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Brain Motor Centers and Pathways
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Stimulation of the surface of the primary motor cortex, at a relatively low threshold, elicits movement of different parts of the body. Moving the site of stimulation laterally across the motor cortex reveals a somatotopic organization, the most medial part corresponding to the lowest extremities and the most lateral parts corresponding to the face and tongue (Figure 12.3). However, the distribution of various body parts over the primary motor cortex is not uniform, resulting in a caricature of a human figure referred to as the motor homunculus, or little person. A relatively large cortical area representation is associated with finer movements, which involve small motor units and hence a larger number of motor neurons that need to be controlled. This is the case, for example, with: The hand, including the four fingers and the opposable thumb, which underlies the amazing manual dexterity of humans.Facial muscles, conveying a variety of facial expressions, which is important for social interaction.The mouth and tongue, involved in vocalization.
Key human anatomy and physiology principles as they relate to rehabilitation engineering
Published in Alex Mihailidis, Roger Smith, Rehabilitation Engineering, 2023
Qussai Obiedat, Bhagwant S. Sindhu, Ying-Chih Wang
When a stimulus occurs, the sensory neurons receive signals through sensory receptors, detect internal or external stimuli, and generate electrical impulses. Touch, pressure, temperature, pain sensation from the skin, muscle spindles embedded in muscles, joint proprioception around joint capsules, and senses of vision, auditory, and olfactory signals are examples of the sensory receptors in the body. Signals from multiple sources travel to the thalamus via ascending pathways in the spinal cord and are further relayed to specific areas of the cerebral cortex for interpretation and integration. The thalamus is the principal relay station for all sensory input, except olfaction, to the cerebral cortex from the spinal cord, brain stem, cerebellum, and other parts of the cerebrum. The primary auditory cortex interprets characteristics of sound and hearing. The primary visual cortex receives inputs concerning shape, color, and movement. The primary olfactory area receives impulses for smell. If an action is required, the primary motor cortex, the region of the cerebral cortex involved in the planning, control, and execution of voluntary movements, transmits nerve impulses to the muscles via motor neurons (i.e., descending pathways) and makes muscles move (e.g., drinking a cup of tea, shooting a basketball, dancing). While performing a sequence of movements, the brain continues to receive feedback such as perception of movement and spatial orientation from the head and body. Besides the motor cortex, the cerebellum and the basal ganglia make essential and distinct contributions to motor control. The cerebellum reduces movement errors by detecting differences between intended and actual movements and modulates movements via its projections to the upper motor neurons. In contrast, inputs to the basal ganglia facilitate proper initiation of movement and prevent unwanted movements by tonic inhibition (Lundy-Ekman 2013).
Review of the Human Brain and EEG Signals
Published in Teodiano Freire Bastos-Filho, Introduction to Non-Invasive EEG-Based Brain–Computer Interfaces for Assistive Technologies, 2020
Alessandro Botti Benevides, Alan Silva da Paz Floriano, Mario Sarcinelli-Filho, Teodiano Freire Bastos-Filho
The primary motor cortex is directly responsible for the coordination of voluntary movements. The left side of Figure 1.4 shows the somatotopic9 map of M1, which correlates some M1 areas with the control of body parts. It is worth noting that more than a half of M1 comprises the control of muscles linked to hands and speech [2].
Modeling of hyper-adaptability: from motor coordination to rehabilitation
Published in Advanced Robotics, 2021
Harry Eberle, Yoshikatsu Hayashi, Ryo Kurazume, Tomohiko Takei, Qi An
When humans move their body to perform a task, many parts of the human brain play important roles. Sensory information integrated in the parietal association area of the brain and the network between parietal area, premotor cortex, and primary motor cortex (M1) are involved in planning a motor command. This planned motor command is sent to the brainstem and the spinal cord through the corticospinal tract. Subcortical systems involve low-dimensional motor primitives (known as synergies) to generate muscle activity. When humans learn a new motor skill, these nervous systems are utilized for adaptation. In the normal adaptation, the cerebellum, basal ganglia, and cerebral cortex are thought to play specialized roles in supervised learning, reinforcement learning, and unsupervised learning, respectively [2].
Identifying the benefits and risks of emerging integration methods for upper limb prosthetic devices in the United States: an environmental scan
Published in Expert Review of Medical Devices, 2019
Marcella A Kelley, Heather Benz, Susannah Engdahl, John F P Bridges
Neuromotor prostheses include the permanent implantation of microelectrode arrays directly into the primary motor cortex or spinal cord to control the prosthetic device via electroneurographic signals (Figure 2(d)) [29,41]. This approach relies on previously used motor pathways so studies have been limited to amputee samples of monkeys and a few humans that exhibited neural firing and multitasking capabilities [36,41]. The potential benefits of cortical integration include multitasking without interruption of other activities, restorative capabilities, sensory feedback and increased control of the device with time and training [28,29,41]. The drawbacks of this method include its invasive nature, its unknown maintenance requirements, the lack of sustained signal strength in the implanted electrodes and high financial costs [29,41]. Research efforts focusing on cortical integration methods have stalled since the early 2000s likely due to its many risks [41].
Effects of local and global spatial patterns in EEG motor-imagery classification using convolutional neural network
Published in Brain-Computer Interfaces, 2020
Jacob Jiexun Liao, Joy Jiayu Luo, Tao Yang, Rosa Qi Yue So, Matthew Chin Heng Chua
We found that both Hands (left + right) always have opposite correlation with Feet across all frequency bands except 36–40 Hz. This is consistent with the fact that the sensorimotor area for Feet is located in the middle of the primary motor cortex whereas the Hands are at the side. For Left vs. Right hands, in general, negative correlation were found at the contralateral side to hand movement (motor imagery) in frequency bands, 20–24, 24–28, 28–32 Hz. The Tongue showed similar trend of correlation with Left and Right hands from 16 to 36 Hz. It showed positive correlation on two sides of the plots except frequency band 16–20 Hz. It did not show contralateral effect as was observed in the case of the Left and Right hands.