Thursday, June 16, 2022

Which Lobe Of The Brain Interprets Auditory Stimuli

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Lobes Of The Brain And What They Control

Four Lobes of the Brain

Each brain hemisphere has four sections, called lobes: frontal, parietal, temporal and occipital. Each lobe controls specific functions.

  • Frontal lobe. The largest lobe of the brain, located in the front of the head, the frontal lobe is involved in personality characteristics, decision-making and movement. Recognition of smell usually involves parts of the frontal lobe. The frontal lobe contains Brocas area, which is associated with speech ability.
  • Parietal lobe. The middle part of the brain, the parietal lobe helps a person identify objects and understand spatial relationships . The parietal lobe is also involved in interpreting pain and touch in the body. The parietal lobe houses Wernickes area, which helps the brain understand spoken language.
  • Occipital lobe. The occipital lobe is the back part of the brain that is involved with vision.
  • Temporal lobe. The sides of the brain, temporal lobes are involved in short-term memory, speech, musical rhythm and some degree of smell recognition.

Relationship To The Auditory System

The auditory cortex is the most highly organized processing unit of sound in the brain. This cortex area is the neural crux of hearing, andin humanslanguage and music. The auditory cortex is divided into three separate parts: the primary, secondary, and tertiary auditory cortex. These structures are formed concentrically around one another, with the primary cortex in the middle and the tertiary cortex on the outside.

The primary auditory cortex is tonotopically organized, which means that neighboring cells in the cortex respond to neighboring frequencies. Tonotopic mapping is preserved throughout most of the audition circuit. The primary auditory cortex receives direct input from the medial geniculate nucleus of the thalamus and thus is thought to identify the fundamental elements of music, such as pitch and loudness.

An evoked response study of congenitally deaf kittens used local field potentials to measure cortical plasticity in the auditory cortex. These kittens were stimulated and measured against a control ) and normal hearing cats. The field potentials measured for artificially stimulated CDC were eventually much stronger than that of a normal hearing cat. This finding accords with a study by Eckart Altenmuller, in which it was observed that students who received musical instruction had greater cortical activation than those who did not.

Smell And Taste: The Chemical Senses

The two most underappreciated senses can be lumped into the broad category of chemical senses. Both olfaction and gustation require the transduction of chemical stimuli into electrical potentials. I say these senses are underappreciated because most people would give up either one of these if they were forced to give up a sense. While this may not shock a lot of readers, take into consideration how much money people spend on the perfume industry annually . Many of us pay a lot more for a favorite brand of food because we prefer the taste. Clearly, we humans care about our chemical senses.

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Substructures Of The Temporal Lobes

The temporal lobe is structurally divided into the superior, middle, inferior and medial gyri.

Superior Temporal Gyrus

âSuperiorâ in anatomical terms means âto the topâ. A âgyrusâ is a ridge on the surface of the brain.

The superior temporal gyrus is situated at the top of the temporal lobes, located somewhat above the ears. The superior temporal gyrus is an area of the temporal lobe which contains other areas with specialized functions.

Some areas of the superior temporal gyrus are vital in auditory processing, including the processing of language. Other areas are specialized for processing a combination of frequencies, whilst others specialize in processing changes in amplitude or frequency.

The superior temporal gyrus has been implicated as being critical in social cognition as well as being involved in the perceptions of emotions from facial expressions .

Auditory Cortex

The auditory cortex, the main arearesponsible for processing auditory information, is located within the temporal lobe.

The auditory cortex is a part of the superior temporal gyrus which essentially receives input from the ears and analyses it.

Once it has done this, the cortex then filters out unnecessary information, and passes on the relevant information to be processed and understood.

This area of the temporal lobes is therefore responsible for processing auditory information, especially important in processing the semantics in language and vision.

Limbic System
Wernickeâs Area

Bumps And Grooves Of The Brain

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In humans, the lobes of the brain are divided by a number of bumps and grooves. These are known as gyri and sulci . The folding of the brain, and the resulting gyri and sulci, increases its surface area and enables more cerebral cortex matter to fit inside the skull.

Image: DJ / CC BY-SA 2.0 Albert Kok / Public Domain

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How Does The Nervous System Work

The basic workings of the nervous system depend a lot on tiny cells called neurons. The brain has billions of them, and they have many specialized jobs. For example, sensory neurons send information from the eyes, ears, nose, tongue, and skin to the brain. Motor neurons carry messages away from the brain to the rest of the body.

All neurons relay information to each other through a complex electrochemical process, making connections that affect the way you think, learn, move, and behave.

Intelligence, learning, and memory. As you grow and learn, messages travel from one neuron to another over and over, creating connections, or pathways, in the brain. It’s why driving takes so much concentration when someone first learns it, but later is second nature: The pathway became established.

In young children, the brain is highly adaptable. In fact, when one part of a young child’s brain is injured, another part often can learn to take over some of the lost function. But as you age, the brain has to work harder to make new neural pathways, making it harder to master new tasks or change set behavior patterns. That’s why many scientists believe it’s important to keep challenging the brain to learn new things and make new connections it helps keeps the brain active over the course of a lifetime.

The Senses

Smell. Olfactory cells in the mucous membranes lining each nostril react to chemicals you breathe in and send messages along specific nerves to the brain.

What Is Temporal Lobe Of The Brain

The cerebral cortex can be divided into four sections, which are known as lobes.The frontal lobe, parietal lobe, occipital lobe and temporal lobe have been associated with different functions ranging from reasoning to auditory perception.

The frontal lobe is located at the front of the brain and is associated with reasoning, motor skills, higher level cognition, and expressive language.

The parietal lobe is located in the middle section of the brain and is associated with processing tactile sensory information such as pressure, touch, and pain.

The temporal lobe is located on the bottom section of the brain. This lobe is also the location of the primary auditory cortex, which is important for interpreting sounds and the language we hear. The hippocampus is also located in the temporal lobe, which is why this portion of the brain is also heavily associated with the formation of memories.

The occipital lobe is located at the back portion of the brain and is associated with interpreting visual stimuli and information. The primary visual cortex, which receives and interprets information from the retinas of the eyes, is located in the occipital lobe.

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Linguistic Factors: Words Versus Nonword Speech

Contrasts between word and nonword speech sounds were conducted to test whether the regions selectively activated by word stimuli are sensitive to phonetic or lexicalsemantic attributes of the stimuli. As discussed earlier, the Pseudoword stimuli differ from the Word stimuli primarily in terms of eliciting fewer explicit lexicalsemantic associations. The Reversed stimuli provide a stronger contrast, differing from the Word stimuli in terms of both phonetic intelligibility and lexicalsemantic content. Pseudoword and Reversed conditions were each contrasted with Tones in order to compare these results with the WordsTones data, and both of these nonword conditions were contrasted directly with the Words condition.

The PseudowordsTones and ReversedTones contrasts yielded results indistinguishable from WordsTones . In each case, bilateral regions at the mid-lateral STG and adjacent STS demonstrated stronger responses to speech sounds than Tones. The location of peak foci were strikingly similar and differed across the three contrasts by an average of only 3.0 mm . No areas showed stronger responses to Tones in either contrast.

Brain Areas And Their Functions

Journey of Sound to the Brain

The brain is divided into areas which are each responsible for different areas of functioning.

The brain can be divided into three basic units: the forebrain, the midbrain and the hindbrain.

These areas are: Occipital lobe, Temporal lobe, Parietal lobe, Frontal lobe.Cerebral cortex, Cerebellum, Hypothalamus,Thalamus,Pituitary gland, Pineal gland, Amygdala, Hippocampas and the Mid- brain.

The image below indicates where the areas are.

Occipital lobe: This is found in the back of the brain. The area is involved with the brain’s ability to recognise objects. It is responsible for our vision.

Temporal lobe: The temporal lobes are found on either side of the brain and just above the ears. The temporal lobes are responsible for hearing, memory, meaning, and language. They also play a role in emotion and learning. The temporal lobes are concerned with interpreting and processing auditory stimuli.

Parietal lobe: The parietal lobes are found behind the frontal lobes, above the temporal lobes, and at the top back of the brain. They are connected with the processing of nerve impulses related to the senses, such as touch, pain, taste, pressure, and temperature. They also have language functions.

Frontal lobe:It is concerned with emotions, reasoning, planning, movement, and parts of speech. It is also involved in purposeful acts such as creativity, judgment, and problem solving, and planning

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Sound Waves Enter The Ear

When a sound occurs, it enters the outer ear, also referred to as the pinna or auricle. The pinna is the visible portion of your ear, and its funnel-like shape is well-engineered: As sound hits the pinna, it filters and amplifies sound waves, and chutes them along into the ear canal, Dr. Mehdizadeh says.

Next, sound waves hit the eardrum, or tympanic membrane, setting it in motion. The eardrum is a paper-thin layer of a membrane that essentially vibrates as soon as sound waves hit itvery similar to a drum, Dr. Mehdizadeh says.

What Are Some Important Structures In The Temporal Lobe

As one of just four lobes in the brain, the temporal lobe is less a discrete organ, and more of a home to numerous other structures. Some of the most important structures in the temporal lobe include:

  • Limbic lobe: This brain region actually intersects with several lobes, but interacts directly with the temporal lobe to influence the limbic system, including automatic emotional reactions such as the fight-or-flight response and the limbic system. The limbic lobe is home to key memory, learning, and attention processing structures such as the amygdala and hippocampus. This brain region also manages a number of automatic, unconscious bodily functions, as well as unconscious emotional states, such as sexual arousal and appetite.
  • Wernicke’s area: This brain region is associated with the understanding and processing of speech.
  • Broca’s area: This brain region aids in the production of speech, though some evidence suggests that, when Broca’s area is damaged, nearby regions may compensate. Together with Wernicke’s area, Broca’s area aids communication.

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Simple Temporal Structure: Tones Versus Noise

Direct comparisons between stimulus conditions were performed to more clearly delineate areas responding differently to different stimuli. Representative SPMs are displayed in Figures 46, and the location of activation peaks for each comparison are given in Table 2.

The Noise and Tones stimuli differ in two important respects . First, the frequency bandwidth of the Noise stimuli is broader and includes much higher frequencies than the Tones stimuli. Second, a prominent feature of the Tones stimuli is a stepwise frequency modulation every 666 ms, whereas the Noise stimuli exhibit no dominant frequency and no coherent frequency modulation. If frequency bandwidth is a major factor controlling auditory cortex activation, then the TonesNoise contrast should reveal areas that are more responsive to Noise than Tones. Alternatively, if auditory cortex is very sensitive to temporal structure in the acoustic signal, then the TonesNoise contrast should reveal areas that are more responsive to Tones.

What Does The Temporal Lobe Control

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The temporal lobe is not a standalone organ. It directly interacts with other regions of the brain, and sends and receives signals to and from the spinal cord, allowing it to communicate with the entire body. Thus damage to the temporal lobe can affect functioning in far-flung organs, and damage to organs completely unrelated to the temporal lobe may impede its ability to receive, process, and respond to various cues.

Because the temporal lobe houses much of the limbic system, the temporal lobe is both heavily influenced by and influences a number of automatic bodily functions, including heart rate, arousal, anxiety, and similar states. Over time, disruptions in these states can affect other bodily functions. For example, early childhood trauma predisposes some people to a chronic state of anxiety that keeps them in a state of fight-or-flight. This floods the body with hormones such as cortisol, and can lead to chronic inflammation, and even health problems such as infertility.

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Your Brain Interprets The Signal

Once sound is converted to electrical signals in the cochlea, these signals travelvia a complex circuit of auditory nerve pathways to the auditory cortex and otherparts of the brain that regulate awareness and sensory perception. .

Sound processing likely occurs in both the cochlea and the brain, Dr. Mehdizadeh says. But most of the neurological processing of sound occurs in the brain, he says.

Brain cells, known as sensory neurons, transmit the sound information to various areas of the brain, including the thalamus, temporal lobe, and auditory cortex, the National Institutes of Health explains. These are known as the auditory pathways.

The auditory pathways process and decode sounds, turning them into something meaningful, like a question, a honking horn, or music. They also help distinguish between nearby, important sounds and less vital background sounds, as well as processing the direction and location of sounds. Many parts of hearing work directly in concert with the vestibular, or balance system, which is located nearby, within the semicircular canals of the inner ear.

“There’s many different centers in the brain that are interpreting and receiving sounds,” Dr. Mehdizadeh says.

How exactly your brain works when it comes to sound is still being explored by researchers. For example, tinnitus, or ringing in the ears, is still poorly understood, even as common as it is.

Where Is The Auditory Cortex

A coronal section of the left hemisphere, showing the primary auditory cortex as well as surrounding auditory regions .

The auditory cortex is found in the temporal lobe. Most of it is hidden from view, buried deep within a fissure called the lateral sulcus. Some auditory cortex is visible on the external surface the brain, however, as it extends to a gyrus called the superior temporal gyrus.

The auditory cortex can be subdivided into multiple regions, although there is still some question about the most appropriate way to create those subdivisions in the human brain. There is general agreement, however, that the auditory cortex consists of a primary areawhich is often referred to as the core regionas well as multiple non-primary areas.

The primary auditory cortex in humans is hidden within the lateral sulcus on a collection of gyri known as Heschls gyri . The precise location of the primary region in humans is variable, however, as is the arrangement of Heschls gyri . For example, in some individuals the primary auditory cortex seems to occupy one Heschls gyrus, while in others it may extend past that gyrus into a neighboring sulcus .

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Brain Response To Auditory Stimuli

  • In human nervous system: Hearing

    The auditory cortex provides the temporal and spatial frames of reference for the auditory data that it receives. In other words, it is sensitive to aspects of sound more complex than frequency. For instance, there are neurons that react only when a sound starts or stops.

  • In speech: Brain functions

    This is the cortical hearing centre where the effects of sound stimuli seem to become conscious and understandable. Surrounding this audito-sensory area of initial crude recognition, the inner and outer auditopsychic regions spread over the remainder of the temporal lobe of the brain, where sound signals of all

Processing Of Auditory Information In The Human Dorsal And Ventral Pfc

How the Brain Reacts to Different Auditory Stimulus

The anatomical and neurophysiological studies performed in nonhuman primates delineate somewhat separable roles for dorsal and ventral frontal lobe regions. How these functional streams in nonhuman primates map onto auditory function in the human brain is, as yet, not completely clear. Although it is well known that speech and language functions rely on the cortex within the inferior frontal gyrus neuroimaging studies have provided evidence that the human frontal lobe is also active during auditory discrimination , auditory detection , auditory attention/oddball tasks , auditory judgments , and auditory working memory . These studies have described discrete activations in DLPFC and VLPFC that are related to the type of information processed. For example, several imaging studies have described activations in DLPFC during auditory spatial localization . Conversely, VLPFC activation , has been noted during auditory non-spatial processes, such as listening to melodies, attending pitch/rhythm, determining sound length, word/voice discrimination and auditory working memory .

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What Does The Temporal Lobe Do

As its position near the temples suggests, the temporal lobe plays a key role in auditory processing. This role includes perceiving sounds, assigning meaning to those sounds, and remembering sounds. Much of the auditory work of the temporal lobe is processed through the superior temporal gyrus, a temporal lobe structure that receives sound input directly from the ear. Some of its other functions include:

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