Wernicke’s aphasia¶
Introduction¶
In 1874, a German psychiatrist named Carl Wernicke published a monograph, :cite:`Wernicke1874`, in which he described how a lesion centered in the superior temporal gyrus disrupted the comprehension of language in one of his patients. This was the cornerstone of a larger effort on his part to classify mental disorders in terms of the anatomy and pathology of the nervous system. He thus founded what today we call neuroscience.
To find out more about his life, see Carl Wernicke.
Since 1874 there have been almost 150 years of refinements to Wernicke’s original observation, which have culminated in the characterization of the neurological disease known variously as sensory, receptive or Wernicke’s aphasia, whose cause is damage (usually from stroke or trauma) to a zone of left posterior superior temporal cortex known as Wernicke’s region.
Where is Wernicke’s region?¶
While the profile of Wernicke’s aphasia is clear and will be reviewed in detail in the following pages, the localization of Wernicke’s region is not. :cite:`Bogen1976` review the first hundred years of attempts to trace its outline and find that it oozes around the temporal lobe like an amoeba, often depending on the wounds of soldiers that the clinician treated in World Wars I or II. The eminent neurosurgeon Wilder Penfield, who pioneered brain mapping for the surgical treatment of epilepsy, in the book coauthored with Lamar Roberts in 1959 that summarized his observations, :cite:`Penfield1959`, offers no less than seven different variations on the size and location of Wernicke’s region. :cite:`Bogen1976` continue reviewing images up to their contemporaries, in 1967, and conclude that nobody agrees on how to delimit Wernicke’s region.
Practice
Google (or yahoo) “Wernicke’s area” and then click on the Images tab. How many drawings agree on the location of Wernicke’s area? How large is the discrepancy among them? How would ‘Wernicke’s area’ fit into Hickok and Poeppel’s model?
Part of the problem is that lesions are not well behaved and can encompass broad swaths of cortex, as seen here:
Fig. 104 Brain excised from a patient with Wernicke’s aphasia¶
Stamped with seal of the School of Medicine, UC Davis. My image is from Linguistics 001. Lecture 18. Brain and Language.
There is such a huge chunk of the temporal lobe missing that whatever linguistic deficit the patient had can not really be localized to a particular area.
You would think that the advent of non-invasive imaging technologies would provide enough predicsion to nail down the location of Wernicke’s area once and for all, but consider the following image:
Fig. 105 Tomographic images of a patient with Wernicke’s aphasia¶
This series is taken from the middle up, with the forehead facing towards the top of the page, so that the left hemisphere is on the right. Don’t be fooled by the cerebral vessicles in the center – the lesion is the dark stain on the right. Again, it is large and must have taken out several cognitive functions.
The size of the
And you would be right, though not in the way that you might think. First of all, I have to point out that Hickok & Poeppel’s model makes no reference to it. In fact, if you did the image search exercise above, you might have concluded that Wernicke’s area could lie almost anywhere between the superior temporal sulcus and the parietal-temporal Spt, though everyone agrees that it excludes auditory cortex. Working in Hickok & Poeppel’s model, :cite:`DeWitt2013` argue that Wernicke’s aphasia encompasses two deficits:
disruption of auditory word forms, as would be expected from damage to the superior temporal sulcus, and
disruption of one’s monitoring of one’s own speech, which they call “inner speech” and adjudicate to the dorsal pathway.
In the rest of this chapter, we will review the clinical description of Wernicke’s aphasia to see how this hypothesis fares.
A description of Wernicke’s aphasia¶
I should point out that, to be diagnosed with aphasia, a patient cannot have any other cognitive disability. That is to say that aphasia is the pre-eminent linguistic disorder and does not depend on a deficit of memory or executive control or any other non-linguistic ability.
A specific sort of linguistic error can be assigned the term paraphasia.
Phonemic paraphasia, neologism, jargon¶
Imagine your favorite doctor joke. It probably begins with “a guy walks into a doctor’s office …” Now imagine that the guy, or gal, is a patient with Wernicke’s aphasia …
[1] Clinician: “Tell me where you live.” Patient: “Well, it’s a meender place and it has two … two of them. For dreaming and pinding after supper. And up and down. Four of down and three of up …” (:cite:`Brookshire2003` p. 155)
[2] Clinician: “What’s the weather like today?” Patient: “Fully under the jimjam and on the altigrabber.” (:cite:`Brookshire2003` p. 155)
[3] Clinician: “What brought you to the hospital?” Patient: “Is this some of the work that we work as we did before? … All right … From when wine [why] I’m here. What’s wrong with me because I … was myself until the taenz took something about the time between me and my regular time in that time and they took the time in that time here and that’s when the the time took around here and saw me around in it’s started with me no time and I bekan [began] work of nothing else that’s the way the doctor find me that way…” (:cite:`Obler1999` p. 43)
Question
What is broken? What is preserved? By the way, I did not misspell any word.
Patients with Wernicke’s aphasia have problems in the selection of phonemes, called phonemic paraphasia, which include addition, omission, or change in position. The usage of bekan for began in example 3 may be an example. :cite:`Damasio1992` p. 535 cites trable for table and pymarid for pyramid. Extensive series of phonemic paraphasias are produced by the two patients in these videos:
Clearly, the more phonemic paraphasias accumulate in a word, the harder it is to understand it, to the extent that the intended word may become unidentifiable. This is the point of neologism, illustrated in another of Damasio’s examples, of hipidomateous for hippopotamus.
Question
Did you notice any neologisms in the three examples above?
Patients with severe Wernicke’s aphasia may produce strings of neologisms with a sprinkling of connecting words, known as jargon. The long stretches of incomprehensible speech in the next video qualify as jargon:
Semantic paraphasias¶
A patient with Wernicke’s aphasia may also fail to select the proper words with which to convey her ideas, though this deficit can be compensated for by the usage of paraphrases. Such semantic paraphasia or empty speech are often quite simple, such as relying on generic terms like thing or stuff to stand in for the more specific words that do not spring to mind. Other times, they become quite elaborate. :cite:`Kandel1995` p. 640 cites the example of a Wernicke’s patient who was asked where he lived and answered, “I came there before here and returned there.” :cite:`Brookshire2003` p. 155 relates the case of a patient with moderate Wernicke’s aphasia who was attempting to explain what he had done on a shopping trip the previous day. He concluded with, “I went down to the thing to do the other one and she was only the last one that ever did it, so I never did.”
The patient in this video produces few neologisms, but she does not come anywhere near making any sense, which we can classify as an extreme failure to select the proper words with which to convey her ideas:
Circumlocution¶
Some Wernicke’s patients “talk around” missing words, a behavior called circumlocution. A patient with moderate Wernicke’s aphasia was attempting to tell the examiner what she had had for breakfast that morning, “This morning for – that meal – the first thing this morning – what I ate – I dined on – chickens, but little – and pig – pork – hen fruit and some bacon, I guess.” (:cite:`Brookshire2003` p. 156)
Logorrhea or press of speech¶
The ease with which Wernicke’s patients produce speech, their circumlocution, and their deficient self-monitoring may contribute to their inclination to run on when they talk. Such an overabundance of speech is referred to as logorrhea or press of speech.
[8] Clinician: “Tell me what you do with a comb.”
Patient: “What do I do with a comb … what I do with a comb. Well a comb is a utensil or some such thing that can be used for arranging and rearranging the hair on the head both by men and by women. One could also make music with it by putting a piece of paper behind and blowing through it. Sometimes it could be used in art – in sculpture, for example, to make a series of lines in soft clay. It’s usually made of plastic and usually black, although it comes in other colors. It is carried in the pocket or until it’s needed, when it is taken out and used, then put back in the pocket. Is that what you had in mind?” (:cite:`Brookshire2003` p. 155)
An analysis of Wernicke’s aphasia¶
It does not seem far-fetched to attribute phonemic and semantic paraphasias to damage to the auditory forms of words in the superior temporal sulcus, and this is in agreement with the lesion data.
But as some of you have pointed out in class, this only seems to be half of the problem.
Summary¶
Symptom |
Wernicke’s aphasia |
|---|---|
comprehension of spoken material |
impaired, mild to severe |
segmental phonology |
impaired: phonemic paraphasia, neologism, jargon |
word selection |
impaired: semantic paraphasia, empty speech |
word semantics |
normal? |
fluency (production of speech) |
(overly) fluent: logorrhea |
production of writing |
normal |
use function words |
normal |
grammaticality |
normal or mildly impaired: paragrammatism |
repetition of what others say |
impaired: (no evidence) |
conversational proficiency, e.g. turn taking |
normal |
concern about impairment |
little to none |
concern about errors |
little to none |
short-term retention & recall of verbal materials |
impaired: (no evidence) |
End notes¶
The next topic¶
The next topic is The sensorimotor interface.
Last edited Aug 22, 2023