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The brachium of superior colliculus (or superior brachium) is a branch that extends laterally from the superior colliculus, and, passing to the thalamus between the pulvinar and the medial geniculate nuclei, is partly continued into an eminence called the lateral geniculate nucleus, and partly into the optic tract.
Specifically, compression or ischemic damage of the mesencephalic tectum, including the superior colliculus adjacent oculomotor (origin of cranial nerve III) and Edinger-Westphal nuclei, causing dysfunction to the motor function of the eye. Classically, it has been associated with three major groups:
The Sprague effect is the phenomenon where homonymous hemianopia, caused by damage to the visual cortex, gets slightly better when the contralesional superior colliculus is destroyed. [1] [2] The effect is named for its discoverer, James Sprague, who observed this phenomenon in 1966 using a cat model. [3]
There are three theories for the explanation of blindsight. The first states that after damage to area V1, other branches of the optic nerve deliver visual information to the superior colliculus, pulvinar [23] [24] and several other areas, including parts of the cerebral cortex. In turn, these areas might then control the blindsight responses.
Stimulation of the periaqueductal gray matter of the midbrain activates enkephalin-releasing neurons that project to the raphe nuclei in the brainstem. 5-HT released from the raphe nuclei descends to the dorsal horn of the spinal cord where it forms excitatory connections with the inhibitory interneurons located in Laminae II (aka the substantia gelatinosa).
The optic tract is a continuation of the optic nerve that relays information from the optic chiasm to the ipsilateral lateral geniculate nucleus (LGN), pretectal nuclei, and superior colliculus. [14] The optic tract represents the first stage in the visual pathway in which visual information is transferred in a homonymous nature. [15]
It arises from the superior colliculus of the mesencephalic (midbrain) tectum, and projects to the cervical and upper thoracic spinal cord levels. [2] It mediates reflex turning of the head and upper trunk in the direction of startling sensory stimuli (visual, auditory, or skin). [2] It arises from the deep layers of the superior colliculus.
In neuroanatomy, the pretectal area, or pretectum, is a midbrain structure composed of seven nuclei and comprises part of the subcortical visual system.Through reciprocal bilateral projections from the retina, it is involved primarily in mediating behavioral responses to acute changes in ambient light such as the pupillary light reflex, the optokinetic reflex, and temporary changes to the ...