The lateral frontal pole: an area unique to humans is involved in the processing of social information

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The difference between humans and non-human primates (NHPs) has accumulated many theories over the years. However, none have proven definitive. Methods that focus on the connectivity of brain regions have shown to be efficacious compared to more limiting approaches that often relied on self-reporting. One of these, the estimation of functional connectivity through resting-state MRI has revealed a uniquely connected area in humans that does not have a homologue in macaques. The lateral frontal pole (FPl) is an area connected uniquely to the parietal and prefrontal cortex, and is associated with higher-order relational thinking. This study investigates its role in multiple modalities, particularly using social information (age and ethnicity), and thus its role in explaining the difference between human and NHPs. Through an adapted relational thinking task using 20 participants, we found that in both non-social and social conditions a cluster in the left anterior frontal cortex is activated in higher versus lower dimensional trials. Further functional connectivity analysis showed that the area had the same unique connectivity pattern to parietal and frontal cortices as the FPl. Additionally, its activation overlaps with voxels which distinctly connect to the angular gyrus, an area strongly connected to the FPl but not neighbouring areas. We conclude it is indeed the FPl, and that it can be activated across modalities. Therefore, this study provides evidence that the FPl may play a role in explaining the differences between human and NHPs. Furthermore, functional connectivity analysis could provide a way to overcome previous limitations.
Faculteit der Sociale Wetenschappen