Simultaneous modeling for Plasma and Brain concentrations

We are looking to build a 3 compartmental model for assessing compound uptake into the brain. We have plasma and brain data for the compound which shows a tri-exponential decline. I have gone through some of the courses offered by Certara but only learnt how to model the plasma data. I have seen there are ways of adding Cobs in the graphical model but dont know how to get the software to understand which Cobs belong to the plasma data (central) and which belongs to the brain data.

Would really appreciate your support and guidance on this issue.

This might only be a problem with naming of the observations. The default name is CObs, but you can change it every time by just clicking the observation box in graphical model editor and provide a different name. Here is the graphical model view:

You can see the field appearing below the graphical model where you can enter a different name. Now you can see a new parameter in the main mapping panel asking for input to the CBrain observation:

Let me know if there are any questions.

Bernd