LAUSR

Working memory capacity, the amount of information one can hold online in mind, has a central role in cognition. Previous electrophysiological and imaging studies revealed the pivotal role of persistent activity within parietal and frontal regions as the neural foundations underpinning working memory capacity. The best candidate molecules determining persistent activity are the brain's major excitatory and inhibitory neurotransmitters, glutamate and gamma-aminobutyric acid (GABA), respectively. However, our knowledge of these neurophysiological determinants in forming working memory capacity is still poor. Using magnetic resonance spectroscopy, we examined the contribution of glutamate and GABA within the left intraparietal sulcus and the left inferior/middle frontal gyrus in tracking working memory capacity. A positive association was found between glutamate within the left intraparietal sulcus and working memory capacity. By utilising resting-state functional MRI, we identified a negative association between parieto-cingulate connectivity and working memory capacity. Individual variation in parieto-cingulate connectivity was explained by glutamatergic concentration in the intraparietal sulcus. Moreover, we found that parieto-cingulate connectivity mediated the relationship between interparietal sulcus glutamate and working memory capacity. This set of findings reveals a novel mechanistic insight by which glutamatergic concentration within the intraparietal sulcus shapes WM capacity via parieto-cingulate connectivity.