I believe he is asking what the lizard brain does outside of cortical functions.
Note: There continues to be widespread confusion that the grid activation pattern is in the limbic system (hippocampus) and not in the cortex. The two are closely associated but the grid activation pattern is clearly located in the cortex.
The hippocampus has place cells - not the same thing at all.
This is a very weak start on an answer to Ed’s question: