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. This type of aphasia allows one to talk fluently but meaningless words and sentences. But in Broca’s aphasia, one can talk at least fewer than four meaningful words at a time. 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 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. You can find the temporal lobe in this walk over the brain surface in the journeys to the brain – 2. The Wernicke’s area lies 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 those to Wernicke’s area. Similarly, whenever we see or read something, the visual area sends that information to Wernicke’s area. Neurons in this area retrieve suitable nouns appropriate to the context from the storeroom, set the language structure, and shoot that to Broca’s area. Broca’s area processes it 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.