how to select a proper location?

Hi Dr. Bau,

Fistly thanks for all you talk and great work. Perhaps here is not a right place, but I have this question and wanted to ask at one of your workshop, but never get a chance due to time. I greatly apprecite if you could please give me a hint before closing this issue.
My question:

I understand it what it means when you say: to activate and deactivate neurons directly. But cannot figure it out how turning on neurons in a specific location?? I mean, what's the method to select a region?? For example, how to select wall in a generated image?

This is something that is vague when reading your related papers, and seeing talk. Maybe this part is quite easy that nobody metion how to do so.

Thank you very much for your time.
Mike