Functional independence of explicit and implicit motor adjustments

Evidence for distinct brain networks in the control of rule-based motor behavior

“…We observed that decoupled reach performance during a 90°rotation was more accurate when the movement required an explicit rule (i.e., toward targets along the horizontal axis) relative to a more implicit sensorimotor realignment (i.e., toward targets along the diagonal axes, importantly, not oriented toward the corners of the visual monitor) (Granek et al, 2013), suggesting damage to a distinct connection between the SPL and the dorsal premotor (PMd) cortex (Pisella et al, 2006;Rizzolatti and Matelli, 2003). Furthermore, performance improves in patients with OA following a delay (Revol et al, 2003;Trillenberg et al, 2007), suggesting a reliance on strategic control networks (Honda et al, 1998;Sulzenbruck and Heuer, 2009) via prefrontal communication with an intact inferior parietal lobule (IPL) or infero-temporal cortex (Pisella et al, 2006).…”

“…For example, if the computer mouse was rotated 45°, a corresponding mental transformation could be approximated, but online feedback would predominate. Instead of relying on the rule, an unconscious sensorimotor realignment (Abeele and Bock, 2003;Sulzenbruck and Heuer, 2009) must occur gradually over multiple attempts (using slow implicit sensorimotor recalibration).…”

Trial-by-trial analysis of intermanual transfer during visuomotor adaptation

“…Implementation of this strategy leads to immediate success on the task. Interestingly, performance deteriorates over subsequent trials, reflecting the operation of an implicit adaptation system that does not have access to the strategy (Mazzoni and Krakauer 2006;Sülzenbrück and Heuer 2009;Taylor et al 2010). In effect, this procedure puts strategic and adaptation processes in opposition to one another (Taylor and Ivry 2011).…”

“…Indeed, although strategic processes can change performance, the evidence suggests that over the course of learning, strategies make a negligible contribution to adaptation of a sensorimotor mapping. Sensorimotor adaptation representations have been shown to be isolated from strategy-based representations, even at the cost of overall performance, when the two systems are put in competition with one another (Mazzoni and Krakauer 2006;Sülzenbrück and Heuer 2009;Taylor et al 2010;Taylor and Ivry 2011).…”

“…Cognitive processes have been suggested, since participants are aware of the experimental perturbations, which results in large performance errors (Malfait and Ostry 2004). The role of awareness in adaptation, or more specifically, strategies that could be developed in response to awareness, has proven to be a controversial topic (Martin et al 1996;Mazzoni and Krakauer 2006;Sülzenbrück and Heuer 2009;Taylor et al 2010;Taylor and Ivry 2011). Awareness of experimental manipulations leads to numerous changes in performance such as rapid improvements in performance (Kagerer et al 1997;Hwang et al 2006;Heuer and Hegele 2008), increased trialby-trial variance, increased reaction times, and decreased aftereffects (Benson et al 2011;Fernandez-Ruiz et al 2011;Saijo and Gomi 2010).…”