are upregulted in the NAc core.31 Thus, this archetype analysis defined a potential NAc core signal. One challenge that remains is to determine whether archetypes indicate subtypes or ‘states,’ with the former being a stable feature found across individuals and the latter being a transitory phase that could be activity dependent. In the case of the D1Sh TAC3-archetype, the fact that we detected it in two monkeys indicates that this archetype is akin to a minor subtype, but other archetypes may indicate transitory cell states. As we gather more data about cell types – for example data on sexual dimorphisms, epigenomic features, physical circuits, and behavioral functions – we believe that the concepts captured by archetypal analysis will be crucial for organizing, describing, and modeling the vast functional heterogenity that charachterizes even simple brain structures like the striatum.
