Visuomotor Training Research Articles

Prism adaptation and spatial neglect: the need for dose-finding studies.

Spatial neglect is a devastating disorder in 50–70% of right-brain stroke survivors, who have problems attending to, or making movements towards, left-sided stimuli, and experience a high risk of chronic dependence. Prism adaptation is a promising treatment for neglect that involves brief, daily visuo-motor training sessions while wearing optical prisms. Its benefits extend to functional behaviors such as dressing, with effects lasting 6 months or longer. Because one to two sessions of prism adaptation induce adaptive changes in both spatial-motor behavior (Fortis et al., 2011) and brain function (Saj et al., 2013), it is possible stroke patients may benefit from treatment periods shorter than the standard, intensive protocol of ten sessions over two weeks—a protocol that is impractical for either US inpatient or outpatient rehabilitation. Demonstrating the effectiveness of a lower dose will maximize the availability of neglect treatment. We present preliminary data suggesting that four to six sessions of prism treatment may induce a large treatment effect, maintained three to four weeks post-treatment. We call for a systematic, randomized clinical trial to establish the minimal effective dose suitable for stroke intervention.

Monitoring of Visuomotor Coordination in Healthy Subjects and Patients with Stroke and Parkinson’s Disease: An Application Study Using the PABLOR-Device

Background: Visuomotor performance can be improved by repetitive training on consecutive days. The aim of this study was to assess the training effect of visuomotor tracking in healthy subjects and hemiparetic patients with stroke and in moderately impaired patients with Parkinson’s disease. Methods: 39 healthy right-handed subjects, 15 patients after acute cerebral artery stroke, and 15 patients with mid-stage Parkinson’s disease were trained with the commercially available, multifunctional PABLOR-device. This handhold device is equipped with force and acceleration sensors and connected to a personal computer for on-line data display and data storage. On three consecutive days the subjects were trained to navigate a target through obstacles in a virtual reality environment. Performance was assessed by modulation of force production and rotation of the hand in a visuomotor tracking paradigm using the PABLOR-device. Results: The main findings were that training of the right dominant hand improved visuomotor coordination of hand rotation movements in both hands in the healthy subjects (p=0.0015). Training of the right affected hand improved visuomotor coordination of hand rotation movements in either patient group (p=0.026). In contrast, training improved the visuomotor coordination of force tracking of the dominant hand only in the healthy subjects (p<0.01). Conclusions: The visuomotor training scenario was effective to improve visually guided hand coordination within three days in the healthy controls and both patient groups. The improvement of hand rotation generalized to the nontrained hand in healthy subjects.

Attention modulates generalization of visuomotor adaptation

Generalization represents the ability to transfer what has been learned in one context to another context beyond limited experience. Because acquired motor representations often have to be reinstated in a different or novel environment, generalization is a crucial part of visuomotor learning. In daily life, training for new motor skills often occurs in a complex environment, in which dividing attentional resources for multiple stimuli is required. However, it is unknown how dividing attention during learning affects the generalization of visuomotor learning. We examined how divided attention during training modulates the generalization of visuomotor rotational adaptation. Participants were trained to adapt to one direction with or without dividing attention to a simultaneously presented visual detection task. Then, they had to generalize rotational adaptation to other untrained directions. We show that visuomotor training with divided attention multiplicatively reduces the gain and sharpens the tuning of the generalization function. We suggest that limiting attention narrowly restricts an internal model, reducing the range and magnitude of transfer. This result suggests that attention modulates a selective subpopulation of neurons in motor areas, those with directional tuning values in or near the training direction.

How the motor-cortex distinguishes among letters, unknown symbols and scribbles. A high density EEG study

Previous research has reported that the perception of written language symbols activates the cortical motor hand representation of the dominant hemisphere also found to be activated during the writing of these symbols. It has been suggested that such motor activation supports reading. Nevertheless, the precise circumstances leading to such activation are still unknown. For instance, several studies suggested that motor activation necessarily depends on specific sensory-motor experience with the stimuli. Some results, however, also indicated that untrained stimuli can elicit the response. Moreover, due to the methods used so far, little is known about the temporal course of the motor activity. Our study explored these open questions using high-density EEG. We measured central alpha event-related desynchronization (ERD) as a marker of cortical motor activation during the observation of Roman letters (alphabet of participants’ mother language), Chinese characters (not familiar to participants), and scribbles. Our results show that the cortical motor system is activated during the perception of all three stimuli in both hemispheres, with ERD stronger in the left (dominant) hemisphere. A significant difference of ERD time-course was observed in the left hemisphere between the observation of symbols (letters and characters) and scribbles. Scribbles elicited significantly faster resynchronization of central alpha than symbols. We suggest that ERD results are due to recognizing all stimuli as traces of hand gestures. Furthermore, differences in ERD found between symbols and scribbles might depend either on visuo-motor training, separating symbols from scribbles, or on stimuli specific features marking their status as either language symbols or scribbles.

A functional magnetic resonance imaging study of visuomotor processing in a virtual reality‐based paradigm: Rehabilitation Gaming System

The Rehabilitation Gaming System (RGS) has been designed as a flexible, virtual-reality (VR)-based device for rehabilitation of neurological patients. Recently, training of visuomotor processing with the RGS was shown to effectively improve arm function in acute and chronic stroke patients. It is assumed that the VR-based training protocol related to RGS creates conditions that aid recovery by virtue of the human mirror neuron system. Here, we provide evidence for this assumption by identifying the brain areas involved in controlling the catching of approaching colored balls in the virtual environment of the RGS. We used functional magnetic resonance imaging of 18 right-handed healthy subjects (24±3years) in both active and imagination conditions. We observed that the imagery of target catching was related to activation of frontal, parietal, temporal, cingulate and cerebellar regions. We interpret these activations in relation to object processing, attention, mirror mechanisms, and motor intention. Active catching followed an anticipatory mode, and resulted in significantly less activity in the motor control areas. Our results provide preliminary support for the hypothesis underlying RGS that this novel neurorehabilitation approach engages human mirror mechanisms that can be employed for visuomotor training.

Effect of Motor Control Program in Improving Gross Motor Function and Postural Control in Children with Sensorineural Hearing Loss-A Pilot Study

Background: Sensorineural hearing loss (SNHL) is the most common type of permanent hearing impairment and results from damage to the inner ear or the nerve pathway. Children with hearing impairment have balance and motor deficits primarily due to concomitant damage to the vestibular structures. Objective: To study the effect of motor control program on improvement of gross motor function and postural control in children with sensorineural hearing loss. Methods: A pre-post testtrial consisting of 10 participants between the age group of 6 to 12 years with the clinical diagnosis of sensorineural hearing loss. Participants received exercise sessions including 10 min of activities in the following categories: eye hand co-ordination and visual motor training, balance training, activities to improve general co-ordination for 3 days a week for 12 weeks. The outcome was assessed in terms of Pediatric Balance scale (PBS), Test for Gross Motor Development (TGMD-2). Result: There was highly significant difference seen in scores of both TGMD-2 and PBS (p<0.01). Conclusion: The findings of the study suggest thatmotor control program including eye-hand co-ordination, visuomotor training, balance training and general co-ordination exercises can be useful to maintain gross motor skills and postural control in children with sensorineural hearing loss.

Corticomotor excitability and plasticity following complex visuomotor training in young and old adults

Previous studies with transcranial magnetic stimulation (TMS) have shown that advancing age may influence plasticity induction in human motor cortex (M1), but these changes have been assessed with TMS-induced paradigms or simple motor tasks. The aim of this study was to examine changes in corticospinal excitability and intracortical inhibition as markers of corticomotor plasticity following complex motor training in young and old adults. Electromyographic recordings were obtained from the right first dorsal interosseous (FDI) muscle of 16 young (20-35 years) and 16 older (aged 60-75 years) adults before and after motor skill training. Motor training consisted of three 6-minute blocks of a complex visuomotor task that required matching the metacarpophalangeal (MCP) joint angle of the index finger using abduction-adduction movements. Single- and paired-pulse TMS over the left M1 was used to assess changes in right FDI motor-evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) before and after each training block. Visuomotor tracking performance was diminished in old compared with young adults throughout training. However, improvement in tracking error was similar for young and old adults (7-24% increase in each training block). For young and old adults, motor training increased FDI MEP amplitude (≥ 20%) and reduced the magnitude of SICI (≥ 19%) after each visuomotor training block, reflecting use-dependent plasticity. However, no difference in corticomotor plasticity (change in MEP or SICI) was observed between young and old adults. Further studies are needed to identify the experimental or behavioral factors that might contribute to the maintenance of corticomotor plasticity in older adults.

Reactivity of alpha rhythms to eyes opening is lower in athletes than non-athletes: A high-resolution EEG study

In the present study, we tested the hypothesis that compared with non-athletes, elite athletes are characterized by a reduction of reactivity of electroencephalographic (EEG) alpha rhythms (about 8–12 Hz) to eyes opening in the condition of resting state, as a possible index of spatially selective cortical activation (i.e. “neural efficiency”). EEG data (56 channels; Eb-Neuro©) were recorded in 18 elite karate athletes and 28 non-athletes during resting state eyes-closed and eyes-open conditions. The EEG data were spatially enhanced by surface Laplacian estimation. Cortical activity was indexed by task-related power decrease (TRPD), namely the alpha power during the eyes-open referenced to the eyes-closed resting condition. Low-frequency alpha TRPD (about 8–10 Hz) was lower in the elite karate athletes than in the non-athletes in frontal (p < 0.00002), central (p < 0.008) and right occipital (p < 0.02) areas. Similarly, high-frequency alpha TRPD (about 10–12 Hz) was lower in the elite karate athletes than in the non-athletes in frontal (p < 0.00009) and central (p < 0.01) areas. These results suggest that athletes' brain is characterized by reduced cortical reactivity to eyes opening in the condition of resting state, in line with the “neural efficiency” hypothesis. The present study motivates future research evaluating the extent to which this general functional brain feature is related to heritable trait or intensive visuo-motor training of elite athletes.

Cortical oscillatory activity and the induction of plasticity in the human motor cortex

Repetitive transcranial magnetic stimulation paradigms such as continuous theta burst stimulation (cTBS) induce long-term potentiation- and long-term depression-like plasticity in the human motor cortex. However, responses to cTBS are highly variable and may depend on the activity of the cortex at the time of stimulation. We investigated whether power in different electroencephalogram (EEG) frequency bands predicted the response to subsequent cTBS, and conversely whether cTBS had after-effects on the EEG. cTBS may utilize similar mechanisms of plasticity to motor learning; thus, we conducted a parallel set of experiments to test whether ongoing electroencephalography could predict performance of a visuomotor training task, and whether training itself had effects on the EEG. Motor evoked potentials (MEPs) provided an index of cortical excitability pre- and post-intervention. The EEG was recorded over the motor cortex pre- and post-intervention, and power spectra were computed. cTBS reduced MEP amplitudes; however, baseline power in the delta, theta, alpha or beta frequencies did not predict responses to cTBS or learning of the visuomotor training task. cTBS had no effect on delta, theta, alpha or beta power. In contrast, there was an increase in alpha power following visuomotor training that was positively correlated with changes in MEP amplitude post-training. The results suggest that the EEG is not a useful state-marker for predicting responses to plasticity-inducing paradigms. The correlation between alpha power and changes in corticospinal excitability following visuomotor training requires further investigation, but may be related to disengagement of the somatosensory system important for motor memory consolidation.

P17-10 Use-dependent motor cortex plasticity following complex visuomotor training in young and old adults

P17-10 Use-dependent motor cortex plasticity following complex visuomotor training in young and old adults

Visuomotor Training Improves Stroke-Related Ipsilesional Upper Extremity Impairments

Background. Unilateral middle cerebral artery infarction has been reported to impair bilateral hand grasp. Methods. Individuals (5 males and 5 females; age 33-86 years) with chronic unilateral middle cerebral artery stroke (4 right lesions and 6 left lesions) repeatedly lifted a 260-g object. Participants were then trained to lift the object using visuomotor feedback via an oscilloscope that displayed their actual grip force (GF) and a target GF, which roughly matched the physical properties of the object. Results.The subjects failed to accurately modulate the predictive GF when relying on somatosensory information from the previous lifts. Instead, for all the lifts, they programmed excessive GF equivalent to the force used for the first lift. The predictive GF was lowered for lifts following the removal of the visual feedback. The mean difference in predictive GF between the lifts before and after visual training was significant (4.35 ± 0.027 N; P ≤ .001; 95% confidence interval [CI] = 3.80-4.88). After removal of visual feedback, there was also a significant mean difference in the applied predictive GF between the “early” and “late” lifts (0.78 ± 0.029 N; P ≤ .006; 95% CI = 0.22-1.35), demonstrating continued increase in predictive GF accuracy. Conclusion. Predictive or feedforward fingertip force generation is impaired in the ipsilesional hand when lifting a novel object with precision grip. Reacquisition of the motor forces for the grasp of objects is possible after stroke. Potentially, retraining grasp control for the ipsilesional hand may translate to improved function and motor learning within the contralesional hand.

The Resting Human Brain and Motor Learning

SummaryFunctionally related brain networks are engaged even in the absence of an overt behavior. The role of this resting state activity, evident as low-frequency fluctuations of BOLD (see [1] for review, [2–4]) or electrical [5, 6] signals, is unclear. Two major proposals are that resting state activity supports introspective thought or supports responses to future events [7]. An alternative perspective is that the resting brain actively and selectively processes previous experiences [8]. Here we show that motor learning can modulate subsequent activity within resting networks. BOLD signal was recorded during rest periods before and after an 11 min visuomotor training session. Motor learning but not motor performance modulated a fronto-parietal resting state network (RSN). Along with the fronto-parietal network, a cerebellar network not previously reported as an RSN was also specifically altered by learning. Both of these networks are engaged during learning of similar visuomotor tasks [9–22]. Thus, we provide the first description of the modulation of specific RSNs by prior learning—but not by prior performance—revealing a novel connection between the neuroplastic mechanisms of learning and resting state activity. Our approach may provide a powerful tool for exploration of the systems involved in memory consolidation.

Effectiveness of Prism Adaptation in Neglect Rehabilitation

This study was conducted to investigate the effectiveness on neglect recovery of a 2-week treatment based on prism adaptation (PA) in comparison to an analogous visuomotor training performed without prisms, ie, neutral pointing (NP). Twenty neglect patients were divided into 2 matched groups, one was submitted to PA (PA group) and the other to NP (NP group) for 10 daily sessions over a period of 2 weeks. After the end of NP treatment, the patients in the NP group were also submitted to PA treatment. Neglect was assessed before and after each treatment and 1 month after the end of the PA treatment. Visuospatial abilities improved after both PA and NP treatment; however, the improvement was significantly higher in the patients in the PA group than in the patients in the NP group. Moreover, when the patients in the NP group were submitted to PA, they further improved up to the level reached by patients in the PA group, ie, to nonpathological scores. Long-lasting beneficial effects of PA were confirmed 1 month from the end of treatment. The leftward recalibration of sensorimotor reference frames induced by PA is effective to obtain proper neglect recovery, although visuomotor training based on pointing might partially improve neglect symptoms.

Illusory movements of the paralyzed limb restore motor cortex activity

In humans, limb amputation or brachial plexus avulsion (BPA) often results in phantom pain sensation. Actively observing movements made by a substitute of the injured limb can reduce phantom pain (V.S. Ramachandran and D. Rogers-Ramachandran, 1996, Proc. R. Soc. London B Biol. Sci. 263, 377–386). The neural basis of phantom limb sensation and its amelioration remains unclear. Here, we studied the effects of visuomotor training on motor cortex (M1) activity in three patients with BPA. Functional magnetic resonance imaging scans were obtained before and after an 8-week training program during which patients learned to match voluntary “movements” of the phantom limb with prerecorded movements of a virtual hand. Before training, phantom limb movements activated the contralateral premotor cortex. After training, two subjects showed increased activity in the contralateral primary motor area. This change was paralleled by a significant reduction in phantom pain. The third subject showed no increase in motor cortex activity and no improvement in phantom pain. We suggest that successful visuomotor training restores a coherent body image in the M1 region and, as a result, directly affects the experience of phantom pain sensation. Artificial visual feedback on the movements of the phantom limb may thus “fool” the brain and reestablish the original hand/arm cortical representation.