[I changed "sensations" to "perceptions", due to @AliceD's comments here.]
Suppose a patient with an amputated limb experiences and reports some phantom perception at the limb:
- the limb just being there
- a gentle touch
Now suppose the corresponding non-amputed limb is exposed to an appropriate stimulus that evokes the same perception.
Do patients usually experience and report that the two perceptions are essentially the same, or do they experience and report significant differences?
The latter could (but would not necessarily) mean that the activity of the receptor cells and/or neurons beyond the liaison (i.e. the more peripheral cells) contributes to the experience (qualia) of a perception, not only the central neurons in appropriate subcortical regions (e.g. the periaqueductal gray in the case of pain) and the somatosensory cortex.
Possible reasons for differences in experience:
The activity patterns of the central system (somatosensory cortex etc.) are significantly different (because they are "produced" differently).
The acitivity patterns of the central system are essentially the same, but the activity of the peripheral systems (one not existing anymore) are different, and contribute to the experience.