Showing papers in "Journal of Motor Behavior in 2013"

The effects of adapted tango on spatial cognition and disease severity in Parkinson's disease.

Abstract: The authors determined effects of community-based adapted tango on spatial cognition and disease severity in Parkinson's disease (PD) while controlling for the effects of social interaction. Thirty-three individuals with mild-to-moderate PD (stage I–III) were assigned to twenty 90-min tango (n = 24) or education (n = 9) lessons over 12 weeks. Disease severity, spatial cognition, balance, and fall incidence were evaluated pre-, post-, and 10–12 weeks postintervention. The authors evaluated differences using t tests and analyses of variance. Twenty-three tango and 8 education participants finished. Tango participants improved on disease severity (p = .008), and spatial cognition (p = .021) compared with education participants. Tango participants also improved in balance (p = .038), and executive function (p = .012). Gains were maintained 10–12 weeks postintervention. Multimodal exercise with structured syllabi may improve disease severity and spatial cognition in PD.

Motor Imagery and Aging

Abstract: Motor imagery (MI) is the mental simulation of an action without its actual execution It has been successfully used through mental practice--the repetition of imagined movements--to optimize motor function either in sport or rehabilitation settings Healthy elderly individuals facing age-related impairments in motor function could also benefit from this method of training-retraining The authors review studies that have investigated MI in physically and mentally healthy adults aged 55 years and older First, they provide an overview of the psychophysical data on MI in the elderly, which show no changes with aging in the ability to imagine simple-usual movements but reveal some age-related alterations in the mental simulation of difficult-unusual movements Second, they present emerging neuroimaging and neurostimulation data revealing that the sensorimotor system is engaged during MI in older adults Finally, the authors emphasize the potential of using mental practice as a safe and easy way to help preserving/improving motor function in the elderly and provide some recommendations for future research in this direction

Terminal Feedback Outperforms Concurrent Visual, Auditory, and Haptic Feedback in Learning a Complex Rowing-Type Task

Abstract: Augmented feedback, provided by coaches or displays, is a well-established strategy to accelerate motor learning. Frequent terminal feedback and concurrent feedback have been shown to be detrimental for simple motor task learning but supportive for complex motor task learning. However, conclusions on optimal feedback strategies have been mainly drawn from studies on artificial laboratory tasks with visual feedback only. Therefore, the authors compared the effectiveness of learning a complex, 3-dimensional rowing-type task with either concurrent visual, auditory, or haptic feedback to self-controlled terminal visual feedback. Results revealed that terminal visual feedback was most effective because it emphasized the internalization of task-relevant aspects. In contrast, concurrent feedback fostered the correction of task-irrelevant errors, which hindered learning. The concurrent visual and haptic feedback group performed much better during training with the feedback than in nonfeedback trials. Auditory feedback based on sonification of the movement error was not practical for training the 3-dimensional movement for most participants. Concurrent multimodal feedback in combination with terminal feedback may be most effective, especially if the feedback strategy is adapted to individual preferences and skill level.

The Shoulder and Elbow Joints and Right and Left Sides Demonstrate Similar Joint Position Sense

Abstract: Proper orientation of the shoulder and elbow is necessary for accurate and precise positioning of the hand. The authors' goal was to compare these joints with an active joint position sense task, while also taking into account the effects of joint flexion angle and arm dominance. Fifteen healthy subjects were asked to replicate presented joint angles with a single degree of freedom active positioning protocol. There were no significant differences in angular joint position sense errors with respect to joint (shoulder vs. elbow) and side (left vs. right). However, when considering linear positioning, errors were lower for the elbow, due to a shorter lever arm. Also, as flexion angles increased toward 90°, there was a consistent pattern of lower errors for both joints.

The Effect of Balance Training on Cervical Sensorimotor Function and Neck Pain

Abstract: The authors' aim was to evaluate the effect of balance training on cervical joint position sense in people with subclinical neck pain. Thirty-four participants were randomly assigned to balance training or to stay active. Sensorimotor function was determined before and after 5 weeks of training by assessing the ability to reproduce the neutral head position and a predefined rotated head position. After balance training, the intervention group showed improved joint repositioning accuracy and decreased pain whereas no effects were observed in the control group. A weak correlation was identified between reduced neck pain intensity and improved joint repositioning. The present data demonstrate that balance training can effectively improve cervical sensorimotor function and decrease neck pain intensity.

Which version/variation of Fitts' law? A critique of information-theory models.

Abstract: Four different versions of Fitts' law have been in use over many years in the ergonomics, psychology, and HCI (Human-Computer Interaction) fields. There appears to have been no critical discussion of the validity of these different versions. The question is asked: Is one better or more valid than others? The aim of this article was to evaluate these commonly used versions and attempt to determine the correct/more valid model. It is concluded that the original form developed by P. M. Fitts (1954) and P. M. Fitts and J. R. Peterson (1964) is the most valid form based on information theory and that the theoretical foundation of the Shannon version suggested by I. S. MacKenzie (1989) is invalid. A version due to A. T. Welford (1968) also has a valid information-theory basis.

Bihemispheric anodal corticomotor stimulation using transcranial direct current stimulation improves bimanual typing task performance.

Abstract: Transcranial direct current stimulation (tDCS) is associated with improved unimanual skilled hand use. The authors assessed effects of bihemispheric anodal corticomotor tDCS (BAC-tDCS) on bimanual skilled hand use. Twenty-eight nondisabled subjects were randomized to either BAC-tDCS or sham-tDCS, 20 min daily for 5 consecutive days. Performance on a bimanual typing (BT) task and a short-term memory (STM) task was assessed daily and at 1-week follow-up. Mean change between Day 1 and Day 5 in BT score with BAC-tDCS (19.4 points; 95% CI [12.82, 25.99]) was significantly greater (p =.04) than change with sham-tDCS (12.5 points; 95% CI [7.6, 17.3]). Neither group retained improvements in BT score at follow-up. BAC-tDCS had no effect on STM. These results may have implications for interventions to improve hand function in persons with bilateral hand dysfunction.

Joint Simon effects in extrapersonal space.

Abstract: Numerous studies have revealed that when people sit next to each other and complete separate parts of a Simon task, response times are shorter when the participants' stimulus appears in front of them than when the stimulus appears in the opposite side of space. According to the action co-representation account of this joint Simon effect (JSE), participants represent each other's responses and the compatibility effects emerge because of a set of facilitatory and inhibitory processes that are similar to those that are activated when individuals perform the entire Simon task alone. D. Guagnano, E. Rusconi, and C. A. Umilta (2010) argued against this account as the sole mechanism based on their finding that a JSE was not observed when participants sat outside of each other's peripersonal space. Notably, the task in the Guagnano et al.'s was a modified version of the conventional JSE task designed to increase the independence of the partners. Here, we reconsider the arguments of Guagnano et al. and report a study in which the authors failed to replicate their key finding. Considering the extant JSE literature, we conclude that the null effect in Guagnano et al.'s study may be an anomaly and that co-representation remains a leading candidate for the critical process underlying JSEs.

Temporal preparation in athletes: a comparison of tennis players and swimmers with sedentary controls.

Abstract: The authors aimed to investigate the effects of different sporting experience on nonspecific temporal preparation. They evaluated temporal preparation in tennis players (an open-skill sport) and their athletic (swimmers, a closed skill-sport) and nonathletic (sedentary students) controls using a go/no-go variable foreperiod paradigm in which one simple condition and two go/no-go conditions (central-go and mixed-go) were included, which can be used to study the temporal aspects of nonspecific preparation with decision making in inhibition with different levels of cognitive load. Tennis players responded faster than nonathletic controls while there was no significant difference relative to the athletic controls. Additionally, the main finding of the present study is that the difference in reaction time between tennis players and nonathletic controls was found selectively for short foreperiods in which temporal uncertainty is higher and less temporal preparation can occur. Moreover, correlation analysis revealed that superior temporal preparation was positively associated with enhanced go/no-go decision making in the higher difficulty condition. Our findings are consistent with tennis players showing superior temporal processing. The absence of a significant effect in athletic controls suggests that there is a specific benefit from tennis training and indicates that temporal preparation may be susceptible to modulation by fitness and appropriate training.

Distinct visual cues mediate aperture shaping for grasping and pantomime-grasping tasks.

Abstract: The authors examined whether the top-down requirements of dissociating the spatial relations between stimulus and response in a goal-directed grasping task renders the mediation of aperture trajectories via relative visual information. To address that issue, participants grasped differently sized target objects (i.e., grasping condition) and also grasped to a location that was dissociated from the target object (i.e., pantomime-grasping condition). Just noticeable difference (JND) values associated with the early through late stages of aperture shaping were computed to examine the extent to which motor output adhered to, or violated, the psychophysical principles of Weber's law. As expected, JNDs during the late stages of the grasping condition violated Weber's law: a result evincing the use of absolute visual information. In contrast, JNDs for the pantomime-grasping condition produced a continuous adherence to Weber's law. Such a result indicates that dissociating a stimulus from a response is a ...

Evaluating the Acute Contributions of Dopaminergic Replacement to Gait With Obstacles in Parkinson's Disease

Abstract: The influence of dopaminergic replacement (DR) on gait in people with Parkinson's disease (PD) is well documented. However, little is known about the acute effects of dopamine on more complex locomotor tasks that require visual guidance to avoid obstacles during gait. The authors investigated the influence of DR on locomotor behavior in a task where movement planning and control might be challenged by the height of the obstacle. The PD group included patients diagnosed with idiopathic PD (n = 12), as well as healthy controls (n = 12). Patients walked and stepped over obstacles of different heights before (OFF) and after (ON) levodopa intake. Spatial adjustments were not modulated by DR, but the step time to perform these anticipatory gait adjustments was longer only in PD-OFF (compared with healthy controls) when approaching the highest obstacle, but not PD-ON. During the crossing phase, trail limb toe clearance of PD patients was shorter than healthy controls only during the OFF state. ON-OFF com...

The Utility of Vision During Action: Multiple Visuomotor Processes?

Abstract: Recently, D. Elliott et al. (2010) asserted that the current control phase of a movement could be segregated in multiple processes, including impulse and limb-target regulation processes. The authors aimed to provide further empirical evidence and determine some of the constraints that govern these visuomotor processes. In 2 experiments, vision was presented or withdrawn when limb velocity was above or below selected velocity criteria. The authors observed that vision provided between 0.8 and 0.9 m/s significantly improved impulse regulation processes while vision provided up to 1.1 m/s significantly increased limb-target regulation processes. These results lend support to D. Elliott et al. and provide evidence that impulse regulation and limb-target regulation can take place at different velocities during a movement.

Temporal Coupling Is More Robust Than Spatial Coupling: An Investigation of Interlimb Coordination After Stroke

Abstract: Interlimb coordination obtained through temporal and spatial coupling is a significant feature of human motor control. To understand the robustness of this capability the authors introduced a method to quantify interlimb coordination strength and compare individuals with asymmetric effector ability poststroke to nondisabled controls. Quantitative analyses determined the relative strength of interlimb coupling with an asymmetric obstacle avoidance task. Participants performed bimanual discrete, multijoint aiming movements in the frontal plane with a vertical barrier positioned midway to the target for one limb. To quantify coupling strength between limbs and groups, we regressed individual participant nonbarrier limb movement time or maximum vertical displacement separately, on barrier limb performance. Temporal and spatial interlimb coupling strength varied across participants in both groups. Barrier limb performance predicted nonbarrier limb behavior; however, interlimb coupling was significantly stronger for the nondisabled compared to the stroke group. In the stroke group, deficits in interlimb coordination affected spatial coupling more than temporal coupling. The decreased coupling strength detected, even in the presence of mild hemiparesis, demonstrates the measure's sensitivity. The authors propose this metric as a powerful assessment of the effectiveness of rehabilitation interventions and to monitor the recovery of bimanual coordination poststroke.

Changes of gait kinematics in different simulators of reduced gravity.

Abstract: Gravity reduction affects the energetics and natural speed of walking and running. But, it is less clear how segmental coordination is altered. Various devices have been developed in the past to study locomotion in simulated reduced gravity. However, most of these devices unload only the body center of mass. The authors reduced the effective gravity acting on the stance or swing leg to 0.16g using different simulators. Locomotion under these conditions was associated with a reduction in the foot velocity and significant changes in angular motion. Moreover, when simulated reduced gravity directly affected the swing limb, it resulted in significantly slower swing and longer foot excursions, suggesting an important role of the swing phase dynamics in shaping locomotor patterns.

Introducing TAMI: An Objective Test of Ability in Movement Imagery

Abstract: Individual ability in mental imagery varies widely across individuals, leading to the development of questionnaires to evaluate mental imagery. Within the domain of movement imagery, questionnaires have previously relied on subjective ratings of vividness, which may be influenced by additional factors such as motor skill confidence, success of imagined actions, and social desirability. These additional factors are of particular importance when making comparisons between samples from different populations, such as athletes versus nonathletes and patients versus healthy individuals. The authors present a novel test of ability in movement imagery (Test of Ability in Movement Imagery [TAMI]) that relies on objective measures and requires participants to make explicit imagined movements from an external perspective. In Study 1, the authors present evidence that young adults perform at a mid-level on the TAMI. In Study 2, they further compare performance on the TAMI with a battery of other measures to better characterize the TAMI by determining its similarities and differences with existing measures. The findings of both studies indicate the TAMI to be a valid and reliable measure of movement imagery ability. The authors additionally discuss future applications of the TAMI to athletic and clinical research.

Accuracy of pattern detection methods in the performance of golf putting.

Abstract: The authors present a comparison of the classification accuracy of 5 pattern detection methods in the performance of golf putting. The detection of the position of the golf club was performed using a computer vision technique followed by the estimation algorithm Darwinian particle swarm optimization to obtain a kinematical model of each trial. The estimated parameters of the models were subsequently used as sample of five classification algorithms: (a) linear discriminant analysis, (b) quadratic discriminant analysis, (c) naive Bayes with normal distribution, (d) naive Bayes with kernel smoothing density estimate, and (e) least squares support vector machines. Beyond testing the performance of each classification method, it was also possible to identify a putting signature that characterized each golf player. It may be concluded that these methods can be applied to the study of coordination and motor control on the putting performance, allowing for the analysis of the intra- and interpersonal var...

Comparing online adjustments to distance and direction in fast pointing movements.

Abstract: It has been suggested that movements are planned in terms of direction and distance. If so, online adjustments to changes in the direction and distance of the movements may also differ. The authors therefore investigated whether fast online movement adjustments are the same for perturbations of the direction and of the distance. While subjects made fast pointing movements, the authors perturbed either target direction or distance or both shortly after movement initiation. Both kinds of perturbations resulted in accurate online adjustments. The latency and intensity of corrections for distance and direction perturbations were quite similar. This suggests that there might be one mechanism controlling both distance and direction perturbations.

Verbal implicit sequence learning in persons who stutter and persons with Parkinson's disease.

Abstract: The authors investigated the integrity of implicit learning systems in 14 persons with Parkinson's disease (PPD), 14 persons who stutter (PWS), and 14 control participants. In a 120-min session participants completed a verbal serial reaction time task, naming aloud 4 syllables in response to 4 visual stimuli. Unbeknownst to participants, the syllables formed a repeating 8-item sequence. PWS and PPD demonstrated slower reaction times for early but not late learning trials relative to controls reflecting delays but not deficiencies in general learning. PPD also demonstrated less accuracy in general learning relative to controls. All groups demonstrated similar limited explicit sequence knowledge. Both PWS and PPD demonstrated significantly less implicit sequence learning relative to controls, suggesting that stuttering may be associated with compromised functional integrity of the cortico-striato-thalamo-cortical loop.

Effects of gradual versus sudden training on the cognitive demand required while learning a novel locomotor task.

Abstract: The cognitive demand required for a range of locomotor tasks has been described for a variety of populations. However, the effect of different training strategies on the cognitive demand required while learning novel locomotor tasks is not well understood and may inform physical rehabilitation. The authors examined whether two training strategies, gradual and sudden training, influenced the cognitive demand required while practicing a novel locomotor task, asymmetric split-belt treadmill walking. Simple reaction times and whole-body kinematics were recorded throughout practice. Gradual training resulted in significantly lower reaction times during much of training, suggesting that gradual training is less cognitively demanding than sudden training, possibly due to a reduction in error feedback or movement planning demands.

Task Difficulty and the Time Scales of Warm-Up and Motor Learning

Abstract: The authors investigated the influence of task difficulty on warm-up decrement and learning across practice sessions. Three groups of participants practiced a star-tracing task over 3 consecutive days with different levels (e.g., easy, medium, hard) of task difficulty. The performance data were modeled with a 2 time scale function that represented the transient, fast time scale process of warm-up decrement superimposed with the persistent, slow time scale process of learning. Movement time decreased as a function of practice with the most difficult condition exhibiting the greatest reduction though still the longest movement time. The 2 time scale model provided a better fit to the data than an exponential or power law function and showed that the 3 difficulty conditions exhibited similar rates of change for the respective slow (i.e., learning) and fast (i.e., warm-up decrement) time scale processes that varied by an order of magnitude. Task difficulty was inversely related to the initial level of warm-up decrement but not the rate of performance recovery early in a practice session. The findings support the postulation that there is a persistent learned component to the initial conditions in subsequent practice sessions but that there is a common time scale of accommodating the transient process of warm-up decrement.

Evaluation scale development, reliability for sitting and standing from the chair for Duchenne muscular dystrophy.

Abstract: The authors aimed to (a) develop a scale to evaluate non-wheelchair-dependent children with Duchenne muscular dystrophy (DMD) while sitting and standing from the chair, (b) test its reliability, and (c) correlate the scores of this scale with the time, the age and the Vignos. Thirty DMD boys performed sit-to-stand and stand-to-sit from the chair 4 times. Scale development was based on a previous movement characterization in healthy children and in DMD children and on suggestions by physical therapists with expertise in DMD. The final version of the scale was submitted to the analysis of reliability. The sitting evaluation consists of phases: flexion, contact of the hip with the chair, extension. The standing evaluation comprehends the phases: flexion; transference; extension. Sitting and standing phases presented an excellent reliability (intraclass correlation coefficient [ICC] ≥ 0.91) and a good reproducibility (ICC ≥ 0.89). The scores generated by sitting on the chair correlated to the time taken to perform the tasks (r = .69) and to the age of the patient (r = .44) and the score of standing from the chair also correlated to the time of performance (r = .66). The sit-to-stand functional evaluation scale DMD is a reliable assessment tool that allows the description and quantification of the functional performance of DMD children.

The influence of robotic guidance on different types of motor timing.

Abstract: Robotic guidance as a means to facilitate motor learning and rehabilitation has received considerable attention during the last few years. However, mixed outcomes suggest that the benefits might be restricted to certain movement characteristics. The authors investigate the effects of robotic guidance on different kinds of motor timing. Two groups of participants performed 2 variants of a circle drawing task in a synchronization-continuation paradigm. One variant was continuous circle drawing (emergent timing), the other variant was intermittent circle drawing (event-based timing). The total duration of movement cycles (absolute timing) and the relative duration of submovements (relative timing) were measured. Half of the participants in each group were guided by a robot device during synchronization (robot-guided group), the other half of the participants received no guidance (control group). Guided participants had superior performance during the synchronization phase with both timing tasks. Dur...

Protracted exercise without overt neuromuscular fatigue influences cortical excitability.

Abstract: The authors’ aim was to determine the cortical mechanisms that underlie the transition from effective performance to its disruption. They thus used transcranial magnetic stimulation (TMS) to study changes of corticospinal excitability after a motor exercise that did not produce overt or perceived neuromuscular fatigue. Forty-four subjects performed either 5 or 10 min of repetitive finger movements paced by tones at 2 Hz, a frequency below the spontaneous movement rate. Changes of corticospinal excitability were assessed with TMS at rest and during motor response preparation (premovement facilitation paradigm). Over time, variability of movement rate increased, while the average movement rate shifted toward self-paced rhythms, without significant changes in other kinematic parameters. Amplitudes of motor evoked potentials at rest decreased depending on task duration and TMS intensity. Moreover, 5-min exercise induced fully compensatory increases in premovement facilitation, while 10-min exercise p...

Learning a New Bimanual Coordination Pattern: Interlimb Interactions, Attentional Focus, and Transfer

Abstract: Because bimanual coordinative stability is governed by interlimb coupling, we examined how learning a new pattern (90°) was reflected in changes in the underlying interlimb interactions. Three interlimb interaction sources were distinguished: integrated timing of feedforward control signals, error corrections based on perceived relative phase, and phase entrainment by contralateral afference. By comparing 4 tasks that involve these interactions to a different extent, changes in the stabilizing contributions of these coupling sources could be studied. Furthermore, we studied how the learning process and changes in the underlying interactions were influenced by attentional focus (internal vs. external), and we examined retention of the learned pattern and transfer to the mirror-symmetrical pattern (270°). Results showed that stability and accuracy of the new pattern increased significantly with learning, due to improved integrated timing and error correction. Integrated timing improved first, possi...

Visual Search Differs But Not Reaction Time When Intercepting a 3D Versus 2D Videoed Opponent

Abstract: The authors aimed to identify differences in (a) visual search and (b) reaction time when athletes sidestepped to intercept 2D versus 3D videoed opponents. They hypothesized that participants would (a) fixate on different parts of the opponent's body and (b) react quicker when responding to the 3D versus 2D opponent due to the added depth cues. A customized integrated stereoscopic system projected the video stimuli and synchronously recorded the gaze and motor behaviors of 10 men when they responded to two- (2D) and three-dimensional (3D) opponents. The number and duration of gaze fixations were coded according to locations on the opponent's body (head, shoulders, arms, trunk, pelvis, legs) or otherwise (other). Mediolateral pelvic movement was used to infer reaction time. Participants spent 16% less time fixating on the trunk and 23% more time outside the 3D opponent's body compared with the 2D stimulus. No reaction time differences were found. Although participants fixated less on the 3D opponent's body and, by inference, invested less perceptual processing toward interpreting the opponent's movements compared with the 2D condition, they performed the interception task equally fast in both conditions. Three-dimensional depth cues may provide more meaningful information per fixation for successful task performance.

Aging effects on sensorimotor integration: a comparison of effector systems and feedback modalities.

Abstract: Research on motor aging has focused on visuomotor effects in limb musculature, with few comparisons across effectors or feedback modalities. The authors examined steady fine force control in oral and manual effectors under visual and auditory feedback in 13 young (19–23 years old) and 13 older (60–77 years old) participants, hypothesizing that force variability would increase with aging (a) more in the finger than the lip and (b) for both feedback modalities. The magnitude of variability increased with age for both visuomotor and audiomotor tasks but age-related differences were greater in the lip than the finger. These results point to increased variability as a potential early marker of changing motor function (prior to loss of strength) that extends beyond the visuomotor system.

Identifying coordinative structure using principal component analysis based on coherence derived from linear systems analysis.

Abstract: Principal component analysis is a powerful and popular technique for capturing redundancy in muscle activity and kinematic patterns. A primary limitation of the correlations or covariances between signals on which this analysis is based is that they do not account for dynamic relations between signals, yet such relations—such as that between neural drive and muscle tension—are widespread in the sensorimotor system. Low correlations may thus be obtained and signals may appear independent despite a dynamic linear relation between them. To address this limitation, linear systems analysis can be used to calculate the matrix of overall coherences between signals, which measures the strength of the relation between signals taking dynamic relations into account. Using ankle, knee, and hip sagittal-plane angles from 6 healthy subjects during overground walking at preferred speed, it is shown that with conventional correlation matrices the first principal component accounted for ∼50% of total variance in ...

Especial skill effect across age and performance level: the nature and degree of generalization.

Abstract: It has been claimed that an especial skill emerges after massive amounts of basketball practice. Despite this no direct evidence is available to support this claim. The authors aimed to shed light on this question. Thirty-seven male basketball players took part representing four groups: 2 groups of senior players, a cadet group, and a group of juniors. Players performed free throw shots from 7 distances including shots from the free throw line (15 ft). It was shown that an especial skill was present in senior players, but not in junior players who had only 3 years of playing experience. The authors present a descriptive model of especial skill and express it using the formalism of a hierarchical Bayesian model to fit the data and estimate the parameters. This model can account not only for the results, which indicate the presence and a substantial degree of generalizability of especial skill to nearby distances, but also for results of the original study on especial skill where it was proposed that specificity in practice leads to the emergence of the especial skill.

Directional adaptation of reactive saccades and hand pointing movements is not independent.

Abstract: It is a matter of debate whether reactive saccades and hand pointing movements share common adaptive mechanism. To find out, the authors used a double-step paradigm in which the direction either of eye or of hand movements was adaptively modified in a first block of 300 trials, and the direction of the other motor system was then modified with opposite polarity in a second block of 300 trials. In a third block, single-step stimuli were used to test for after effects. The authors found that subjects adapted in the second block less well than in the first, and that aftereffects were adequate for the first rather than the second block. When the second block was extended to 500 trials, adaptation was still poor but aftereffects were now adequate for the second block. From this the authors concluded that double-step adaptation of the first motor system interferes with the subsequent adaptation of the other motor system (i.e., the adaptive mechanisms for eyes and hand are not independent).

Striatal Denervation Pattern Predicts Levodopa Effects on Sequence Learning in Parkinson's Disease

Abstract: Mild to moderate Parkinson's disease shows more denervation in the posterodorsal striatum and sparing of the anteroventral striatum. Dopaminergic medications can interfere with anteroventral striatum function by overdosing this relatively intact structure. The authors determined how regional striatal denervation affects medication-associated sequence learning impairment in Parkinson's disease. Eighteen Parkinson's patients performed motor sequence learning on and off levodopa. Patients underwent 11C-dihydrotetrabenazine positron emission tomography scans to measure nigrostriatal denervation. Patients with more preserved putamen were more likely to exhibit levodopa-associated sequence learning impairments. Furthermore, the ratio of denervation in the anterior to posterior dorsal putamen predicted the level of learning differences on and off levodopa. These results demonstrate that the spatial pattern of nigrostriatal dopaminergic denervation predicts medication responsiveness for motor sequence lea...