How efficient are central mechanisms for the learning and retention of coincident timing actions?

We compared the adaptive strategy and retention capacity of a deafferented subject and control subjects when intercepting, with a sliding-throw, an ap parent movement coming at various speeds. Subjects were submitted to five p ractice sessions (30 trials per session) and to a retention test. The throw ing kinematics was analysed, and spatial and temporal performance errors we re measured. With practice, the deafferented subject showed modifications i n movement initiation strategies and throwing patterns. With a slow apparen t movement, the deafferented subject's initial behavior was characterized b y short movement initiation and movement times. With practice, she showed a n important increase in movement time in session 5, allowing longer visual control and leading to better temporal and spatial accuracy than that shown in session 1. In the retention session, the deafferented patient showed a late movement initiation strategy, similar to that of the control subjects. This increased movement initiation time was accompanied by an improved tem poral accuracy compared to the deafferented subject's early results. Howeve r, spatial accuracy improvement was labile and could not be maintained over the retention interval. At the fast speed, all temporal components of the response, namely, movement initiation time (MIT), movement time (MT), and d isk travel time (DTT), were similar for the deafferented and control subjec ts. Overall, the deafferented subject reduced her temporal error through pr actice, tho ugh without attaining the control subjects' accuracy. However, with a fast-moving stimulus, she showed a deteriorated spatial accuracy, ev en doubling her spatial errors at retention. In brief, the deafferented sub ject achieved proper temporal (perceptivo-cognitive) lasting control of her interceptive action, whereas spatial (sensorimotor) regulation raised mnem onic problems. (C) 1999 Elsevier Science Ltd. All rights reserved.