In these cases, the lesion was usually in the cervical spinal cord, but in one case it was thoracic (Johnson et al., 2000). A proposed mechanism is that pathological features of these entities, such as gliosis and haemosiderin, provoke spontaneous activation of spinal itch neurons.
Other differences between the two include the camera, with the Moto Z Force featuring a 21 MP rear camera, compared to the 13 MP camera of the Moto Z, and of course, the display of the Moto Z Force is also shatterproof.
The Motorola Moto Z and Moto Z Play both run on Android 6.0.1 Marshmallow with very little modification from pure Android. They have a couple of extra apps on board, such as Moto Migrate, but the experience on both devices is a very close to vanilla Android experience.