When I was studying for my PhD at the University of California at Berkeley, I spent an awful lot of my weekends asking teenagers to lie still in a magnetic resonance imaging (MRI) scanner. While they were lying as still as they could they also had to answer questions they saw on the screen.
We were interested in which parts of the brain these young people were using when they completed an analogical reasoning task. They saw three pictures and were asked to choose the fourth picture to complete the relationships, for example dress is to wardrobe, as milk is to fridge.
We found that association cortex – the parts of the brain that bring together information from many other regions – was used to answer these questions and, importantly, that these regions are activated more and more as you get older.
Fast forward a few years and I’m now a member of the Neuroscience in Psychiatry Network (NSPN), a collaboration between the University of Cambridge and University College London, funded by the Wellcome Trust.
NSPN aims to better understand the biological mechanisms that lead to young people developing a variety of mental health disorders. The network includes experts in epidemiology, adolescent psychopathology, cognition and brain development who are investigating the question of adolescent mental health from multiple angles.
I’m in the MRI team, which has collected brain scans from 300 young people between the ages of 14 and 24. This time, instead of asking them to complete questions while they were lying in the scanner, we took structural MRI scans. These are different to the brain scans we use to assess what the brain is doing (“functional MRI”) and they look really beautiful.
One of the measures we extract is “cortical thickness” – the depth of the outside layer of the brain (the cortex) that contains synapses. A synapse is where two brain cells (neurons) join together and transmit messages. We have around 100 billion neurons but 100 trillion synapses in our brains. It is the complexity of these connections that allows humans to generate and understand complex thoughts and feelings, including being able to solve analogies in the real world.