Grid cells are known to exist elsewhere in the brain—for example, in the entorhinal cortex. There are preliminary hints that grid cells may exist in neocortex too, but this hasn't yet been firmly established. Displacement cells, on the other hand, have never been observed anywhere—they're just hypothesized cells Hawkins predicts must exist, assuming his theory is true. So I took him to be making a few distinct claims: 1) grid cells also exist in neocortex, 2) displacement cells exist 3) displacement cells are located in neocortex.