Neurotransmitters are chemical substances crucial to the proper functioning of the brain, responsible for carrying messages between neurons and other kinds of cells.
As such, they're a fundamental part of how neurons relay signals to other cells, but not just that – according to a new study, neurotransmitter activity can even indicate how good (or bad) we are at math.
In the research, two neurotransmitters were analyzed: glutamate and gamma-aminobutyric acid (GABA) – already known to relate to brain plasticity and our ability to learn – with researchers looking closely at the left intraparietal sulcus (IPS) part of the brain in particular.
Glutamate and GABA actually have complementary roles in the brain, because glutamate excites neurons, whereas GABA inhibits them, a balance that is thought to be important in taking on board new information.
What's more, the IPS has previously been linked to skill in mathematics, but here the team wanted to study this brain location and these neurotransmitters over a longer period of time, and in people rather than animal models.
"In contrast to previous studies on humans or animals that focused on narrower developmental stages, our cross-sectional-longitudinal study suggests that the link between plasticity and brain excitation and inhibition across different stages is unlikely to be immutable," says neuroscientist Roi Cohen Kadosh from the University of Oxford in the UK.
In other words, the relationship between these neurotransmitters and cognitive ability seems to change over time – in fact, it completely flips.
In the study, a total of 255 young people aged from six years old to university students were recruited as participants, with follow-up tests at a later date carried out by a subset of the group.
Combining the data from the first and second math tests with MRI scans showed that neurotransmitter levels recorded at the earlier date could predict math skill on the later date, an average of 1.5 years later.
In children higher GABA levels and lower glutamate levels were associated with being better at arithmetic, but in the older, adult volunteers it was those that showed lower GABA levels and higher glutamate levels in the IPS who performed the best at the math tasks they were given.
"Our finding of developmental switches in the link between GABA and glutamate and academic achievement highlights a general, unknown principle of plasticity," says Kadosh.
Exactly why this flip happens isn't entirely understood, though it appears that somewhere along the line between childhood and adulthood these neurotransmitters start to work differently – along with all the other biological changes that happen as we grow up.
One possibility floated by the researchers is that increased GABA levels in early developmental phases boost learning in mathematics, but that as we get older the same higher GABA levels can impair our math skills. Further studies will be required to find out for sure.
Eventually, the findings outlined here could even be used to help teachers find approaches that keep kids interested in math – one of the core subjects taught at school, with applications in just about every walk of life.
"Our findings also have important implications for the development of brain-based interventional programs, which we hope to examine in the future," Kadosh says.
The research has been published in PLOS Biology.