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Comparison of Accessibility Tools for Biomechanical Analysis of Medical Devices: What Experts Think
Published in Jack M. Winters, Molly Follette Story, Medical Instrumentation, 2006
Melissa R. Lemke, Jack M. Winters
Movements of slow or moderate speed often are thought of as sequential transitions in posture, which are carried out through contracting different skeletal muscles according to voluntary commands integrated with continuous peripheral sensory information. It is often necessary to simultaneously control multiple muscles at the same joint or different joints to obtain or maintain particular body positions (e.g., elbow and shoulder extension, reaching while standing). Many degrees of freedom exist within human joints, typically more than required to specify endpoints (e.g., hand position and orientation). The brain and spinal cord often select from numerous alternative postural sequences to complete a given task. The brain and spinal cord organize numerous possible movement patterns into a connected hierarchy within the premotor cortex, sensorimotor cortex, brainstem, spinal cord, and other structures such as the cerebellum and peripheral nerves. Some autonomic reflexes (e.g., knee jerk, flexion withdrawal) are organized at the spinal cord level, while other complex motions are organized in higher brain centers [5,6]. Although described in very minimal detail here, coordinated movement often requires many physiological systems to be fully synchronized so that motor commands for maintaining or changing postures can be effectively selected, executed, and attuned.
Preparation for Action: One of the Key Functions of the Motor Cortex
Published in Alexa Riehle, Eilon Vaadia, Motor Cortex in Voluntary Movements, 2004
For comparison, the percentages of execution-related selectivity are plotted in Figure 8.6B for the same sample of neurons. It is interesting to note that during execution many more selective activity changes were encountered than nonselective ones, whereas the percentages of selective neurons in relation to individual movement parameters did not vary as strongly in relation to both movement parameter and cortical area as they did during preparation. Furthermore, the number of "mixed" neurons (black bars) increased significantly compared to preparation. The fact that during preparation virtually all selective neurons changed their activity in relation to only one movement parameter — and not to a combination of parameters ("mixed") — suggests that movement preparation seems to be performed by rather segregated neuronal networks, each of which is responsible for processing information about that single movement parameter only. Conversely, the high number of "mixed" neurons present during execution suggests that common output networks, which represent the whole movement rather than single movement parameters, may be used. Finally, the fact that about two-thirds of primary motor cortical neurons changed their activity in relation to prior information (see percentages indicated in Figure 8.6 for each cortical area) demonstrates clearly the strong involvement of this area in preparatory processes. Hence, preparation for action is one of the key functions of motor cortical structures, including the primary motor and the premotor cortex.
Brain Motor Centers and Pathways
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Focal lesions of premotor areas are generally manifested in impairment of the ability to choose the appropriate course of action. Lesions of the ventral premotor cortex impair the ability to use visual information about an object to control the hand so as to grasp an object in a manner that is appropriate for the object’s size, shape, and orientation. Lesions of the dorsal premotor cortex, or supplementary motor area, impact the ability to learn and recall arbitrary sensorimotor transformations, such as temporal sequences of movements or conditional stimulus–response associations. Lesions of prefrontal areas associated with the supplementary motor area produce deficiencies in the initiation and termination of movements.
Altered brain functional connectivity in the frontoparietal network following an ice hockey season
Published in European Journal of Sport Science, 2023
Melissa S. DiFabio, Daniel R. Smith, Katherine M. Breedlove, Ryan T. Pohlig, Thomas A. Buckley, Curtis L. Johnson
Our analysis of the FPN revealed significantly increased functional connectivity between the bilateral posterior parietal cortices over the course of one season. Within the FPN, the PPC is where most sensory information is integrated (Ekman, Fiebach, Melzer, Tittgemeyer, & Derrfuss, 2016). It receives sensory information directly from the visual and somatosensory cortices and projects to the premotor cortex, and thus plays a crucial role in motor planning based on sensory information, especially in planning and controlling a motor response (Iacoboni, 2006). Our findings of altered functional connectivity in the bilateral PPC may have unique implications for athletes as proper execution of motor control in athletics is critical to injury prevention and performance. Even a momentary disruption in carrying out a motor command can result in serious and potentially career-ending injuries, such as non-contact anterior cruciate ligament tears (Swanik, 2015). We did not study musculoskeletal injury incidence in this study, but future studies should consider examining the relationship between FPN functional connectivity and injuries.
An exploration of motor learning concepts relevant to use of speech-generating devices
Published in Assistive Technology, 2019
Elena Dukhovny, Jennifer J. Thistle
The development of motor learning can be measured behaviorally as well as through neuroimaging. Observing the performance of the skill and measuring its speed and accuracy provided the foundational evidence for motor learning. As noted above, seminal researchers proposing motor learning theories based their stages on characteristics of observable behavior (Fitts & Posner, 1967; Gentile, 1972). As a result, we define improved typing skill as increased speed and accuracy of typing. Brain imaging techniques (e.g., EEG, fMRI) afford us the ability to further characterize motor learning by identifying regions of the brain that are activated when engaging in motor skill learning tasks. There is some controversy about the specific regions (Wu, Kansaku, & Hallett, 2004), but evidence is converging to suggest that motor movement activates the left dorsal premotor cortex, bilateral supplementary motor cortex, bilateral motor cortex, left primary somatosensory cortex, left superior parietal lobule, left thalamus, bilateral putamen, and cerebellum (Hardwick, Rottschy, Miall, & Eickhoff, 2013).