Wernicke's Area

Wernicke's area, traditionally identified as Brodmann area 22, resides in the superior temporal gyrus in the dominant cerebral hemisphere, typically the left^[1]. For approximately 95% of right-handed individuals and 70% of left-handed individuals, the dominant hemisphere is the left one^[2].

Named after Carl Wernicke, a 19th-century German neurologist, it plays a critical role in the comprehension of speech. Wernicke discovered this area while studying individuals with specific types of aphasia^[3]. Despite its long-standing association solely with language processing, recent research suggests its involvement in other complex tasks, such as music perception^[4].

Wernicke's area is primarily associated with the comprehension of spoken language. Damage to this area often results in Wernicke's aphasia, a condition where individuals can produce fluent speech, but what they say might not make sense, and they often have difficulty understanding spoken language^[6].

The term "Wernicke's area" is usually pronounced as "VUR-ni-kees" area, although some English speakers pronounce it as "WUR-ni-kees" area. The name comes from the German neurologist Carl Wernicke, who is known for his research on the brain region involved in language comprehension. The original German pronunciation leans more towards the "V" sound, but both versions are commonly heard in English-speaking countries.

Here's an exploration of language comprehension within the context of Wernicke's area:

• Auditory Comprehension: When we listen to spoken language, auditory signals are first processed in the primary auditory cortex. These signals are then relayed to Wernicke's area, where the sounds are interpreted as meaningful linguistic units like words and phrases^[7].

• Reading Comprehension: When reading, visual information of the written text is processed in the primary visual cortex, and related linguistic information is subsequently relayed to Wernicke's area for comprehension^[8].

Wernicke's area doesn't work in isolation. For fluent language comprehension and production, it needs to communicate with other language-related regions, especially Broca's area in the frontal lobe. The arcuate fasciculus is a bundle of nerve fibers that facilitates this connection^[9].

After comprehending linguistic input, Wernicke's area interacts with Broca's area to produce a coherent verbal response. For instance, after understanding a question (Wernicke's area's role), a person can formulate and verbalise an appropriate answer (Broca's area's role)^[9].

Beyond just recognising words, Wernicke's area is believed to play a role in semantic processing – understanding the meanings of words and sentences. This involves integrating individual word meanings into coherent, contextually relevant messages^[10].

While Wernicke's area is primarily associated with comprehension, it's also linked to the production of grammatically and semantically correct, fluent speech. A person with damage to this area might produce fluent but nonsensical speech, a condition known as Wernicke's aphasia or fluent aphasia^[11].

People with Wernicke's aphasia often produce sentences that have correct grammar but lack meaningful content. They might use non-existent or irrelevant words, making their speech difficult to understand^[11].

Interestingly, individuals with this condition might not recognise their own speech errors, showcasing the role of Wernicke's area in self-monitoring of language comprehension and production^[12].

Modern research suggests that Wernicke's area might be involved in integrating information from various sensory modalities. This would align with the notion of our brain being a multimodal organ, where comprehending speech might also involve, to some extent, visual, somatosensory, and motor processes^[13].

While the classical model of language localisation places Wernicke's area strictly in the left hemisphere, more recent research has shown that the brain can be quite adaptable. In some left-handed individuals or those who have had injuries to the left hemisphere early in life, Wernicke's area or its functional equivalent might be found in the right hemisphere^[14].

A lesion in Wernicke's area can disrupt this process at the comprehension stage. As a result, while the individual can produce speech (since Broca's area might be intact), they often produce sentences that are grammatically correct but lack meaning or are nonsensical. Moreover, they have difficulty understanding the spoken language^[9].