Auditory cortex: characteristics and functions of this region of the brain

The cortex of the brain includes areas that specialize in specific tasks. This is the case, for example, of the auditory cortex.

We will dedicate the following lines to better understand the function of this part of the brain, its characteristics and the most important regions. Likewise, we will see with what other parts of the nervous system and the human body it is connected to perform its functions.

    What is the auditory cortex of the brain? Location and features

    The auditory cortex of the brain is part of this organ responsible for processing all the information we receive through the auditory system, that is, the sounds picked up by the ears. Its location is in the temporal lobe and in this area we can find it in the so-called Heschl area, formed by transverse convolutions.

    Another way to find this area is to go to the map of old Brodmann neighborhoods, because the auditory cortex the brain occupies parts 41, 42 and part 22, In this card. This region of the cerebral cortex is found both in the brain of humans and in the large number of vertebrate animal species.

    Parts and structure

    In terms of structure, the auditory cortex of the brain can be subdivided into primary (A1), secondary (A2), and tertiary (A3) auditory cortex. The primer is approximately 3 millimeters thick. At the macrostructural level, we have already seen that it is located in the Heschl zone, occupying half of this entire zone.

    If we go to the microstructure, we can find several ways to study this part of the brain.. For example, at the level of neuronal arrangement or cytoarchitecture, part A1 would be part of the so-called koniocortex, a grouping of granular-appearing neurons. The cerebral auditory cortex A1 has several layers, showing a higher density in the numbers II and IV. As for III, it is characterized by the existence of pyramidal-type cells.

    If we focus on the chemical composition, or the chemoarchitecture, we will find that the A1 zone is largely composed of CO, cytochrome oxidase and AChE, acetylcholinesterase. To finish, the distribution of myelin, or myeloarchitecture, denotes high concentrations of this substance in the primary part, Precisely where more sensory projections occur.

    Precisely because of this great myelination, the auditory cortex of the brain of the primary type (A1) can be easily observed by magnetic resonance imaging.

    In the case of primates, and more specifically in humans, we can divide this area, from the most central to the most peripheral, like the core, the inner belt and the outer belt. The nucleus would house the A1 section and also the rostral part or R. The inner girdle would house the auditory cortex, the secondary brain, that is to say the A2 area. Finally, the outer strip is where one would find the tertiary section, or A3.

    The auditory cortex of the brain is part of the so-called neocortex. This area is characterized by the need for some stimulation during development in order to perform all functions correctly. In this sense, in order for the auditory cortex to perform its tasks in a normal way, it must have been exposed to different auditory frequencies in the early stages of the body’s life.

    Functions of the auditory cortex of the brain

    The function of the auditory cortex of the brain, as is evident, is to process the data picked up by the auditory system. If that part of the brain did not do this task, no matter how structurally the ears were functioning properly, we would have no way of being able to use the sense of hearing because there would be no reception and no reception. interpretation of the sounds picked up. by this system.

    For this reason, some brain damage due to trauma, disease, stroke, or tumors that damage this area, can cause functional deafness whether the ears are not affected or not. However, although the sounds cannot be interpreted, these subjects still show reflex behaviors in the face of some.

    The explanation for this phenomenon is that before reaching the auditory cortex of the brain, there is an initial processing of information that takes place in the brainstem and in the midbrain.

    Outraged, each group of neurons in the auditory cortex the brain specializes in processing sounds belonging to a certain frequency. In this way, we can see that from one end the neurons that process low frequencies (from 2 Hz) are located and as we move towards the other end of this crust the cells . frequencies, up to 128 Hz.

    Due to this phenomenon, there are frequency maps or tonotopic maps that indicate exactly which area of ​​the auditory cortex the brain is engaged in specific sound frequencies. This region of the brain, by interpreting the data obtained by the ear, is able to locate where sounds are coming from and to identify and classify them.

    It is not yet clear how this part of the brain is able to perform this activity with such precision, because identifying the continuum of a particular sound, ignoring the rest of the noise that is constantly being heard, is something. extremely complex. One theory is that the key is in the spatial location of the sound source, but when it is constantly changing isn’t a problem for the brain’s auditory cortex, so there must be some other explanation.

    In turn, the auditory cortex the brain is able to discern between different tones, harmony and timing of notes. This facet is very well observed in terms of musical performance and how we are able to distinguish each sound, coming from a whole range of instruments, and interpret them all together.

    We have already seen that the auditory cortex of the brain is divided into three parts (primary, secondary and tertiary) and that it is also neuronally structured by the type of sound frequencies that they handle. Outraged, zone A1 also has connections with other regions of the nervous system such as the thalamus, And more specifically with the area of ​​the medial geniculate nucleus.

    It is believed that this part is one of the responsible for interpreting the volume of sound and also the perceived tones.

      Types of auditory cortex dysfunction

      There are different pathologies that can be caused by injuries or abnormalities in the auditory cortex of the brain.

      We have already mentioned cortical-type deafness, which occurs when the A1 area is damaged and therefore the individual cannot properly process the sounds that the ears hear.

      If the lesions, on the other hand, affect the secondary or tertiary area, there are other pathologies that the subject can develop. For example, if the damaged area is in the right hemisphere, that person might have it. problems recognizing the tone of sounds, which is called pleasure. He might have a hard time getting the lines right. In this case, the disease would be called dysprosody.

      It could even affect other sensory regions, for example those that have to do with visual memory. In the event that the injury affects the left hemisphere, we find other possibilities. The best known are aphasias, which are linked to difficulties in understanding or using language. One is Wernicke’s, which prevents him from understanding and repeating the words he hears.

      Another common aphasia is anomic aphasia, whereby the person experiencing it has problems in being able to remember the name of an item.. There could also be another aphasia known as sensory transcortical, which also affects speech understanding. The last of the possible aphasias is that of acoustic behavior and amnesia, which would cause him problems to repeat a sequence of words.

      also, with damage to the auditory cortex, the left hemisphere brain may also suffer from verbal amnesia, Which would also make the floor difficult for the person. The fun that we have seen in the other hemisphere can also occur here, also related to the auditory agony, the inability to process the stimuli that it receives through the ear, in this case.

      But it can happen that the injury or disease has affected the auditory cortex to the brain of both hemispheres of the brain, which would imply bilateral type disease. In this type we find this auditory agnosia we were talking about as well as deafness of the verbal type, that is to say unable to process the words that the ears hear.

      Bibliographical references:

      • Delahay, F., Regulis, S. (2006). The brain and music. UNAM scientific dissemination journal.
      • Jara, N., Délano, PH (2014). Progress of the auditory cortex. Journal of Otorhinolaryngology and Neck Surgery.
      • On the left, MA, Oliver, DL, Malmierca, MS (2009). Mechanisms of plasticity (functional and activity-dependent) in adults and auditory brain development Journal of Neurology.
      • Terreros, G., Wipe, B., León, A., Délano, PH (2013). From the auditory cortex to the cochlea: Progression of the auditory efferent system. Journal of Otorhinolaryngology and Head and Neck Surgery.

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