Replication and discrimination of limb movement velocity

It is well known that proprioception is composed of the senses of movement and position. Whereas tests of position sense are quite commonly used, test s of the acuity in perception of movement velocity are scarce. In the prese nt study we examined some novel tests for assessing the sense of limb movem ent velocity, involving replication and discrimination of single-joint move ment velocity. Specifically, we investigated: (1) whether replication of li mb movement velocity is more accurate following active criterion movements as compared to passive; (2) whether antagonist muscle contraction during pa ssive limb movement enhances velocity discrimination; (3) how criterion mov ement velocity influences response accuracy; (4) the relationship between m ovement velocity and movement extent during velocity replication; and (5) w hether subjects really base discrimination of velocities on perceived veloc ity. Sixteen healthy subjects participated in four tests (I-IV). For each t est, horizontal abductions were performed about the right. glenohumeral joi nt from the sagittal plane. The subjects were required to actively replicat e the velocity of either an active (Test I) or passive (Test II) criterion movement, or judge whether a passive/semipassive (passive during antagonist muscle contraction) movement was faster or slower than a previous passive/ semipassive criterion movement (Test III/IV). The results revealed higher r esponse accuracy for Test I compared to Test II and for slower movements co mpared to faster, bur no difference in response accuracy between Test III a nd TV. For velocity discrimination, the analysis revealed that the subjects based their judgment on the difference between criterion and comparison ve locity rather than time or extent cues.