How does individuality develop?

20 May 2013
Posted by Hannah Critchlow.

Hannah -   And now, my paper this month where it's been published in the journal Science and it's really trying to uncover how are our personalities and our individualities shaped. 

Well, scientists have been interested in this for a very long time and there's a number of ways that you can start to glean information about it.  So, you can look at monozygotic twins that are pretty much identical in terms of their genetic makeup and you can look at twins that have been adopted at birth, and there are cases where there are striking similarities between those adopted monozygotic twins.  They may laugh in exactly the same way or have the similar sense of humour, but then conversely, there's also cases of identical twins that have been brought up in the same environment, by the same parents, and yet, they've got very, very different personalities.  So, what's going on there?

David -   So, even that these people have got the same genetic makeup, they Knockout Micemay turn out differently and even if they've got the same genetic makeup, they might turn out the same.  So, it's very difficult to know what's causing these different behaviour traits.  Is it genetics or is it environment?

Hannah -   Exactly and so, scientists in this study wanted to get a little bit closer to trying to understand that.  So, they looked at mice that were kind of from the same inbred strain.  So, they were genetically incredibly similar and they put them all together in a very large cage.  They're 40 of these mice that had a very rich environment.  So, lots of things for these mice to play with.  At the same time, the researchers were able to tag each of these mice with a GPS system so they could monitor how much of the mice run around and whether they were exploring lots of different levels within this massive cage, and they collected this data over 3 months.  And then after that 3-month period, they started to peer into the brains of these mice and they looked at a particular area of the brain called the hippocampus which is buried deep in the brain and it's involved in learning and memory, and also navigation.  And they looked specifically within the hippocampus and even smaller region called the dentate gyrus which is one of the few areas of the brain where new brain cells are being born throughout life.  And it's thought that the birth of these new brain cells is involved in how we can create new memories and also cope with novelty in our environment.  And they found that the mice that were in enriched environment had lots of play, had a higher number of nerve cells being born in this dentate gyrus.  In fact, it was over twice as many new nerve cells being born within this 3-month extended period.  And then they zoomed in even further and they looked at this set of 40 mice that were in the enriched environment. 

Now, there's a great degree of variation between those mice that roamed around and explored a lot and then there was some mice that were not fast about exploring.  And again, they saw a correlation between the amount of new nerve cells that were being born and the amount at which these mice were roaming around. 

Really, the next logical question to me is, what is it about these very genetically similar mice that were kept in the same environment, why did some explore more than others?  And that's something that scientists haven't really fully got the grips with.  But what the researchers are saying in this paper is that when viewed from an educational and psychological perspective, the results of this experiment suggests that an enriched environment fosters a development of individuality.  And it's also maybe important to note that in humans, smaller hippocampi have been found in adults who suffered from neglect or stress as children, and that might be related to this fewer new nerve cells that are born in the dentate gyrus of the hippocampus.

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