Neurological Examination, clinical cases and neuropsychological ...

23/07/54
The extrapyramidal system is a neural network located in the
brain that is part of the motor system involved in the coordination of movement.
The system is called "extrapyramidal" to distinguish it from the tracts of the motor
cortex that reach their targets by traveling through the "pyramids" of the medulla.
The pyramidal pathways (corticospinal and some corticobulbar tracts) may directly
innervate motor neurons of the spinal cord or brainstem (anterior (ventral) horn
cells or certain cranial nerve nuclei), whereas the extrapyramidal system centers
around the modulation and regulation (indirect control) of anterior (ventral) horn
cells.
Extrapyramidal tracts are chiefly found in the reticular formation of the pons and
medulla, and target neurons in the spinal cord involved in reflexes, locomotion,
complex movements, and postural control. These tracts are in turn modulated by
various parts of the central nervous system, including the nigrostriatal pathway,
the basal ganglia, the cerebellum, the vestibular nuclei, and different sensory
areas of the cerebral cortex. All of these regulatory components can be considered
part of the extrapyramidal system, in that they modulate motor activity without
directly innervating motor neurons.
Corticospinal tract damage
Damage to the descending motor pathways anywhere
along the trajectory from the cerebral cortex to the lower
end of the spinal cord gives rise to a set of symptoms
called the "upper motor neuron syndrome". A few days
after the injury to the upper motor neurons a pattern of
motor signs and symptoms appears, including spasticity,
the decreased vigor (and increased threshold) of
superficial reflexes, a loss of the ability to perform fine
movements, and an extensor plantar response known as
the Babinski sign. [
The frontal eye fields (FEF) is a region located in the premotor cortex,
which is part of the frontal cortex of the primate brain.
Function
The cortical area called frontal eye fields (FEF) plays an important role in the control of
visual attention and eye movements. Electrical stimulation in the FEF elicits saccadic eye
movements. The FEF have a topographic structure and represents saccade targets in
retinotopic coordinates.
The frontal eye field is reported to be activated during the initiation of eye movements,
such as voluntary saccades and pursuit eye movements. There is also evidence that it
plays a role in purely sensory processing and that it belongs to a “fast brain” system
through a superior colliculus – medial dorsal nucleus –FEF ascending pathway.In
humans, its earliest activations in regard to visual stimuli occur at 45 ms with activations
related to changes in visual stimuli within 45–60 ms (these are comparable with
response times in the primary visual cortex). This fast brain pathway also provides
auditory input at even shorter times starting at 24 ms and being affected by auditory
characteristics at 30–60 ms. The FEF constitutes together with the supplementary eye
fields (SEF), the intraparietal sulcus (IPS) and the superior colliculus (SC) one of the most
important brain areas involved in the generation and control of eye movements,
particularly in the direction contralateral to the frontal eye fields' location.
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