Brain anatomy tracks different learning signals in boys and girls

A study of 138 young people found that brain regions linked to reward, memory and decision-making were associated with learning-related EEG signals in different ways in females and males.

A Frontiers in Neuroscience study suggests that the brain’s structure may help explain why children and adolescents differ in how they learn associations, with some of those links appearing to vary by sex. The research examined 138 participants aged seven to 21 and found that grey matter volumes in reward-related regions were tied to event-related potentials, or ERPs, which are brief brain responses measured by EEG during learning. In females, several of the strongest relationships involved the striatum and medial frontal areas, while males showed a different pattern that centred more on the hippocampus and amygdala.

The findings build on a wider body of research showing that brain volume and maturation follow different trajectories in males and females. Large imaging studies have reported that women tend to have relatively more grey matter in some cortical regions, including parts of the prefrontal cortex and cingulate cortex, while men often show greater volume in subcortical structures such as the hippocampus and amygdala. Other work has linked sex hormones and developmental stage to these anatomical differences, reinforcing the idea that biology, not just experience, shapes how the adolescent brain develops.

In the new study, researchers paired structural MRI with an associative learning task in which participants had to work out, through trial and error, which response rule applied to a series of visual cues. The task was designed to separate early rule discovery from later rule use. Behaviourally, the two groups performed similarly overall, although reaction times were faster during the later, more practised phase of the task than during the early learning phase. The authors said this supports the view that the task captured a shift from active learning to rule application.

The clearest sex-related associations appeared in female participants. Early-stage stimulus processing was linked to grey matter in the left putamen and lentiform nucleus, while later-stage stimulus processing was tied to the subgenual anterior cingulate. During feedback processing, later-stage P300 amplitude, a marker often associated with context updating and attention to outcomes, correlated with grey matter in the right nucleus accumbens, putamen and medial orbitofrontal cortex. The study also found that some of these relationships were stronger in females than in males, particularly those involving the subgenual anterior cingulate and medial orbitofrontal cortex.

Male participants showed a different set of links. Early feedback-related P300 amplitude was associated with grey matter in a cluster spanning the left hippocampus and amygdala, and early onset-related activity also related to grey matter in other striatal regions. The authors say the pattern supports a broader framework in which reinforcement learning depends on developing striatal and orbitofrontal circuits, with the N400 and P300 reflecting different aspects of that process. While many of the sex differences in correlation strength did not remain significant after correction, the overall results point to a developing brain in which structure and function are closely intertwined, and not always in the same way for boys and girls.