The kinaesthetic senses

This review of kinaesthesia, the senses of limb position and limb movement, has been prompted by recent new observations on the role of motor commands in position sense. They make it necessary to reassess the present-day views of the underlying neural mechanisms. Peripheral receptors which contribute to kinaesthesia are muscle spindles and skin stretch receptors. Joint receptors do not appear to play a major role at most joints. The evidence supports the existence of two separate senses, the sense of limb position and the sense of limb movement. Receptors such as muscle spindle primary endings are able to contribute to both senses. While limb position and movement can be signalled by both skin and muscle receptors, new evidence has shown that if limb muscles are contracting, an additional cue is provided by centrally generated motor command signals. Observations using neuroimaging techniques indicate the involvement of both the cerebellum and parietal cortex in a multi-sensory comparison, involving operation of a forward model between the feedback during a movement and its expected profile, based on past experience. Involvement of motor command signals in kinaesthesia has implications for interpretations of certain clinical conditions.