How the brain of patient with Aphasia responds to speech sound?

Aphasia or (Aphemia)

• Aphasia (or aphemia) is a loss or impairment of the ability to produce and/or comprehend language, due to brain damage. It is not a result of deafness or muscle paralysis, and it does not necessarily affect intelligence.
• Usually, aphasias are a result of damage to the language centers of the brain (like Broca's area). These areas are almost always located in the left hemisphere, and in most people this is where the ability to produce and comprehend language is found. However in a very small number of people language ability is found in the right hemisphere.
• Damage to these language areas can be caused by a stroke, traumatic brain injury, or other head injury. Aphasia may also develop slowly, as in the case of a brain tumor or progressive neurological disease. All these types of aphasia are classified as secondary.
• Primary aphasia is a relatively rare condition with no known cause and often no other symptoms.
• Aphasia may co-occur with speech disorders such as dysarthria or apraxia of speech, which also result from brain damage.
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Classification of Aphasia

The locationist model

• Broca's aphasia have damage to the frontal lobe of the brain. These individuals frequently speak in short, meaningful phrases that are produced with great effort. Broca's aphasia is thus characterized as a nonfluent aphasia. Affected people often omit small words such as "is", "and", and "the". For example, a person with Broca's aphasia may say, "Walk dog" meaning, "I will take the dog for a walk". The same sentence could also mean "You take the dog for a walk", or "The dog walked out of the yard", depending on the circumstances. Individuals with Broca's aphasia are able to understand the speech of others to varying degrees. Because of this, they are often aware of their difficulties and can become easily frustrated by their speaking problems. Individuals with Broca's aphasia often have right-sided weakness or paralysis of the arm and leg because the frontal lobe is also important for body movement.
• Damage to the temporal lobe may result in a fluent aphasia that is called Wernicke's aphasia. Individuals with Wernicke's aphasia may speak in long sentences that have no meaning, add unnecessary words, and even create new "words".
• Ludwig Lichtheim proposed five other types of Aphasia
• Pure Word Deafness (all understanding impaired, but expressive channels intact).
• Conduction Aphasia (speech, writing and silent reading intact, but repetition, reading aloud and dictation impaired).
• Apraxia of Speech Which is now considered a separate disorder in itself.
• Transcortical Motor Aphasia (Understanding of speech, writing, repetition and reading intact, but impaired voluntary speech and writing).
• Transcortical Sensory Aphasia,(Impaired comprehension of
• ANOMIA is another type of aphasia proposed under what is commonly known as the Boston-Neoclassical model, which is essentially a difficulty with naming. The sufferer may have difficulties naming certain words, linked by their grammatical type (e.g. difficulty naming verbs and not nouns) or by their semantic category (e.g. difficulty naming words relating to photography but nothing else) or a more general naming difficulty. Sufferers are usually aware and it is comparable to a 'tip of the tongue' sensation experienced by most people.
• A final type of aphasia, global aphasia, results from damage to extensive portions of the language areas of the brain. Individuals with global aphasia have severe communication difficulties and will be extremely limited in their ability to speak or comprehend language
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The cognitive neuropsychological model:-

The cognitive neuropsychological model builds on cognitive neuropsychology. It assumes that language processing can be broken down into a number of modules, each of which has a specific function. Hence there is a module which recognises phonemes as they are spoken and a module which stores formulated phonemes before they are spoken. Use of this model clinically involves conducting a battery of assessment

Phoneme

In human language, a phoneme is the theoretical representation of a sound. It is a sound of a language as represented (or imagined) without reference to its position in a word or phrase. A phoneme, therefore, is the conception of a sound in the most neutral form possible and distinguishes between different words or morphemes — changing an element of a word from one phoneme to another produces either a different word or obvious nonsense
Any of the following can be considered Aphasia
• inability to comprehend speech
• inability to read (alexia)
• inability to write (agraphia)
• inability to speak, without muscle paralysis
• inability to form words
• inability to name objects (anomia)
• poor enunciation
• excessive creation and use of personal neologisms (jargon aphasia)
• inability to repeat a phrase
• persistent repetition of phrases
• other language impairment
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Types of Aphasia

• The common types of aphasia are
• Broca's aphasia (expressive aphasia)
• Wernicke's aphasia (receptive aphasia)
• Nominal aphasia (anomic aphasia)
• Global aphasia
• Conduction aphasia
• It is worth noting that a combination of the above is possible.
• A few less common varieties include
• Transcortical motor aphasia
• Subcortical motor aphasia
• Transcortical sensory aphasia
• Subcortical sensory aphasia
• Mixed transcortical aphasia
• Acquired eleptiform aphasia (Landau Kleffner Syndrome


What are sound waves?

• ~ Sound waves are waves of air pressure.
• ~ If one plots air pressure, then the peaks correspond to points of maximum compression, and the
• troughs, points of maximum rarefaction.
• ~ Amplitude is the difference between minimum and maximum pressure and is perceived as
• loudness.
• ~ Frequency is the number of peaks that go by a fixed point in one second.
• ~ The normal range of frequencies audible to humans is 20 to 20,000 Hz (the number of waves
• per second). We are most sensitive to frequencies between 2000 to 4000 Hz, the frequency range
• of the spoken words.
• The Physiology of the Senses
• Transformations For Perception and Action
• Tutis Vilis http://www.physpharm.fmd.uwo.ca/undergrad/sensesweb/

How does sound energy reach inner ear?

What is the function of round window?

Auditory afferents activation

How is the frequency of sound coded?

• Helmholtz noted that the basilar membrane is narrow and stiff (like a high string on a piano) near the oval window, and wide and floppy (like a low string) at the other end.
• Because of this, each portion of the basilar membrane vibrates maximally for a particular frequency of sound.
• High frequency sounds maximally displace the hair cells near the oval window while low frequency sounds maximally displace hair cells at the other end.
• Thus sound frequency is topographically represented on the basilar membrane (place coding).
• (i.e. frequency is coded by which neuron is activated, not necessarily by its firing rate. This is like labeled lines in the sense of touch)

How is loudness coded?

The cue to sound direction

Role of Superior Olive in sound localization

The columnar structure in primary auditory cortex

What happens beyond auditory cortex?

The probable sequence of activity that occurs when a person repeats a written word

What happens to each information in each area?

Neuroplasticity-Treatment in Aphasia

An overview of neuroplasticity in Aphasia

• After a stroke or traumatic brain injury, a zone of residual speech function exists between damaged and undamaged regions within language processing areas in brain.
• Within this zone, there are areas that can be improved using precise patterns of stimulation.
• The stimulation of undamaged neurons in this area can increase their functionality—an adaptation that contributes or responds to speech sound in a patient with Aphasia.


• Neuroplasticity is referred to as the ability of the brain neurons to compensate for sustained injuries thereby adjusting their activity according to stimulation from the environment. This proven ability of the brain to regenerate itself is the basis for the treatment of Aphasics.
• Healthy neurons may also be stimulated to adjust their activity to process hearing information, an adaptation that contributes to the hypothesis of treatment of Aphasia.

How it works

• The acoustic characteristics of speech supply a listener with cues enabling identification of both the phonetic content of the message as well as information pertaining to who is speaking and the intention of the message.
• Linguistic information is necessary to distinguish the meaning of the message (consonants and vowels).
• Paralinguistic information conveys the intention, or how the message is expressed (e.g., statement versus question, angry versus happy emotional state).
• Paralinguistic acoustic elements add a multidimensional aspect to speech that is separate from the phonetic information of the verbal message.

• Acoustic characteristics: The source-filter model of speech production states that speech comprises:
• (i) vibration of the vocal folds reacting to airflow from the lungs (source)
• (ii) the shape of the vocal tract, tongue, lips, and jaw (filter) (Fant, 1960).
• Generally but not exclusively, paralinguistic information is conveyed by the source.
• linguistic information is conveyed by particular filter shapes.

• Repeated constant external stimulation thru’ adjusted sound waves and words in high or low pitch in the form of time phased locked activity and concomitantly noting down the evoked potential status of language area of brain as a reference in treatment could provide a hope to the aphasic patients.


Dr Tejinder Mohan Aggarwal
MBBS GAMS
DIRECTOR
PHOENIX HOSPITAL
SCO 8 SECTOR 16 PANCHKULA 134109 HARYANA INDIA
FORMER: *Research Associate,
CS & E, Florida Atlantic University (FAU), Boca Raton Fl 33431 USA