Passive mechanical factors governing head and neck movements at the onset of sudden falls in the cat.

The head and neck movements of 16 cats undergoing sudden, unexpected falls have been assessed as a study preliminary to the investigation of reflex responses to the same stimulus. Six of the cats were studied while normal, and similarly tested at a later date to examine for any changes induced by making these animals pitch and roll insensitive, or by labyrinthectomy. The head and neck always described a sterotyped pattern of movement, consisting of progressive dorsiflexion of the neck without rotation of the head in space. This was unaltered by partial or complete loss of eighth nerve function. These findings are consistent with the head and neck movements of a falling cat being predominantly passive in origin, at least for the first 200 msec or so of an unexpected fall.