Where does the brain process sound? (see here!)

In this article we are going to answer the question ‘’Where does the brain process sound?’’ and 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 information already processed to the rest of the nervous system.

Where does the brain process sound?

The brain processes sound in the primary auditory cortex located in the temporal lobe and finally in the frontal and parietal lobes.

The ear, the organ of hearing, is a complex structure that is divided into outer, middle and inner ear.

The outer ear has three parts, the pinna (the ear), the external auditory canal, and the outer layers of the tympanic membrane (the eardrum), and its main function is to pick up sound. The middle ear, made up of the hammer, anvil and stapes, acts as a transmitter of sound waves.

While the inner ear is the one that has the auditory and balance function, which depend on the cochlea and the vestibular apparatus.

The ear performs its auditory function by making the physical sound stimulus perceptible in three stages:

1. Transmission or conduction of the physical energy of the sound stimulus captured in the auditory pinna to the organ of Corti, located in the middle part of the inner ear and made up of hair cells.

2. Transformation of mechanical energy into electrical energy, which is then transferred to the auditory nerve.

3. Transmission of electrical energy to the cerebral cortex. The appreciation of sounds is a function of the auditory areas of the cortex.

Auditory function in the outer ear

The pinna picks up sound waves and sends them to the tympanic membrane. The human ear is practically immobile and is oriented towards the sound by movements of the head.

In addition, it contributes to the localization of the origin of the sound: the fact of having two ears separated by the head makes the sound reach both ears with a time and phase difference, which serves to locate the sound in the horizontal plane.

While those responsible for locating the sound in the vertical plane are the folds of the pavilion.

Auditory function in the middle ear

It is responsible for transmitting sound energy from the tympanic membrane to the inner ear. 

Upon entering the middle ear, the tympanic membrane vibrates and this movement is transferred to the hammer, the hammer to the anvil and this to the stapes. The latter will transmit the vibration to the inner ear.

Auditory function of the inner ear

The organ with which it is heard is the brain. To do this, the cochlea is previously in charge of converting acoustic signals into electrical impulses so that they are interpreted as sounds in the brain.

In addition, it will be in charge of discriminating the different sounds according to their frequency, it encodes the stimuli in time according to their cadence and they are filtered to facilitate understanding.

The 5 auditory areas of the brain

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 through our ears and becomes experienced by us.

The auditory areas of our brain include both the auditory pathways, which consist of bundles of fibers that carry information from the ear to the brain and vice versa, as well as the areas of the brain dedicated to hearing.

These brain areas are the brainstem together with the superior olive complex, the lemniscus and the colliculus; the thalamus and the primary auditory cortex.

In addition, it is necessary to note 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, along with the auditory pathways, of transporting information to the brain through electrical impulses.

Role of the auditory pathways

Like the rest of sensory modalities, the auditory system is composed of a series of pathways and primary centers in 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 neural circuit 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 emit a response or reaction to the auditory stimulus.

Non-primary pathway

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 bring together several different sensory messages, but which are being given at the same time, to select those that must be processed more 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.

1. Cochlear nuclei

Cochlear nuclei are found on the surface of the brain stem, their main function being to examine the intensity of sound, as well as its onset, duration, and end. In addition, they also provide information to the brain about the frequency of the sound, that is, whether it is bass or high-pitched sounds.

2. Superior olive complex

One of the most complex systems of the auditory brain is the upper olive complex. Its dense neural network is designed to analyze and filter all acoustic information that is directed to the cerebral cortex.

3. Lateral lemniscus and colliculus

The nucleus of the lateral lemniscus is involved in encoding the duration of the most complex sounds.

On the other hand, the colliculus is divided into the dorsal and external cortex and the central nucleus, which is composed of a large number of neurons.

The dorsal and external cortex is engaged in examining acoustic information and in 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, 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 specialized zones in one function. These areas are the dorsal area, the middle area and the ventral area.

Dorsal area

Neurons in the dorsal area send projections to the secondary auditory cortex. These neurons tend to respond to various different sensory stimuli.

Ventral zone

Its neurons travel to the primary auditory cortex and are also involved in the analysis of the frequency of sound, maintaining 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 are located in the upper area of the temporal lobe, where they extend through the angular gyrus towards the Silvio fissure; there they meet the transverse gyrus of Heschl.

This brain area can in turn be divided into two regions differentiated by the organization of their neurons and by their functions. These areas are as follows.

  • The A1 area is composed of neurons that determine the spatial representation of the stimulus.
  • The A2 area is dedicated to locating sound in external space, examining complex sounds, and is closely related to auditory memory.

Finally, the area surrounding these two areas is in charge of analyzing and integrating the auditory information with the other sensory information that the person perceives.

Hearing, communication and brain activity

Hearing is the first step in developing communication skills. This is how children learn to recognize their parents; in fact, babies begin to notice sounds when they are in their mother’s womb. Hearing is also essential when learning to speak since children learn by imitating sounds.

Although the hearing is not the only form of communication, hearing loss affects the way we speak and interact.

Older people with hearing loss are more likely to develop other problems (for example, an inability to think clearly or remember) than people with normal hearing. The ability to hear in both ears facilitates understanding and allows you to deduce where sounds are coming from.

Our brain adapts to hearing loss

Other research carried out by the University of Colorado Boulder, concludes that the brain reorganizes when you suffer from hearing loss, even if it is mild. The researchers used scanners to analyze the brains of people with hearing loss and found that shortly after hearing loss, the rest of the senses began to gain relevance.

The scans showed activation of the frontal lobe, where we find memory, when these people were preparing to hear sounds.

In addition, another study showed that the continued use of hearing aids re-adapted the brain of these patients and this resembled that of a person with healthy hearing.

In conclusion, hearing needs the brain to function properly and mental health can be affected by hearing loss.

For this reason, we must pay close attention to our hearing health by monitoring our hygiene and, above all, carry out periodic examinations to confirm if there has been any change in our hearing.

If you want to share an experience with us, leave us your comments, we will read you!

FAQS: Where does the brain process sound?

Does brain make sound?

No, the brain does not make sounds, instead the brain converts the impulses it receives through the ear into sounds that we can understand.

How does the brain detect sound?

Sound waves enter the outer ear, then these signals reach the brain through the auditory nerve.

Where is the hearing center in the brain?

The primary auditory cortex or A1 is the region of the human brain responsible for processing auditory information. It is located in the temporal lobe.

Why do I hear noises in my brain?

Tinnitus occurs due to the existence of an auditory memory that is formed in our brain.

Why do I hear sounds that are not there?

The sensation of hearing, seeing or smelling objects that are not there relates to hallucinations. These can also be as intense and as true as experiences of the senses.

In this article we answered the question ‘’Where does the brain process sound?’’ and we talked 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 information already processed to the rest of the nervous system.

If you have any questions or comments please let us know!

References

National Institutes of Health (US, & Biological Sciences Curriculum Study. (2013). Information about Hearing, Communication, and Understanding. Retrieved November 22, 2020, from Nih.gov website

Purves, D., Augustine, G. J., Fitzpatrick, D., Katz, L. C., Anthony-Samuel LaMantia, McNamara, J. O., & S Mark Williams. (2013). The Auditory Cortex. Retrieved November 22, 2020, from Nih.gov website

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