Chapter 27 - Speech and Language Flashcards
Overview: in the vast majority of people, the primary functions for explicitly semantic processing are located in which hemisphere?
Left!
Overview: The links between speech sounds and their meanings are mainly represented in the …… cortex
left temporal cortex
Overview: The circuitry for the motor commands that organise meaningful speech production is mainly in the ……. cortex
left frontal cortex
The emotional content of speech is governed largely by ……
the right hemisphere
Define aphasia.
Aphasias (Gr., “without utterance”) are a collection of syndromes that feature diminished or abolished ability to comprehend and/or to produce language as a vehicle for communicating meaningful statements, while sparing the ability to perceive the relevant stimuli and to produce intelligible words.
As a consequence of the early observations done by Paul Broca and Carl Wernicke, two rules about the localisation of language are commonly taught. Which?
- Lesions of the left frontal lobe (Broca’s area) affect the ability to PRODUCE language efficiently.
- Damage to the left temporal lobe (Wernicke’s area) causes difficulty UNDERSTANDING spoken language
There is Wernicke’s aphasia, and Broca’s aphasia. There’s a third category of language deficiency syndromes, and aphasia, which?
Conduction aphasia.
What is conduction aphasia?
These disorders arise from lesions to the pathways connecting the relevant temporal and frontal regions, such as the arcuate fascicles in the subcortical white matter the links Broca’s and Wenicke’s areas.
What is commonly the problem in patients suffering from conduction aphasia?
These patients may have difficulty to produce appropriate responses to heard communication, even though the communication is understood.
“I am a sig … no…man…uh,well ….again” These words are emitted slowly and with great effort. What type of aphasia?
This is Broca’s aphasia, a disorder that affects the ability to produce language efficiently. This patient suffered a stroke that affected his left posterior frontal lobe.
“Boy, I’m sweating, I’m awful nervous, you know, once a while I get caught up, I can’t get caught up, I can’t mention the tarripoi, a month ago, quite a little. I’ve done a lot well, I impose a lot, while, on the other hand, you know what I mean, I have to run around, look it over, trebbin and all that sort of stuff. “ What type of aphasia?
This is Wernicke’s aphasia, a difficulty in understanding spoken language. In Wernicke’s aphasia, speech is fluent and well structured, but makes little or no sense because words and meanings are not correctly linked. This patient had suffered a stroke affecting his left temporal lobe.
Halting speech is a characteristic of Wernicke’s or Broca’s aphasia?
Broca
Grammar adequate is a characteristic of Wernicke’s or Broca’s aphasia?
Wernicke
Contrived or inappropriate words is a characteristic of Wernicke’s or Broca’s aphasia?
Wernicke
Tendency to repeat phrases or words (perseveration) is a characteristic of Wernicke’s or Broca’s aphasia?
Broca
Disordered syntax is a characteristic of Wernicke’s or Broca’s aphasia?
Broca
Fluent speech is a characteristic of Wernicke’s or Broca’s aphasia?
Wernicke
Little spontaneous repetition is a characteristic of Wernicke’s or Broca’s aphasia?
Wernicke
Disordered structure of individual words is a characteristic of Wernicke’s or Broca’s aphasia?
Broca
Syntax adequate is a characteristic of Wernicke’s or Broca’s aphasia?
Wernicke
Comprehension not intact is a characteristic of Wernicke’s or Broca’s aphasia?
Wernicke
Comprehension intact is a characteristic of Wernicke’s or Broca’s aphasia?
Broca
What are the alternative names of Broca’s aphasia?
Motor aphasia, expressive aphasia, or production aphasia.
What are the alternative names of Wernicke’s aphasia?
Sensory aphasia, receptive aphasia.
Until the 1960s, observations about language localisation and laterlization were based primarily on patients with brain lesions of varying severity, location, and ethology. Up until that time, the inevitable uncertainties of clinical findings had allowed some sceptics to argue that language and other complex cognitive functions might not be localised or even laterlized in the brain. Definitive evidence came from what?
Split-brain patients!
A split-brain patient that is blind-folded and told to identify an object in his right hand would …
do it as easily as anyone.
A split-brain patient that is blind-folded and told to identify an object in his left hand would …
Using the right hemisphere, most split-brain patients could produce only an indirect description that relied on rudimentary words and phrases rather than the precise lexical symbol for the object. I.e. “a round thing” instead of “a ball”.
What is tachistoscopic presentation.
That is the name of a technique used to present visual information to the hemispheres independently.
Approximately x out of 10 people are right-handed.
9!
Why do left-handed people have the opposite lateralisation of language?
Fooled you? They don’t, actually! The large number of tests for language lateralizaiton indicate that 97% of humans - including the majority of left-handers - have explicitly verbal language function in the left hemisphere. Although, right-hemisphere dominance for language is more common for left-handers.
The differing language functions of the left and right hemispheres have naturally inspired neurologists and neuropsychologists to search for some structural correlate of behavioural lateralisation. Did they find anything?
Yes, naturally. Norman Geschwind and his colleagues at Harvard Medical School found in the 1960s an asymmetry in the superior aspect of the temporal lobe known as the plane temporale. This area is significantly larger on the left side in about two-thirds of human subjects studied post-mortem.
Norman Geschwind and his colleagues at Harvard Medical School found in the 1960s an asymmetry in the superior aspect of the temporal lobe known as the plane temporale. This area is significantly larger on the left side in about two-thirds of human subjects studied post-mortem. How does this correlate explain language laterlization?
It doesn’t, really. The fact that a detectable plan asymmetry is present in only 67% of human brains while the preeminence of language in the left hemisphere is evident in 97% of the population argues that this association has some other cause.
Several techniques have been developed that allow the assessment of hemispheric attributes in neurological patients with an intact corpus callosum and in normal subjects. Mention one method you need to know.
The Wada test developed by Juhn Wada at the Montreal Neurological Institute in the 1960s.
How does the Wada test work?
In the Wada test, a short-acting anaesthetic is injected into the patient’s left carotid artery; this procedure briefly “anaesthetises” the left hemisphere and thus tests the functional capabilities of the affected half of the brain. If the left hemisphere is indeed “dominant” for language, then the patient becomes transiently aphasic while carrying out an ongoing verbal task such as counting. This procedure is potentially dangerous.
Mention one noninvasive method for testing language lateralisation.
Tachistoscopic presentation can be used, and one can expect the information given to the right hemisphere to have a slight delay in the behavioural response - since it probably has to travel to the left hemisphere.
What is intraoperative mapping?
Electrical stimulation of the cortex during operations can be used to make sure any cuts in the cortex (usually used for very dramatic cases of epilepsy) don’t affect structures vital for language.
George Ojemann and his group at the University of Washington has done studies using electrophysiological recording methods during operations, and has found information that helps nuance what we know about the localisation of language functions in the brain.
Ojemann found that the brain regions involved in language are only approximately those indicated by textbook treatments and that their locations differ unpredictably among individuals. Equally unexpected, bilingual patients do not necessarily use the same bit of cortex for storing the names of the same object in two different languages. OMG I KNEW IT
Critique the types of studies done on patients during surgery.
They are not done on people who are “normal”. This is not necessarily a representative group of people.
What is the most obvious effect of lesions to the right hemisphere language areas?
The most obvious effect of such lesion sis a loss of the normal rhythm, stress and tonal variation of speech - called prosody - that imparts additional meaning to verbal communication.
Which regions of the right hemisphere, specifically, are associated with aprosodias - deficiencies in prosody?
The cortical regions on the right side that correspond to Broca’s and Wernicke’s areas and related regions in the left hemisphere.
Ursula Beluga and her colleagues at the Salk Institute examined the cortical localisations of sign language abilities in patients who had suffered lesions of either the right or left hemisphere. What were their findings?
Patients with left-hemisphere lesions had measurable deficits in sign production and comprehension when compared to normal signers.
Patients with right-hemisphere lesions did not have such signing “aphasias”. Instead they had impairments in visuospatial processing, emotional processing, and emotional tone. All these findings similar to that of speaking individuals.
