very similar developmental algorithm to any other mammal’s brain. The sequence of development is the same. Sometimes, we even have the same ‘dead ends’.
So what makes the human brain different to an ape’s?
Basically, if you disregard all the similarities and ask me what makes humans different to all other primates, the first difference is the number of neurons: humans have the largest number of neurons in the cerebral cortex. The elephant might have a larger brain, but they haven’t got the same kind of scaling rules – they have a less efficient way of packaging neurons. Also, what is surprising is how long the human brain’s development takes. You hear from police and insurance companies how irresponsible some people in their midtwenties are when driving, for example, and if you look at the brain at that stage, it still isn’t fully developed. Myelination occurs much later than we thought – if you compare a chimpanzee brain and a human brain, the chimpanzee brain has essentially finished developing by the age of 3, whereas human brains keep developing for much, much longer.
What is myelination?
The human brain has interconnecting fibres between neurons, and these fibres initially conduct in an inefficient way. Then, the brain produces myelin around them, which sort of insulates the neurons. After that, they are much more efficient. Myelination can be another form of plasticity – whenever you learn something or train in a certain skill, you actually reconfigure the fibres in your brain.
What sort of age would you say that the human brain is fully developed?
That’s actually the whole theme of the exhibition – it’s a dynamic structure which is reflecting age and environment. To answer your question, you can define it in many different ways. If you’re interested in the point at which we have the largest, thickest brain, then it’s at around 10 or 11 years of age. After that, you have all the myelination, which will peak at around 25 or so. It also depends on the particular brain region.
You spoke about how the brain develops through childhood, but also how it deteriorates when we age. How does that happen? Is it essentially the same process in reverse, or is it a completely different mechanism?
OK, so all of your neurons in your cerebral cortex were born with you – you cannot replace them after that. So, if they are looked after – if you are more active, you don’t have conditions like diabetes, and so on – this helps you to live with this set of neurons for longer without developing dementia, Alzheimer’s or Parkinson’s, for example. If you look at some of the markers which reveal some of these neurodegenerative diseases, some of them can be seen 10, 15 or 20 years before manifestation of the disease. It’s interesting to look at the whole life of a brain, because maybe you and I already have some kind of susceptibility to a disease. Perhaps it’s better not to know.
In your line of work, how much is there left to discover?
There are some very surprising findings emerging all the time. It’s a little too specialist for me to go into detail here, but for instance progenitors, which are a type of stem cell, were only discovered in the last 10 or 15 years. We’re only now beginning to understand the variety of these progenitors. Almost every year we discover a new one.
Also, we are now beginning to understand how these neurons migrate in the developing brain. The process of building the brain is such that the neurons are actually generated quite far away from where they are destined, so they have to migrate long distances to make it to their destination. That makes the brain very vulnerable, because if you disrupt this migration through things like alcohol or radiation, then you end up with a “mixed-up” delivery of these cells, and they can form flawed circuits. For a while you can compensate for it, but it may eventually manifest either as epilepsy or as cognitive disorders such as schizophrenia, autism, ADHD or dyslexia. 1 in 10 of the population has dyslexia, just under 1 in 100 may develop schizophrenia, 1 in 68 has autism, and 1 in about 200 has epilepsy. These numbers suggest that we have to start from the very beginning to understand brain diseases. These disorders might manifest in the second decade of your life, like schizophrenia tends to do, but they all have a developmental origin.
So in the future, might there be a way of discovering ways of stopping these disorders from developing?
Exactly. If you look at some of the trends in neurodegenerative disorders such as Alzheimer’s and Parkinson’s, it is much easier to prevent them if we understand the mechanisms behind them.
Brain Diaries – Modern Neuroscience in Action opens at the Museum of Natural History on 10th March.
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