Influence of reaching direction on visuomotor adaptation: An explorative study

Abstract

Robotics is increasingly used in rehabilitation therapy of the hemiparetic arm after stroke. Several studies performed adaptation experiments to gain more insight in the underlying learning processes. In these studies adaptation during reaching movements in different directions is assessed. No information about influence of direction on the amount of learning to these separate directions is present. In this paper we assessed the effect of reaching direction on visuomotor learning. Forty healthy subjects performed 48 movements to five different directions during adaptation to a 30 degrees visuomotor rotation. The execution error was defined as the initial direction error at peak velocity and after 100 ms after onset of the movement. The amount of learning was defined as the difference between the start value and the end value of the execution error. A significant higher amount of adaptation in the movement towards the contralateral part of the body (-72) compared to reaching towards other directions was observed. When possible feedback and corrections mechanisms are taken into account; results indicate that subjects adapt most towards -72 direction and least towards -144 direction. Data of healthy elderly and stroke survivors would be essential to test whether observed results are present in these populations as well, which could have implications for motor relearning in rehabilitation therapy.

Nature, timing, and type of augmented feedback in motor skill relearning

“…From the description of the experiment it could be derived that most studies provided summary feedback. Only one study focused on the effect of providing summary versus faded feedback [31] and found similar results for the summary and the faded training group. Visual Different types of augmented feedback were used solely or combined, see table 2.3.…”

“…Four studies were non-randomized controlled studies (level of evidence of IV) [30][31][32][33]. Nine studies had a pre-post treatment measurement design (level of evidence of VI) [22,[34][35][36][37][38][39][40][41].…”

“…Main motor function outcome measures were grip strength, range of motion, velocity, precision and finger fractionation. Thirteen [22-24, 27, 28, 30, 34, 35, 38, 39, 41-43] out of 23 studies found a beneficial effect on motor functions, five studies [26,32,33,36,40] found an inconclusive effect, and four studies found no effect [12,25,29,31]. No adverse effects were reported on motor function outcome measures.…”

“…No adverse effects were reported on motor activities outcome measures. Four studies [30][31][32]35] did not use any motor activities tests, see table 2.4.…”

“…Visual Different types of augmented feedback were used solely or combined, see table 2.3. Solely visual feedback is used in four studies [26,31,34,40]. Of these studies, one study found a beneficial effect on motor functions [34], one study no effect [31], and two studies found an inconclusive effect [26,40].…”