Temporal Aspects of Visual Extinction
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Transcript 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
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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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