The primary auditory cortex is organized tonotopically, although its organisation is complex, and the details are beyond the scope of this article. The primary auditory cortex (A1) is located in the superior temporal gyrus, right under the lateral fissure. Note: A good way to remember what information passes through each geniculate body is that music goes to medial and light goes to lateral. Projections from the medial geniculate body proceed then to the primary auditory cortex. The MGB does not act as a simple relay centre: it has reciprocal connections with the auditory cortex and mediates refinement of the incoming information. These fibres project to the ipsilateral medial geniculate body (MGB) in the thalamus (recall that vision is relayed on the lateral geniculate body). Inferior Colliculus and Medial Geniculate Bodyįibres ascending through the lateral lemniscus from both cochlear nuclei and from the superior olivary nuclei arrive at the inferior colliculus, where all these fibres carrying auditory information converge. Therefore, hearing problems can be conductive or sensorineural but are rarely central.Īdobe Stock, Licensed to TeachMeSeries Ltdįig 3 – Information from each cochlear nucleus is transmitted bilaterally. above the level of the cochlear nucleus) will not lead to serious hearing impairment. This is important because supranuclear lesions (i.e. For that reason, information from both ears travels bilaterally in each lateral lemniscus. In summary, in both the dorsal and ventral nuclei, some fibres decussate while others do not. It also projects upwards through the lateral lemniscus. The superior olivary nucleus is located just next to the trapezoid body. Although the ventral cochlear nuclei neurons decussate at the trapezoid body, some fibres synapse at the ipsilateral superior olivary nucleus. However, most fibres from the ventral cochlear nucleus decussate to the contralateral superior olivary nuclei in a region known as the trapezoid body. Other fibres ascend in the ipsilateral lateral lemniscus.įrom the ventral cochlear nucleus, some fibres also ascend in the lateral lemniscus bilaterally.
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