Saturday, August 13, 2022

Where Is Speech Located In The Brain

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C Computation Of Semantic And Syntactic Relations

How does your brain decode garbled speech?

Empirically, there are three basic methodological approaches to investigate syntactic and semantic processes during sentence comprehension. The first is to vary the presence/absence of syntactic information or of semantic information . The second approach is to introduce syntactic or semantic errors in sentences. The third is to vary the complexity of the syntactic structure or the difficulty of semantic interpretation . All these approaches have been used in fMRI studies published in the last 15 years.

In general, these studies found activations at different locations in the anterior and posterior temporal cortex as well as in the IFG. The picture that emerges from these studies may be less clear than some researchers had hoped . However, once we take both stimulus type and task as well as neuroarchitectonic subdivisions of language-relevant brain regions into consideration, a picture emerges that is worth presenting as a tentative state of the art model. Once these different aspects are considered, the reported activation pattern provides a surprisingly coherent picture even across typologically different languages. We will first consider activations in the temporal lobe and then those in the IFG.

The Evolution Of Language

The auditory dorsal stream also has non-language related functions, such as sound localization and guidance of eye movements. Recent studies also indicate a role of the ADS in localization of family/tribe members, as a study that recorded from the cortex of an epileptic patient reported that the pSTG, but not aSTG, is selective for the presence of new speakers. An fMRI study of fetuses at their third trimester also demonstrated that area Spt is more selective to female speech than pure tones, and a sub-section of Spt is selective to the speech of their mother in contrast to unfamiliar female voices.

General Inability To Speak And Understand Language

Widespread damage to the brains language centers can result in global aphasia. People with global aphasia will have an extremely hard time expressing and understanding language.

People with neurodegenerative diseases, such as Alzheimers disease, often experience loss of speech slowly over time. This is called primary progressive aphasia .

PPA is not Alzheimers disease but can be a symptom of Alzheimers disease. PPA can also be an isolated disorder without the other symptoms of Alzheimers disease. Some people with PPA have normal memories and can continue leisure activities and sometimes even work.

Unlike aphasia that results from stroke or brain trauma, PPA results from slow deterioration of one or more areas of the brain used in speech and language.

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What Makes Human Language Special

When did spoken language first emerge as a tool of communication, and how is it different from the way in which other animals communicate?

As Prof. Mark Pagel, at the School of Biological Sciences at the University of Reading in the United Kingdom, explains in a question and answer feature for BMC Biology, human language is quite a unique phenomenon in the animal kingdom.

While other animals do have their own codes for communication to indicate, for instance, the presence of danger, a willingness to mate, or the presence of food such communications are typically repetitive instrumental acts that lack a formal structure of the kind that humans use when they utter sentences.

  • that it is compositional, meaning that it allows speakers to express thoughts in sentences comprising subjects, verbs, and objects
  • that it is referential, meaning that speakers use it to exchange specific information with each other about people or objects and their locations or actions

Expressive Aphasia Vs Other Aphasias

The Brain: Broca

Patients with expressive aphasia, also known as Broca’s aphasia, are individuals who know “what they want to say, they just cannot get it out”. They are typically able to comprehend words, and sentences with a simple syntactic structure , but are more or less unable to generate fluent speech. Other symptoms that may be present include problems with fluency, articulation, word-finding, word repetition, and producing and comprehending complex grammatical sentences, both orally and in writing.

This specific group of symptoms distinguishes those who have expressive aphasia from individuals with other types of aphasia. There are several distinct “types” of aphasia, and each type is characterized by a different set of language deficits. Although those who have expressive aphasia tend to retain good spoken language comprehension, other types of aphasia can render patients completely unable to understand any language at all, unable to understand any spoken language , whereas still other types preserve language comprehension, but with deficits. People with expressive aphasia may struggle less with reading and writing ” rel=”nofollow”> alexia) than those with other types of aphasia.:480500 Although individuals with expressive aphasia tend to have a good ability to self-monitor their language output , other types of aphasics can seem entirely unaware of their language deficits.

Major characteristics of different types of acute aphasia

Type of aphasia
Fluent

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Lobes Of The Brain And What They Control

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.

Blood Supply To The Brain

Two sets of blood vessels supply blood and oxygen to the brain: the vertebral arteries and the carotid arteries.

The external carotid arteries extend up the sides of your neck, and are where you can feel your pulse when you touch the area with your fingertips. The internal carotid arteries branch into the skull and circulate blood to the front part of the brain.

The vertebral arteries follow the spinal column into the skull, where they join together at the brainstem and form the basilar artery, which supplies blood to the rear portions of the brain.

The circle of Willis, a loop of blood vessels near the bottom of the brain that connects major arteries, circulates blood from the front of the brain to the back and helps the arterial systems communicate with one another.

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Wernicke’s Area Location And Function

Wernicke’s area is the region of the brain that is important for language development. It is located in the temporal lobe on the left side of the brain and is responsible for the comprehension of speech, while Broca’s area is related to the production of speech. Language development or usage can be seriously impaired by damage to Wernicke’s area of the brain.

When this area of the brain is damaged, a disorder known as Wernicke’s aphasia can result, with the person being able to speak in phrases that sound fluent yet lack meaning.

D Localization Of Integration: Ifg Or Stg

Language Pathways and Aphasia, Animation

Psycholinguistic models on sentences comprehension assume a processing phase during which syntactic and semantic information interact with each other and are integrated to achieve interpretation. Some models hold that the different information types interact at any time during comprehension or after an initial syntactic structure building phase . Neuroimaging approaches have discussed two different regions as possible sites where integration takes place. Some researchers assume that the final integration of syntactic and semantic information takes place in the left posterior STG, whereas others assume that unification of different language-relevant information types is located in the left IFG. Interestingly, the crucial neuroimaging studies these proposals are based on all show activation in both the IFG and the STG .

It is clear, however, that the posterior temporal cortex is crucial in binding the verb and its arguments and more generally for integration across domains and that the inferior frontal gyrus support different language aspects within its subregions . Interactions between semantic aspects and syntax, as seen in studies manipulating semantics by lexical-semantic ambiguity , semantic relatedness , or semantic constraint due to animacy , are located in the more anterior portions of the IFG , but not in BA 44 . From this, we may conclude that the IFG’s role as a region of combining semantic and syntactic information may be restricted to its more anterior parts.

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How Language Changes Our Perception

However, does switching between different languages also alter our experience of the world that surrounds us?

Journalist Flora Lewis once wrote, in an opinion piece for The New York Times titled The Language Gap, that:

Language is the way people think as well as the way they talk, the summation of a point of view. Its use reveals unwitting attitudes. People who use more than one language frequently find themselves having somewhat different patterns of thought and reaction as they shift.

Research now shows that her assessment was absolutely correct the language that we use does change not only the way we think and express ourselves, but also how we perceive and interact with the world.

A study that appeared in the journal Psychological Science, for instance, has describe how bilingual speakers of English and German tend to perceive and describe a context differently based on the language in which they are immersed at that moment.

When speaking in German, the participants had a tendency to describe an action in relation to a goal. For example, That person is walking toward that building.

To the contrary, when speaking in English, they would typically only mention the action: That person is walking.

What Is The Gray Matter And White Matter

Gray and white matter are two different regions of the central nervous system. In the brain, gray matter refers to the darker, outer portion, while white matter describes the lighter, inner section underneath. In the spinal cord, this order is reversed: The white matter is on the outside, and the gray matter sits within.

Gray matter is primarily composed of neuron somas , and white matter is mostly made of axons wrapped in myelin . The different composition of neuron parts is why the two appear as separate shades on certain scans.

Each region serves a different role. Gray matter is primarily responsible for processing and interpreting information, while white matter transmits that information to other parts of the nervous system.

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Descending Control Of Face And Throat

Vocalizations and orofacial movements are controlled by several brainstem nuclei, such as the trigeminal motor nucleus innervating jaw musculature, the hypoglossal nucleus driving tongue movements, the facial nucleus controlling face and lip movements, and finally the ambiguus nucleus innervating the vocal folds in the larynx. In addition, vocalizations depend on a tight control of respiratory muscles. These nuclei relate to brainstem central pattern generators that produce cyclic activity for behaviors like chewing, swallowing, drinking, laughing and swallowing . It is most likely that these circuits were recruited and remodeled for the development of human speech, as for example, respiratory movements have to be much more controlled during speech than during primate vocalizations .

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  • So whether we lose a language through not speaking it or through aphasia, it may still be there in our minds, which raises the prospect of using technology to untangle the brains intimate nests of words, thoughts and ideas, even in people who cant physically speak. Neurologists are already having some success: one device can eavesdrop on your inner voice as you read in your head, another lets you control a cursor with your mind, while another even allows for remote control of another persons movements through brain-to-brain contact over the internet, bypassing the need for language altogether.

    For some people, such as those with locked-in syndrome or motor neurone disease, bypassing speech problems to access and retrieve their minds language directly would be truly transformative.

    Copyright 2015 The Wellcome Trust. Some rights reserved.

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    How Wernickes Area Was Discovered

    Early neuroscientists were interested in discovering where certain abilities were localized in the brain. This localization of brain function suggests that certain abilities, such as producing and understanding language, are controlled by certain parts of the brain.

    One of the pioneers of this research was a French neurologist named Paul Broca. During the early 1870s, Paul Broca discovered a region of the brain associated with the production of spoken language. He found that damage to this area resulted in problems producing language.

    Broca described how one patient known as Leborgne could understand language although he could not speak aside from isolated words and a few other utterances. When Leborgne died, Broca conducted a postmortem exam on the man’s brain and found a lesion in an area of the frontal lobe. This area of the brain is now referred to as Broca’s area and is associated with the production of speech.

    About 10 years later, a neurologist named Carl Wernicke identified a similar type of problem in which patients were able to speak but were not able to actually comprehend language. Examining the brains of patients suffering from this language problem revealed lesions at a junction of the parietal, temporal, and occipital lobes.

    This region of the brain is now known as Wernicke’s area and is associated with the understanding of spoken and written language.

    Talking To Ourselves: The Science Of The Little Voice In Your Head

    If we want to understand whats happening in the brain when people hear voices, we first need to understand what happens during ordinary inner speech

    Most of us will be familiar with the experience of silently talking to ourselves in our head. Perhaps youre at the supermarket and realise that youve forgotten to pick up something you needed. Milk! you might say to yourself. Or maybe youve got an important meeting with your boss later in the day, and youre simulating silently in your head how you think the conversation might go, possibly hearing both your own voice and your bosss voice responding.

    This is the phenomenon that psychologists call inner speech, and theyve been trying to study it pretty much since the dawn of psychology as a scientific discipline. In the 1930s, the Russian psychologist Lev Vygotsky argued that inner speech developed through the internalisation of external, out-loud speech. If this is true, does inner speech use the same mechanisms in the brain as when we speak out loud?

    So the evidence that inner speech and speaking out loud share similar brain mechanisms seems pretty convincing. One worry, though, is whether the inner speech we get people to do in experiments is the same as our everyday experience of inner speech. As you might imagine, its quite hard to study inner speech in a controlled, scientific manner, because it is an inherently private act.

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    Stroke Victims With Aphasia

    Researchers wanted to understand how the brain organizes knowledge of written languagereading and spellingsince that there is a genetic blueprint for spoken language but not the more recently evolved written system.

    More specifically, they wanted to know if written language was dependent on spoken language in literate adults. If it was, then one would expect to see similar errors in speech and writing. If it wasnt, one might see that people dont necessarily write what they say.

    The team studied five stroke victims with aphasia, or difficulty communicating. Four had difficulty writing sentences with the proper suffixes, but had few problems speaking the same sentences. The last individual had the opposite problemtrouble speaking but unaffected writing.

    The researchers showed the individuals pictures and asked them to describe the action. One person would say, The boy is walking, but write, the boy is walked. Or another would say, Dave is eating an apple and then write, Dave is eats an apple.

    Auditory Networks In The Monkey

    How do our brains process speech? – Gareth Gaskell

    The primate auditory cortex is organized in three concentrical rings located in the superior temporal lobe, in which there is a core region containing primary and secondary auditory areas, a belt region surrounding it, that houses higher order auditory regions, and a parabelt area that projects to surrounding cortices of the temporal, parietal and frontal lobes . From these regions, two main processing streams emerge: Firstly, a dorsal component projects to inferior parietal and frontal areas, partly emerging from area Tpt, an important node in posterior auditory cortex. Secondly, there is a ventral component that runs anteriorly along the superior temporal lobe, reaching ventrolateral prefrontal areas . The dorsal component performs time-dependent analyses of the stimulus and is involved in sound localization, while the ventral pathway is related to stimulus identification and has strong connectivity with the limbic, anterior temporal regions .

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    The Cell Structure Of The Brain

    The brain is made up of two types of cells: neurons and glial cells, also known as neuroglia or glia. The neuron is responsible for sending and receiving nerve impulses or signals. Glial cells are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin and facilitate signal transmission in the nervous system. In the human brain, glial cells outnumber neurons by about 50 to one. Glial cells are the most common cells found in primary brain tumors.

    When a person is diagnosed with a brain tumor, a biopsy may be done, in which tissue is removed from the tumor for identification purposes by a pathologist. Pathologists identify the type of cells that are present in this brain tissue, and brain tumors are named based on this association. The type of brain tumor and cells involved impact patient prognosis and treatment.

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