Neural Correlates of Reach Errors

Abstract

Reach errors may be broadly classified into errors arising from unpredictable changes in target location, called target errors, and errors arising from miscalibration of internal models (e.g., when prisms alter visual feedback or a force field alters limb dynamics), called execution errors. Execution errors may be caused by miscalibration of dynamics (e.g., when a force field alters limb dynamics) or by miscalibration of kinematics (e.g., when prisms alter visual feedback). Although all types of errors lead to similar on-line corrections, we found that the motor system showed strong trial-by-trial adaptation in response to random execution errors but not in response to random target errors. We used functional magnetic resonance imaging and a compatible robot to study brain regions involved in processing each kind of error. Both kinematic and dynamic execution errors activated regions along the central and the postcentral sulci and in lobules V, VI, and VIII of the cerebellum, making these areas possible sites of plastic changes in internal models for reaching. Only activity related to kinematic errors extended into parietal area 5. These results are inconsistent with the idea that kinematics and dynamics of reaching are computed in separate neural entities. In contrast, only target errors caused increased activity in the striatum and the posterior superior parietal lobule. The cerebellum and motor cortex were as strongly activated as with execution errors. These findings indicate a neural and behavioral dissociation between errors that lead to switching of behavioral goals and errors that lead to adaptation of internal models of limb dynamics and kinematics.

Neural mechanisms underlying auditory feedback control of speech

“…Activation of right cerebellar lobule 8 has been associated with increased sequence complexity (Bohland and Guenther, 2006) and limb motor task complexity (Habas et al, 2004;Habas and Cabanis, 2006). This area has also been associated specifically with motor error correction, becoming active when unexpected execution errors were induced during a reaching task (Diedrichsen et al, 2005). This result is consistent with the present finding of increased lobule 8 activation when sensory error was introduced.…”

Evidence for the Flexible Sensorimotor Strategies Predicted by Optimal Feedback Control

“…Trial-to-trial adaptation has been found in perturbations of the hand (Thoroughman and Shadmehr, 2000;Donchin et al, 2003) but not the target (Diedrichsen et al, 2005). Here, we replicate the latter finding: in our target perturbation experiments trial-totrial adaptation turns out to be negligible.…”

“…One possible explanation is that, in sessions with perturbations, trial-totrial adaptation (Thoroughman and Shadmehr, 2000;Donchin et al, 2003) causes the system to be in a different state every time an unperturbed trial is encountered. However, in target perturbation paradigms, trial-to-trial adaptation is negligible (Diedrichsen et al, 2005) (see also below). Another possible explanation is that target perturbations are for some reason misinterpreted as an increase in sensory noise, in which case the "optimal" thing to do is reduce the reliance on sensory feedback, causing suboptimal performance.…”

Noninvasive cortical stimulation enhances motor skill acquisition over multiple days through an effect on consolidation

“…In the context of brain stimulation and localization, the distinction between adaptation and skill is particularly important because they appear to be mediated by separate neural substrates. For example, finger-tapping skill tasks typically show learning-related activation in contralateral M1 (22,31), whereas adaptation tasks, such as visuomotor rotation, predominantly activate posterior parietal cortex and cerebellum (32)(33)(34).…”