Sensory and intrinsic coordination of movement

A recently generalized theory of perceptual guidance (general tau theory) w as used to analyse coordination in skilled movement. The theory posits that (i) guiding movement entails controlling closure of spatial and/or force g aps between effecters and goals, by sensing and regulating the tau s of the gaps (the time-to-closure at current closure rate), (ii) a principal way o f coordinating movements is keeping the rs of different gaps in constant ra tio (known as tau-coupling), and (iii) intrinsically paced movements are gu ided and coordinated by tau-coupling onto a tau-guide, tau(g), generated in the nervous system and described by the equation tau(g) = 0.5(t-T-2/t) whe re T is the duration of the body movement and t is the time from the start of the movement. Kinematic analysis of hand to mouth movements by human adu lts, with eyes open or closed, indicated that hand guidance was achieved by maintaining, during 80-85% of the movement, the tau-couplings tau(alpha)-t au(t) and tau(t)-tau(g), where tau(t) is tau of the hand-mouth gap, tau(alp ha) is tau of the angular gap to be closed by steering the hand and tau(g) is an intrinsic tau-guide.