Spinal drive results from the complex dynamic interaction between the central program in the lower thoracolumbar spine and proprioceptive feedback from the body in the absence of central control by the brain as in complete spinal cord injury (SCI). After SCI, the spinal cord under the lesion site does not become silent but continues to maintain active and functional neuronal properties albeit modified.
Video Spinal locomotion
Spinal drive component
Centrally-generated patterns
The spinal cord performs a rhythmic and sequential activation of the muscles in motion. The central pattern generator (CPG) provides basic locomotor rhythms and synergies by integrating commands from various sources that serve to start or modulate its output to meet environmental requirements. CPG in the lumbosacral spinal cord segment is an important component of the total circuit that produces and controls posture and locom. These spinal circuits can function independently in the absence of declining inputs from the brain to produce stable posture and movement and even modulate activities to adjust for changing conditions (eg, bypassing obstacles). This ability increases with training (spinal plastisity) and it is therefore believed that the spinal cord has the ability to learn and memorize.
Sensory feedback
Sensory feedback comes from the muscles, joints, tendons and afferents of the skin as well as of the particular senses and dynamically adjusts the locomotor pattern of the spinal cord with environmental requirements. These afferent sensory receptors see tissue deformation of the amount of pressure (stretching or simple, placement), direction of movement, velocity and velocity at which movement is occurring.
Maps Spinal locomotion
Sensor Modulation CPG
The dynamic interaction between the spinal cord and the sensory input is confirmed by modulating the transmission in the locomotor pathway by depending on the state and phase. For example, the proprioceptive input of the extensor can, during the stance, adjust the time and amplitude of the limb muscle activity to the driving speed but is silenced during the cycle swing phase. Similarly, afferent skin participates primarily in leg correction and foot placement while standing on uneven terrain, but skin stimulation can lead to different types of responses depending on when they occur in the step cycle. It is important to note that the input of the hip seems to play an important role in the movement of the spine. Experiments on spinal animals show that when one leg is held with a flexed hip, the movement on that side stops while the rest of the body continues walking. However, when the extremity stops extended at the hip joint to the point normally reached at the end of the position during walking, suddenly flexes and begins running again as long as the limbs are the position to receive the back weight. Another work confirms the importance of the afferent hip for the generation of locomotor rhythm because hip flexion will eliminate the rhythm while the extension will increase it.
The spinal cord processes and interprets proprioception in a manner similar to the way the visual system processes information. When we look at paintings, the brain interprets the total visual field, as opposed to processing each pixel of information independently, and then taking a picture. Each time the spinal cord receives an information ensemble of all the receptors throughout the body that denotes a proprioceptive "image" that represents time and space, and calculates which next exciting neuron based on the most recent "image" is felt. The importance of CPG is not only its ability to generate repetitive cycles, but also to receive, interpret, and predict the proper sequence of actions during each part of the step cycle, that is, state dependency. The peripheral input then provides important information from which the probability of a particular set of neurons active at a given time can be well tuned to a particular situation during the specific phase of the step cycle. A very good example of this is when a mechanical stimulus is applied to the dorsum of a cat's claw. When the stimulus is applied during the swing phase, the flexor flexor muscles are vibrant, and the result is an increased flexibility to bypass the barrier that creates the stimulus. However, when the same stimulus is applied when standing, the extensor feels good. Thus, the functional connectivity between the mechanoreceptors and the specific interneuronal population in the spinal cord varies according to the physiological state. Even the monosinaptic input effectiveness of the muscle spindle to the motor neuron changes easily from one part of the step cycle to another, according to whether the subject is running or walking.
In the absence of CPG, control by the brain as is the case with complete spinal cord injury, sensory feedback is essential in generating rhythmic motors. First, locomotor movements can be initiated or blocked by some afferent proprioceptive inputs. Another work confirms the importance of the afferent hip for the generation of locomotor rhythm because hip flexion will eliminate the rhythm while the extension will increase it. Second, proprioceptive afferents can participate in adjusting the speed of walking, in determining the duration of the cycle as a whole, and in arranging the subfase structure of step cycles (ie, swings, horses), which are necessary for the adaptation of the speed and coupling of the interlimb. Third, afferent afferentoceptive is involved in regulating the level of muscle activity through various reflex pathways.
Evidence of development
Ultrasound footage has been taken in the womb image of a human fetus on 13-14 weeks of pregnancy "creeping and climbing" and producing alternating steps. The onset of stepping on the fetus precedes the development and myelinition of the most declining brain pathway strongly suggests the human locomotor spinal cord CPM and the coordination of sensory feedback and plasticity. Collectively, research in the first year of postnatal shows that the locomotor continuum extends from the neonatal step to the onset of independent walking further demonstrates human movement is controlled by CPG and the interaction of sensory inputs.
Rehabilitation
The spinal cord injured is a "spinal cord" that changes. After SCI, the supraspinal and spinal sources of motion control differ substantially from those before the injury, resulting in an altered spinal cord. The posture and locomosi stability arises from the interaction between the peripheral nervous system (PNS) and the central nervous system (CNS) to work synergistically, each system having intrinsic activation and inhibition patterns that can produce coordinated motor output.
Electrical stimulation
Many experiments have shown that electrical stimulation (ES) from lumbosacral enlargement and dorsal roots may induce locomotor EMG patterns and even hind legs in low and chronic spinal animals and humans. Increased amplitude of stimulation results in increased amplitude of EMG and increased frequency of rhythmic activity. The high-frequency stimulation (& gt; 70 Hz) produces tonic activity in the leg muscles, which indicates that upper lumbar stimulation can activate the neural structure which then recruits the interneurons involved in the CPG.
Training treadmill
The treadmill training (better known as a weight supported treadmill exercise) can be applied manually (therapist) or robotic assistance. In manual treadmill training, the therapist provides assistance to facilitate upright posture and normal stepping patterns. Therapeutic help can be given in the patient's pelvis, legs and feet, and the third therapist who controls the treadmill setting. In robot-assisted treadmill training, the device replaces the therapist's needs to assist the patient in producing a normal jumping pattern. Currently, there are three different models available: Lokomat Hocoma, HealthSouth AutoAmbulator, and Mechanized Gait Trainer II. The Lokomat is a gait-style orthosis consisting of a computer controlled exoskeleton that is secured to the patient's leg when supported on a treadmill. In addition to belt-driven treadmills and uplift, HealthSouth AutoAmbulator also includes a pair of articulated arm (which moves hip and knee joints) and two vertical structures that serve as a computer control and weight-loss mechanism. Unlike the first two, Mekanized Gait Trainer II does not work together with a treadmill; it is based on a crank gear system and a rocker that provides limb movements similar to an elliptical trainer. Robot-assisted treadmill training is developed with three objectives: 1. to reduce the therapist's physical demand and time, 2. to improve the repetition of kinematics steps, and 3. to increase the volume of locomotor training.
In humans with clinically complete SCI, there is evidence that treadmill training can improve some aspects of walking with the help of weight support. Dietz and colleagues reported that after a few weeks of treadmill training, the level of heavy weights that can be imposed on the clinically complete SCI subject's foot during the treadmill goes significantly increased. When stepping on a weight-bearing treadmill, rhythmic leg muscle activation patterns can be obtained on clinically complete subjects who otherwise can not voluntarily produce muscle activity in their legs. A recent study has shown that the extent of extensor leg muscle activity recorded in a clinically complete SCI subject is significantly increased over several weeks of step training. Interestingly, SCI's clinically incomplete clinical ability to step up in response to step training, but its rate of improvement has not yet reached a level that allows full independence of assistance during full load. In large part because of the knowledge gained from the study of spinning animals, two general principles have emerged to draw the spinal circuit that results in steps:
- A weight-backed treadmill exercise improves the lumbosacral spinal cord's ability to produce weight-bearing movements.
- The sensory input pattern provided during locomotor training is essential to encourage the plasticity mediating motor recovery.
See also
- Central pattern generator
- Central nervous system
- Locomotive
- Proprioception
- Spine cable
- spinal cord injury
- Special senses
References
External links
- www.wingsforlife.com
- www.addlestonechiro.com
- www.sci-info-pages.com/levels.html
- The Losing Man
- [1]
- The research for this Wikipedia entry involves Dr. Jaynie Yang for online seminars
- Research for this page includes a review paper by Dr. Edgerton
- The research for this Wikipedia entry was performed as part of the Locomotion Neuromechanics course (APPH 6232) offered at the School of Applied Physiology at Georgia Tech.
Source of the article : Wikipedia
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