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The tectum is the region of the brain located at the dorsal, or back section, of the brain stem, in the mid-section of the brain. The word tectum is Latin for "roof," indicating this region's position in regard to the brain stem. The midbrain tectum also has projections that lead to the spinal cord, allowing for a quick response time to stimuli. In mammals, its function is to process auditory input and as well as some visual reflexes. In non-mammals, the tectum comprises the main visual area of the brain, similar to the function of the cerebral cortex in mammals.
There are two main receptor types in the tectum: the superior colliculi and the inferior colliculi. The superior colliculi control primary eye movements and preliminary visual processing in humans. Visual input is collected from the retina and impulses are then transmitted to the superior colliculi. Eye movement, and even head turning and arm-reaching movements, are then initiated in response to the stimuli.
The inferior colliculi is concerned with auditory processes. It is located just below the superior colliculi, and the two work together to integrate sound location data and visual input in order to give a sense of space and location. Sound waves are collected by the cochlea, the inner part of the ear, and transmitted via the auditory nerve to the inferior colliculi. From there, these impulses are then transmitted to the thalamus and processed by the auditory cortex. It is a complicated process that occurs in microseconds.
Diseases of the tectum are rare, but do occur in about 10% of children aged three to 16, caused by a spontaneous growth of the glial cell. This type of brain tumor is slow-growing, and is commonly asymptomatic. When symptoms do occur, they may include headaches, nausea, vomiting, and erratic eye movements or an irregular gait. Surgical removal is limited because of the delicate structure of the tectum, and radiation is not recommended. Diagnostic tests, such as physical examination, a computed axial tomography (CT) scan, or biopsy may be performed, and prognosis is usually positive with regular monitoring.
Many areas of the brain are still not understood completely, and research is ongoing. Study of the tectum of the midbrain in both mammals and non-mammals have yielded much information about how different species process outside stimuli. Further research may contribute to advances in medicine for disorders like Parkinson's disease and stroke, where hearing and vision are adversely affected.
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