Carl Wernicke: image source: Wikimedia
What is Wernicke’s aphasia?
In 1874 – after Paul Broca’s discovery of Broca’s area and Broca’s aphasia – Carl Wernicke described a different type of aphasia: a type that allows talk fluently but meaningless words and sentences. In contrast to those affected with Broca’s aphasia, in which they can talk fewer than four words at a time, those affected by this type talk fluently. However, anyone can notice their problem – their words contain no meanings. And, they repeat the same word over and over again. According to Argyle E. Hillis, they seem to unaware of their errors in contrast to those with Broca’s aphasia. One tends to think they are talking another language we cannot understand. Not only talking, but writing and reading also follow a similar pattern. Hence, this type of aphasia is called fluent aphasia (Broca’s aphasia is called non-fluent aphasia). Since Carl Wernicke described this, it is also called Wernicke’s aphasia.
You can find out how an individual with Wernicke’s aphasia converse with others by watching this video clip.
So, Wernicke’s aphasia occurs as a result of damage to the Wernicke’s area. Where is it in the brain?
Wernicke’s area lies in the temporal lobe (visit the journeys to the brain:2- A walk over the brain surface) at a place close to the area (auditory) that contains cells specialized in processing hearing information (Figure 1). Whenever we hear something, the hearing area receives information from the ear and then sends this information to Wernicke’s area. Similarly, whenever we see or read something, the visual area receives it and then sends that information to Wernicke’s area. Neurons in this area work hard to retrieve suitable nouns appropriate to the context from the storeroom, set the language structure, and shoot the processed information to Broca’s area to set the next steps to produce speech.
How do Wernicke’s neurons connect with Broca’s neurons?
As shown in Figure 2, Wernicke’s neurons connect with Broca’s neurons through a super-highway, called “arcuate Fasciculus”. This is a bundle of neurons dedicated to this task.
How do Wernicke’s neurons die?
Wernicke’s neurons die due to disruption of the blood supply to the temporal lobe where Wernicke’s area resides. Most commonly, a blood clot that blocks a branch (the inferior branch) of the left middle cerebral artery is the culprit.