Anatomical Location
In the vast majority of individuals (about 95%), language centers are lateralized to the left (dominant) hemisphere (contralateral to the dominant right hand). Wernicke's area is spatially separated from the primary sensory and motor cortical areas.
- Superior temporal gyrus — the area occupies its posterior half (Brodmann area 22, specifically 22b).
- Inferior parietal lobule — includes the adjacent angular gyrus (gyrus angularis) and supramarginal gyrus (Brodmann areas 39 and 40).
- Planum temporale — an anatomical region whose size correlates with hemispheric dominance.
These critical language structures are arranged around the lateral sulcus (Sylvian fissure).
Function of the Sensory Speech Center
Wernicke's area is responsible for the impressive component of speech — the ability to comprehend external speech and accurately perceive one's own.
The underlying mechanism relies on the analysis of incoming information:
- The primary auditory cortex (transverse temporal gyri of Heschl) perceives sounds and transmits impulses to Wernicke's area.
- The brain differentiates words from non-verbal acoustic signals.
- In Wernicke's area, information is decoded: heard sounds are analyzed, matched with words, and the semantic structure of the utterance is constructed.
In addition to auditory input, this area receives afferent signals from secondary visual fields (forming the basis for reading and writing) and the cortical tactile association areas (for Braille reading).
Connections with Other Structures
Verbal communication requires the transmission of formulated semantic meaning to motor speech centers.
- Arcuate fasciculus (fasciculus arcuatus) — an association fiber tract connecting Wernicke's sensory speech center to Broca's motor speech center. It transmits neural impulses carrying the intended message for further vocalization programming.
Blood Supply
Wernicke's area is supplied with blood from the territory of the middle cerebral artery (MCA). The cortex surrounding the angular and supramarginal gyri receives blood from the angular and posterior parietal branches.
Clinical Significance and Lesion Symptoms
A lesion in Wernicke's area (such as an ischemic stroke in the MCA territory) results in sensory aphasia (also known as fluent aphasia).
Key clinical manifestations:
- Impaired phonemic hearing: the patient loses the ability to distinguish phonemes (meaning-differentiating sound units), impairing spoken language comprehension.
- Altered expressive speech: speech remains effortless, rapid (fluent), and phonetically well-articulated, but lacks semantic meaning.
- Associated symptoms: bilateral temporal lobe lesions may cause euphoria and auditory hallucinations.
MRI Findings in Infarction: On diffusion-weighted imaging (DWI) and FLAIR sequences, the infarcted area appears as a hyperintense region. On T2-weighted images, the lesion is located above the lateral sulcus. If the lesion extends deep toward the lateral ventricle wall, it may involve the optic radiation, causing right homonymous hemianopsia (loss of the right half of the visual field). Involvement of the precentral region leads to hemiparesis.