Horse Choking itself??

[Bright Spark]

I know of a horse that leans on a gate or stable door and leans on her throat pressing down quite hard in order to make herself choke. she isn't breathing in any air when she does this and does it randomly she may only do it once a week. What is she doing and why? anyone know?

 

[Equi]

Does she choke on food at all? Or have a cough at all? Is it more near the jaw or down the neck?

 

[Bright Spark]

No she doesn't choke on food or have a cough and she leans on the throat latch area. Beginning to think it may just be a habit