I thought I’d explain in this post why it is that I’m fascinated with the phenomenon that is aphasia. The main reason it’s so interesting is that it can manifest itself in very different ways. Aphasia is a result of brain injury, most commonly strokes, head trauma or neurodegenerative diseases like dementia and Parkinson’s. So the effects observed in language depend on which part of the brain’s language areas were damaged; yet, not even this is necessarily consistent or predictable. Some of the stranger and more surprising effects can be seen in bilingual patients who can regain the use of one language but not the other, inadvertently switch language or communicate using a mixture of the two languages.
When discussing aphasia you can’t go without a mention to Broca and Wernicke. In a nutshell, Broca’s aphasia, or non-fluent aphasia, describes problems in producing language which are not due to impaired physical speech systems. Someone with Broca’s aphasia may say:
to mean “I will take the dog for a walk” . On the other hand, in Wernicke’s aphasia, or fluent aphasia, the patient can use complex sentences and speak fluently, however, the words they use don’t make sense and can include made up words. When trying to say “The dog needs to go out so I will take him for a walk”, they may actually say:
“You know that smoodle pinkered and that I want to get him round and take care of him like you want before”.
Although it can be much harder to understand what a person with Wernicke’s aphasia means to say compared to a person with Broca’s aphasia, the person is usually completely unaware that their speech makes no sense. They also can find it to more difficult to understand speech.
In other cases a patient can suffer from global aphasia  – this is the difficulty with all aspects of language including reading (alexia), writing (agraphia), naming objects (anomia), producing and comprehending speech.
These types don’t always fit so neatly when diagnosing an aphasic who speaks more than one language (a polyglot). Bilinguals who suffer from aphasia can have different levels of impairment in each of their languages. Another problem they face is the separation of the languages and using the right one at the right time. A common occurrence is pathological switching and mixing; pathological switching is the use of one language for one single utterance, then using the other language for a second utterance , whereas mixing is the use of different languages within a single utterance. (Fabbro et al. define an utterance as “a self-contained segment of speech that stands on its own and conveys its own independent meaning”).
Bilingual aphasics can also recover their languages at different rates. There is much debate in research over whether it is the first language learnt (L1), or the more frequently used language that recovers first. For more on this read Recovery Patterns of Bilingual Aphasia. The video below shows how people can sometimes recover their weaker language (L2) first, as after a gunshot to the head, the man has more trouble getting to grips with his native Spanish, whilst being more proficient in English, his L2.
Another interesting facet of aphasia is the effect of damage to language areas of the brain in deaf people. It seems that signed and spoken language are not all that differently represented in the brain , and evidence suggests that language is not dependent on the modality (i.e. speaking, listening, writing), meaning that a deaf aphasic will have problems signing. I’ll explore this in more depth in an upcoming post on aphasia in sign language.
1. The Internet Stroke Center, www.strokecenter.org
2. NHS Choices, www.nhs.uk
3. Fabbro, F., Skrap, M., & Aglioti, S. (2000) Pathological switching between languages after frontal lesions in a bilingual patient. J Neurol Neurosurg Psychiatry, 68, 650-652
4. Hickok, G., Bellugi, U., Klima, E. S., (1998) The neural organization of language: evidence from sign language aphasia. Trends in Cognitive Science, 2, 129-136