Adaptive spatial alignment and strategic perceptual-motor control.

Abstract

When starting limb and target locations were simultaneously visible in a visuomotor task, performance during prism exposure was nearly perfect, but aftereffects were absent. When starting limb location was not visible, accurate exposure performance was slow to develop, but aftereffects were substantial. Adaptive spatial alignment of sensorimotor spaces and strategic perceptual-motor control to coordinate sensorimotor systems are distinct processes. However, realignment is dependent on whether the exposure task evokes control strategies that enable detection of misalignment. If the task can be performed solely by coding the visible difference between limb and target locations, misalignment detection is disabled. If movement is initiated by target location and then the limb is controlled by the visible difference between target and limb, the discordance between initialized and terminal locations enables misalignment detection and realignment.

Functional Anatomy of Nonvisual Feedback Loops during Reaching: A Positron Emission Tomography Study

“…These differences may be related to the fact that the motor reaching task we investigated here was more "rudimentary" than the tasks considered in earlier experiments. The present study differs, indeed, from earlier studies by at least one of the following aspects: (1) vision of the moving limb was never allowed, preventing visual feedback loops from operating; (2) no estimation of the reaching error was provided during or at the end of trial, prohibiting motor learning (Jordan 1990;Redding and Wallace 1996); (3) the subjects reached to the target directly without the mediation of a manipulandum or a joystick, avoiding the need for complex visuomotor transformations; (4) targets were seen in binocular vision and not through a virtual display system that provides conflicting vergence and accommodation signals, thus requiring adaptive behavior by preventing real depth perception; (5) oculomotor activity was strictly controlled allowing precise evaluation of arm reaching-related changes in rCBF. Our data suggest that basic reaching movements performed without visual guidance involve a less distributed cortical network and rely more consistently on cerebellar structures than the visually more complex motor tasks usually studied.…”

The effect of cerebellar cortical degeneration on adaptive plasticity and movement control

“…Such a persistence of the deficit is interesting, as it allows an insight into the underlying pathology. It is thought that adaptive improvement is based on two distinct processes, a recalibration of sensory-to-motor transformation rules, and strategic control by anticipations, associative stimulus-response pairings, and other workaround schemes; in contrast, retention, transfer, and de-adaptation are thought to reflect recalibration alone (Bock 2005;McNay and Willingham 1998;Redding 1996). If so, the persistence of an adaptation deficit in our patients would indicate that recalibration but not strategic control is impaired by cerebellar degeneration.…”

Eye-Position Signals in the Dorsal Visual System Are Accurate and Precise on Short Timescales

“…Even if not corrected, however, the misrepresentation may be masked during everyday behavior because of the availability of other spatial cues and strategies (e.g., visual guidance). In that case, there would be no error signal to drive calibratory processes (Redding and Wallace, 1996) and the misrepresentations might be detectable in the laboratory.…”