Updates in the Treatment of Post-Stroke Pain.

PURPOSE OF REVIEW: To provide an overview of the current treatment strategies for common subtypes of post-stroke pain. RECENT FINDINGS: There is growing research interest in non-pharmacological treatment approaches for chronic pain, including neurostimulation as well as lifestyle and psychosocial interventions. Newer pharmacotherapy research includes cannabinoids and NMDA-receptor antagonists as well as bee venom. Persistent post-stroke headache is an increasingly appreciated entity, though the role of novel chronic migraine treatments for post-stroke headache is not known. Overall, most treatment approaches to post-stroke pain lack high-quality evidence. Stroke survivors are in need of effective treatments based on methodologically sound evidence. To address the interplay of clinical and psychosocial factors that contribute to post-stroke pain, it may be reasonable to adopt a multimodal treatment strategy incorporating both lifestyle interventions and conventional therapies.

A qualitative study on the use of personal information technology by persons with spinal cord injury.

PURPOSE: Previous work has shown that information technology (IT), such as personal computers and other digital devices (e.g. tablets, laptops, etc.), software, online resources and hand-held communication tools (e.g. cellphones), has benefits for health and well-being for persons with chronic health conditions. To date, the ways that persons with spinal cord injury (SCI) use IT in their daily activities has not been fully explored. Thus, the purpose of the study was to obtain an in-depth perspective of how people with SCI regularly use IT to gain insight on ways IT can be used to support health and well-being in the community for this population. METHODS: Semi-structured interviews were conducted with community-dwelling persons with SCI (N = 10) who identified themselves as frequent-or-daily-users of IT. Qualitative content analysis was used to identify the ways that persons with SCI use personal IT. RESULTS: Ten themes related to IT use were identified: (1) Modifications allowing access to IT; (2) Convenience of IT and its perceived value; (3) IT as a scheduler/planner; (4) Challenges; (5) Contributions of IT to participation; (6) Access to information; (7) Influence of IT on well-being; (8) IT as a connector; (9) Issues of IT acquisition; and (10) Desires for future devices/technology. CONCLUSIONS: The findings suggest that IT use by people with SCI contributes to general health and well-being, by increasing access to SCI-related health information and opportunity for social participation. Despite the benefits offered by IT, persons with SCI have identified a degree of skepticism about the reliability and applicability of the health information they find online. Future work on developing and implementing IT for health and well-being post-SCI should take into account consumers' perspectives to facilitate uptake. Implications for Rehabilitation There is a need for a more refined understanding of how people with spinal cord injury (SCI) use information technology (IT) in their daily lives in order to understand how IT can support health and well-being post-injury in the community. IT use holds implications for the physical and mental well-being of persons with SCI. IT allows access to a variety of information, and facilitates participation in the community. The enthusiasm for the use of IT is tempered by a degree of skepticism about the reliability and applicability of the health information available online. This highlights the need to raise awareness of existing sources vetted for this population, and to develop content that meets the particular health needs for SCI.

Motor learning and its sensory effects: time course of perceptual change and its presence with gradual introduction of load.

A complex interplay has been demonstrated between motor and sensory systems. We showed recently that motor learning leads to changes in the sensed position of the limb (Ostry DJ, Darainy M, Mattar AA, Wong J, Gribble PL. J Neurosci 30: 5384-5393, 2010). Here, we document further the links between motor learning and changes in somatosensory perception. To study motor learning, we used a force field paradigm in which subjects learn to compensate for forces applied to the hand by a robotic device. We used a task in which subjects judge lateral displacements of the hand to study somatosensory perception. In a first experiment, we divided the motor learning task into incremental phases and tracked sensory perception throughout. We found that changes in perception occurred at a slower rate than changes in motor performance. A second experiment tested whether awareness of the motor learning process is necessary for perceptual change. In this experiment, subjects were exposed to a force field that grew gradually in strength. We found that the shift in sensory perception occurred even when awareness of motor learning was reduced. These experiments argue for a link between motor learning and changes in somatosensory perception, and they are consistent with the idea that motor learning drives sensory change.

Sensory change following motor learning.

Here we describe two studies linking perceptual change with motor learning. In the first, we document persistent changes in somatosensory perception that occur following force field learning. Subjects learned to control a robotic device that applied forces to the hand during arm movements. This led to a change in the sensed position of the limb that lasted at least 24 h. Control experiments revealed that the sensory change depended on motor learning. In the second study, we describe changes in the perception of speech sounds that occur following speech motor learning. Subjects adapted control of speech movements to compensate for loads applied to the jaw by a robot. Perception of speech sounds was measured before and after motor learning. Adapted subjects showed a consistent shift in perception. In contrast, no consistent shift was seen in control subjects and subjects that did not adapt to the load. These studies suggest that motor learning changes both sensory and motor function.

Generalization of dynamics learning across changes in movement amplitude.

Studies on generalization show the nature of how learning is encoded in the brain. Previous studies have shown rather limited generalization of dynamics learning across changes in movement direction, a finding that is consistent with the idea that learning is primarily local. In contrast, studies show a broader pattern of generalization across changes in movement amplitude, suggesting a more general form of learning. To understand this difference, we performed an experiment in which subjects held a robotic manipulandum and made movements to targets along the body midline. Subjects were trained in a velocity-dependent force field while moving to a 15 cm target. After training, subjects were tested for generalization using movements to a 30 cm target. We used force channels in conjunction with movements to the 30 cm target to assess the extent of generalization. Force channels restricted lateral movements and allowed us to measure force production during generalization. We compared actual lateral forces to the forces expected if dynamics learning generalized fully. We found that, during the test for generalization, subjects produced reliably less force than expected. Force production was appropriate for the portion of the transfer movement in which velocities corresponded to those experienced with the 15 cm target. Subjects failed to produce the expected forces when velocities exceeded those experienced in the training task. This suggests that dynamics learning generalizes little beyond the range of one's experience. Consistent with this result, subjects who trained on the 30 cm target showed full generalization to the 15 cm target. We performed two additional experiments that show that interleaved trials to the 30 cm target during training on the 15 cm target can resolve the difference between the current results and those reported previously.

Somatosensory plasticity and motor learning.

Motor learning is dependent upon plasticity in motor areas of the brain, but does it occur in isolation, or does it also result in changes to sensory systems? We examined changes to somatosensory function that occur in conjunction with motor learning. We found that even after periods of training as brief as 10 min, sensed limb position was altered and the perceptual change persisted for 24 h. The perceptual change was reflected in subsequent movements; limb movements following learning deviated from the prelearning trajectory by an amount that was not different in magnitude and in the same direction as the perceptual shift. Crucially, the perceptual change was dependent upon motor learning. When the limb was displaced passively such that subjects experienced similar kinematics but without learning, no sensory change was observed. The findings indicate that motor learning affects not only motor areas of the brain but changes sensory function as well.

Effects of human arm impedance on dynamics learning and generalization.

Previous studies have demonstrated anisotropic patterns of hand impedance under static conditions and during movement. Here we show that the pattern of kinematic error observed in studies of dynamics learning is associated with this anisotropic impedance pattern. We also show that the magnitude of kinematic error associated with this anisotropy dictates the amount of motor learning and, consequently, the extent to which dynamics learning generalizes. Subjects were trained to reach to visual targets while holding a robotic device that applied forces during movement. On infrequent trials, the load was removed and the resulting kinematic error was measured. We found a strong correlation between the pattern of kinematic error and the anisotropic pattern of hand stiffness. In a second experiment subjects were trained under force-field conditions to move in two directions: one in which the dynamic perturbation was in the direction of maximum arm impedance and the associated kinematic error was low and another in which the perturbation was in the direction of low impedance where kinematic error was high. Generalization of learning was assessed in a reference direction that lay intermediate to the two training directions. We found that transfer of learning was greater when training occurred in the direction associated with the larger kinematic error. This suggests that the anisotropic patterns of impedance and kinematic error determine the magnitude of dynamics learning and the extent to which it generalizes.

Modifiability of generalization in dynamics learning.

Studies on plasticity in motor function have shown that motor learning generalizes, such that movements in novel situations are affected by previous training. It has been shown that the pattern of generalization for visuomotor rotation learning changes when training movements are made to a wide distribution of directions. Here we have found that for dynamics learning, the shape of the generalization gradient is not similarly modifiable by the extent of training within the workspace. Subjects learned to control a robotic device during training and we measured how subsequent movements in a reference direction were affected. Our results show that as the angular separation between training and test directions increased, the extent of generalization was reduced. When training involved multiple targets throughout the workspace, the extent of generalization was no greater than following training to the nearest target alone. Thus a wide range of experience compensating for a dynamics perturbation provided no greater benefit than localized training. Instead, generalization was complete when training involved targets that bounded the reference direction. This suggests that broad generalization of dynamics learning to movements in novel directions depends on interpolation between instances of localized learning.

Neural averaging in motor learning.

The capacity for skill development over multiple training episodes is fundamental to human motor function. We have studied the process by which skills evolve with training by progressively modifying a series of motor learning tasks that subjects performed over a 1-mo period. In a series of empirical and modeling studies, we show that performance undergoes repeated modification with new learning. Each in a series of prior training episodes contributes such that present performance reflects a weighted average of previous learning. Moreover, we have observed that the relative weighting of skills learned wholly in the past changes with time. This suggests that the neural substrate of skill undergoes modification after consolidation.

Motor learning by observing.

Learning complex motor behaviors like riding a bicycle or swinging a golf club is based on acquiring neural representations of the mechanical requirements of movement (e.g., coordinating muscle forces to control the club). Here we provide evidence that mechanisms matching observation and action facilitate motor learning. Subjects who observed a video depicting another person learning to reach in a novel mechanical environment (imposed by a robot arm) performed better when later tested in the same environment than subjects who observed similar movements but no learning; moreover, subjects who observed learning of a different environment performed worse. We show that this effect is not based on conscious strategies but instead depends on the implicit engagement of neural systems for movement planning and control.