2/12/2024 0 Comments Auditory tube cadaver![]() When paying greater attention to a task (for example, in anticipation of a reward or during opposite-sex social encounters), the IC is more active. Additionally, the IC is more active when perceiving communication by a member of the same species, indicating a special interest in salient environmental noises. When an unexpected or loud sound occurs, the IC helps to mediate the ensuing startle response. The auditory and visual inputs regarding where a sound originated are also joined by somatosensory inputs from the spinal cord and cranial nerves, which researchers hypothesize aid one’s ability to orient the body toward the source of the sound. While their purpose is unknown, the theory is that they help map physical space with both modalities of information. Some cells in IC respond to contralateral visual field stimuli, sending and receiving information from the superior colliculi. Not only does the IC allow for sound localization by integrating the input from both ears, but it also receives many non-auditory inputs. Cells in the IC are selectively active depending on the horizontal and vertical angle from which sound arrives at the ears of the listener and the rhythm of those sounds. Interestingly, the IC pitch representation differs between those who speak tonal languages, such as Chinese, and those who speak non-tonal languages. Differences in the gray matter density and activity level of the IC modulate the perception and dislike of harmonic dissonance, likely related to pitch discrimination. Discrimination between two different concurrent pitches is achieved in the IC and aided by the timing of their arrival at the IC. Pitch location in the cochlea is also mappable within the central nucleus. The central nucleus sends tonotopically organized efferent fibers, ultimately to the primary auditory cortex in the temporal lobe. The central nucleus is so named because the other two regions encircle it it is the largest nucleus and the major site of auditory inputs to the IC. The dorsal and external cortices are the major sites of non-auditory input to the IC, discussed below. ![]() There are three regions of the IC: the central nucleus, the dorsal cortex, and the external cortex. Another major source of output runs to the contralateral IC and lateral lemniscus. The major output from the IC runs through the brachium of the inferior colliculus to excite the medial geniculate nucleus of the thalamus. There is a hypothesis that they play a role in refining the auditory information conducted to higher structures. A minority of neurons are GABAergic and inhibit neurons in the medial geniculate body and contralateral IC. The IC contains mostly glutamatergic neurons, which receive and integrate auditory input from the cortex, medial geniculate nucleus, cerebellum, lateral lemniscus, and the contralateral IC. This cortical input, allows for top-down modulation of IC response to frequency, intensity, duration, and location of auditory stimuli, and may play a role in discrimination of multiple different sound sources. Glutamatergic cells in layers V and VI of the auditory cortex project principally to the ipsilateral IC, with the majority of cortical input coming from layer V. The two sets of colliculi (superior and inferior) comprise the quadrigeminal cistern, part of the tectum or “roof” of the midbrain. Each set of colliculi resembles two symmetrical bumps. ![]() Their location is on the dorsal surface of the rostral midbrain, ventral to the lateral lemniscus. The two ICs lie rostral to the trochlear nerve and just caudal to the superior colliculi.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |