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Summary lecture 7 and literature - Motor control
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This is an extensive summary of the seventh lecture and corresponding literature about motor control of the course Neurocognition.
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25-10-2021 1Table of content
Lecture 7 – Motor control......................................................................................................................1
The motor system: Hierarchy and neural components......................................................................1
The motor system: Perception and cognition.....................................................................................5
Movement disorders..........................................................................................................................6
Summary 7 – Motor control...................................................................................................................7
Chapter 14 – Brain control of movement...........................................................................................7
Haaland et al. (2017) – The neuropsychology of movement and movement disorders:
Neuroanatomical and cognitive considerations...............................................................................11
Lecture 7 – Motor control
The motor system: Hierarchy and neural components
Movement hierarchy
Reflexes (lowest level)
˃ Fixed, rapid, automatic movements triggered in response to a specific sensory stimulus
˃ Little voluntary control, but can be modulated
Automated movements
˃ Postural: combination of reflex and volition used to maintain an upright position with respect to
gravity
˃ Rhythmic: initiation and termination is voluntary, but the actual movement is more stereotyped
Voluntary movements (highest level)
˃ Intentional, goal directed movements
˃ Initiated entirely from the CNS
˃ Performance improves with practices
˃ Reflex and postural movements compensate for the effects of the intended action
Muscle structure
Muscles attach to the skeleton at the origin and insertion
Muscles are collections of many muscle fibers
function:
˃ Movement: muscles are organized into antagonistic pairs, with extensors extending the joint and
flexors contract the joint
˃ Proprioceptive information via muscle spindles and golgi tendon organs.
Lower motor neurons of spinal cord
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Lower motor neurons project from the ventral horn of the spinal cord
˃ Alpha motor neurons cause contraction of the skeletal muscles
˃ Gamma motor neurons adjust the tension in the muscle spindle fibers so they can accurately detect a
stretch
The motor unit is the alpha motor neuron and all the muscle fibers it innervates
Spinal motor circuits: reflexes
Reflexes are simple movements coordinated by the spinal cord
Proprioceptors detect a stretch and trigger a motor response to counteract the stretch
Spinal motor circuits: central pattern generators
Neurons within the spinal cord influence rhythmic behaviors.
˃ Excitatory interneurons stimulate alpha motor neurons to cause a muscle contraction
˃ Inhibitory interneurons are also stimulated, eventually overwhelming the excitation
˃ After a period of inactivity, excitation resumes
˃ Inhibitory interneurons cross the midline, causing alternating contraction and relaxation
Descending motor pathways
Upper motor neurons from the primary motor cortex project to the spinal
cord
About 80% of the axons of the upper motor neurons decussate at the
medulla, forming the lateral corticospinal tract
About 10% decussate at the point where they exit the spinal cord
The remainder remain ipsilateral
Motor cortex
The primary motor cortex (M1) in the frontal lobe, anterior to the central sulcus
M1 has a somatotopic organization, similar to S1
Cortical motor areas
The lateral premotor area, supplementary motor are, and presupplementary area are anterior to M1
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