Random thought: assuming grid cell firing is based on integration of sensory input, I wonder if that’s why most sensors are “mounted” on the head: to conserve training of grid cells?
Are there any animals with high power senses not mounted on the head, are there different populations of grid cells for that non-head sense? Do animals with very inflexible necks have different place cell circuitry?
Or perhaps more directly, are the populations of touch sensor grid cells different than sight, sound? Is their transform circuitry different, e.g. bypassing head position integration?
Skin, fingers, muscles, etc are also sensors.
But sensed information is finally associated in the brain.
I think there is no reason nature should follow above sense and sensor way,
but to me it seems most efficient in this environment in terms of various perspectives.
So, I think what we can see is just all phenomena remaining in the nature.
If some spices are under different environment to environment where human lives, I guess mechanisms might be different with what we have.
Vestibular information (acceleration or whatnot of the head) is sent to a lot of regions, although probably via other cortical regions. For example, some cells in primary visual cortex are influenced by head rotation. It still needs to account for eye movements. I’m not sure how important vestibular information is for other senses.