Outcomes of ipsilateral position matching and velocity discrimination are uncorrelated

• The central nervous system processes sensory input from proprioceptors to form a state estimate of body configuration, which represents proprioception on theconscious level. Proprioception can be divided in two submodalities: sense of movement and sense of position. It is unclear whether tests, involving psychophysical methods and assessing proprioceptive acuity, can separate between perception of movement and position and thus, measure specific proprioception submodalities. In order to investigate if position matching and velocity discrimination tests can separate perception of position and perception of movement, correlations between outcomes of these tests were analyzed. Sixteen young healthy right-handed and gender balanced subjects performed movements in the right glenohumeral joint in all tests. In the ipsilateral position matching test subjects replicated an arm location, achieved in a criterion movement. Movements were performed from positions Q, 4Q and 80- degrees to target positions 16, 32, 48 and 64 degrees with respect to the body sagittal plane. Four conditions, different in terms of movement mode to the target position during criterion and replication movement, were used: passive-active, passive-passive, active-active, semipassive-semipassive. In the latter condition subjects slightly resisted the passive movement. In the ipsilateral velocity discrimination test subjects assessed if a latter comparison arm movement was faster or slower than a previous criterion movement. Criterion movements were performed at velocities of 3Q and 5Q deg/s. T wo conditions were used: passive-passive and semipassive-semipassive. Variable errors (VE) andjust noticeable differences (JND) were measures of proprioceptive acuity in the position matching and velocity discrimination, respectively. Hierarchical cluster analysis (H CA) and principal component analysis (PCA) were applied to study correlations between outcomes in conditions of both tests. In the H CA solution, the position matchi ng and velocity discrimination conditions were located in clusters on opposite poles of the cluster structure. The PCA results were interpreted for six significant components. The position matching and velocity discrimination conditions loaded mainly on components one to five and on component six, respectively. Both the H CA and the PCA separated all test conditions in t wo groups: one contained the position matching and another the velocity discrimination conditions. There were no clear differences between conditions within each group. The study showed that the outcomes VE and JND of the position matching and velocity discrimination, respectively, are mainly uncorrelated. This implies that these tests likely measure different proprioceptive perceptual components or their different combinations. The position matching and velocity discrimination tests could in general separate between perception of position and movement, although no direct evidence was obtained for ex act match of each test with specific proprioception submodality. Much clearer separation of the measured outcomes could be achieved in subjects, heterogeneous with respect to proprioceptive acuity, i.e. with larger variability of performance.

Publikations- och innehållstyp

ref (ämneskategori)

kon (ämneskategori)