Download Temporal Aspects of Visual Extinction

Chapter 14: Motor System
 Chris Rorden
University of South Carolina
Norman J. Arnold School of Public Health
Department of Communication Sciences and Disorders
University of South Carolina
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Cortical Level
 Prefrontal Cortex
 Responsible for manipulating
discrete and skilled voluntary
movements through planning
and innervation of muscles
 Refers to highly conscious
planning and sequencing
 Site of reasoning, thinking,
planning
Primary Sensory (parietal)
Primary Motor (frontal)
Premotor (frontal)
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Sensorimotor Cortex Areas (1)
 Premotor Cortex
 30% of Motor Fibers
 Info from thalamus,
cerebellum, basal ganglia
 Has some skilled patterns
which are well learned
 Lesion(s) in the inferior
premotor cortex in the left
hemisphere is often
associated with verbal
apraxia
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Sensorimotor Cortex Areas (2)
 Primary Motor Cortex
 30% of motor fibers
 2% from Betz Cells which are
large to support long axons
 Corticospinal tract – (superior
2/3) Voluntary Movements of
muscles controlled via spinal
nerves.
 Corticobulbar tract – (inferior
1/3) Facial and Associated
Muscles – project to cranial
nerve nuclei.
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Sensorimotor Cortex Areas (2)
Primary Sensory Cortex
40% of motor fibers
– Project through motor
cortex with modulation of
sensory information
– Corticopontine tract (pons)
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Physiology of Motor Cortex
Highly Organized in Form of
Homunculus
Discovered by Penfield and
Roberts who used electrical
stimulation of cortex on
patients in surgery
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Cranial Nerves Spinal Nerves
 Corticospinal Tract
– From upper two thirds of primary motor cortex, premotor cortex
and sensory cortex
– Through Corona Radiata to Internal Capsule and Pes
Pedunculi in the Midbrain
 Corticobulbar Tract
– From lower third of motor cortex and adjacent area to corona
radiata through internal capsule, pes pedunculi across midline
to lower cranial nuclei
– Crossed: oculomotor, abducens, trigeminal, facial, vagus,
glossopharyngeal and hypoglossal
– Uncrossed: trochlear
– Some duplication of tracts offers redundancy
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Pyramidal Tract Fibers
Corona Radiata (fibers tracts between IC and cortex)
Internal
Internal
4 3
Capsule,
Capsule,
Anterior
86
Posterior
Limb
Limb
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Pyramid
Lateral
Corticospinal
Tract
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Path of upper motor neurons
Lateral: Skeletal Muscle Fingers, Toes, Forearm
Anterior: Axial and Girdle muscles
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Clinical Considerations
Lesions in corticospinal fibers result in spastic
hemiplegia
Lesions in corticobulbar fibers result in
paralysis of facial, lingual, palatal and
laryngeal muscles. More bilateral innervation
causes less paralysis
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Clinical Considerations
Upper Motor Neuron
symptoms
– Flaccid followed by spastic
hemiplegia
– Increased Muscle Tone
– + Babinski Sign
– Hyperreflexias
– Loss of Abdominal Reflexes
– Alternating Hemiplegia (Some
Fibers that are crossed and
uncrossed)
Normal reflex
Negative Babinski
Abnormal
Positive Babinski
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Clinical Considerations
Lower motor neuron symptoms
– Damage to LMN eliminates the function of the
motor unit
– Lesion affecting the LMN causes weakness of
muscles and reduces tendon reflexes
– Muscle tone is flaccid
– Can be seen in muscular dystrophy and
myasthenia gravis
– Absent or greatly reduced Babinski
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