Sensory and intrinsic coordination of movement

A recently generalized theory of perceptual guidance (general τ theory) was used to analyse coordination in skilled movement. The theory posits that (i) guiding movement entails controlling closure of spatial and/or force gaps between effectors and goals, by sensing and regulating the τs of the gaps (the time-to-closure at current closure rate), (ii) a principal way of coordinating movements is keeping the τs of different gaps in constant ratio (known as τ-coupling), and (iii) intrinsically paced movements are guided and coordinated by τ-coupling onto a τ-guide, τg, generated in the nervous system and described by the equation τg = 0.5(t minus T2/t) where 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 adults, with eyes open or closed, indicated that hand guidance was achieved by maintaining, during 80 to 85% of the movement, the τ-couplings τα-τr and τr-τg, where τr is τ of the hand-mouth gap, τα is τ of the angular gap to be closed by steering the hand and τg is an intrinsic τ-guide.