People are used to living with sound. The fact of hearing everything that we have around us is something that we have so internalized that we do not even stop to think about how this information enters our ears and becomes experienced by us.
In this article we will talk about the auditory areas of the brain which, together with the auditory system, is responsible for collecting these signals sent by the auditory nerves and sending the already processed information to the rest of the nervous system.
The auditory areas of our brain include both the auditory pathways, which consist of bundles of fibers that transport information from the ear to the brain and vice versa, and the areas of the brain dedicated to hearing
These brain areas are the brainstem along with the superior olivary complex, the lemniscus and the colliculus; the thalamus and the primary auditory cortex.
In addition, it is necessary to point out the importance of the function of the auditory nerve. This nerve is essential for our hearing. Composed of more than 30,000 neurons, it is responsible, together with the auditory pathways, for transporting information to the brain through electrical impulses.
Like the rest of the sensory modalities, The auditory system is made up of a series of pathways and primary centers of the brain whose function is to process and transport auditory information.
In the case of the auditory pathways we find the primary auditory pathway whose sole purpose is to transport auditory information, and the non-primary pathway which also integrates other sensory modalities.
Primary auditory pathway
The primary auditory pathway is a short neuronal circuit and with the ability to transport information very quickly, since it is made up of thick myelinated fibers.
Its only task is to transport the information that is collected by the cochlea, performing decoding and interpretation tasks at each of the levels. This information is transferred from one level to another until it reaches the auditory cortex.
However, before the information reaches the auditory cortex, the thalamus integrates the information and prepares to issue a response or reaction to auditory stimulus.
Non-primary route
After the first level, which integrates both auditory pathways as one, a part of this pathway known as the non-primary pathway deviates, joining the ascending reticular pathway, which integrates sensory information of all types
The main function of this pathway is to gather several different sensory messages, which are occurring at the same time, to select those that must be processed most urgently.
Parts of the brain stem involved in hearing
The brain stem is the structure through which almost all sensory pathways pass and its function is to communicate the spinal cord, cerebellum and brain. In it we can locate the nuclei corresponding to the auditory system in the brain These are the following.
The cochlear nuclei are located on the surface of the brain stem, its main function being to examine the intensity of the sound, as well as its beginning, duration and end. In addition, they also provide information to the brain about the frequency of the sound, that is, whether it is low-pitched or high-pitched sounds.
2. Superior olive grove complex
One of the most complex systems of the auditory brain is the superior olivary complex. Its dense neural network is designed to analyze and filter all acoustic information which goes to the cerebral cortex.
3. Lateral lemniscus and colliculus
The nucleus of the lateral lemniscus is involved in encoding the duration of more complex sounds.
Besides, The colliculus divides into the dorsal and outer cortex and the central nucleus which is made up of a large number of neurons.
The dorsal and outer cortex is dedicated to examining acoustic information and recognizing complex sounds. While the central core analyzes the frequency of the sound and divides it into bass or treble.
The thalamus and auditory cortex
Other areas of the brain involved in hearing are the thalamus and the auditory cortex. Let’s see how they work.
auditory thalamus
The auditory thalamus, also known as the Medial Geniculate Body (MGC), receives fibers from both the dorsal and external cortex of the colliculus and its central nucleus. This part of the thalamus is divided into three areas specialized in one function. These areas are: the dorsal area, the middle area and the ventral area.
Neurons in the dorsal zone send projections to the secondary auditory cortex. These neurons tend to respond to various different sensory stimuli.
ventral area
Its neurons travel to the primary auditory cortex and They are also involved in the analysis of the frequency of sound maintaining the latency between communications.
primary auditory cortex
In people, The auditory cortex covers 8% of the entire surface of the cerebral cortex
This primary auditory cortex consists of more than twelve different auditory fields that They are located in the upper area of ​​the temporal lobe, where they extend through the angular gyrus towards the Sylvian fissure; there they meet Heschl’s transverse gyri.
This brain area can be divided into two regions differentiated by the organization of its neurons and their functions. These areas are as follows.
Finally, the area surrounding these two areas is responsible for analyzing and integrating auditory information with the other sensory information that the person perceives.
