Variations in neuromodulatory chemical signatures define compartments in macaque cortex

Subcortical neuromodulatory systems exhibit widespread projections that influence the output of cortical circuits. These modulatory systems have been portrayed as providing global signals to the entirety of cortex based on their widespread innervation. This innervation is not necessarily predictive of the levels of the neuromodulatory molecules that actually provide these signals to cortex. In the present study, we examine tissue concentrations of dopamine, noradrenaline, and serotonin to see how they locally vary across multiple areas of the macaque cortex. Our results indicate that different cortical areas exhibit varying levels of dopamine, noradrenaline, and serotonin. Using cluster analysis, we examine how similar cortical regions are to each other, finding that similarities in neurochemical content are shared by areas that exhibit similar functionality. Altogether, these findings demonstrate that neurochemical signatures vary across cortical regions and help define unique, local neuromodulatory signaling compartments.