Wernicke’s Area: Location and Function

Wernicke’s area is a structure of the brain that is believed to be involved in language comprehension, specifically the comprehension of speech sounds. It is also considered to be the receptive language center of the brain.

In the majority of people, Wernicke’s area is located within the left cerebral hemisphere, specifically near the back of the temporal lobe.

The exact location of Wernicke’s area is still debated, although it is typically thought to be near a large groove known as the lateral sulcus, near the junction between the parietal and the temporal lobes.

Wernicke’s Area Vs Broca’s Area

Wernicke's area and Broca's area are crucial for language but they serve distinct functions. 

Wernicke's area, located in the posterior part of the temporal lobe, is primarily responsible for language comprehension. It helps us understand both spoken and written language. 

Broca's area, found in the frontal lobe, is essential for speech production. It enables us to form words and construct grammatically correct sentences. 

Damage to Wernicke's area typically results in fluent but nonsensical speech with impaired comprehension, while damage to Broca's area leads to halting, effortful speech with intact understanding.

Function

While the exact boundaries and functions of Wenicke’s area remain subjects of ongoing research and debate, research has found some functions this area may play a role in:

1. Auditory Word-Form Recognition: The anterior superior temporal gyrus (STG) functions as an auditory word-form area, crucial for recognizing spoken words in humans and vocalizations in primates (DeWitt & Rauschecker, 2013).
2. Language Comprehension: While important for language understanding, Wernicke’s area is part of a larger comprehension network rather than the sole center for this function.
3. Speech Production Monitoring: The posterior STG is involved in monitoring self-produced speech, contributing to the auditory feedback loop during speech production (DeWitt & Rauschecker, 2013).
4. Phonological Retrieval: Wernicke’s area activates mental representations of speech sounds before articulation, bridging language comprehension and production (DeWitt & Rauschecker, 2013).
5. Sensorimotor Integration: As part of the auditory dorsal stream, it links auditory processing with motor aspects of speech, facilitating language production (Hickok & Poeppel, 2007).
6. Sequence Processing and Syntax: Recent research suggests a role in processing complex syntactic structures and computing relationships within sentences (Friederici, 2012; Rauschecker, 2011).
7. Broader Language Network: Wernicke’s area interacts with other regions, including Broca’s area, as part of an extensive language processing network.

Historical Context:

Initially, Broca's and Wernicke's areas were seen as distinct centers for speech production and comprehension respectively. 

Wernicke’s area would choose which words are needed for speech, while Broca’s area is responsible for taking these words and generating the movements needed to vocalize them.

The Wernicke-Geschwind model later proposed a network connecting these areas. Modern neuroscience, however, reveals a more complex, distributed language system. 

Wernicke's area, once thought to be solely responsible for language comprehension, is now understood as part of a broader language network, interacting with multiple brain regions for various language functions.

Damage

Carl Wernicke discovered that damage to the posterior region of the superior temporal gyrus resulted in a distinct type of aphasia.

While Broca’s aphasia is characterized by non-fluent, effortful speech with preserved comprehension, Wernicke’s patients exhibited fluent speech but significant comprehension difficulties.

Symptoms of Wernicke’s aphasia include:

• Fluent but disordered speech
• Impaired understanding of spoken language
• Difficulty with silent reading comprehension
• Use of inappropriate or nonsensical words (paraphasias)
• Creation of new, meaningless words (neologisms)
• Unawareness of their own speech errors
• Inability to repeat words or phrases accurately
• Normal speech rhythm and intonation despite content errors

The understanding of damage to Wernicke’s area has been refined over the years. The exact location and extent of damage leading to Wernicke’s aphasia can vary, suggesting a more distributed language network.

Isolated damage to Wernicke’s area that spares underlying white matter may not always cause severe receptive aphasia (DeWitt & Rauschecker, 2013).

Likewise, some patients with lesions in classical Wernicke’s area have shown relatively intact word comprehension, indicating other regions may also contribute to this function (DeWitt & Rauschecker, 2013).

This highlights the complexity of language processing in the brain and the ongoing refinement of our understanding of Wernicke’s area and its associated aphasia.

Discovery

Around the time of Wernicke’s Area discovery, neuroscientists were trying to understand a new perspective of the brain.

Few suggested that the cerebral hemispheres of the brain were not equal in terms of function and that the left hemisphere performed different roles than the right hemisphere and vice versa.

Through post-mortem examinations, Broca discovered that there was damage to an area in the left hemisphere in these individuals, which is named Broca’s area.

A few years after Broca, German neurologist Carl Wernicke, who was said to be heavily inspired by Broca, found a similar problem with speech in some of his patients.

However, the issues with these patients differed from Broca’s patients as they could produce speech but could not comprehend language. These individuals would speak fluently but with disordered speech, impaired understanding of speech, and impaired silent reading.

When examining the brains of these patients, it was discovered that there was a lesion at the junction of the parietal, temporal, and occipital lobes in the left cerebral hemisphere, which he coined Wernicke’s Area.

How Did This Discovery Impact Psychology?

Wernicke’s discovery had a profound impact on the field of psychology, particularly in advancing the concept of lateralization of brain functions.

By identifying a specific area in the left hemisphere crucial for language comprehension, Wernicke provided strong evidence against the then-prevalent holistic view of brain function.

This work, along with Broca’s earlier findings, was instrumental in establishing the idea that different cognitive functions are localized to specific brain regions, predominantly in one hemisphere.

Wernicke’s contribution thus played a key role in shaping our understanding of the brain’s functional organization and laid the groundwork for modern neurolinguistics.